1
|
Leckie JN, Joel MM, Martens K, King A, King M, Korngut LW, de Koning APJ, Pfeffer G, Schellenberg KL. Highly Elevated Prevalence of Spinobulbar Muscular Atrophy in Indigenous Communities in Canada Due to a Founder Effect. NEUROLOGY-GENETICS 2021; 7:e607. [PMID: 34250227 PMCID: PMC8267784 DOI: 10.1212/nxg.0000000000000607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 06/01/2021] [Indexed: 11/24/2022]
Abstract
Objective Spinobulbar muscular atrophy (SBMA) is an X-linked adult-onset neuromuscular disorder that causes progressive weakness and androgen insensitivity in hemizygous males. This condition is reported to be extremely rare, but has higher prevalence in certain populations due to multiple founder effects. Anecdotal observations of a higher prevalence of SBMA in patients of Indigenous descent in Saskatchewan led us to perform this study, to estimate the disease prevalence, and to attempt to identify a founder effect. Methods For our prevalence estimation, we identified patients with confirmed SBMA diagnosis from the Saskatoon neuromuscular clinic database for comparison with population data available from Statistics Canada. For our haplotype analysis, participants with SBMA were recruited from 2 neuromuscular clinics, as well as 5 control participants. Clinical data were collected, as well as a DNA sample using saliva kits. We performed targeted quantification of DXS1194, DXS1111, DXS135, and DXS1125 microsatellite repeats and the AR GGC repeat to attempt to identify a disease haplotype and compare it with prior studies. Results We estimate the prevalence of SBMA among persons of Indigenous descent in Saskatchewan as 14.7 per 100,000 population. Although we believe that this is an underestimate, this still appears to be the highest population prevalence for SBMA in the world. A total of 21 participants were recruited for the haplotype study, and we identified a unique haplotype that was shared among 13 participants with Indigenous ancestry. A second shared haplotype was identified in 2 participants, which may represent a second founder haplotype, but this would need to be confirmed with future studies. Conclusions We describe a very high prevalence of SBMA in western Canadians of Indigenous descent, which appears to predominantly be due to a founder effect. This necessitates further studies of SBMA in these populations to comprehensively ascertain the disease prevalence and allow appropriate allocation of resources to support individuals living with this chronic disease.
Collapse
Affiliation(s)
- Jamie N Leckie
- Hotchkiss Brain Institute (J.N.L., M.M.J., K.M., L.W.K., G.P.), Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Alberta; Department of Medicine (A.K.), and Department of Community Health and Epidemiology (M.K.), University of Saskatchewan, Saskatoon; Alberta Child Health Research Institute (A.P.J.d.K., G.P.), Department of Medical Genetics, University of Calgary, Alberta; and Division of Neurology (K.L.S.), Department of Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Matthew M Joel
- Hotchkiss Brain Institute (J.N.L., M.M.J., K.M., L.W.K., G.P.), Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Alberta; Department of Medicine (A.K.), and Department of Community Health and Epidemiology (M.K.), University of Saskatchewan, Saskatoon; Alberta Child Health Research Institute (A.P.J.d.K., G.P.), Department of Medical Genetics, University of Calgary, Alberta; and Division of Neurology (K.L.S.), Department of Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Kristina Martens
- Hotchkiss Brain Institute (J.N.L., M.M.J., K.M., L.W.K., G.P.), Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Alberta; Department of Medicine (A.K.), and Department of Community Health and Epidemiology (M.K.), University of Saskatchewan, Saskatoon; Alberta Child Health Research Institute (A.P.J.d.K., G.P.), Department of Medical Genetics, University of Calgary, Alberta; and Division of Neurology (K.L.S.), Department of Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Alexandra King
- Hotchkiss Brain Institute (J.N.L., M.M.J., K.M., L.W.K., G.P.), Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Alberta; Department of Medicine (A.K.), and Department of Community Health and Epidemiology (M.K.), University of Saskatchewan, Saskatoon; Alberta Child Health Research Institute (A.P.J.d.K., G.P.), Department of Medical Genetics, University of Calgary, Alberta; and Division of Neurology (K.L.S.), Department of Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Malcolm King
- Hotchkiss Brain Institute (J.N.L., M.M.J., K.M., L.W.K., G.P.), Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Alberta; Department of Medicine (A.K.), and Department of Community Health and Epidemiology (M.K.), University of Saskatchewan, Saskatoon; Alberta Child Health Research Institute (A.P.J.d.K., G.P.), Department of Medical Genetics, University of Calgary, Alberta; and Division of Neurology (K.L.S.), Department of Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Lawrence W Korngut
- Hotchkiss Brain Institute (J.N.L., M.M.J., K.M., L.W.K., G.P.), Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Alberta; Department of Medicine (A.K.), and Department of Community Health and Epidemiology (M.K.), University of Saskatchewan, Saskatoon; Alberta Child Health Research Institute (A.P.J.d.K., G.P.), Department of Medical Genetics, University of Calgary, Alberta; and Division of Neurology (K.L.S.), Department of Medicine, University of Saskatchewan, Saskatoon, Canada
| | - A P Jason de Koning
- Hotchkiss Brain Institute (J.N.L., M.M.J., K.M., L.W.K., G.P.), Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Alberta; Department of Medicine (A.K.), and Department of Community Health and Epidemiology (M.K.), University of Saskatchewan, Saskatoon; Alberta Child Health Research Institute (A.P.J.d.K., G.P.), Department of Medical Genetics, University of Calgary, Alberta; and Division of Neurology (K.L.S.), Department of Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Gerald Pfeffer
- Hotchkiss Brain Institute (J.N.L., M.M.J., K.M., L.W.K., G.P.), Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Alberta; Department of Medicine (A.K.), and Department of Community Health and Epidemiology (M.K.), University of Saskatchewan, Saskatoon; Alberta Child Health Research Institute (A.P.J.d.K., G.P.), Department of Medical Genetics, University of Calgary, Alberta; and Division of Neurology (K.L.S.), Department of Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Kerri L Schellenberg
- Hotchkiss Brain Institute (J.N.L., M.M.J., K.M., L.W.K., G.P.), Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Alberta; Department of Medicine (A.K.), and Department of Community Health and Epidemiology (M.K.), University of Saskatchewan, Saskatoon; Alberta Child Health Research Institute (A.P.J.d.K., G.P.), Department of Medical Genetics, University of Calgary, Alberta; and Division of Neurology (K.L.S.), Department of Medicine, University of Saskatchewan, Saskatoon, Canada
| |
Collapse
|
2
|
MacLean HE, Favaloro JM, Warne GL, Zajac JD. Double-strand DNA break repair with replication slippage on two strands: a novel mechanism of deletion formation. Hum Mutat 2006; 27:483-9. [PMID: 16619235 DOI: 10.1002/humu.20327] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We have characterized an unusual family with two different androgen receptor (AR) gene deletions, in which we propose a novel mechanism of deletion formation has occurred. Affected individuals have the X-linked disorder androgen insensitivity syndrome, and we previously showed that different family members have deletions of different exons of the AR gene. We have now fully sequenced the deletions from affected individuals, and confirmed the presence of different deletions in different affected family members. Most affected and heterozygote individuals have a 4,430-bp deletion of exon 5 that occurred between repeated GTGGCAT motifs in introns 4 and 5. One affected hemizygous individual has a 4,033-bp deletion of exons 6 and 7 that occurred between repeated CCTC motifs in introns 5 and 7. The intron 5 breakpoint junctions of the two deletions are only 11 bp apart. Surprisingly, the maternal grandmother of the original index case was found to be mosaic for both deletional events, as well as having the normal AR gene. Karyotyping ruled out 47,XXX trisomy, indicating triple mosaicism for the two different deleted AR alleles and a normal AR allele. This triple mosaicism must have occurred early in embryonic development, as both deletions were passed on to different children. Based on these findings, we propose a novel mechanism of deletion formation. We suggest that during AR gene replication, a double strand DNA break occurred in intron 5, and that a variant of replication slippage occurred on both newly synthesized strands between the repeat motifs of microhomology, leading to the formation of the two different AR gene deletions.
Collapse
Affiliation(s)
- Helen E MacLean
- Department of Medicine, University of Melbourne, Austin Health, Heidelberg, Australia.
| | | | | | | |
Collapse
|
3
|
Affiliation(s)
- Thierry Alcindor
- Division of Haematology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | | |
Collapse
|
4
|
Sadlon TJ, Dell'Oso T, Surinya KH, May BK. Regulation of erythroid 5-aminolevulinate synthase expression during erythropoiesis. Int J Biochem Cell Biol 1999; 31:1153-67. [PMID: 10582344 DOI: 10.1016/s1357-2725(99)00073-4] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Erythroid tissue is the major site of heme production in the body. The synthesis of heme and globin chains is coordinated at both the transcriptional and post-transcriptional levels to ensure that virtually no free heme or globin protein accumulates. The key rate-controlling enzyme of the heme biosynthetic pathway is 5-aminolevulinate synthase (ALAS) and an erythroid-specific isoform (ALAS2) is up-regulated during erythropoiesis. Differentiation of embryonic stem cells with a disrupted ALAS2 gene has established that expression of this gene is critical for erythropoiesis and cannot be compensated by expression of the ubiquitous isoform of the enzyme (ALAS1). Interestingly, heme appears to be important for expression of globin and other late erythroid genes and for erythroid cell differentiation although the mechanism of this effect is not clear. Transcriptional control elements that regulate the human gene for ALAS2 have been identified both in the promoter and in intronic enhancer regions. Subsequent translation of the ALAS2 mRNA is dependent on an adequate iron supply. The mechanism by which transcription of the gene for ALAS2 is increased by erythropoietin late in erythropoiesis remains an interesting issue. Erythropoietin action may result in altered levels of critical erythroid transcription factors or modulate the phosphorylation/acetylation status of these factors. Defects in the coding region of the gene for ALAS2 underlie the disease state X-linked sideroblastic anemia. In this review, we focus on the regulation and function of erythroid-specific 5-aminolevulinate synthase during erythropoiesis and its role in the X-linked sideroblastic anemia.
Collapse
Affiliation(s)
- T J Sadlon
- Department of Biochemistry, University of Adelaide, SA, Australia
| | | | | | | |
Collapse
|
5
|
Allikmets R, Raskind WH, Hutchinson A, Schueck ND, Dean M, Koeller DM. Mutation of a putative mitochondrial iron transporter gene (ABC7) in X-linked sideroblastic anemia and ataxia (XLSA/A). Hum Mol Genet 1999; 8:743-9. [PMID: 10196363 DOI: 10.1093/hmg/8.5.743] [Citation(s) in RCA: 292] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
X-linked sideroblastic anemia and ataxia (XLSA/A) is a recessive disorder characterized by an infantile to early childhood onset of non-progressive cerebellar ataxia and mild anemia with hypochromia and microcytosis. A gene encoding an ATP-binding cassette (ABC) transporter was mapped to Xq13, a region previously shown by linkage analysis to harbor the XLSA/A gene. This gene, ABC7, is an ortholog of the yeast ATM1 gene whose product localizes to the mitochondrial inner membrane and is involved in iron homeostasis. The full-length ABC7 cDNA was cloned and the entire coding region screened for mutations in a kindred in which five male members manifested XLSA/A. An I400M variant was identified in a predicted transmembrane segment of the ABC7 gene in patients with XLSA/A. The mutation was shown to segregate with the disease in the family and was not detected in at least 600 chromosomes of general population controls. Introduction of the corresponding mutation into the Saccharomyces cerevisiae ATM1 gene resulted in a partial loss of function of the yeast Atm1 protein. In addition, the human wild-type ABC7 protein was able to complement ATM1 deletion in yeast. These data indicate that ABC7 is the causal gene of XLSA/A and that XLSA/A is a mitochondrial disease caused by a mutation in the nuclear genome.
Collapse
Affiliation(s)
- R Allikmets
- Intramural Research Support Program, SAIC-Frederick and Laboratory of Genomic Diversity, National Cancer Institute, Building 560, Room 21-18, Frederick Cancer Research and Development Center, Frederick, MD 21702-1201, USA
| | | | | | | | | | | |
Collapse
|
6
|
Four New Mutations in the Erythroid-Specific 5-Aminolevulinate Synthase (ALAS2) Gene Causing X-Linked Sideroblastic Anemia: Increased Pyridoxine Responsiveness After Removal of Iron Overload by Phlebotomy and Coinheritance of Hereditary Hemochromatosis. Blood 1999. [DOI: 10.1182/blood.v93.5.1757.405a12_1757_1769] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
X-linked sideroblastic anemia (XLSA) in four unrelated male probands was caused by missense mutations in the erythroid-specific 5-aminolevulinate synthase gene (ALAS2). All were new mutations: T647C, C1283T, G1395A, and C1406T predicting amino acid substitutions Y199H, R411C, R448Q, and R452C. All probands were clinically pyridoxine-responsive. The mutation Y199H was shown to be the first de novo XLSA mutation and occurred in a gamete of the proband’s maternal grandfather. There was a significantly higher frequency of coinheritance of the hereditary hemochromatosis (HH)HFE mutant allele C282Y in 18 unrelated XLSA hemizygotes than found in the normal population, indicating a role for coinheritance ofHFE alleles in the expression of this disorder. One proband (Y199H) with severe and early iron loading coinherited HH as a C282Y homozygote. The clinical and hematologic histories of two XLSA probands suggest that iron overload suppresses pyridoxine responsiveness. Notably, reversal of the iron overload in the Y199H proband by phlebotomy resulted in higher hemoglobin concentrations during pyridoxine supplementation. The proband with the R452C mutation was symptom-free on occasional phlebotomy and daily pyridoxine. These studies indicate the value of combined phlebotomy and pyridoxine supplementation in the management of XLSA probands in order to prevent a downward spiral of iron toxicity and refractory anemia.
Collapse
|
7
|
Four New Mutations in the Erythroid-Specific 5-Aminolevulinate Synthase (ALAS2) Gene Causing X-Linked Sideroblastic Anemia: Increased Pyridoxine Responsiveness After Removal of Iron Overload by Phlebotomy and Coinheritance of Hereditary Hemochromatosis. Blood 1999. [DOI: 10.1182/blood.v93.5.1757] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
X-linked sideroblastic anemia (XLSA) in four unrelated male probands was caused by missense mutations in the erythroid-specific 5-aminolevulinate synthase gene (ALAS2). All were new mutations: T647C, C1283T, G1395A, and C1406T predicting amino acid substitutions Y199H, R411C, R448Q, and R452C. All probands were clinically pyridoxine-responsive. The mutation Y199H was shown to be the first de novo XLSA mutation and occurred in a gamete of the proband’s maternal grandfather. There was a significantly higher frequency of coinheritance of the hereditary hemochromatosis (HH)HFE mutant allele C282Y in 18 unrelated XLSA hemizygotes than found in the normal population, indicating a role for coinheritance ofHFE alleles in the expression of this disorder. One proband (Y199H) with severe and early iron loading coinherited HH as a C282Y homozygote. The clinical and hematologic histories of two XLSA probands suggest that iron overload suppresses pyridoxine responsiveness. Notably, reversal of the iron overload in the Y199H proband by phlebotomy resulted in higher hemoglobin concentrations during pyridoxine supplementation. The proband with the R452C mutation was symptom-free on occasional phlebotomy and daily pyridoxine. These studies indicate the value of combined phlebotomy and pyridoxine supplementation in the management of XLSA probands in order to prevent a downward spiral of iron toxicity and refractory anemia.
Collapse
|
8
|
Stavropoulou C, Mignon C, Delobel B, Moncla A, Depetris D, Croquette MF, Mattei MG. Severe phenotype resulting from an active ring X chromosome in a female with a complex karyotype: characterisation and replication study. J Med Genet 1998; 35:932-8. [PMID: 9832041 PMCID: PMC1051487 DOI: 10.1136/jmg.35.11.932] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
We report on the characterisation of a complex chromosome rearrangement, 46,X,del(Xq)/47,X,del(Xq),+r(X), in a female newborn with multiple malformations. Cytogenetic and molecular methods showed that the del(Xq) contains the XIST locus and is non-randomly inactivated in all metaphases. The tiny r(X) chromosome gave a positive FISH signal with UBE1, ZXDA, and MSN cosmid probes, but not with a XIST cosmid probe. Moreover, it has an active status, as shown by a very short (three hour) terminal BrdU pulse followed by fluorescent anti-BrdU antibody staining. The normal X is of paternal origin and both rearranged chromosomes originate from the same maternal chromosome. We suggest that both abnormal chromosomes result from the three point breakage of a maternal isodicentric idic(X)(q21.1). Finally, the phenotype of our patient is compared to other published cases and, despite the absence of any 45,X clone, it appears very similar to those with a 45,X/46,X,r(X) karyotype where the tiny r(X) is active.
Collapse
Affiliation(s)
- C Stavropoulou
- INSERM U491, Faculté de Médecine Timone, Marseille, France
| | | | | | | | | | | | | |
Collapse
|
9
|
Surinya KH, Cox TC, May BK. Identification and characterization of a conserved erythroid-specific enhancer located in intron 8 of the human 5-aminolevulinate synthase 2 gene. J Biol Chem 1998; 273:16798-809. [PMID: 9642238 DOI: 10.1074/jbc.273.27.16798] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Thirty five kilobases of sequence encompassing the human erythroid 5-aminolevulinate synthase (ALAS2) gene have been determined. Analysis revealed a very low GC content, few repetitive elements, and evidence for the insertion of a reverse-transcribed mRNA sequence and a neighboring gene. We have investigated whether introns 1, 3, and 8, which correspond to DNase I-hypersensitivity sites in the structurally related mouse ALAS2 gene, affect expression of the human ALAS2 promoter in transient expression assays. Whereas intron 3 was marginally inhibitory, introns 1 and 8 of the human gene stimulated promoter activity. Intron 8 harbored a strong erythroid-specific enhancer activity which was orientation-dependent. Deletion analysis of this region localized enhancer activity to a fragment of 239 base pairs. Transcription factor binding sites clustered within this region include GATA motifs and CACCC boxes, critical regulatory sequences of many erythroid cell-expressed genes. These sites were also identified in the corresponding intron of both the murine and canine ALAS2 genes. Mutagenesis of these conserved sites in the human intron 8 sequence and transient expression analysis in erythroid cells established the functional importance of one GATA motif and two CACCC boxes. The GATA motif bound GATA-1 in vitro. The two functional CACCC boxes each bound Sp1 or a related protein in vitro, but binding of the erythroid Krüppel-like factor and the basic Krüppel-like factor could not be detected. The intron 8 enhancer region was not activated by GATA-1 together with Sp1 in transactivation experiments in COS-1 cells indicating the involvement of a related Sp1 protein or of another unidentified erythroid factor. Overall, these results demonstrate that a GATA-1-binding site and CACCC boxes located within the human ALAS2 intron 8 are critical for the erythroid-specific enhancer activity in transfected erythroid cells, and due to the conserved nature of these binding sites across species, it seems likely that these sites play a functional role in the tissue-restricted expression of the gene in vivo.
Collapse
Affiliation(s)
- K H Surinya
- Department of Biochemistry, University of Adelaide, Adelaide, South Australia, Australia 5005
| | | | | |
Collapse
|
10
|
Yorifuji T, Muroi J, Kawai M, Uematsu A, Sasaki H, Momoi T, Kaji M, Yamanaka C, Furusho K. Uniparental and functional X disomy in Turner syndrome patients with unexplained mental retardation and X derived marker chromosomes. J Med Genet 1998; 35:539-44. [PMID: 9678697 PMCID: PMC1051363 DOI: 10.1136/jmg.35.7.539] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We analysed parental origin and X inactivation status of X derived marker (mar(X)) or ring X (r(X)) chromosomes in six Turner syndrome patients. Two of these patients had mental retardation of unknown cause in addition to the usual Turner syndrome phenotype. By FISH analysis, the mar(X)/r(X) chromosomes of all patients retained the X centromere and the XIST locus at Xq13.2. By polymorphic marker analysis, both patients with mental retardation were shown to have uniparental X disomy while the others had both a maternal and paternal contribution of X chromosomes. By RT-PCR analysis and the androgen receptor assay, it was shown that in one of these mentally retarded patients, the XIST on the mar(X) was not transcribed and consequently the mar(X) was not inactivated, leading to functional disomy X. In the other patient, the XIST was transcribed but the r(X) appeared to be active by the androgen receptor assay. Our results suggest that uniparental disomy X may not be uncommon in mentally retarded patients with Turner syndrome. Functional disomy X seems to be the cause of mental retardation in these patients, although the underlying molecular basis could be diverse. In addition, even without unusual dysmorphic features, Turner syndrome patients with unexplained mental retardation need to be investigated for possible mosaicism including these mar(X)/r(X) chromosomes.
Collapse
Affiliation(s)
- T Yorifuji
- Department of Paediatrics, Kyoto University Hospital, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Mahtani MM, Willard HF. Physical and genetic mapping of the human X chromosome centromere: repression of recombination. Genome Res 1998; 8:100-10. [PMID: 9477338 DOI: 10.1101/gr.8.2.100] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Classical genetic studies in Drosophila and yeast have shown that chromosome centromeres have a cis-acting ability to repress meiotic exchange in adjacent DNA. To determine whether a similar phenomenon exists at human centromeres, we measured the rate of meiotic recombination across the centromere of the human X chromosome. We have constructed a long-range physical map of centromeric alpha-satellite DNA (DXZ1) by pulsed-field gel analysis, as well as detailed meiotic maps of the pericentromeric region of the X chromosome in the CEPH family panel. By comparing these two maps, we determined that, in the proximal region of the X chromosome, a genetic distance of 0.57 cM exists between markers that span the centromere and are separated by at least the average 3600 kb physical distance mapped across the DXZ1 array. Therefore, the rate of meiotic exchange across the X chromosome centromere is <1 cM/6300 kb (and perhaps as low as 1 cM/17,000 kb on the basis of other physical mapping data), at least eightfold lower than the average rate of female recombination on the X chromosome and one of the lowest rates of exchange yet observed in the human genome.
Collapse
Affiliation(s)
- M M Mahtani
- Department of Genetics, Stanford University School of Medicine, Stanford, California 94305-5120, USA
| | | |
Collapse
|
12
|
Koc S, Harris JW. Sideroblastic anemias: variations on imprecision in diagnostic criteria, proposal for an extended classification of sideroblastic anemias. Am J Hematol 1998; 57:1-6. [PMID: 9423809 DOI: 10.1002/(sici)1096-8652(199801)57:1<1::aid-ajh1>3.0.co;2-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Sideroblastic anemias are caused by a diversity of hereditary, congenital, or acquired disorders. Criteria used in describing sideroblastic anemias vary widely among standard medical textbooks and even so have been imprecisely applied in the literature. Recent discoveries concerning the basic pathophysiologic mechanisms involving the molecular biology of nuclear and mitochondrial DNA, erythroid ALA synthase (ALAS-2), and iron transport have made the classification of sideroblastic anemias very complex. We recommend a more precise evaluation and documentation of the components that characterize the sideroblastic abnormality and propose an extended classification of the sideroblastic anemias.
Collapse
Affiliation(s)
- S Koc
- Department of Medicine, Case Western Reserve University, School of Medicine at MetroHealth Medical Center, Cleveland, Ohio 44101, USA.
| | | |
Collapse
|
13
|
Donnelly AJ, Partington MW, Ryan AK, Mulley JC. Regional localisation of two non-specific X-linked mental retardation genes (MRX30 and MRX31). AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 64:113-20. [PMID: 8826460 DOI: 10.1002/(sici)1096-8628(19960712)64:1<113::aid-ajmg19>3.0.co;2-q] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Two genes responsible for X-linked mental retardation have been localised by linkage analysis. MRX30 maps to a 28 cM region flanked by the loci DXS990 (Xq21.3) and DXS424 (Xq24). A significant multipoint lod score of 2.78 was detected between the loci DXS1120 and DXS456. MRX31 maps to a 12 cM region that spans the centromere from DXS1126 (Xp11.23) to DXS1124 (Xq13.3). Significant two-point lod scores, at a recombination fraction of zero, were obtained with the loci DXS991 (Zmax = 2.06), AR (Zmax = 3.44), PGK1P1 (Zmax = 2.06) and DXS453 (Zmax = 3.31). The MRX30 localisation overlaps that of MRX8, 13, 20 and 26 and defines the position of a new MRX gene on the basis of a set of non-overlapping regional localisations. The MRX31 localisation overlaps the localisations of many of the pericentromeric MRX loci (MRX 1, 4, 5, 7, 8, 9, 12, 13, 14, 15, 17, 20, 22 and 26). There are now at least 8 distinct loci associated with non-specific mental retardation on the X chromosome defined, in order from pter to qter, by localisation for MRX24, MRX2, MRX10, MRX1, MRX30, MRX27, FRAXE and MRX3.
Collapse
Affiliation(s)
- A J Donnelly
- Department of Cytogenetics and Molecular Genetics, Women's and Children's Hospital, Adelaide, Australia
| | | | | | | |
Collapse
|
14
|
Raynaud M, Gendrot C, Dessay B, Moncla A, Ayrault AD, Moizard MP, Toutain A, Briault S, Villard L, Ronce N, Moraine C. X-linked mental retardation with neonatal hypotonia in a French family (MRX15): gene assignment to Xp11.22-Xp21.1. AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 64:97-106. [PMID: 8826458 DOI: 10.1002/(sici)1096-8628(19960712)64:1<97::aid-ajmg17>3.0.co;2-n] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Linkage analysis was performed in a family with non-specific X-linked mental retardation (MRX 15). Hypotonia in infancy was the most remarkable physical manifestation. The severity of mental deficiency was variable among the patients, but all of them had poor or absent speech. Significant lod scores at a recombination fraction of zero were detected with the marker loci DXS1126, DXS255, and DXS573 (Zmax = 2.01) and recombination was observed with the two flanking loci DXS164 (Xp21.1) and DXS988 (Xp11.22), identifying a 17 cM interval. This result suggests a new gene localization in the proximal Xp region. In numerous families with non-specific X-linked mental retardation (MRX), the corresponding gene has been localized to the paracentromeric region in which a low recombination rate impairs the precision of mapping.
Collapse
Affiliation(s)
- M Raynaud
- Unité de Génétique Hospital Bretonneau, Tours, France
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Noble JS, Taylor GR, Losowsky MS, Hall R, Turner G, Mueller RF, Stewart AD. Linkage analysis of a large pedigree with hereditary sideroblastic anaemia. J Med Genet 1995; 32:389-92. [PMID: 7616548 PMCID: PMC1050436 DOI: 10.1136/jmg.32.5.389] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A large pedigree showing a history of pyridoxine responsive X linked sideroblastic anaemia was screened with several polymorphic DNA markers from the X chromosome. Linkage analysis between each marker and disease status was performed, giving a maximum two point lod score of 3.64 at zero recombination with the microsatellite marker PGK1P1 at Xq11.2-12. Close linkage to PGK at Xq13.3, one of the candidate regions for X linked sideroblastic anaemia, was excluded. Linkage to DNA markers distal to PGK and at Xp21 was also excluded. Multipoint linkage analysis was performed with markers located between Xq11.2-21. The maximum map specific lod score obtained was 3.56 at PGK1P1 (Xq11.2-12). Linkage remained significant over the interval 20 cM proximal to PGK1P1 and 5 cM distal to PGK1P1, with definite exclusion around the PGK locus. The most likely location of the gene involved in sideroblastic anaemia in this pedigree is therefore within the pericentromeric region of the X chromosome. This region includes the erythroid 5-aminolaevulinate synthetase gene of the haem synthesis pathway, which is a candidate gene for X linked sideroblastic anaemia located at Xp11.21.
Collapse
Affiliation(s)
- J S Noble
- Yorkshire Regional Genetics Service, St James's University Hospital, Leeds, UK
| | | | | | | | | | | | | |
Collapse
|
16
|
Bottomley SS, May BK, Cox TC, Cotter PD, Bishop DF. Molecular defects of erythroid 5-aminolevulinate synthase in X-linked sideroblastic anemia. J Bioenerg Biomembr 1995; 27:161-8. [PMID: 7592563 DOI: 10.1007/bf02110031] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The erythroid-specific isozyme of 5-aminolevulinate synthase (ALAS2), the first and rate-limiting enzyme of heme biosynthesis, is expressed concomitantly with the differentiation and maturation of the erythroid cell in order to accommodate generation of the large amounts of heme required for hemoglobin production. During the past few years the ALAS2 gene and its transcript have been characterized and the amino acid sequence of the enzyme deduced. The human genetic disorder X-linked sideroblastic anemia, previously postulated to be caused by defects of ALAS, has now been analyzed at the molecular and tissue-specific level. A heterogeneous group of point mutations in the catalytic domain of the ALAS2 enzyme has been found to cause the disorder. Impaired activity of recombinant mutant ALAS2 enzymes has also been demonstrated. Characterization of molecular defects in individuals with X-linked sideroblastic anemia has provided improved diagnosis for at-risk family members.
Collapse
Affiliation(s)
- S S Bottomley
- Department of Medicine, University of Oklahoma College of Medicine, Oklahoma City 73104, USA
| | | | | | | | | |
Collapse
|
17
|
May BK, Dogra SC, Sadlon TJ, Bhasker CR, Cox TC, Bottomley SS. Molecular regulation of heme biosynthesis in higher vertebrates. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1995; 51:1-51. [PMID: 7659773 DOI: 10.1016/s0079-6603(08)60875-2] [Citation(s) in RCA: 113] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- B K May
- Department of Biochemistry, University of Adelaide, Australia
| | | | | | | | | | | |
Collapse
|
18
|
Abstract
The startling morphological abnormalities of sideroblastic anaemia contrasts our uncertainty about its cause. Studies are hampered by the fact that the abnormality resides in the dividing and differentiating erythroblast which is difficult to obtain pure and in large numbers, and in which many levels of metabolic control must coexist. Recent molecular biology approaches have confirmed abnormalities of erythroid delta-aminolaevulinic acid synthase as the cause of X-linked, pyridoxine-responsive sideroblastic anaemia and mitochondrial DNA deletions as the most common cause of congenital macrocytic sideroblastic anaemia. They have also identified a second X-linked sideroblastic anaemia locus linked to phosphoglycerate kinase and associated with ataxia. An association between sideroblastic anaemia and the use of an oral copper chelating agent has highlighted unexplained links between erythroid copper and iron metabolism. Management decisions in relation to pyridoxine treatment, iron reduction, family studies, genetic counselling and antenatal diagnosis have in recent years become of practical relevance to families with known cases of congenital sideroblastic anaemia and careful documentation of the clinical outcome of these cases and of other family members is invaluable. Parallel and integrated studies on the molecular biology of erythroid differentiation are revealing the range of possible controlling influences on erythroblasts and defining the circumstances for each, allowing studies on the cause of the most prevalent form of sideroblastic anaemia (the idiopathic acquired form) and those inherited forms that are not X-linked to be approached with a much clearer perspective.
Collapse
Affiliation(s)
- A May
- University of Wales College of Medicine, Cardiff, UK
| | | |
Collapse
|
19
|
Gedeon AK, Mulley JC, Kozman H, Donnelly A, Partington MW. Localisation of the gene for X-linked reticulate pigmentary disorder with systemic manifestations (PDR), previously known as X-linked cutaneous amyloidosis. AMERICAN JOURNAL OF MEDICAL GENETICS 1994; 52:75-8. [PMID: 7977467 DOI: 10.1002/ajmg.1320520115] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
X-linked reticulate pigmentary disorder (PDR), previously reported as X-linked cutaneous amyloidosis (MIM#301220), is characterized by brown pigmentation of the skin which follows the lines of Blaschko in females but appears as reticulate sheets in males. Males may suffer severe gastrointestinal disorders in infancy with failure to thrive and early death. Nowadays symptomatic treatment allows survival and other manifestations may appear such as corneal dystrophy with severe photophobia or chronic respiratory disease. Amyloid deposition in the skin may be no more than an age-dependent secondary manifestation. The PDR gene was localised by linkage analysis to Xp21-p22. The background genetic map is Xpter-DXS996-22.5-DXS207-3.3-DXS999-3.3-DXS36 5-14.2-DXS989-4.1-3'DMD-3.5- DXS997-1.0-STR44-9.3-DYSI-2.3-DXS1068-11.0-DX S228 with distances between markers given in cM. Recombinants detected with DXS999 distally and DXS228 proximally, define the limits to the localisation. Linkage was found with several markers within this interval. Peak lod scores of 3.21 at theta = 0.0 were obtained between PDR and DXS989 and between PDR and 5'DYSI within the dystrophin locus.
Collapse
Affiliation(s)
- A K Gedeon
- Department of Cytogenetics and Molecular Genetics, Women's and Children's Hospital, North Adelaide, Australia
| | | | | | | | | |
Collapse
|
20
|
Gedeon A, Kerr B, Mulley J, Turner G. Pericentromeric genes for non-specific X-linked mental retardation (MRX). AMERICAN JOURNAL OF MEDICAL GENETICS 1994; 51:553-64. [PMID: 7943039 DOI: 10.1002/ajmg.1320510453] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Extensive linkage analyses in three families with non-specific X-linked mental retardation (MRX) have localized the gene in each family to the pericentromeric region of the chromosome. The MRX17 gene is localized with a peak lod of 2.41 (theta = 0.0) with the trinucleotide repeat polymorphism at the androgen receptor (AR) gene locus. This gene lies in the interval between the markers DXS255 and DXS990, as defined by recombinants. The MRX18 gene maps to the interval between the markers DXS538 and DXS1126, with a peak lod score of 2.01 (theta = 0.0) at the PFC gene locus. In the third family (Family E) with insufficient informative meioses for assignment of an MRX acronym, the maximum lod score is 1.8 at a recombination fraction of zero for several marker loci between DXS207 and DXS426. Exclusions from the regions of marker loci spanning Xq support the localization of the MRX gene in Family E to the pericentromeric region. Localizations of these and other MRX genes have determined that MRX2 and MRX19 map to distal Xp, MRX3, and MRX6 map to distal Xq, whilst the majority cluster in the pericentromeric region. In addition, we confirm that there are at least two distinct MRX genes near the centromere as delineated by the non-overlapping regional localizations of MRX17 and MRX18. Determination of these non-overlapping localizations is currently the only means of classifying non-syndromal forms of mental retardation and determining the minimum number of MRX loci.
Collapse
Affiliation(s)
- A Gedeon
- Department of Cytogenetics and Molecular Genetics, Women's and Children's Hospital, Australia
| | | | | | | |
Collapse
|
21
|
Cox TC, Bottomley SS, Wiley JS, Bawden MJ, Matthews CS, May BK. X-linked pyridoxine-responsive sideroblastic anemia due to a Thr388-to-Ser substitution in erythroid 5-aminolevulinate synthase. N Engl J Med 1994; 330:675-9. [PMID: 8107717 DOI: 10.1056/nejm199403103301004] [Citation(s) in RCA: 100] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
BACKGROUND X-linked sideroblastic anemia is usually associated with reduced 5-aminolevulinate synthase activity in erythroid cells, and some cases are responsive to treatment with pyridoxine, the precursor to the cofactor of the enzyme. The recently identified gene for an erythroid-specific 5-aminolevulinate synthase isoenzyme and its localization to the X chromosome make it likely that one or more defects in this gene underlie the anemia. METHODS Using a polymorphic dinucleotide-repeat sequence in the erythroid 5-aminolevulinate synthase gene, we confirmed the linkage of this gene to the disorder in a family with X-linked pyridoxine-responsive sideroblastic anemia. We therefore sought evidence of a nucleotide-sequence abnormality in the erythroid 5-aminolevulinate synthase gene by analyzing enzymatically amplified DNA. RESULTS DNA-sequencing studies in two affected males and one carrier female in the kindred demonstrated a cytosine-to-guanine change at nucleotide 1215 (in exon 8). This change results in the substitution of serine for threonine at amino acid residue 388, near the lysine that binds the pyridoxal phosphate cofactor. In expression studies, the activity of the mutant enzyme was reduced relative to that of the wild type, and this reduction was comparable to that in erythroid cells of the proband during relapse of the anemia; the enzyme activity expressed in the presence of pyridoxine was comparable to that in the proband's marrow cells during remission. Although the affinity of the mutant enzyme for pyridoxal phosphate was not altered, the mutation appears to introduce a conformational change at the active site of the enzyme. CONCLUSIONS We identified a point mutation resulting in an amino acid change near the pyridoxal phosphate-binding site of the erythroid 5-aminolevulinate synthase isoenzyme as the underlying defect in a kindred with X-linked pyridoxine-responsive sideroblastic anemia.
Collapse
Affiliation(s)
- T C Cox
- Department of Biochemistry, University of Adelaide, Australia
| | | | | | | | | | | |
Collapse
|
22
|
Jardine PE, Cotter PD, Johnson SA, Fitzsimons EJ, Tyfield L, Lunt PW, Bishop DF. Pyridoxine-refractory congenital sideroblastic anaemia with evidence for autosomal inheritance: exclusion of linkage to ALAS2 at Xp11.21 by polymorphism analysis. J Med Genet 1994; 31:213-8. [PMID: 7912287 PMCID: PMC1049745 DOI: 10.1136/jmg.31.3.213] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A son and daughter of unaffected parents had transfusion dependent, pyridoxine-refractory sideroblastic anaemia from birth. Their haemoglobin levels were 4.3 and 6.4 g/dl, respectively. delta-Aminolaevulinate synthase activity in erythroblasts from fractionated marrow of the sister was 135 pmol delta-aminolaevulinate formed/10(6) erythroblasts/hour (normal range = 110-650 pmol). While mutations of the erythroid-specific delta-aminolaevulinate synthase gene (ALAS2) at Xp11.21 have been reported in patients with X linked sideroblastic anaemia, sequence analysis of the ALAS2 gene in the son did not identify any mutations in the coding region, the intron/exon boundaries, or the 1 kb 5' promoter region. A useful polymorphism was found in the 3' region of the ALAS2 gene, a G to A transition, 220 nt 3' of the AATAAA polyadenylation signal. Mismatch PCR at this site and subsequent discrimination by XmnI restriction analysis of 148 alleles identified the gene frequency of this polymorphism to be 25%. Analysis of the inheritance of this intragenic polymorphism showed that the affected sibs received different maternal alleles at the ALAS2 locus, excluding mutations in this gene as the cause of their sideroblastic anaemia. Furthermore, the absence of a dimorphic erythrocyte population in the mother, coupled with the demonstration of random X inactivation in her peripheral leucocytes, showed that the mother was not the carrier of any X linked sideroblastic anaemia mutation. These results strongly suggest that the sideroblastic anaemia in this family is an autosomal recessive trait.
Collapse
Affiliation(s)
- P E Jardine
- Department of Clinical Genetics, Institute of Child Health, St Michaels Hill, Bristol, UK
| | | | | | | | | | | | | |
Collapse
|
23
|
Abstract
New primer pair sequences specific for 25 loci in the Xp11-q22.1 region are described. Eighteen of the pairs span segments containing significant CA dinucleotide repeats, with 9 of these revealing polymorphisms of greater than 50% heterozygosity. Four of the CA-containing segments occur in probes previously reported to detect RFLPs, while the remaining 14 are from newly isolated clones. STSs were also developed for 7 other RFLP-only loci. All of these 25 STSs plus 11 other published STR markers have been fine-mapped with respect to chromosomal breakpoints, defining 15 subintervals in Xp11-Xq22. This map of 36 STSs, nearly all of which are associated with markers that are genetically mapped and/or highly polymorphic, will significantly aid efforts to construct a complete physical map of this region and to correlate it with the high-density genetic map.
Collapse
Affiliation(s)
- D F Barker
- Department of Physiology, University of Utah Medical School, Salt Lake City 84108
| | | |
Collapse
|
24
|
Affiliation(s)
- G H Elder
- Department of Medical Biochemistry, University of Wales College of Medicine, Cardiff
| |
Collapse
|