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Eboreime J, Choi SK, Yoon SR, Sadybekov A, Katritch V, Calabrese P, Arnheim N. Germline selection of PTPN11 (HGNC:9644) variants make a major contribution to both Noonan syndrome's high birth rate and the transmission of sporadic cancer variants resulting in fetal abnormality. Hum Mutat 2022; 43:2205-2221. [PMID: 36349709 PMCID: PMC10099774 DOI: 10.1002/humu.24493] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 09/20/2022] [Accepted: 10/12/2022] [Indexed: 11/10/2022]
Abstract
Some spontaneous germline gain-of-function mutations promote spermatogonial stem cell clonal expansion and disproportionate variant sperm production leading to unexpectedly high transmission rates for some human genetic conditions. To measure the frequency and spatial distribution of de novo mutations we divided three testes into 192 pieces each and used error-corrected deep-sequencing on each piece. We focused on PTPN11 (HGNC:9644) Exon 3 that contains 30 different PTPN11 Noonan syndrome (NS) mutation sites. We found 14 of these variants formed clusters among the testes; one testis had 11 different variant clusters. The mutation frequencies of these different clusters were not correlated with their case-recurrence rates nor were case recurrence rates of PTPN11 variants correlated with their tyrosine phosphatase levels thereby confusing PTPN11's role in germline clonal expansion. Six of the PTPN11 exon 3 de novo variants associated with somatic mutation-induced sporadic cancers (but not NS) also formed testis clusters. Further, three of these six variants were observed among fetuses that underwent prenatal ultrasound screening for NS-like features. Mathematical modeling showed that germline selection can explain both the mutation clusters and the high incidence of NS (1/1000-1/2500).
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Affiliation(s)
- Jordan Eboreime
- Department of Biological Sciences, Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, USA
| | - Soo-Kyung Choi
- Department of Biological Sciences, Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, USA
| | - Song-Ro Yoon
- Department of Biological Sciences, Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, USA
| | - Anastasiia Sadybekov
- Department of Chemistry, Bridge Institute, University of Southern California, Los Angeles, California, USA
| | - Vsevolod Katritch
- Department of Chemistry, Bridge Institute, University of Southern California, Los Angeles, California, USA
| | - Peter Calabrese
- Department of Quantitative and Computational Biology, University of Southern California, Los Angeles, California, USA
| | - Norman Arnheim
- Department of Biological Sciences, Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, USA
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Abstract
Some de novo human mutations arise at frequencies far exceeding the genome average mutation rate. Examples include the common mutations at one or a few sites in the genes that cause achondroplasia, Apert syndrome, multiple endocrine neoplasia type 2B, and Noonan syndrome. These mutations are recurrent, provide a gain of function, are paternally derived, and are more likely to be transmitted as the father ages. Recent experiments have tested whether the high mutation frequencies are due to an elevated mutation rate per cell division, as expected, or to an advantage of the mutant spermatogonial stem cells over wild-type stem cells. The evidence, which includes the surprising discovery of testis mutation clusters, rules out the former model but not the latter. We propose how the mutations might alter spermatogonial stem cell function and discuss how germline selection contributes to the paternal age effect, the human mutational load, and adaptive evolution.
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Affiliation(s)
- Norman Arnheim
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, California 90089-2910; ,
| | - Peter Calabrese
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, California 90089-2910; ,
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Yoon SR, Choi SK, Eboreime J, Gelb B, Calabrese P, Arnheim N. Age-dependent germline mosaicism of the most common noonan syndrome mutation shows the signature of germline selection. Am J Hum Genet 2013; 92:917-26. [PMID: 23726368 DOI: 10.1016/j.ajhg.2013.05.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2012] [Revised: 04/19/2013] [Accepted: 05/03/2013] [Indexed: 12/11/2022] Open
Abstract
Noonan syndrome (NS) is among the most common Mendelian genetic diseases (∼1/2,000 live births). Most cases (50%-84%) are sporadic, and new mutations are virtually always paternally derived. More than 47 different sites of NS de novo missense mutations are known in the PTPN11 gene that codes for the protein tyrosine phosphatase SHP-2. Surprisingly, many of these mutations are recurrent with nucleotide substitution rates substantially greater than the genome average; the most common mutation, c.922A>G, is at least 2,400 times greater. We examined the spatial distribution of the c.922A>G mutation in testes from 15 unaffected men and found that the mutations were not uniformly distributed across each testis as would be expected for a mutation hot spot but were highly clustered and showed an age-dependent germline mosaicism. Computational modeling that used different stem cell division schemes confirmed that the data were inconsistent with hypermutation, but consistent with germline selection: mutated spermatogonial stem cells gained an advantage that allowed them to increase in frequency. SHP-2 interacts with the transcriptional activator STAT3. Given STAT3's function in mouse spermatogonial stem cells, we suggest that this interaction might explain the mutant's selective advantage by means of repression of stem cell differentiation signals. Repression of STAT3 activity by cyclin D1 might also play a previously unrecognized role in providing a germline-selective advantage to spermatogonia for the recurrent mutations in the receptor tyrosine kinases that cause Apert syndrome and MEN2B. Looking at recurrent mutations driven by germline selection in different gene families can help highlight common causal signaling pathways.
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Shinde DN, Elmer DP, Calabrese P, Boulanger J, Arnheim N, Tiemann-Boege I. New evidence for positive selection helps explain the paternal age effect observed in achondroplasia. Hum Mol Genet 2013; 22:4117-26. [PMID: 23740942 PMCID: PMC3781639 DOI: 10.1093/hmg/ddt260] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
There are certain de novo germline mutations associated with genetic disorders whose mutation rates per generation are orders of magnitude higher than the genome average. Moreover, these mutations occur exclusively in the male germ line and older men have a higher probability of having an affected child than younger ones, known as the paternal age effect (PAE). The classic example of a genetic disorder exhibiting a PAE is achondroplasia, caused predominantly by a single-nucleotide substitution (c.1138G>A) in FGFR3. To elucidate what mechanisms might be driving the high frequency of this mutation in the male germline, we examined the spatial distribution of the c.1138G>A substitution in a testis from an 80-year-old unaffected man. Using a technology based on bead-emulsion amplification, we were able to measure mutation frequencies in 192 individual pieces of the dissected testis with a false-positive rate lower than 2.7 × 10−6. We observed that most mutations are clustered in a few pieces with 95% of all mutations occurring in 27% of the total testis. Using computational simulations, we rejected the model proposing an elevated mutation rate per cell division at this nucleotide site. Instead, we determined that the observed mutation distribution fits a germline selection model, where mutant spermatogonial stem cells have a proliferative advantage over unmutated cells. Combined with data on several other PAE mutations, our results support the idea that the PAE, associated with a number of Mendelian disorders, may be explained primarily by a selective mechanism.
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Affiliation(s)
- Deepali N Shinde
- The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint First Authors
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Choi SK, Yoon SR, Calabrese P, Arnheim N. Positive selection for new disease mutations in the human germline: evidence from the heritable cancer syndrome multiple endocrine neoplasia type 2B. PLoS Genet 2012; 8:e1002420. [PMID: 22359510 PMCID: PMC3280958 DOI: 10.1371/journal.pgen.1002420] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Accepted: 10/19/2011] [Indexed: 01/15/2023] Open
Abstract
Multiple endocrine neoplasia type 2B (MEN2B) is a highly aggressive thyroid cancer syndrome. Since almost all sporadic cases are caused by the same nucleotide substitution in the RET proto-oncogene, the calculated disease incidence is 100-200 times greater than would be expected based on the genome average mutation frequency. In order to determine whether this increased incidence is due to an elevated mutation rate at this position (true mutation hot spot) or a selective advantage conferred on mutated spermatogonial stem cells, we studied the spatial distribution of the mutation in 14 human testes. In donors aged 36-68, mutations were clustered with small regions of each testis having mutation frequencies several orders of magnitude greater than the rest of the testis. In donors aged 19-23 mutations were almost non-existent, demonstrating that clusters in middle-aged donors grew during adulthood. Computational analysis showed that germline selection is the only plausible explanation. Testes of men aged 75-80 were heterogeneous with some like middle-aged and others like younger testes. Incorporating data on age-dependent death of spermatogonial stem cells explains the results from all age groups. Germline selection also explains MEN2B's male mutation bias and paternal age effect. Our discovery focuses attention on MEN2B as a model for understanding the genetic and biochemical basis of germline selection. Since RET function in mouse spermatogonial stem cells has been extensively studied, we are able to suggest that the MEN2B mutation provides a selective advantage by altering the PI3K/AKT and SFK signaling pathways. Mutations that are preferred in the germline but reduce the fitness of offspring increase the population's mutational load. Our approach is useful for studying other disease mutations with similar characteristics and could uncover additional germline selection pathways or identify true mutation hot spots.
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Affiliation(s)
- Soo-Kyung Choi
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, United States of America
| | - Song-Ro Yoon
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, United States of America
| | - Peter Calabrese
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, United States of America
| | - Norman Arnheim
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, United States of America
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Tiemann-Boege I, Curtis C, Shinde DN, Goodman DB, Tavaré S, Arnheim N. Product length, dye choice, and detection chemistry in the bead-emulsion amplification of millions of single DNA molecules in parallel. Anal Chem 2009; 81:5770-6. [PMID: 19601653 DOI: 10.1021/ac900633y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The amplification of millions of single molecules in parallel can be performed on microscopic magnetic beads that are contained in aqueous compartments of an oil-buffer emulsion. These bead-emulsion amplification (BEA) reactions result in beads that are covered by almost-identical copies derived from a single template. The post-amplification analysis is performed using different fluorophore-labeled probes. We have identified BEA reaction conditions that efficiently produce longer amplicons of up to 450 base pairs. These conditions include the use of a Titanium Taq amplification system. Second, we explored alternate fluorophores coupled to probes for post-PCR DNA analysis. We demonstrate that four different Alexa fluorophores can be used simultaneously with extremely low crosstalk. Finally, we developed an allele-specific extension chemistry that is based on Alexa dyes to query individual nucleotides of the amplified material that is both highly efficient and specific.
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Yoon SR, Qin J, Glaser RL, Wang Jabs E, Wexler NS, Sokol R, Arnheim N, Calabrese P. The ups and downs of mutation frequencies during aging can account for the Apert syndrome paternal age effect. PLoS Genet 2009; 5:e1000558. [PMID: 19593369 PMCID: PMC2700275 DOI: 10.1371/journal.pgen.1000558] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2009] [Accepted: 06/12/2009] [Indexed: 11/18/2022] Open
Abstract
Apert syndrome is almost always caused by a spontaneous mutation of paternal origin in one of two nucleotides in the fibroblast growth factor receptor 2 gene (FGFR2). The incidence of this disease increases with the age of the father (paternal age effect), and this increase is greater than what would be expected based on the greater number of germ-line divisions in older men. We use a highly sensitive PCR assay to measure the frequencies of the two causal mutations in the sperm of over 300 normal donors with a wide range of ages. The mutation frequencies increase with the age of the sperm donors, and this increase is consistent with the increase in the incidence rate. In both the sperm data and the birth data, the increase is non-monotonic. Further, after normalizing for age, the two Apert syndrome mutation frequencies are correlated within individual sperm donors. We consider a mathematical model for germ-line mutation which reproduces many of the attributes of the data. This model, with other evidence, suggests that part of the increase in both the sperm data and the birth data is due to selection for mutated premeiotic cells. It is likely that a number of other genetic diseases have similar features.
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Affiliation(s)
- Song-Ro Yoon
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, United States of America
| | - Jian Qin
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, United States of America
| | - Rivka L. Glaser
- Department of Biology, Stevenson University, Stevenson, Maryland, United States of America
| | - Ethylin Wang Jabs
- Departments of Genetics and Genomic Sciences, Pediatrics, and Developmental and Regenerative Biology, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Nancy S. Wexler
- Departments of Neurology and Psychiatry, Columbia University Medical Center, New York, New York, United States of America
- Hereditary Disease Foundation, New York, New York, United States of America
| | - Rebecca Sokol
- Department of Obstetrics and Gynecology and Department of Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Norman Arnheim
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, United States of America
| | - Peter Calabrese
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, United States of America
- * E-mail:
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Abstract
The polymerase chain reaction makes it possible to analyse DNA sequences in a single cell and has led to a new approach for constructing genetic maps. We describe a procedure called 'sperm typing' which can accurately classify individual meiotic products as recombinant of non-recombinant. This permits the linkage relationships among DNA polymorphisms to be determined without pedigree analysis.
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Affiliation(s)
- N Arnheim
- Department of Biological Sciences, University of Southern California, Los Angeles 90089-1340
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Qin J, Subramanian J, Arnheim N. Detection of meiotic DNA breaks in mouse testicular germ cells. Methods Mol Biol 2009; 557:165-181. [PMID: 19799182 DOI: 10.1007/978-1-59745-527-5_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The study of location and intensity of double-strand breaks (DSBs) in mammalian systems is more challenging than in yeast because, unlike yeast, the progression through meiosis is not synchronous and only a small fraction of all testis cells are actually at the stage where DSB formation is initiated. We devised a quantitative approach that is sensitive enough to detect the position of rare DNA strand breaks in mouse germ cell-enriched testicular cell populations. The method can detect DNA breaks at any desired location in the genome but is not specific for DSBs-overhangs, nicks, or gaps with a free 3' OH group are also detected. The method was successfully used to compare testicular cells from mouse strains that possess or lack an active recombination hot spot at the H2-Ea gene. Breaks that were due to meiotic hot spot activity could be distinguished from the background of DNA breaks. This highly sensitive approach could be used to study other biological processes where rare DNA breaks are generated.
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Affiliation(s)
- Jian Qin
- Fluidigm Corporation, South San Francisco, CA, USA
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Choi SK, Yoon SR, Calabrese P, Arnheim N. A germ-line-selective advantage rather than an increased mutation rate can explain some unexpectedly common human disease mutations. Proc Natl Acad Sci U S A 2008; 105:10143-8. [PMID: 18632557 PMCID: PMC2474563 DOI: 10.1073/pnas.0801267105] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2008] [Indexed: 11/18/2022] Open
Abstract
Two nucleotide substitutions in the human FGFR2 gene (C755G or C758G) are responsible for virtually all sporadic cases of Apert syndrome. This condition is 100-1,000 times more common than genomic mutation frequency data predict. Here, we report on the C758G de novo Apert syndrome mutation. Using data on older donors, we show that spontaneous mutations are not uniformly distributed throughout normal testes. Instead, we find foci where C758G mutation frequencies are 3-4 orders of magnitude greater than the remaining tissue. We conclude this nucleotide site is not a mutation hot spot even after accounting for possible Luria-Delbruck "mutation jackpots." An alternative explanation for such foci involving positive selection acting on adult self-renewing Ap spermatogonia experiencing the rare mutation could not be rejected. Further, the two youngest individuals studied (19 and 23 years old) had lower mutation frequencies and smaller foci at both mutation sites compared with the older individuals. This implies that the mutation frequency of foci increases as adults age, and thus selection could explain the paternal age effect for Apert syndrome and other genetic conditions. Our results, now including the analysis of two mutations in the same set of testes, suggest that positive selection can increase the relative frequency of premeiotic germ cells carrying such mutations, although individuals who inherit them have reduced fitness. In addition, we compared the anatomical distribution of C758G mutation foci with both new and old data on the C755G mutation in the same testis and found their positions were not correlated with one another.
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Affiliation(s)
- Soo-Kyung Choi
- Molecular and Computational Biology Program, University of Southern California, 1050 Childs Way, Los Angeles, CA 90089-2910
| | - Song-Ro Yoon
- Molecular and Computational Biology Program, University of Southern California, 1050 Childs Way, Los Angeles, CA 90089-2910
| | - Peter Calabrese
- Molecular and Computational Biology Program, University of Southern California, 1050 Childs Way, Los Angeles, CA 90089-2910
| | - Norman Arnheim
- Molecular and Computational Biology Program, University of Southern California, 1050 Childs Way, Los Angeles, CA 90089-2910
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Abstract
Our understanding of the details of mammalian meiotic recombination has recently advanced significantly. Sperm typing technologies, linkage studies, and computational inferences from population genetic data have together provided information in unprecedented detail about the location and activity of the sites of crossing-over in mice and humans. The results show that the vast majority of meiotic recombination events are localized to narrow DNA regions (hot spots) that constitute only a small fraction of the genome. The data also suggest that the molecular basis of hot spot activity is unlikely to be strictly determined by specific DNA sequence motifs in cis. Further molecular studies are needed to understand how hot spots originate, function and evolve.
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Affiliation(s)
- Norman Arnheim
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, CA 90089-2910, USA.
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Qin J, Calabrese P, Tiemann-Boege I, Shinde DN, Yoon SR, Gelfand D, Bauer K, Arnheim N. The molecular anatomy of spontaneous germline mutations in human testes. PLoS Biol 2007; 5:e224. [PMID: 17760502 PMCID: PMC1951783 DOI: 10.1371/journal.pbio.0050224] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2007] [Accepted: 06/19/2007] [Indexed: 12/05/2022] Open
Abstract
The frequency of the most common sporadic Apert syndrome mutation (C755G) in the human fibroblast growth factor receptor 2 gene (FGFR2) is 100-1,000 times higher than expected from average nucleotide substitution rates based on evolutionary studies and the incidence of human genetic diseases. To determine if this increased frequency was due to the nucleotide site having the properties of a mutation hot spot, or some other explanation, we developed a new experimental approach. We examined the spatial distribution of the frequency of the C755G mutation in the germline by dividing four testes from two normal individuals each into several hundred pieces, and, using a highly sensitive PCR assay, we measured the mutation frequency of each piece. We discovered that each testis was characterized by rare foci with mutation frequencies 10(3) to >10(4) times higher than the rest of the testis regions. Using a model based on what is known about human germline development forced us to reject (p < 10(-6)) the idea that the C755G mutation arises more frequently because this nucleotide simply has a higher than average mutation rate (hot spot model). This is true regardless of whether mutation is dependent or independent of cell division. An alternate model was examined where positive selection acts on adult self-renewing Ap spermatogonial cells (SrAp) carrying this mutation such that, instead of only replacing themselves, they occasionally produce two SrAp cells. This model could not be rejected given our observed data. Unlike the disease site, similar analysis of C-to-G mutations at a control nucleotide site in one testis pair failed to find any foci with high mutation frequencies. The rejection of the hot spot model and lack of rejection of a selection model for the C755G mutation, along with other data, provides strong support for the proposal that positive selection in the testis can act to increase the frequency of premeiotic germ cells carrying a mutation deleterious to an offspring, thereby unfavorably altering the mutational load in humans. Studying the anatomical distribution of germline mutations can provide new insights into genetic disease and evolutionary change.
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Affiliation(s)
- Jian Qin
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, United States of America
| | - Peter Calabrese
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, United States of America
| | - Irene Tiemann-Boege
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, United States of America
| | - Deepali Narendra Shinde
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, United States of America
| | - Song-Ro Yoon
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, United States of America
| | - David Gelfand
- Program in Core Research, Roche Molecular Systems, Alameda, California, United States of America
| | - Keith Bauer
- Program in Core Research, Roche Molecular Systems, Alameda, California, United States of America
| | - Norman Arnheim
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, United States of America
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Shelbourne PF, Keller-McGandy C, Bi WL, Yoon SR, Dubeau L, Veitch NJ, Vonsattel JP, Wexler NS, Arnheim N, Augood SJ. Triplet repeat mutation length gains correlate with cell-type specific vulnerability in Huntington disease brain. Hum Mol Genet 2007; 16:1133-42. [PMID: 17409200 DOI: 10.1093/hmg/ddm054] [Citation(s) in RCA: 144] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Huntington disease is caused by the expansion of a CAG repeat encoding an extended glutamine tract in a protein called huntingtin. Here, we provide evidence supporting the hypothesis that somatic increases of mutation length play a role in the progressive nature and cell-selective aspects of HD pathogenesis. Results from micro-dissected tissue and individual laser-dissected cells obtained from human HD cases and knock-in HD mice indicate that the CAG repeat is unstable in all cell types tested although neurons tend to have longer mutation length gains than glia. Mutation length gains occur early in the disease process and continue to accumulate as the disease progresses. In keeping with observed patterns of cell loss, neuronal mutation length gains tend to be more prominent in the striatum than in the cortex of low-grade human HD cases, less so in more advanced cases. Interestingly, neuronal sub-populations of HD mice appear to have different propensities for mutation length gains; in particular, smaller mutation length gains occur in nitric oxide synthase-positive striatal interneurons (a relatively spared cell type in HD) compared with the pan-striatal neuronal population. More generally, the data demonstrate that neuronal changes in HD repeat length can be at least as great, if not greater, than those observed in the germline. The fact that significant CAG repeat length gains occur in non-replicating cells also argues that processes such as inappropriate mismatch repair rather than DNA replication are involved in generating mutation instability in HD brain tissue.
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Clark VJ, Ptak SE, Tiemann I, Qian Y, Coop G, Stone AC, Przeworski M, Arnheim N, Di Rienzo A. Combining sperm typing and linkage disequilibrium analyses reveals differences in selective pressures or recombination rates across human populations. Genetics 2006; 175:795-804. [PMID: 17151245 PMCID: PMC1800598 DOI: 10.1534/genetics.106.064964] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A previous polymorphism survey of the type 2 diabetes gene CAPN10 identified a segment showing an excess of polymorphism levels in all population samples, coinciding with localized breakdown of linkage disequilibrium (LD) in a sample of Hausa from Cameroon, but not in non-African samples. This raised the possibility that a recombination hotspot is present in all populations and we had insufficient power to detect it in the non-African data. To test this possibility, we estimated the crossover rate by sperm typing in five non-African men; these estimates were consistent with the LD decay in the non-African, but not in the Hausa data. Moreover, resequencing the orthologous region in a sample of Western chimpanzees did not show either an excess of polymorphism level or rapid LD decay, suggesting that the processes underlying the patterns observed in humans operated only on the human lineage. These results suggest that a hotspot of recombination has recently arisen in humans and has reached higher frequency in the Hausa than in non-Africans, or that there is no elevation in crossover rate in any human population, and the observed variation results from long-standing balancing selection.
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Affiliation(s)
- Vanessa J Clark
- Department of Human Genetics, University of Chicago, Chicago, Illinois 60637, USA
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Wyrobek AJ, Eskenazi B, Young S, Arnheim N, Tiemann-Boege I, Jabs EW, Glaser RL, Pearson FS, Evenson D. Advancing age has differential effects on DNA damage, chromatin integrity, gene mutations, and aneuploidies in sperm. Proc Natl Acad Sci U S A 2006; 103:9601-6. [PMID: 16766665 PMCID: PMC1480453 DOI: 10.1073/pnas.0506468103] [Citation(s) in RCA: 256] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
This study compares the relative effects of advancing male age on multiple genomic defects in human sperm [DNA fragmentation index (DFI), chromatin integrity, gene mutations, and numerical chromosomal abnormalities], characterizes the relationships among these defects and with semen quality, and estimates the incidence of susceptible individuals for a well characterized nonclinical nonsmoking group of 97 men (22-80 years). Adjusting for confounders, we found major associations between age and the frequencies of sperm with DFI and fibroblast growth factor receptor 3 gene (FGFR3) mutations associated with achondroplasia (P < 0.01) with no evidence for age thresholds. However, we found no associations between age and the frequencies of sperm with immature chromatin, aneuploidies/diploidies, FGFR2 mutations (Apert syndrome), or sex ratio in this cohort. There were also no consistent correlations among genomic and semen-quality endpoints, except between DFI and sperm motility (r = -0.65, P < 0.001). These findings suggest there are multiple spermatogenic targets for genomically defective sperm with substantially variable susceptibilities to age. Our findings predict that as healthy males age, they have decreased pregnancy success with trends beginning in their early reproductive years, increased risk for producing offspring with achondroplasia mutations, and risk of fathering offspring with Apert syndrome that may vary across cohorts, but with no increased risk for fathering aneuploid offspring (Down, Klinefelter, Turner, triple X, and XYY syndromes) or triploid embryos. Our findings also suggest that the burden of genomic damage in sperm cannot be inferred from semen quality, and that a small fraction of men are at increased risk for transmitting multiple genetic and chromosomal defects.
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Affiliation(s)
- A J Wyrobek
- Biosciences Directorate, Lawrence Livermore National Laboratory, 1 Cyclotron Road, Livermore, CA 94550, USA.
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Tiemann-Boege I, Calabrese P, Cochran DM, Sokol R, Arnheim N. High-resolution recombination patterns in a region of human chromosome 21 measured by sperm typing. PLoS Genet 2006; 2:e70. [PMID: 16680198 PMCID: PMC1456319 DOI: 10.1371/journal.pgen.0020070] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2006] [Accepted: 03/23/2006] [Indexed: 12/05/2022] Open
Abstract
For decades, classical crossover studies and linkage disequilibrium (LD) analysis of genomic regions suggested that human meiotic crossovers may not be randomly distributed along chromosomes but are focused instead in “hot spots.” Recent sperm typing studies provided data at very high resolution and accuracy that defined the physical limits of a number of hot spots. The data were also used to test whether patterns of LD can predict hot spot locations. These sperm typing studies focused on several small regions of the genome already known or suspected of containing a hot spot based on the presence of LD breakdown or previous experimental evidence of hot spot activity. Comparable data on target regions not specifically chosen using these two criteria is lacking but is needed to make an unbiased test of whether LD data alone can accurately predict active hot spots. We used sperm typing to estimate recombination in 17 almost contiguous ~5 kb intervals spanning 103 kb of human Chromosome 21. We found two intervals that contained new hot spots. The comparison of our data with recombination rates predicted by statistical analyses of LD showed that, overall, the two datasets corresponded well, except for one predicted hot spot that showed little crossing over. This study doubles the experimental data on recombination in men at the highest resolution and accuracy and supports the emerging genome-wide picture that recombination is localized in small regions separated by cold areas. Detailed study of one of the new hot spots revealed a sperm donor with a decrease in recombination intensity at the canonical recombination site but an increase in crossover activity nearby. This unique finding suggests that the position and intensity of hot spots may evolve by means of a concerted mechanism that maintains the overall recombination intensity in the region. Meiotic crossover events are not randomly distributed across the human genome, but are concentrated in many small regions of a few kb with high recombination rates compared to surrounding regions. How the distribution of recombination events affects the association of different alleles along the chromosome (linkage disequilibrium, or LD) was recently addressed using sperm typing in regions already known or suspected to contain unusually high recombination intensities. In the current paper, the authors used sperm typing to examine recombination in a region not known or suspected of containing recombination hot spots. They first established the crossover distribution pattern within a 103-kb region of human Chromosome 21. Then, they compared their data to predictions of crossover distributions estimated by statistical analyses of polymorphism in the region. They found a good concordance between the two, although it was not perfect. To the authors' knowledge, this work is the first to compare LD-based estimates of recombination to sperm-typing data from regions not previously known or suspected of containing recombination hot spots. In addition, one of the studied hot spots revealed an example of a decrease in recombination intensity with a concurrent increase at a nearby site. This unique observation suggests that the activity of hot spots may evolve in a concerted fashion such that the overall recombination activity of the region is maintained.
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Affiliation(s)
- Irene Tiemann-Boege
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, United States of America
| | - Peter Calabrese
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, United States of America
| | - David M Cochran
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, United States of America
| | - Rebecca Sokol
- Obstetrics, Gynecology and Medicine, and Women's Hospital, Health Sciences Campus, University of Southern California, Los Angeles, California, United States of America
| | - Norman Arnheim
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, United States of America
- * To whom correspondence should be addressed. E-mail:
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17
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Wesoly J, Agarwal S, Sigurdsson S, Bussen W, Van Komen S, Qin J, van Steeg H, van Benthem J, Wassenaar E, Baarends WM, Ghazvini M, Tafel AA, Heath H, Galjart N, Essers J, Grootegoed JA, Arnheim N, Bezzubova O, Buerstedde JM, Sung P, Kanaar R. Differential contributions of mammalian Rad54 paralogs to recombination, DNA damage repair, and meiosis. Mol Cell Biol 2006; 26:976-89. [PMID: 16428451 PMCID: PMC1347043 DOI: 10.1128/mcb.26.3.976-989.2006] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Homologous recombination is a versatile DNA damage repair pathway requiring Rad51 and Rad54. Here we show that a mammalian Rad54 paralog, Rad54B, displays physical and functional interactions with Rad51 and DNA that are similar to those of Rad54. While ablation of Rad54 in mouse embryonic stem (ES) cells leads to a mild reduction in homologous recombination efficiency, the absence of Rad54B has little effect. However, the absence of both Rad54 and Rad54B dramatically reduces homologous recombination efficiency. Furthermore, we show that Rad54B protects ES cells from ionizing radiation and the interstrand DNA cross-linking agent mitomycin C. Interestingly, at the ES cell level the paralogs do not display an additive or synergic interaction with respect to mitomycin C sensitivity, yet animals lacking both Rad54 and Rad54B are dramatically sensitized to mitomycin C compared to either single mutant. This suggests that the paralogs possibly function in a tissue-specific manner. Finally, we show that Rad54, but not Rad54B, is needed for a normal distribution of Rad51 on meiotic chromosomes. Thus, even though the paralogs have similar biochemical properties, genetic analysis in mice uncovered their nonoverlapping roles.
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Affiliation(s)
- Joanna Wesoly
- Department of Cell Biology and Genetics, Erasmus MC, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands
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18
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Chen PC, Dudley S, Hagen W, Dizon D, Paxton L, Reichow D, Yoon SR, Yang K, Arnheim N, Liskay RM, Lipkin SM. Contributions by MutL homologues Mlh3 and Pms2 to DNA mismatch repair and tumor suppression in the mouse. Cancer Res 2005; 65:8662-70. [PMID: 16204034 DOI: 10.1158/0008-5472.can-05-0742] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Germ line DNA mismatch repair mutations in MLH1 and MSH2 underlie the vast majority of hereditary non-polyposis colon cancer. Four mammalian homologues of Escherichia coli MutL heterodimerize to form three distinct complexes: MLH1/PMS2, MLH1/MLH3, and MLH1/PMS1. Although MLH1/PMS2 is generally thought to have the major MutL activity, the precise contributions of each MutL heterodimer to mismatch repair functions are poorly understood. Here, we show that Mlh3 contributes to mechanisms of tumor suppression in the mouse. Mlh3 deficiency alone causes microsatellite instability, impaired DNA-damage response, and increased gastrointestinal tumor susceptibility. Furthermore, Mlh3;Pms2 double-deficient mice have tumor susceptibility, shorter life span, microsatellite instability, and DNA-damage response phenotypes that are indistinguishable from Mlh1-deficient mice. Our data support previous results from budding yeast that show partial functional redundancy between MLH3 and PMS2 orthologues for mutation avoidance and show a role for Mlh3 in gastrointestinal and extragastrointestinal tumor suppression. The data also suggest a mechanistic basis for the more severe mismatch repair-related phenotypes and cancer susceptibility in Mlh1- versus Mlh3- or Pms2-deficient mice. Contributions by both MLH1/MLH3 and MLH1/PMS2 complexes to mechanisms of mismatch repair-mediated tumor suppression, therefore, provide an explanation why, among MutL homologues, only germ line mutations in MLH1 are common in hereditary non-polyposis colon cancer.
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Affiliation(s)
- Peng-Chieh Chen
- Department of Medicine and Biological Chemistry, University of California, Irvine, California, USA
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19
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Abstract
Recombination and microsatellite mutation in humans contribute to disorders including cancer and trinucleotide repeat (TNR) disease. TNR expansions in wild-type yeast may arise by flap ligation during lagging-strand replication. Here we show that overexpression of DNA ligase I (CDC9) increases the rates of TNR expansion, of TNR contraction, and of mitotic recombination. Surprisingly, this effect is observed with catalytically inactive forms of Cdc9p protein, but only if they possess a functional PCNA-binding site. Furthermore, in vitro analysis indicates that the interaction of PCNA with Cdc9p and Rad27p (Fen1) is mutually exclusive. Together our genetic and biochemical analysis suggests that, although DNA ligase I seals DNA nicks during replication, repair, and recombination, higher than normal levels can yield genetic instability by disrupting the normal interplay of PCNA with other proteins such as Fen1.
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Affiliation(s)
- Jaichandar Subramanian
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, 90089-2910, USA
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20
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Qin J, Richardson LL, Jasin M, Handel MA, Arnheim N. Mouse strains with an active H2-Ea meiotic recombination hot spot exhibit increased levels of H2-Ea-specific DNA breaks in testicular germ cells. Mol Cell Biol 2004; 24:1655-66. [PMID: 14749381 PMCID: PMC344187 DOI: 10.1128/mcb.24.4.1655-1666.2004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We devised a sensitive method for the site-specific detection of rare meiotic DNA strand breaks in germ cell-enriched testicular cell populations from mice that possess or lack an active recombination hot spot at the H2-Ea gene. Using germ cells from adult animals, we found an excellent correlation between the frequency of DNA breaks in the 418-bp H2-Ea hot spot and crossover activity. The temporal appearance of DNA breaks was also studied in 7- to 18-day-old mice with an active hot spot during the first waves of spermatogenesis. The number of DNA breaks detected rose as leptotene and zygotene spermatocytes populate the testis with a peak at day 14 postpartum, when leptotene, zygotene, and early pachytene spermatocytes are the most common meiotic prophase I cell types. The number of DNA breaks drops precipitously 1 day later, when middle to late pachytene spermatocytes become the dominant subtype. The recombination-related breaks in the hot spot likely reflect SPO11-induced double-strand breaks and/or recombination intermediates containing free 3' hydroxyl groups.
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Affiliation(s)
- Jian Qin
- Program in Molecular and Computational Biology, University of Southern California, Los Angeles, California 90089-1340, USA
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21
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Wexler NS, Lorimer J, Porter J, Gomez F, Moskowitz C, Shackell E, Marder K, Penchaszadeh G, Roberts SA, Gayán J, Brocklebank D, Cherny SS, Cardon LR, Gray J, Dlouhy SR, Wiktorski S, Hodes ME, Conneally PM, Penney JB, Gusella J, Cha JH, Irizarry M, Rosas D, Hersch S, Hollingsworth Z, MacDonald M, Young AB, Andresen JM, Housman DE, De Young MM, Bonilla E, Stillings T, Negrette A, Snodgrass SR, Martinez-Jaurrieta MD, Ramos-Arroyo MA, Bickham J, Ramos JS, Marshall F, Shoulson I, Rey GJ, Feigin A, Arnheim N, Acevedo-Cruz A, Acosta L, Alvir J, Fischbeck K, Thompson LM, Young A, Dure L, O'Brien CJ, Paulsen J, Brickman A, Krch D, Peery S, Hogarth P, Higgins DS, Landwehrmeyer B. Venezuelan kindreds reveal that genetic and environmental factors modulate Huntington's disease age of onset. Proc Natl Acad Sci U S A 2004; 101:3498-503. [PMID: 14993615 PMCID: PMC373491 DOI: 10.1073/pnas.0308679101] [Citation(s) in RCA: 499] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Huntington's disease (HD) is an autosomal dominant neurodegenerative disease caused by a triplet (CAG) expansion mutation. The length of the triplet repeat is the most important factor in determining age of onset of HD, although substantial variability remains after controlling for repeat length. The Venezuelan HD kindreds encompass 18,149 individuals spanning 10 generations, 15,409 of whom are living. Of the 4,384 immortalized lymphocyte lines collected, 3,989 DNAs were genotyped for their HD alleles, representing a subset of the population at greatest genetic risk. There are 938 heterozygotes, 80 people with variably penetrant alleles, and 18 homozygotes. Analysis of the 83 kindreds that comprise the Venezuelan HD kindreds demonstrates that residual variability in age of onset has both genetic and environmental components. We created a residual age of onset phenotype from a regression analysis of the log of age of onset on repeat length. Familial correlations (correlation +/- SE) were estimated for sibling (0.40 +/- 0.09), parent-offspring (0.10 +/- 0.11), avuncular (0.07 +/- 0.11), and cousin (0.15 +/- 0.10) pairs, suggesting a familial origin for the residual variance in onset. By using a variance-components approach with all available familial relationships, the additive genetic heritability of this residual age of onset trait is 38%. A model, including shared sibling environmental effects, estimated the components of additive genetic (0.37), shared environment (0.22), and nonshared environment (0.41) variances, confirming that approximately 40% of the variance remaining in onset age is attributable to genes other than the HD gene and 60% is environmental.
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Affiliation(s)
- Nancy S Wexler
- Columbia University, 1051 Riverside Drive, New York, NY 10032, USA.
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22
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Brohede J, Arnheim N, Ellegren H. Single-molecule analysis of the hypermutable tetranucleotide repeat locus D21S1245 through sperm genotyping: a heterogeneous pattern of mutation but no clear male age effect. Mol Biol Evol 2003; 21:58-64. [PMID: 14530459 DOI: 10.1093/molbev/msg242] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Single molecule genotyping of the hypermutable microsatellite locus D21S1245 was used for studying how the rate and pattern of mutation varied between alleles and different age groups. In total, 203 mutation events were scored from the genotyping of DNA corresponding to an estimated 8623 sperm cells from eight different men. Allele-specific mutation rates ranged from 0.007 to 0.052, a heterogeneity related in part to variation in the mutation rate among three allelic lineages identified after allele sequencing. Alleles from these lineages differed in the overall repeat structure of this complex microsatellite locus. Also, the pattern of mutation varied between lineages in that they differed in the relative proportions of expansion and contraction mutations. Surprisingly, a group of four men aged 18-23 years showed a higher mean mutation rate than a group of four men aged 48-56 years. To some extent this age difference can probably be explained by a bias in the distribution of alleles from the three allelic lineages among the age groups. However, the absence of a clear male age effect is at odds with the idea of an increasing male mutation rate with age, which is thought to arise from the continuous replication of germline cells throughout adulthood.
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Affiliation(s)
- Jesper Brohede
- Department of Evolutionary Biology, Uppsala University, Uppsala, Sweden
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23
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Yoon SR, Dubeau L, de Young M, Wexler NS, Arnheim N. Huntington disease expansion mutations in humans can occur before meiosis is completed. Proc Natl Acad Sci U S A 2003; 100:8834-8. [PMID: 12857955 PMCID: PMC166399 DOI: 10.1073/pnas.1331390100] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Single-molecule DNA analysis of testicular germ cells isolated by laser capture microdissection from two Huntington disease patients showed that trinucleotide repeat expansion mutations were present before the end of the first meiotic division, and some mutations were present even before meiosis began. Most of the larger Huntington disease mutations were found in the postmeiotic cell population, suggesting that expansions may continue to occur during meiosis and/or after meiosis is complete. Defining the germ-line cell compartments where the trinucleotide repeat expansions occur could help to elucidate the underlying mechanisms of instability.
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Affiliation(s)
- Song-Ro Yoon
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, CA 90089-1340, USA
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24
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Abstract
We build a mathematical model for the mutation process of microsatellites during polymerase chain reaction (PCR) using the theory of branching processes. Based on the model, we develop a method to estimate the mutation rate of microsatellites per PCR cycle and the probability of expansion by maximizing a quasi-likelihood of the observed data. We show by simulations that the proposed estimation method can accurately recover the relationship between the mutation rate and number of repeat units. The theoretical basis for the proposed method is also given. We apply the method to experimental data on poly-A and poly-CA repeats.
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Affiliation(s)
- Yinglei Lai
- Department of Mathematics, University of Southern California, Los Angeles, CA 90089-1113, USA
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25
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Arnheim N, Calabrese P, Nordborg M. Hot and cold spots of recombination in the human genome: the reason we should find them and how this can be achieved. Am J Hum Genet 2003; 73:5-16. [PMID: 12772086 PMCID: PMC1180590 DOI: 10.1086/376419] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2003] [Accepted: 04/10/2003] [Indexed: 11/03/2022] Open
Affiliation(s)
- Norman Arnheim
- Molecular and Computational Biology Program, University of Southern California, 835 West 37th Street, SHS 172, Los Angeles, CA 90089-1340, USA.
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26
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Nenguke T, Aladjem MI, Gusella JF, Wexler NS, Arnheim N. Candidate DNA replication initiation regions at human trinucleotide repeat disease loci. Hum Mol Genet 2003; 12:1021-8. [PMID: 12700170 DOI: 10.1093/hmg/ddg111] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The positions of DNA replication initiation regions (IRs) at three human trinucleotide repeat (TNR) disease loci were examined in order to characterize the role played by IRs in explaining the known locus-specific variation in TNR instability levels. Using three different normal cell lines, candidate IRs were identified at the HD, SCA-7 and SBMA loci. At each locus the IR is less than 3.6 kb from the CAG/CTG repeat tract. Preliminary studies with a cell line homozygous for an HD disease mutation indicated no change in the position of the candidate IR in spite of the mutation. Comparison with experimental results from model systems suggests that a complex relationship may exist between instability and the proximity and/or orientation of the repeats with respect to an IR.
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Affiliation(s)
- Taurai Nenguke
- Program in Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089-1340, USA
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27
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Shinde D, Lai Y, Sun F, Arnheim N. Taq DNA polymerase slippage mutation rates measured by PCR and quasi-likelihood analysis: (CA/GT)n and (A/T)n microsatellites. Nucleic Acids Res 2003; 31:974-80. [PMID: 12560493 PMCID: PMC149199 DOI: 10.1093/nar/gkg178] [Citation(s) in RCA: 166] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
During microsatellite polymerase chain reaction (PCR), insertion-deletion mutations produce stutter products differing from the original template by multiples of the repeat unit length. We analyzed the PCR slippage products of (CA)n and (A)n tracts cloned in a pUC18 vector. Repeat numbers varied from two to 14 (CA)n and four to 12 (A)n. Data was generated on approximately 10 single molecules for each clone type using two rounds of nested PCR. The size and peak areas of the products were obtained by capillary electrophoresis. A quasi- likelihood approach to the analysis of the data estimated the mutation rate/repeat/PCR cycle. The rate for (CA)n tracts was 3.6 x 10(-3) with contractions 14 times greater than expansions. For (A)n tracts the rate was 1.5 x 10(-2) and contractions outnumbered expansions by 5-fold. The threshold for detecting 'stutter' products was computed to be four repeats for (CA)n and eight repeats for (A)n or approximately 8 bp in both cases. A comparison was made between the computationally and experimentally derived threshold values. The threshold and expansion to contraction ratios are explained on the basis of the active site structure of Taq DNA polymerase and models of the energetics of slippage events, respectively.
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Affiliation(s)
- Deepali Shinde
- Program in Molecular and Computational Biology and Department of Mathematics, University of Southern California, Los Angeles, CA 90089, USA
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28
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Tiemann-Boege I, Navidi W, Grewal R, Cohn D, Eskenazi B, Wyrobek AJ, Arnheim N. The observed human sperm mutation frequency cannot explain the achondroplasia paternal age effect. Proc Natl Acad Sci U S A 2002; 99:14952-7. [PMID: 12397172 PMCID: PMC137526 DOI: 10.1073/pnas.232568699] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The lifelong spermatogonial stem cell divisions unique to male germ cell production are thought to contribute to a higher mutation frequency in males. The fact that certain de novo human genetic conditions (e.g., achondroplasia) increase in incidence with the age of the father is consistent with this idea. Although it is assumed that the paternal age effect is the result of an increasing frequency of mutant sperm as a man grows older, no direct molecular measurement of the germ-line mutation frequency has been made to confirm this hypothesis. Using sperm DNA from donors of different ages, we determined the frequency of the nucleotide substitution in the fibroblast growth factor receptor 3 (FGFR3) gene that causes achondroplasia. Surprisingly, the magnitude of the increase in mutation frequency with age appears insufficient to explain why older fathers have a greater chance of having a child with this condition. A number of alternatives may explain this discrepancy, including selection for sperm that carry the mutation or an age-dependent increase in premutagenic lesions that remain unrepaired in sperm and are inefficiently detected by the PCR assay.
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Affiliation(s)
- Irene Tiemann-Boege
- Molecular and Computational Biology Program, University of Southern California, Los Angeles 90089-1340, USA
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29
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Affiliation(s)
| | | | | | - Rene Hubert
- University of Southern California Los Angeles California
| | - Lin Zhang
- University of Southern California Los Angeles California
| | - Karin Schmitt
- University of Southern California Los Angeles California
| | - Norman Arnheim
- University of Southern California Los Angeles California
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30
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Abstract
Meiotic recombination was studied in DNA mismatch repair (MMR)-deficient mice using a strain carrying a Pms2 knockout mutation. Using single-sperm typing, recombination was analyzed over five intervals on four chromosomes in four Pms2 -/- animals. A total of 1936 meioses were studied and compared to 1848 meioses from three Pms2 +/+ controls. A smaller study was carried out on a single interval in each of two chromosomes in an MMR-deficient mouse homozygous for the Msh2 knockout mutation. A total of 792 meioses were examined in the Msh2 -/- and 880 meioses in the Msh2 +/+ animal. Recombination fractions were not significantly different in either of the MMR-deficient mouse strains when compared to MMR-proficient controls. Our results appear to conflict with mouse embryonic stem (ES) cell gene-targeting experiments where MMR plays a major role in determining the efficiency of homologous recombination between nonidentical sequences. A number of possibilities could explain the apparent lack of a significant effect on meiosis.
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Affiliation(s)
- J Qin
- Molecular Biology Program, University of Southern California, 835 West 37th St., Los Angeles, CA 90089-1340, USA
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31
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Affiliation(s)
- S Pathak
- Department of Chemistry and Molecular Biology Program, University of Southern California Los Angeles, California 90089, USA
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32
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Guan T, Kehlenbach RH, Schirmer EC, Kehlenbach A, Fan F, Clurman BE, Arnheim N, Gerace L. Nup50, a nucleoplasmically oriented nucleoporin with a role in nuclear protein export. Mol Cell Biol 2000; 20:5619-30. [PMID: 10891499 PMCID: PMC86026 DOI: 10.1128/mcb.20.15.5619-5630.2000] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2000] [Accepted: 04/19/2000] [Indexed: 11/20/2022] Open
Abstract
We present here a detailed analysis of a rat polypeptide termed Nup50 (formerly NPAP60) that was previously found to be associated with the nuclear pore complex (F. Fan et al., Genomics 40:444-453, 1997). We have found that Nup50 (and/or a related 70-kDa polypeptide) is present in numerous rat cells and tissues. By immunofluorescence microscopy, Nup50 was found to be highly concentrated at the nuclear envelope of rat liver nuclei, whereas in cultured NRK cells it also is abundant in intranuclear regions. On the basis of immunogold electron microscopy of both rat liver nuclear envelopes and NRK cells, we determined that Nup50 is specifically localized in the nucleoplasmic fibrils of the pore complex. Microinjection of anti-Nup50 antibodies into the nucleus of NRK cells resulted in strong inhibition of nuclear export of a protein containing a leucine-rich nuclear export sequence, whereas nuclear import of a protein containing a classical nuclear localization sequence was unaffected. Correspondingly, CRM1, the export receptor for leucine-rich export sequences, directly bound to a fragment of Nup50 in vitro, whereas several other import and export receptors did not significantly interact with this fragment. Taken together, our data indicate that Nup50 has a direct role in nuclear protein export and probably serves as a binding site on the nuclear side of the pore complex for export receptor-cargo complexes.
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Affiliation(s)
- T Guan
- Departments of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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33
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Han LL, Keller MP, Navidi W, Chance PF, Arnheim N. Unequal exchange at the Charcot-Marie-Tooth disease type 1A recombination hot-spot is not elevated above the genome average rate. Hum Mol Genet 2000; 9:1881-9. [PMID: 10915777 DOI: 10.1093/hmg/9.12.1881] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
An increasing number of human diseases and syndromes are being found to result from micro-duplications or microdeletions arising from meiotic recombination between homologous repeats on the same chromosome. The first microduplication syndrome delineated, Charcot-Marie-Tooth disease type 1A (CMT1A), results from unequal crossing over between two >98% identical 24 kb repeats (CMT1A-REPs) on chromosome 17. In addition to its medical significance, the CMT1A region has features that make it a unique resource for detailed analysis of human unequal recombination. Previous studies of CMT1A patients showed that the majority of unequal crossovers occurred within a small region (<1 kb) of the REPs suggesting the presence of a recombination hot-spot. We directly measured the frequency of unequal recombination in the hot-spot region using sperm from four normal individuals. Surprisingly, unequal recombination between the REPs occurs at a rate no greater than the average rate for the male genome (approximately 1 cM/Mb) and is the same as that expected for equally aligned REPs. This conclusion extends to humans the findings in yeast that recombination between repeated sequences far apart on the same chromosome may occur at similar frequencies to allelic recombination. Finally, the CMT1A hot-spot stands in sharp contrast to the human MS32 mini-satellite-associated hot-spot that exhibits highly enhanced recombination initiation in addition to positional specificity. One possibility is that the CMT1A hot-spot may consist of a region with genome average recombination potential embedded within a recombination cold-spot.
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Affiliation(s)
- L L Han
- Molecular Biology Program, Center for Computational and Experimental Genomics, University of Southern California, 835 West 37th Street, Los Angeles, CA 90089-1340, USA
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Lien S, Szyda J, Schechinger B, Rappold G, Arnheim N. Evidence for heterogeneity in recombination in the human pseudoautosomal region: high resolution analysis by sperm typing and radiation-hybrid mapping. Am J Hum Genet 2000; 66:557-66. [PMID: 10677316 PMCID: PMC1288109 DOI: 10.1086/302754] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Accurate genetic and physical maps for the human pseudoautosomal region were constructed by use of sperm typing and high-resolution radiation-hybrid mapping. PCR analysis of 1,912 sperm was done with a manual, single-sperm isolation method. Data on four donors show highly significant linkage heterogeneity among individuals. The most significant difference was observed in a marker interval located in the middle of the Xp/Yp pseudoautosomal region, where one donor showed a particularly high recombination fraction. Longitudinal models were fitted to the data to test whether linkage heterogeneity among donors was significant for multiple intervals across the region. The results indicated that increased recombination in particular individuals and regions is compensated for by reduced recombination in neighboring intervals. To investigate correspondence between physical and genetic distances within the region, we constructed a high-resolution radiation-hybrid map containing 29 markers. The recombination fraction per unit of physical distance varies between regions ranging from 13- to 70-fold greater than the genome-average rate.
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Affiliation(s)
- S Lien
- Department of Animal Science, Agricultural University of Norway, Aas, Norway
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Girardet A, McPeek MS, Leeflang EP, Munier F, Arnheim N, Claustres M, Pellestor F. Meiotic segregation analysis of RB1 alleles in retinoblastoma pedigrees by use of single-sperm typing. Am J Hum Genet 2000; 66:167-75. [PMID: 10631148 PMCID: PMC1288323 DOI: 10.1086/302715] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/1999] [Accepted: 09/29/1999] [Indexed: 12/18/2022] Open
Abstract
In hereditary retinoblastoma, different epidemiological studies have indicated a preferential paternal transmission of mutant retinoblastoma alleles to offspring, suggesting the occurrence of a meiotic drive. To investigate this mechanism, we analyzed sperm samples from six individuals from five unrelated families affected with hereditary retinoblastoma. Single-sperm typing techniques were performed for each sample by study of two informative short tandem repeats located either in or close to the retinoblastoma gene (RB1). The segregation probability of mutant RB1 alleles in sperm samples was assessed by use of the SPERMSEG program, which includes experimental parameters, recombination fractions between the markers, and segregation parameters. A total of 2,952 single sperm from the six donors were analyzed. We detected a significant segregation distortion in the data as a whole (P=.0099) and a significant heterogeneity in the segregation rate across donors (.0092). Further analysis shows that this result can be explained by segregation distortion in favor of the normal allele in one donor only and that it does not provide evidence of a significant segregation distortion in the other donors. The segregation distortion favoring the mutant RB1 allele does not seem to occur during spermatogenesis, and, thus, meiotic drive may result either from various mechanisms, including a fertilization advantage or a better mobility in sperm bearing a mutant RB1 gene, or from the existence of a defectively imprinted gene located on the human X chromosome.
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Affiliation(s)
- A Girardet
- Laboratoire de Génétique Moléculaire, Institut de Biologie, and Institut de Génétique Humaine, Centre National de la Recherche Scientifique, Unité Propre de Recherche 1142, 34060 Montpellier, France.
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36
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Grewal RP, Cancel G, Leeflang EP, Dürr A, McPeek MS, Draghinas D, Yao X, Stevanin G, Alnot MO, Brice A, Arnheim N. French Machado-Joseph disease patients do not exhibit gametic segregation distortion: a sperm typing analysis. Hum Mol Genet 1999; 8:1779-84. [PMID: 10441343 DOI: 10.1093/hmg/8.9.1779] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Segregation distortion has been reported to occur in a number of the trinucleotide repeat disorders. On the basis of a sperm typing study performed in patients of Japanese descent with Machado-Joseph disease (MJD), it was reported that disease alleles are preferentially transmitted during meiosis. We performed a sperm typing study of five MJD patients of French descent and analysis of the pooled data shows a ratio of mutant to normal alleles of 379:436 (46.5:53.5%), which does not support meiotic segregation distortion. To confirm these results, sperm typing analysis was also performed using a polymorphic marker, D14S1050, closely linked to the MJD1 gene. Among 910 sperm analyzed, the allele linked to the disease chromosome was detected in 50.3% of the samples and the allele linked to the normal chromosome was found in 49.6% of the sperm. The difference in frequency of these two alleles is not significant ( P = 0.8423). Likelihood-based analysis of segregation distortion in the single sperm data using the SPERMSEG program also showed no support for segregation distortion at the gamete level in this patient population. The previous report on the Japanese patients also suggested that disease allele stability may be influenced by a trans effect of an intragenic polymorphism (987 G/C) in the wild-type allele. All of the French patients were heterozygous for this polymorphism. However, analysis of the variance in repeat number in sperm from the French MJD patients overlapped significantly with the variance in repeat number observed in the C/C homozygous Japanese patients.
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Affiliation(s)
- R P Grewal
- Program in Molecular Biology, SHS 172, 835 West 37th Street, University of Southern California, Los Angeles, CA 90089-1340, USA
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37
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Navidi W, Arnheim N. Combining Data from Polymerase Chain Reaction DNA Typing Experiments: Applications to Sperm Typing Data. J Am Stat Assoc 1999. [DOI: 10.1080/01621459.1999.10474175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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38
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Abstract
DNA sequence polymorphisms were sought in the coding region and at the exon-intron boundaries of the human XPF gene, which plays a role in nucleotide excision repair. Based on a survey of 38 individuals, we found six single nucleotide polymorphisms, one in the 5' non-coding region of the XPF gene, and five in the 2751 bp coding region. At each site, the frequency of the rarer allele varies from about 0.01 to over 0.38. Except for the 5' non-coding and one coding sequence polymorphism, the rarer alleles for the remaining four polymorphisms were found only in heterozygotes. Of the five polymorphisms in the coding region, one is silent, one results in a conserved amino acid difference, and the remaining three result in non-conserved amino acid differences. Because of its biological function in nucleotide excision repair, functionally significant XPF gene polymorphisms are candidates for influencing cancer susceptibility and overall genetic stability. Nucleotide sequence diversity estimates for XPF are similar to the lipoprotein lipase and beta-globin genes.
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Affiliation(s)
- F Fan
- Program in Molecular Biology, University of Southern California, Los Angeles, CA, USA.
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39
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Yao X, Buermeyer AB, Narayanan L, Tran D, Baker SM, Prolla TA, Glazer PM, Liskay RM, Arnheim N. Different mutator phenotypes in Mlh1- versus Pms2-deficient mice. Proc Natl Acad Sci U S A 1999; 96:6850-5. [PMID: 10359802 PMCID: PMC22005 DOI: 10.1073/pnas.96.12.6850] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Deficiencies in DNA mismatch repair (MMR) result in increased mutation rates and cancer risk in both humans and mice. Mouse strains homozygous for knockouts of either the Pms2 or Mlh1 MMR gene develop cancer but exhibit very different tumor spectra; only Mlh1(-/-) animals develop intestinal tumors. We carried out a detailed study of the microsatellite mutation spectra in each knockout strain. Five mononucleotide repeat tracts at four different chromosomal locations were studied by using single-molecule PCR or an in vivo forward mutation assay. Three dinucleotide repeat loci also were examined. Surprisingly, the mononucleotide repeat mutation frequency in Mlh1(-/-) mice was 2- to 3-fold higher than in Pms2(-/-) animals. The higher mutation frequency in Mlh1(-/-) mice may be a consequence of some residual DNA repair capacity in the Pms2(-/-) animals. Relevant to this idea, we observed that Pms2(-/-) mice exhibit almost normal levels of Mlh1p, whereas Mlh1(-/-) animals lack both Mlh1p and Pms2p. Comparison between Mlh1(-/-) animals and Mlh1(-/-) and Pms2(-/-) double knockout mice revealed little difference in mutator phenotype, suggesting that Mlh1 nullizygosity is sufficient to inactivate MMR completely. The findings may provide a basis for understanding the greater predisposition to intestinal cancer of Mlh1(-/-) mice. Small differences (2- to 3-fold) in mononucleotide repeat mutation rates may have dramatic effects on tumor development, requiring multiple genetic alterations in coding regions. Alternatively, this strain difference in tumor spectra also may be related to the consequences of the absence of Pms2p compared with the absence of both Pms2p and Mlh1p on as yet little understood cellular processes.
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Affiliation(s)
- X Yao
- Molecular Biology Program, University of Southern California, Los Angeles, CA 90089-1340, USA
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40
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Abstract
Several human neurodegenerative diseases result from expansion of CTG/CAG or CGG/CCG triplet repeats. The finding that single-stranded CNG repeats form hairpin-like structures in vitro has led to the hypothesis that DNA secondary structure formation is an important component of the expansion mechanism. We show that single-stranded DNA loops containing 10 CTG/CAG or CGG/CCG repeats are inefficiently repaired during meiotic recombination in Saccharomyces cerevisiae. Comparisons of the repair of DNA loops with palindromic and nonpalindromic sequences suggest that this inefficient repair reflects the ability of these sequences to form hairpin structures in vivo.
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Affiliation(s)
- H Moore
- Department of Biology, Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599-3280, USA
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41
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Leeflang EP, Tavaré S, Marjoram P, Neal CO, Srinidhi J, MacFarlane H, MacDonald ME, Gusella JF, de Young M, Wexler NS, Arnheim N. Analysis of germline mutation spectra at the Huntington's disease locus supports a mitotic mutation mechanism. Hum Mol Genet 1999; 8:173-83. [PMID: 9931325 DOI: 10.1093/hmg/8.2.173] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Trinucleotide repeat disease alleles can undergo 'dynamic' mutations in which repeat number may change when a gene is transmitted from parent to offspring. By typing >3500 sperm, we determined the size distribution of Huntington's disease (HD) germline mutations produced by 26 individuals from the Venezuelan cohort with CAG/CTG repeat numbers ranging from 37 to 62. Both the mutation frequency and mean change in allele size increased with increasing somatic repeat number. The mutation frequencies averaged 82% and, for individuals with at least 50 repeats, 98%. The extraordinarily high mutation frequency levels are most consistent with a mutation process that occurs throughout germline mitotic divisions, rather than resulting from a single meiotic event. In several cases, the mean change in repeat number differed significantly among individuals with similar somatic allele sizes. This individual variation could not be attributed to age in a simple way or to ' cis ' sequences, suggesting the influence of genetic background or other factors. A familial effect is suggested in one family where both the father and son gave highly unusual spectra compared with other individuals matched for age and repeat number. A statistical model based on incomplete processing of Okazaki fragments during DNA replication was found to provide an excellent fit to the data but variation in parameter values among individuals suggests that the molecular mechanism might be more complex.
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Affiliation(s)
- E P Leeflang
- Molecular Biology Program and Department of Mathematics, University of Southern California, Los Angeles, CA 90089-1340, USA
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42
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Girardet A, Lien S, Leeflang EP, Beaufrère L, Tuffery S, Munier F, Arnheim N, Claustres M, Pellestor F. Direct estimation of the recombination frequency between the RB1 gene and two closely linked microsatellites using sperm typing. Eur J Hum Genet 1999; 7:239-42. [PMID: 10196709 DOI: 10.1038/sj.ejhg.5200250] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
In this study, single sperm typing has been used for high-resolution recombination analysis between the retinoblastoma gene and two closely linked extragenic microsatellites (D13S284 and D13S1307). The analysis of 1198 single sperm from three donors allowed the determination of recombination fractions between RB1.20 and D13S284 and RB1.20 and D13S1307 of 0.022 and 0.033, respectively. These results show that RB1 gene and the two microsatellites are closely linked, which validates their potential use in indirect genetic diagnosis of retinoblastoma.
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Affiliation(s)
- A Girardet
- Laboratoire de Biochimie Génétique, CHU de Montpellier, France.
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Lien S, Cockett NE, Klungland H, Arnheim N, Georges M, Gomez-Raya L. High-resolution gametic map of the sheep callipyge region: linkage heterogeneity among rams detected by sperm typing. Anim Genet 1999; 30:42-6. [PMID: 10050282 DOI: 10.1046/j.1365-2052.1999.00430.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The callipyge locus (CLPG) causing muscular hypertrophy in domestic sheep has previously been mapped to the distal part of ovine chromosome 18. In this study, an accurate multipoint linkage map consisting of six microsatellite markers in this chromosomal region was constructed based on the analysis of 1145 single sperm cells. The best supported order of markers was OARHH47-ILSTS54-MCM38-CSSM18-IDVGA30-BM S1561. The log odds against the second most likely order, which has a reversal of the closely linked markers CSSM18 and IDVGA30, was 5.026. Sperm typing can be used to examine a large number of meioses in single individuals, and therefore, was exploited to study individual variability of recombination rate in rams of different callipyge genotypes. The results revealed statistically significant linkage heterogeneity among rams (P < 0.05) for marker interval OARHH47-CSSM18, with individual recombination fractions varying from 0.209 to 0.357.
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Affiliation(s)
- S Lien
- Department of Animal Science, Agricultural University of Norway, Aas, Norway
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44
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Korobova O, Lane PW, Perry J, Palmer S, Ashworth A, Davisson MT, Arnheim N. Patchy fur, a mouse coat mutation associated with X-Y nondisjunction, maps to the pseudoautosomal boundary region. Genomics 1998; 54:556-9. [PMID: 9878259 DOI: 10.1006/geno.1998.5528] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Patchy fur is a semidominant X-linked mutation in the mouse, resulting in a sparse coat. The Paf mutation also alters the normal segregation of the X and the Y chromosomes during male meiosis by causing nondisjunction at anaphase I. Analysis of 1139 female meioses from an intersubspecific backcross using 15 PCR-based markers localizes Paf to an approximately 0.2-cM interval that includes the pseudoautosomal boundary. The meiotic nondisjunction phenotype may result from a chromosomal rearrangement that includes pseudoautosomal sequences and affects XY pairing.
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Affiliation(s)
- O Korobova
- Molecular Biology Program, University of Southern California, Los Angeles, California, 90089-1340, USA
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45
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Jackson GR, Salecker I, Dong X, Yao X, Arnheim N, Faber PW, MacDonald ME, Zipursky SL. Polyglutamine-expanded human huntingtin transgenes induce degeneration of Drosophila photoreceptor neurons. Neuron 1998; 21:633-42. [PMID: 9768849 DOI: 10.1016/s0896-6273(00)80573-5] [Citation(s) in RCA: 367] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder. Disease alleles contain a trinucleotide repeat expansion of variable length, which encodes polyglutamine tracts near the amino terminus of the HD protein, huntingtin. Polyglutamine-expanded huntingtin, but not normal huntingtin, forms nuclear inclusions. We describe a Drosophila model for HD. Amino-terminal fragments of human huntingtin containing tracts of 2, 75, and 120 glutamine residues were expressed in photoreceptor neurons in the compound eye. As in human neurons, polyglutamine-expanded huntingtin induced neuronal degeneration. The age of onset and severity of neuronal degeneration correlated with repeat length, and nuclear localization of huntingtin presaged neuronal degeneration. In contrast to other cell death paradigms in Drosophila, coexpression of the viral antiapoptotic protein, P35, did not rescue the cell death phenotype induced by polyglutamine-expanded huntingtin.
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Affiliation(s)
- G R Jackson
- Department of Neurology, University of California, Los Angeles School of Medicine, 90095, USA
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46
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Abstract
We studied the gene for the trinucleotide repeat disorder X-linked spinal and bulbar muscular atrophy (SBMA) to quantify the spectrum of mutations and gain insight into genetic anticipation. This analysis was performed using single sperm typing from an affected individual. This method allows the quantification of large numbers of meioses and therefore provides accurate information about genetic instability of the CAG repeat expansions which cause SBMA. Among 198 X chromosome-containing sperm cells, 20% had a CAG repeat number equal to the donor's somatic DNA of 49 CAG repeats, 56% were expansions, and 24% contractions. Most of the expansions (84%) and contractions (94%) were between 1 and 3 CAG repeats. These results are consistent with those obtained from one previously studied SBMA patient and reveal greater CAG repeat instability in sperm than in somatic tissue. Our results indicate that in SBMA, in contrast to sperm typing analysis of Huntington's disease, there is relative stability of the CAG repeat number during paternal transmissions and that the spectrum of mutations is narrow. These results are in agreement with the limited available clinical data and suggest that anticipation may not be a significant feature of this disease.
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Affiliation(s)
- R P Grewal
- Molecular Biology Program, University of Southern California, Los Angeles 90089-1340, USA
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47
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Prolla TA, Baker SM, Harris AC, Tsao JL, Yao X, Bronner CE, Zheng B, Gordon M, Reneker J, Arnheim N, Shibata D, Bradley A, Liskay RM. Tumour susceptibility and spontaneous mutation in mice deficient in Mlh1, Pms1 and Pms2 DNA mismatch repair. Nat Genet 1998; 18:276-9. [PMID: 9500552 DOI: 10.1038/ng0398-276] [Citation(s) in RCA: 280] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Germline mutations in the human MSH2, MLH1, PMS2 and PMS1 DNA mismatch repair (MMR) gene homologues appear to be responsible for most cases of hereditary non-polyposis colorectal cancer (HNPCC; refs 1-5). An important role for DNA replication errors in colorectal tumorigenesis has been suggested by the finding of frequent alterations in the length of specific mononucleotide tracts within genes controlling cell growth, including TGF-beta receptor type II (ref. 6), BAX (ref. 7) and APC (ref. 8). A broader role for MMR deficiency in human tumorigenesis is implicated by microsatellite instability in a fraction of sporadic tumours, including gastric, endometrial and colorectal malignancies. To better define the role of individual MMR genes in cancer susceptibility and MMR functions, we have generated mice deficient for the murine homologues of the human genes MLH1, PMS1 and PMS2. Surprisingly, we find that these mice show different tumour susceptibilities, most notably, to intestinal adenomas and adenocarcinomas, and different mutational spectra. Our results suggest that a general increase in replication errors may not be sufficient for intestinal tumour formation and that these genes share overlapping, but not identical functions.
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Affiliation(s)
- T A Prolla
- Howard Hughes Medical Institute, and Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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48
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Abstract
We propose a new experimental protocol, ExonPCR, which is able to identify exon boundaries in a cDNA even in the absence of any genomic clones. ExonPCR can bypass the isolation, characterization, and DNA sequencing of subclones of genomic DNA to determine exon boundaries: a major effort in the process of positional cloning. Given a cDNA sequence, ExonPCR uses a series of "adaptive" steps to analyze the PCR products from cDNA and genomic DNA thereby revealing the approximate positions of "hidden" exon boundaries in the cDNA. The nucleotide sequence of adjacent intronic regions is determined by ligation-mediated PCR. Primers adjacent to the "hidden" exon boundaries are used to amplify genomic DNA followed by limited DNA sequencing of the PCR product. The method was successfully tested on the 3-kb hMSH2 cDNA with 16 known exons and the 9-kb PRDII-BF1 cDNA with a previously unknown number of exons. We subsequently developed the ExonPCR algorithm and software to direct the experimental protocol using a strategy that is analogous to that used in the game "Twenty Questions." Through the use of ExonPCR, the search for disease-causing mutations can be initiated almost immediately after cDNA clones in a genetically mapped region become available. This approach would be most valuable in gene discovery strategies that focus initially on cDNA isolation.
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Affiliation(s)
- G Xu
- Molecular Biology Program, University of Southern California, Los Angeles 90089-1340, USA
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49
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Sun F, Benson G, Arnheim N, Waterman M. Pooling strategies for establishing physical genome maps using FISH. J Comput Biol 1998; 4:467-86. [PMID: 9385540 DOI: 10.1089/cmb.1997.4.467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Often, in biological studies, it is necessary to identify an organism's chromosomes. In some organisms the individual chromosomes can be identified by staining procedures while many other species have a very large number of chromosomes, often of similar size, which defy identification by traditional staining methods. We have devised strategies, based on fluorescent in situ hybridization (FISH), which allow the assignment of a preset number of probes to each chromosome without prior chromosome identification. By hybridizing mixtures of probes labeled with different colored fluorescent molecules, the chromosomal origin of each probe can be determined.
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Affiliation(s)
- F Sun
- Department of Genetics, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
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50
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Abstract
Fragile X syndrome results from the unstable expansion of a CGG repeat within the FMR1 gene. Three classes of FMR1 alleles have been identified, normal alleles with 6-60 repeats, premutations with 60-200 repeats, and full mutations with > 230 repeats. Premutations are exquisitely unstable upon transmission. Normal alleles, while generally stable upon transmission, are thought to have different intrinsic mutation frequencies, such that some normal alleles may be predisposed towards expansion while others may be more resistant to such change. One variable that may account for this difference is the occurrence of one or more AGG triplets punctuating the normal CGG repeat. The AGG interruptions lead to alleles that have equivalent overall length but different lengths of perfect repeats. To test the influence of the length of perfect repeats on stability, we examined the CGG repeat of single sorted sperm from two males, each with 39 total repeats, but distinct AGG interruption patterns. Sorted sperm of each donor showed -15% variation in repeat length, consistent with previous studies of sorted sperm at other triplet repeat loci. However, when discounting the majority variation of +/-1 repeat, the male with 29 perfect repeats showed 3% expansion changes while the donor with only 19 perfect repeats had none (< 0.9%). Moreover, > 90% of all variant sperm, including all those observed with expansions, showed expansion or contraction of the 3' end of the repeat array. These data are consistent with the hypothesis that perfect repeat tracts influence the repeat stability and that changes of the FMR1 repeat exhibit polarity.
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Affiliation(s)
- C B Kunst
- Howard Hughes Medical Institute, Emory University School of Medicine, Atlanta, GA 30322, USA
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