The change in differing leukocyte populations during vaccination to bovine respiratory disease and their correlations with lung scores, health records, and average daily gain

Bovine respiratory disease (BRD) is the most economically important disease in U.S. feedlots. Infection can result in morbidity, mortality, and reduced average daily gain. Cheap and reliable genetic methods of prediction and protection from BRD would be highly advantageous to the industry. The immune response may correlate with BRD incidence. Cattle (n = 2,182) were vaccinated against common viral and bacterial pathogens of BRD. Two blood samples were collected, one during booster vaccination and one 21d later, enabling 3 phenotypes for each trait [prebooster (pre), postbooster (post), and delta (post minus pre)]. From the blood samples innate and adaptive responses [counts of white blood cells (WBC), neutrophils, lymphocytes, monocytes, eosinophils, and basophils] were measured. In addition, feedlot ADG and binary traits [health records (HR; 0 = healthy, 1 = ill) and lung scores (LS; collected at harvest; 0 = no lesions, 1 = lesions)] were also recorded. Traits ADG, HR, and LS have all been significantly correlated with infection to BRD. In this investigation we aimed to find correlations between the immune response and ADG, HR, and LS to find an easily measurable trait that would be a good predictor of BRD resistance after vaccination. The results showed an average positive delta for the innate immune response (eosinophils, basophils, neutrophils), whereas the adaptive immune response had an average negative delta (lymphocytes). Overall, we discovered that the immune responses had moderately high heritabilities (h(2); lowest: delta monocytes, 0.21 ± 0.05; greatest: pre lymphocytes: 0.5 ± 0.05), with lymphocytes having the greatest h(2) throughout the study (h(2) ≥ 0.41). All genetic correlations were calculated using bivariate REML models. Although LS did not significantly correlate with any of the immune phenotypes, both ADG (post lymphocytes, -0.24 ± 0.12) and HR (pre eosinophils, -0.67 ± 0.29; delta WBC, -0.5 ± 0.24, and delta lymphocytes, -0.67 ± 0.21) did. All the significant genetic correlations with HR were negative; resistance to BRD appears to be a function of greater delta lymphocytes and WBC. The increase in eosinophils may potentially link its role in decreasing lymphocytes. These results may enable producers to predict if revaccination, quarantine, and breeding of animals is required to reduce the incidence of BRD postvaccination. In addition, immunological phenotypes maybe used to aid genomic selection indices to select animals with greater rates of protection after BRD vaccination.

TGFB-induced factor (TGIF): a candidate gene for psychosis on chromosome 18p

Schizophrenia (SC) and bipolar disorder (BP) share many clinical features, among them psychosis. We previously identified a putative gene locus for psychosis on chromosome 18p in a sample from the Central Valley of Costa Rica (CVCR) population. The present study replicated the association to a specific allele of microsatellite marker D18S63 on 18p11.3, using a newly collected sample from the CVCR. A combined analysis of both samples, plus additional subjects, showed that this specific allele on D18S63, which lies within an intron on the TGFB-induced factor (TGIF) gene, is strongly associated (P-value=0.0005) with psychosis. Eleven additional SNP markers, spanning five genes in the region, were analyzed in the combined sample from the CVCR. Only the four SNPs within the TGIF gene were in strong linkage disequilibrium with D18S63 (D'=1.00). A specific haplotype for all five markers within the TGIF gene showed evidence of association (P-value=0.011) to psychosis. A second, distinct haplotype, containing a newly identified nonsynonymous polymorphism in exon 5 of the TGIF gene, showed a nonsignificant trend towards association to psychosis (P-value=0.077). TGIF is involved in neurodevelopment, neuron survival and controls the expression of dopamine receptors. Altogether, our results point to the possible involvement of TGIF in the pathophysiology of psychotic disorders in the CVCR population.

Evaluation of tight junction protein 1 encoding zona occludens 1 as a candidate gene for albuminuria in a Mexican American population

Albuminuria, a hallmark of diabetic nephropathy, has been shown to be significantly heritable in multiple studies. Therefore, the identification of genes that affect susceptibility to albuminuria may lead to novel avenues of intervention. Current evidence suggests that the podocyte and slit diaphragm play a key role in controlling the selective sieve of the glomerular filtration barrier, and podocyte-specific genes have been identified that are necessary for maintaining its integrity. We therefore investigated the role of gene variants of tight junction protein (TJP1) which encodes another slit diaphragm-associated protein zona occludens 1 as risk factors for albuminuria in the San Antonio Family Diabetes/Gallbladder Study (SAFDGS), which consists of extended Mexican-American families with a high prevalence of type 2 diabetes. Albuminuria, defined as an albumin (mg/dl) to creatinine (mg/dl) ratio (ACR) of 0.03, which is approximately equivalent to a urinary albumin excretion (UAE) >30 mg/day, was present in a total of 14.9% of participants, and 31% had type 2 diabetes. The TJP1 exons, flanking intronic sequence, and putative proximal promoter regions were investigated in this population. Twentynine polymorphisms, including 7 nonsynonymous SNPs, were identified and genotyped in all subjects of this study for association analysis. Three sets of correlated SNPs, which include 3 exonic SNPs, were nominally associated with ACR (p value range 0.007-0.049); however, the association with the discrete trait albuminuria was not significant (p value range 0.094-0.338). We conclude that these variants in TJP1 do not appear to be major determinants for albuminuria in the SAFDGS; however, they may play a minor role in its severity in this Mexican-American population. Further examination of the TJP1 gene region in this and other cohorts will be useful to determine whether ZO-1 plays a significant role in glomerular permselectivity.

PHC3, a component of the hPRC-H complex, associates with E2F6 during G0 and is lost in osteosarcoma tumors

Polyhomeotic-like 3 (PHC3) is a ubiquitously expressed member of the polycomb gene family and part of the human polycomb complex hPRC-H. We found that in normal cells PHC3 associated with both hPRC-H complex components and with the transcription factor E2F6. In differentiating and confluent cells, PHC3 and E2F6 showed nuclear colocalization in a punctate pattern that resembled the binding of polycomb bodies to heterochromatin. This punctate pattern was not seen in proliferating cells suggesting that PHC3 may be part of an E2F6-polycomb complex that has been shown to occupy and silence target promoters in G(0). Previous loss of heterozygosity (LoH) analyses had shown that the region containing PHC3 underwent frequent LoH in primary human osteosarcoma tumors. When we examined normal bone and human osteosarcoma tumors, we found loss of PHC3 expression in 36 of 56 osteosarcoma tumors. Sequence analysis revealed that PHC3 was mutated in nine of 15 primary osteosarcoma tumors. These findings suggest that loss of PHC3 may favor tumorigenesis by potentially disrupting the ability of cells to remain in G(0).

Golli-MBP copy number analysis by FISH, QMPSF and MAPH in 195 patients with hypomyelinating leukodystrophies

The inherited disorders of CNS myelin formation represent a heterogeneous group of leukodystrophies. The proteolipoprotein (PLP1) gene has been implicated in two X-linked forms, Pelizaeus-Merzbacher disease (PMD) and spastic paraplegia type 2, and the gap junction protein alpha12 (GJA12) gene in a recessive form of PMD. The myelin basic protein (MBP) gene, which encodes the second most abundant CNS myelin protein after PLP1, presents rearrangements in hypomyelinating murine mutants and is always included in the minimal region deleted in 18q- patients with an abnormal hypomyelination pattern on cerebral MRI. In this study, we looked at the genomic copy number at the Golli-MBP locus in 195 patients with cerebral MRI suggesting a myelin defect, who do not have PLP1 mutation. Although preliminary results obtained by FISH suggested the duplication of Golli-MBP in 3 out of 10 patients, no abnormal gene quantification was found using Quantitative Multiplex PCR of Short Fluorescent fragments (QMPSF), Multiplex Amplifiable Probe Hybridization (MAPH), or another FISH protocol using directly-labelled probes. Pitfalls and interest in these different techniques to detect duplication events are emphasised. Finally, the study of this large cohort of patients suggests that Golli-MBP deletion or duplication is rarely involved in inherited defects of myelin formation.

Association analyses of the neuregulin 1 gene with schizophrenia and manic psychosis in a Hispanic population

OBJECTIVE

This study used the population of the Central Valley of Costa Rica (CVCR) and phenotyping strategies alternative to DSMIV classifications to investigate the association of neuregulin 1 with schizophrenia.

METHOD

Using 134 family trios with a history of psychosis, we genotyped six of the seven markers originally identified to be associated with schizophrenia in Iceland.

RESULTS

The neuregulin Icelandic haplotype was not associated with schizophrenia in the CVCR population. However, a novel haplotype was found to be overrepresented in subjects with functional psychosis (global P-value > 0.05). Stratification of the sample by history of mania suggests that this haplotype may be preferentially over-transmitted to persons with a history of manic psychosis.

CONCLUSION

These results suggest that the neuregulin 1 gene is unlikely to play a major role in predisposing to schizophrenia in the CVCR. Further studies in the CVCR and other Latin American populations should be performed in order to corroborate these findings.

Promise and challenge: Markers of prostate cancer detection, diagnosis and prognosis

Approximately 1 man in 6 will be diagnosed with prostate cancer during his life lifetime, and over 200,000 men in the U.S. are diagnosed with prostate cancer annually. Since the widespread adoption of PSA testing, about 60–70% of men at risk in the U.S. have had a blood test for prostate cancer. With this, prostate cancer death rates have decreased, yet only slightly. Thirty thousand men still die each year from this disease. PSA testing fails to identify a small but significant proportion of aggressive cancers, and only about 30% of men with a “positive” PSA have a positive biopsy. Additionally, of men who are treated for prostate cancer, about 25% require additional treatment, presumably due to disease recurrence. Also of concern is the growing evidence that there are some prostate cancers for which treatment may not be necessary. Very long-term studies from the U.S. and Europe, following men with prostate cancer have found that some tumors do not progress over time. In these individuals, prostate cancer treatment is unnecessary and harmful as these men do not benefit from treatment but will be at risk of treatment-related side effects and complications. They suggest a fundamental problem with prostate cancer: it is not possible, at this time, to predict the natural history of the disease. It is for these reasons that the most important challenge in prostate cancer today is the inability to predict the behavior of an individual tumor in an individual patient. Here we review issues related to performance and validation of biomarkers with a focus on “doing no harm”, and bearing in mind that it is the ultimate goal of early detection to save lives. Improved diagnostic and prognostic biomarkers are needed for prostate cancer, and the use of these markers should ultimately translate into increased life span and quality of life. The ultimate goal would be to not only have accurate biomarkers suitable for early diagnosis, but also biomarkers that identify men at greatest risk of developing aggressive disease. Technology has been brought to bear on this problem, and the major approaches are genomics, expression analysis, and proteomics. Proteomics and DNA methylation assays may soon be used in sensitive and specific diagnostic testing of serum and tissues for cancer. Expression arrays may be used to establish both a more specific diagnosis and prognosis for a particular tumor. The proteome is only beginning to be understood, and alternative splicing and post-translational modifications of proteins such as glycosylation and phosphorylation are challenging areas of study. Finally, risk assessment and prognosis are being pursued through analysis of genomic polymorphisms (single nucleotide polymorphisms, SNPs). This huge task is only beginning, and requires the combined expertise of molecular epidemiologists, oncologists, surgeons, pathologists, and basic scientists.

Chromosome 18 suppresses prostate cancer metastases

Loss of heterozygosity and allelic imbalance data has shown that there are two distinct regions of loss on chromosome 18q associated with the progression of prostate cancer (CaP). To investigate the functional significance of chromosome 18q loci in CaP, we utilized the technique of microcell-mediated chromosome transfer to introduce an intact chromosome 18 into the human prostate cancer cell line, PC-3. Three of the resulting hybrid lines were compared to the PC-3 cells in vitro and in vivo. The hybrid cell lines, containing an intact copy of the introduced chromosome 18, exhibited a substantial reduction in anchorage-dependent and independent growth in vitro. These hybrid cell lines also made smaller tumors in nude mice following subcutaneous injection compared to PC-3 cells. Because tumor growth was not completely eliminated by introduction of chromosome 18, we assessed the ability of the hybrids to metastasize to bone after intra-cardiac inoculation in a nude mouse model. Mice inoculated with PC-3 hybrids containing intact copies of chromosome 18 had significantly fewer bone metastases and dramatically improved survival compared to PC-3 cells. In addition, the introduction of chromosome 18 significantly reduced tumor burden in extraskeletal sites. This was not because of differences in growth rates because mice bearing hybrids were monitored for metastases over twice as long as mice bearing PC-3 cells. Taken together, these data suggest that chromosome 18 has a functional role in CaP to suppress growth and metastases. Identification of the responsible gene(s) may lead to molecular targets for drug discovery.

Regions of allelic imbalance in the distal portion of chromosome 12q in gastric cancer

AIMS

To define regions of loss on the distal portion of chromosome 12q in gastric adenocarcinoma.

METHODS

Microsatellite analysis on chromosome 12 was performed on 19 human gastric cancer cell lines using 77 markers, 71 of which were within or distal to 12q21; some portions of this region showed extended regions of homozygosity (ERHs) in 10 of 19 gastric cancer cell lines. In addition, microdissected tumour cells from 76 primary gastric adenocarcinomas were examined using 13 markers of interest implicated by the cell line data; 70% of these showed allelic imbalance (AI) at one or more markers in or distal to 12q21.

RESULTS

Mapping ERHs in the cell lines and sites of AI in the tumours identified three regions that contain putative tumour suppressor genes: region A is located within 2.8 Mb between markers D12S1667 and D12S88; region B, within 1.9 Mb between markers D12S1607 and D12S78; and region C, in 0.74 Mb between markers D12S342 and D12S324. Fluorescence in situ hybridisation (FISH) analysis in two cell lines confirmed that two of the ERHs reflected deletions, not amplifications, of D12S81 in region A and D12S340 in region C. FISH analysis of marker D12S1075 within an ERH containing region B in one cell line showed neither amplification nor deletion. AI on 12q was not associated with prognosis, but was associated with ethnicity of the patient.

CONCLUSIONS

These results identify regions on chromosome 12 that appear to contain tumour suppressor genes important in the development of gastric cancer.

Genetic mapping of a novel X-linked recessive colobomatous microphthalmia

Colobomatous microphthalmia is a common ocular malformation with a heterogeneous phenotype. The majority of cases without associated systemic abnormalities have an autosomal dominant inheritance pattern [McKusick, 1990: Mendelian inheritance in man]. A few isolated cases with autosomal recessive transmission have been described [Zlotogora et al., 1994: Am J Med Genet 49:261--262]. To our knowledge, no cases of X-linked colobomatous microphthalmia that are not a part of a syndrome or a multisystem disorder have been reported. In this study, we describe a genetic and clinical evaluation of a large pedigree in which colobomatous microphthalmia is segregating in an X-linked recessive fashion. Based on recombination breakpoint analysis, we have determined that the critical interval exists between markers DXS989 and DXS441, placing the disease locus on the proximal short arm or the proximal long arm of the X chromosome. Using linkage analysis, we obtained two-point lod scores of 2.71 at zero recombination with markers DXS1058, DXS6810, DXS1199, and DXS7132. Overlapping multipoint analysis established a broad maximum from marker DXS1068 to marker DXS7132, a region spanning approximately 28 cM. This study provides evidence for the presence of a new locus for colobomatous microphthalmia.

A novel human amino acid transporter, hNAT3: cDNA cloning, chromosomal mapping, genomic structure, expression, and functional characterization

Amino acid transporters are proteins that transport amino acids across the membrane. We report here the isolation and characterization of a novel human cDNA clone encoding a protein of 547 amino acids. This protein shares approximately 50% amino acid sequence homology with the amino acid transporters mouse mNAT and its orthologs, rat SN1 and human g17, and mouse GlnT/ATA1 and ATA2. Expression of this cRNA in Xenopus oocytes revealed that the strongest transport activities were specific for l-alanine. In addition, hNAT3 is a Na(+)- and pH-dependent, low-affinity transporter and partially tolerates substitution of Na(+) by Li(+). Since this protein has sequence and functional similarities to the previously identified system N amino acid transporters, we named this protein hNAT3. The genomic DNA sequence encoding the transcript of hNAT3 spans over 14 kb with 16 exons and 15 introns. Using fluorescence in situ hybridization, we mapped the hNAT3 gene to human chromosome 12q12-q13. By RT-PCR of embryonic and adult human tissues, hNAT3 was detected to be predominantly expressed in the liver and to a much lesser extent in the muscle, kidney, and pancreas. The data obtained in this study are likely to offer critical clues for identification of amino acid transporter-associated diseases.

A major locus for fasting insulin concentrations and insulin resistance on chromosome 6q with strong pleiotropic effects on obesity-related phenotypes in nondiabetic Mexican Americans

Insulin resistance and hyperinsulinemia are strong correlates of obesity and type 2 diabetes, but little is known about their genetic determinants. Using data on nondiabetics from Mexican American families and a multipoint linkage approach, we scanned the genome and identified a major locus near marker D6S403 for fasting "true" insulin levels (LOD score 4.1, empirical P<.0001), which do not crossreact with insulin precursors. Insulin resistance, as assessed by the homeostasis model using fasting glucose and specific insulin (FSI) values, was also strongly linked (LOD score 3.5, empirical P<.0001) with this region. Two other regions across the genome were found to be suggestively linked to FSI: a location on chromosome 2q, near marker D2S141, and another location on chromosome 6q, near marker D6S264. Since several insulin-resistance syndrome (IRS)-related phenotypes were mapped independently to the regions on chromosome 6q, we conducted bivariate multipoint linkage analyses to map the correlated IRS phenotypes. These analyses implicated the same chromosomal region near marker D6S403 (6q22-q23) as harboring a major gene with strong pleiotropic effects on obesity and on lipid measures, including leptin concentrations (e.g., LOD(eq) for traits-specific insulin and leptin was 4.7). A positional candidate gene for insulin resistance in this chromosomal region is the plasma cell-membrane glycoprotein PC-1 (6q22-q23). The genetic location on chromosome 6q, near marker D6S264 (6q25.2-q26), was also identified by the bivariate analysis as exerting significant pleiotropic influences on IRS-related phenotypes (e.g., LOD(eq) for traits-specific insulin and leptin was 4.1). This chromosomal region harbors positional candidate genes, such as the insulin-like growth factor 2 receptor (IGF2R, 6q26) and acetyl-CoA acetyltransferase 2 (ACAT2, 6q25.3-q26). In sum, we found substantial evidence for susceptibility loci on chromosome 6q that influence insulin concentrations and other IRS-related phenotypes in Mexican Americans.

Chromosome 18 suppresses the tumorigenicity of prostate cancer cells

Microcell-mediated chromosome transfer allows for the introduction of normal chromosomes into tumor cells in an effort to identify putative tumor suppressor genes. We have used this approach to introduce an intact copy of chromosome 18 into the prostate cancer cell line DU145, and independently to introduce human chromosomes 8 and 18 into the prostate cancer cell line TSU-PR1. Introduction of an extra copy of human chromosome 8 had no effect on the growth properties in vitro or the tumorigenicity in vivo of TSU-PR1 cells. However, microcell hybrids containing an introduced copy of human chromosome 18 exhibited a longer population doubling time, retarded growth in soft agar, and slowed tumor growth in athymic nude mice. These experiments provide functional evidence for the presence of one or more tumor suppressor genes on human chromosome 18 that are involved in prostate cancer.

The spectrum of growth abnormalities in children with 18q deletions

The objective of this study was to assess the spectrum of growth abnormalities in children with 18q deletions. The growth axis of 50 individuals with a cytogenetically and molecularly confirmed 18q deletion was investigated by determining height, growth velocity, insulin-like growth factor I (IGF-I), IGF-binding protein-3, bone maturation, and response to pituitary stimulants of GH. Children with 18q deletions are short; 64% have a height more than -2 SD below the mean. Affected children also grow slowly; 68% have a growth velocity more than -1 SD below the mean. Half of the individuals have delayed bone maturation. Growth factors are skewed downward; 72% of the IGF-I values and 83% of the IGF-binding protein-3 values are below the mean for chronological age. Similarly, 72% of the children had a reduced or absent response to either of the GH stimulants, arginine and clonidine. In the total group of 50 children only 2 were normal for all parameters evaluated. Short stature and poor growth are common features of individuals with 18q deletions. GH deficiency is common in this cohort of patients and probably plays a role in the short stature seen in many of the affected individuals.

A major susceptibility locus influencing plasma triglyceride concentrations is located on chromosome 15q in Mexican Americans

Although several genetic forms of rare or syndromic hypertriglyceridemia have been reported, little is known about the specific chromosomal regions across the genome harboring susceptibility genes for common forms of hypertriglyceridemia. Therefore, we conducted a genomewide scan for susceptibility genes influencing plasma triglyceride (TG) levels in a Mexican American population. We used both phenotypic and genotypic data from 418 individuals distributed across 27 low-income, extended Mexican American families. For the analyses, TG values were log transformed (ln TG). We used a variance-components technique to conduct multipoint linkage analyses for localizing susceptibility genes that determine variation in TG levels. We used an approximately 10-15-cM map, which was made on the basis of information from 295 microsatellite markers. After accounting for the effects of sex and sex-specific age terms, we found significant evidence for linkage (LOD = 3.88) of ln TG levels to a genetic location between the markers GABRB3 and D15S165 on chromosome 15q. This putative locus explains 39.7+/-7% (P=.000012) of total phenotypic variation in ln TG levels. Suggestive evidence was found for linkage of ln TG levels to two different locations on chromosome 7, which are approximately 85 cM apart from each other. Also, there is some evidence for linkage of high-density lipoprotein cholesterol concentrations to a genetic location near one of the regions on chromosome 7. In conclusion, we found strong evidence for linkage of ln TG levels to a genetic location on chromosome 15q in a Mexican American population, which is prone to disease conditions such as type 2 diabetes and the insulin-resistance syndrome that are associated with hypertriglyceridemia. This putative locus appears to have a major influence on ln TG variation.

Identification of two distinct regions of allelic imbalance on chromosome 18Q in metastatic prostate cancer

Like most cancers, prostate cancer (CaP) is believed to be the result of the accumulation of genetic alterations within cells. Previous studies have implicated numerous chromosomal regions with elevated rates of allelic imbalance (AI), using mostly primary CaPs with an unknown disease outcome. These regions of AI are proposed sites for tumor suppressor genes. One of the regions previously implicated as coding for at least one tumor suppressor gene is the long arm of chromosome 18 (18q). To confirm this observation, as well as to narrow the critical region for this putative tumor suppressor, we analyzed 32 metastatic CaP specimens for AI on chromosome 18q. Thirty-one of these 32 specimens (96.8%) exhibited AI at one or more loci on chromosome 18q. Our analysis using 17 polymorphic markers revealed statistically significant AI on chromosome 18q at 3 markers, D18S35, D18S64 and D18S461. Using these markers as a guide, we have been able to identify 2 distinct minimum regions of AI on 18q. The first region is between the genetic markers D18S1119 and D18S64. The second region lies more distal on the long arm of the chromosome and is between the genetic markers D18S848 and D18S58. To determine if 18q loss is a late event in the progression of CaP, we also examined prostatic intraepithelial neoplasia (PIN) and primary prostate tumors from 17 patients for AI with a subset of 18q markers. We found significantly higher AI in the metastatic samples. Our results are consistent with 18q losses occurring late in CaP progression.

Identification of two distinct regions of allelic imbalance on chromosome 18Q in metastatic prostate cancer

Like most cancers, prostate cancer (CaP) is believed to be the result of the accumulation of genetic alterations within cells. Previous studies have implicated numerous chromosomal regions with elevated rates of allelic imbalance (AI), using mostly primary CaPs with an unknown disease outcome. These regions of AI are proposed sites for tumor suppressor genes. One of the regions previously implicated as coding for at least one tumor suppressor gene is the long arm of chromosome 18 (18q). To confirm this observation, as well as to narrow the critical region for this putative tumor suppressor, we analyzed 32 metastatic CaP specimens for AI on chromosome 18q. Thirty-one of these 32 specimens (96.8%) exhibited AI at one or more loci on chromosome 18q. Our analysis using 17 polymorphic markers revealed statistically significant AI on chromosome 18q at 3 markers, D18S35, D18S64 and D18S461. Using these markers as a guide, we have been able to identify 2 distinct minimum regions of AI on 18q. The first region is between the genetic markers D18S1119 and D18S64. The second region lies more distal on the long arm of the chromosome and is between the genetic markers D18S848 and D18S58. To determine if 18q loss is a late event in the progression of CaP, we also examined prostatic intraepithelial neoplasia (PIN) and primary prostate tumors from 17 patients for AI with a subset of 18q markers. We found significantly higher AI in the metastatic samples. Our results are consistent with 18q losses occurring late in CaP progression.

Haplosufficiency of the melancortin-4 receptor gene in individuals with deletions of 18q

The melanocortin-4 receptor (MC4R) is a seven, transmembrane G-protein-coupled receptor whose ligand, alpha-melanocyte-stimulating hormone (alpha-MSH), is a post-translational derivative of pro-opiomelanocortin (POMC). The regulatory pathway, of which MC4R is a part, has become an area of intense interest because of its potential role in obesity. Three studies have identified individuals with dominantly inherited obesity segregating with mutations in the MC4R gene. It has been hypothesized that the mutation found in these subjects resulted in a loss of gene function resulting in obesity due to haploinsufficiency of the MC4R gene. We have been studying the molecular basis of the phenotype of individuals with large deletions of chromosome 18q. Due to its location at 18q21.3, the MC4R gene is hemizygous in approximately one-third of the individuals in our study. If hemizygosity of the MC4R gene results in haploinsufficiency-induced obesity, then individuals with deletions of 18q whose deletions include the MC4R gene should be obese in comparison with those individuals whose deletion does not include the gene. Our data indicate no difference in obesity among those deleted and not deleted for the gene. This supports the hypothesis that the MC4R gene product is haplosufficient and the involvement of MC4R in obesity may reflect a dominant negative effect.

Variable disease severity associated with a Paget's disease predisposition gene

We have recently identified a region on the long arm of chromosome 18 that carries a predisposition gene for Paget's disease using linkage analysis. This region was explored because of earlier studies demonstrating the presence of a gene for another bone disorder, familial expansile osteolysis (FEO) within this region. FEO has many similarities to Paget's disease including osteoclast abnormalities and viral-like nuclear inclusions. Therefore, it was proposed that FEO and Paget's disease are disorders resulting from mutations at the same locus. For our linkage study, we utilized a large kindred with a high incidence of Paget's disease. The propositus in this family had polyostotic disease symptoms beginning at age 31. During the process of characterizing this family, four other family members were diagnosed with Paget's disease. One of the proband's siblings was asymptomatic but had high normal serum alkaline phosphatase levels; Paget's disease was identified only after bone scanning (at age 50). This implies that the predisposition gene does not consistently cause severe disease and raises a question concerning the mechanism of predisposition: Does the predisposition gene affect the age of onset and/or the severity of disease? To further explore this question, two individuals from this kindred, under age 30 and carrying the affected haplotype, were evaluated for early onset Paget's disease. No evidence of disease was observed after thorough evaluation. This implies that the age of onset is highly variable for this locus, indicating variable expression of disease in individuals carrying the same mutation.

Molecular, morphometric and functional analyses demonstrate that the growth hormone deficient little mouse is not hypomyelinated

To study the effects of naturally occurring growth hormone deficiency type I on CNS myelination, we compared the myelination of brains from little and wild-type littermate mice using molecular, histological, morphometric, and functional analyses. The little mouse produces only 6-8% of normal levels of growth hormone (GH) and approximately 20% of normal circulating levels of insulin-like growth factor 1 (IGF-1). Our data show that the expression of myelin basic protein (MBP) and proteolipid protein (PLP) of the little brain exhibit the same temporal pattern and amount as that of the wild-type brain. Furthermore, the density and size of myelinated axons and the myelin sheath thickness in the corpus callosum, anterior commissure and the optic nerve are comparable in the little and wild-type brains. These regions are reduced in size in the little mouse brain proportionate to the overall reduction in brain size implying a reduction in the total number of neurons. Therefore, it follows that the total myelin content is reduced, but when normalized to brain size, the myelin concentration is unchanged. Myelin staining patterns of whole brains were identical. Moreover, functional analysis of the visual pathway indicated no difference between the little and control mice. These results are inconsistent with previous reports of hypomyelination in the little mouse and suggest that this form of GH deficiency does not adversely affect the myelination process except possibly through neuronal proliferation. However, since axon size and density are maintained, the neuronal growth may conversely be inherently limited by other restricted brain growth.

Congenital anomalies and anthropometry of 42 individuals with deletions of chromosome 18q

Deletions of chromosome 18q are among the most common segmental aneusomies compatible with life. The estimated frequency is approximately 1/40,000 live births [Cody JD, Pierce JF, Brkanac Z, Plaetke R, Ghidoni PD, Kaye CI, Leach RJ. 1997. Am. J. Med. Genet. 69:280-286]. Most deletions are terminal encompassing as much as 36 Mb, but interstitial deletions have also been reported. We have evaluated 42 subjects with deletions of 18q at our institution. This is the largest number of individuals with this chromosome abnormality studied by one group of investigators. Here we report the physical findings in these individuals. We have compared our findings with those of previously reported cases and have found a significantly different incidence of several minor anomalies in our subjects. We also describe here several anomalies not previously reported in individuals with deletions of 18q, including short frenulum, short palpebral fissures, disproportionate short stature, overlap of second and third toes, and a prominent abdominal venous pattern. Characteristics found in subjects were analyzed for correlation with cytogenetic breakpoints. Several traits were found to correlate with the extent of the deletion. Large deletions were associated with significantly decreased head circumference and ear length as well as the presence of proximally placed and/or anomalous thumbs. Individuals with the smallest deletions were more likely to have metatarsus adductus. Although relatively few genotype/phenotype correlations were apparent, these data demonstrate that correlations with breakpoint are possible. This implies that more correlations will become evident when the more precise molecularly based genotyping is completed. These correlations will identify critical regions on the chromosome in which genes responsible for specific abnormal phenotypes are located.

Genetic linkage of the dentinogenesis imperfecta type III locus to chromosome 4q

Dentinogenesis imperfecta type III (DGI-III) is an autosomal-dominant disorder of dentin formation which appears in a tri-racial southern Maryland population known as the "Brandywine isolate". This disease has suggestive evidence of linkage to the long arm of human chromosome 4 (LOD score of 2.0) in a family presenting with both juvenile periodontitis and DGI-III. The purpose of this study was to screen a family presenting with only DGI-III to determine if this locus was indeed on chromosome 4q. Furthermore, we wanted to determine if DGI-III co-localized with dentinogenesis imperfecta type II (DGI-II), which has been localized to 4q21-q23. Therefore, a large kindred from the Brandywine isolate was identified, oral examination performed, and blood samples collected from 21 family members. DNA from this family was genotyped with 6 highly polymorphic markers that span the DGI-II critical region of chromosome 4q. Analysis of the data yielded a maximum two-point LOD score of 4.87 with a marker for the dentin matrix protein 1 (DMP1) locus, a gene contained in the critical region for DGI-II. Our results demonstrated that the DGI-III locus is on human chromosome 4q21 within a 6.6 cM region that overlaps the DGI-II critical region. These results are consistent with the hypothesis that DGI-II is either an allelic variant of DGI-III or the result of mutations in two tightly linked genes.

Gene expression patterns in cell lines from patients with 18q- syndrome

Some studies have suggested that for trisomies, some genes are expressed far in excess of the expected 150% level and that this "dysregulation" is one of the mechanisms for the pathogenesis of trisomies. In an attempt to generalize this result to a monosomy, we examined mRNA isolated from lymphoblastoid cell lines derived from patients with 18q- syndrome, a deletion syndrome involving loss of the distal long arm of chromosome 18. Expression levels of ten chromosome 18 genes were compared between cell lines from eight patients with 18q- syndrome and four diploid controls. Gene expression was investigated by a quantitative reverse-transcription polymerase chain reaction (RT-PCR) method. With the exception of the transcription factor NFATC1, which shows a tendency towards gene dosage compensation (the expression pattern correlates with IgA deficiency), all of the other genes were expressed at a level proportional to their gene copy number. This was true regardless of mRNA abundance or different patterns of gene expression (ubiquitous versus tissue-specific gene expression). These results indicate that, unlike dysregulated gene expression apparent in some trisomies, this monosomic syndrome is largely due to consequences of reduced gene expression.

Genetic pattern of prostate cancer progression

Genetic alterations in primary prostate cancer (CaP) have been extensively studied, yet little is known about the genetic mechanisms underlying progression of primary CaP to metastatic prostate cancer. As a result, it is not possible to distinguish clinically indolent localized disease from potentially life-threatening tumors with high metastatic potential. To address this question, we collected tissue from 34 autopsy-derived metastases, samples rarely analyzed in previous studies. These were compared to a separate set of 17 prostatectomy specimens containing 22 foci of CaP associated with 49 examples of high-grade prostatic intraepithelial neoplasia (PIN), a histological precursor of CaP. We compared the loss of heterozygosity (LOH) profiles of high-grade PIN, primary CaP and metastases by analyzing 33 microsatellite markers previously found to have high frequencies of LOH in primary CaP. These markers were on chromosomes 5q, 6q, 7q, 8p, 9p, 10q, 11p, 13q, 16q, 17, 18q and 21q. In addition, markers on chromosomes 4p, 11q, 14q and 20q with no reported LOH in primary CaP were analyzed to determine the frequency of background LOH. In PIN lesions, the rate of LOH was significant only at D5S806 (20%) and D16S422 (29%). In addition, different PIN lesions within the same prostate gland were genetically diverse, indicating divergent evolution of synchronous neoplastic precursor lesions. LOH frequency was progressively higher in primary CaP and metastatic lesions. In primary CaP, significant losses occurred at the 8p, 10q, 11p, 16q, 17p, 18q and 21q loci (range 17-43%). Distinct patterns of LOH frequencies were observed in primary CaP compared with metastases. Although some loci (D16S422, D17S960, D21S156) showed similar frequencies of LOH in primary CaP and metastatic CaP, most other loci showed up to 7-fold metastasis-related increases. The metastatic samples revealed previously unrecognized prostate cancer LOH at D5S806, D6S262, D9S157, D13S133 and D13S227. These significant stage-specific differences in LOH frequency specify genetic loci that may play key roles in CaP progression and could represent clinically useful biomarkers for CaP aggressiveness.

Linkage of type 2 diabetes mellitus and of age at onset to a genetic location on chromosome 10q in Mexican Americans

Since little is known about chromosomal locations harboring type 2 diabetes-susceptibility genes, we conducted a genomewide scan for such genes in a Mexican American population. We used data from 27 low-income extended Mexican American pedigrees consisting of 440 individuals for whom genotypic data are available for 379 markers. We used a variance-components technique to conduct multipoint linkage analyses for two phenotypes: type 2 diabetes (a discrete trait) and age at onset of diabetes (a truncated quantitative trait). For the multipoint analyses, a subset of 295 markers was selected on the basis of optimal spacing and informativeness. We found significant evidence that a susceptibility locus near the marker D10S587 on chromosome 10q influences age at onset of diabetes (LOD score 3.75) and is also linked with type 2 diabetes itself (LOD score 2.88). This susceptibility locus explains 63.8%+/-9.9% (P=. 000016) of the total phenotypic variation in age at onset of diabetes and 65.7%+/-10.9% (P=.000135) of the total variation in liability to type 2 diabetes. Weaker evidence was found for linkage of diabetes and of age at onset to regions on chromosomes 3p, 4q, and 9p. In conclusion, our strongest evidence for linkage to both age at onset of diabetes and type 2 diabetes itself in the Mexican American population was for a region on chromosome 10q.

Evidence for a novel osteosarcoma tumor-suppressor gene in the chromosome 18 region genetically linked with Paget disease of bone

Paget disease of bone, or "osteitis deformans," is a bone disorder characterized by rapid bone remodeling resulting in abnormal bone formation. It is the second most common metabolic bone disease after osteoporosis, affecting 3%-5% of subjects aged >40 years. Recent evidence suggests that predisposition to Paget disease may have a genetic component. Genetic linkage analysis of families with multigenerational Paget disease shows linkage to a region of chromosome 18q near the polymorphic locus D18S42. Approximately 1% of Paget patients develop osteosarcoma, which represents an increase in risk that is several thousandfold over that of the general population. Osteosarcoma in Paget patients is the underlying basis for a significant fraction of osteosarcomas occurring after age 60 years. Our analysis of tumor-specific loss of constitutional heterozygosity (LOH) in 96 sporadic osteosarcomas has identified a putative tumor-suppressor locus that maps to chromosome 18q. We have localized this tumor-suppressor locus between D18S60 and D18S42, a region tightly linked to familial Paget disease. Analysis of osteosarcomas from patients with Paget disease revealed that these tumors also undergo LOH in this region. These findings suggest that the association between Paget disease and osteosarcoma is the result of a single gene or two tightly linked genes on chromosome 18.

Cloning, chromosomal localization and promoter analysis of the human transcription factor YY1

Yin Yang 1 (YY1) is a protein that activates and represses transcription of a large number of cellular and viral genes. In addition, studies suggest that YY1 may play an important role in development and differentiation. Here, we report the isolation and analysis of a YY1 genomic clone from a lambda human liver library. Fluorescence in situ hybridization with the YY1 clone has localized the YY1 gene to chromosome 14 band q32. A major YY1 gene transcription initiation site has been mapped to 478 bp upstream of the ATG translation start site. The proximal promoter contains multiple Sp1 transcription factor binding sites but lacks a consensus TATA or CCAAT box. Transient transfections and detailed deletion analyses localized the promoter to no more than 277 bp upstream from the major transcription start site. Finally, we have found that overexpression of the adenovirus E1A protein represses expression of a reporter gene directed by the YY1 promoter.

Identification of cryptic rearrangements in patients with 18q- deletion syndrome

The majority of patients with 18q- syndrome appear cytogenetically to have a terminal deletion of the long arm of chromosome 18. These 18q- patients are diagnosed by use of standard cytogenetic banding techniques, which have resolution insufficient for precise genotyping. In our effort to obtain a thorough genotype, we have analyzed the DNA from 35 patients who originally were diagnosed as having de novo terminal deletions of chromosome 18. Molecular analysis was performed with polymorphic markers throughout the 18q- region. Cytogenetic FISH was performed with two human 18q telomeric probes, a chromosome 18-specific alpha-satellite probe, and whole chromosome 18-specific paint. Of 35 patients previously reported to have terminal deletions of 18q, we found that 5 (14%) have more-complex cryptic rearrangements and that 3 (9%) retain the most distal portion of 18q, consistent with an interstitial rather than a terminal deletion. These findings indicate that a standard karyotype can lead to insufficient characterization in 18q- syndrome. This has important ramifications for phenotype mapping of this syndrome, as well as for proper prognosis.

Chromosomal sublocalization of the transcribed human telomere repeat binding factor 2 gene and comparative mapping in the mouse

Telomere repeat binding factor 2 (TERF2) is one of two recently cloned mammalian telomere binding protein genes. TERF2 binds as a dimer with high affinity to the double-stranded TTAGGG telomeric repeat through an evolutionarily conserved myb-type DNA binding domain. TERF2 prevents telomere end-to-end fusion and may be important in maintaining genomic stability. We localized the transcribed TERF2 gene to human chromosome 16q22.1, tightly linked to the EST HUM000S343. The mouse Terf2 gene is situated by itself in a newly defined "bin" on chromosome 8 one crossover distal to Psm10 and Sntb2. Human TERF2 and mouse Terf2 are therefore part of a large evolutionarily conserved linkage group comprised of at least 25 known paralogous genes between human chromosome 16q and mouse chromosome 8.

Chromosome 18q paracentric inversion in a family with mental retardation and hearing loss

We report on a mother and child with a paracentric inversion of the long arm of chromosome 18: 46,XX,inv(18)(q21.1q23). The child had findings in common with those seen in 18q- syndrome including: microcephaly, epicanthal folds, midface hypoplasia, and abnormally modeled ears, dermatoglyphic whorls on fingertips, clubfeet, hearing loss, and developmental delay. The mother and several maternal relatives had mild mental retardation and hearing loss. Magnetic resonance imaging of the child's brain showed abnormal myelination. Molecular studies including PCR-based markers for the MBP locus and fluorescent in situ hybridization with a P1 genomic clone on mother and child demonstrated only one copy of the MBP locus (18q23) with the deletion extending beyond the MBP locus. Therefore, the deletion in the MBP region may account for the abnormal myelination seen in the patient. The other clinical findings, including mental retardation and hearing loss in this family, may reflect disruption of distal or proximal genes within the deleted MBP region or at the more proximal breakpoint 18q21.1, and may represent a contiguous gene syndrome. Further study of this family may help define those genes functioning in the MBP region that contribute to the phenotype of 18q- syndrome.

Further characterization of the murine collagenase (type IVB) gene promoter and analysis of mRNA expression in murine tissues

The collagenase B type IV (Col4B) gene is highly expressed in the osteoclast, the primary bone-resorbing cell. However, factors that regulate expression of the Col4B gene are not well characterized. A murine P1 genomic clone containing a 94 kb sequence insert which contains the Col4B gene was isolated. A 4 kb EcoR1 DNA fragment containing the 5' flanking sequence of the gene was further subcloned and restriction mapped. Putative transcription factors such as SRY, Lyf-1, and GATA1 and 2, binding motifs were identified by sequence analysis in this promoter region. Enhancer and suppressor regions were mapped by transient expression of Col4B gene promoter deletion mutant-luciferase reporter gene constructs in HepG2 cells. Col4B mRNA expression in different murine tissues was analyzed by reverse transcription-polymerase chain reaction and demonstrated high levels of expression in bone, clavaria, spleen and thymus. This promoter provides a valuable tool for targeting gene expression to the osteoclast.

A pore mutation in a novel KQT-like potassium channel gene in an idiopathic epilepsy family

Epileptic disorders affect about 20-40 million people worldwide, and 40% of these are idiopathic generalized epilepsies (IGEs; ref. 1). Most of the IGEs that are inherited are complex, multigenic diseases. To address basic mechanisms for epilepsies, we have focused on one well-defined class of IGEs with an autosomal-dominant mode of inheritance: the benign familial neonatal convulsions (BFNC; refs 2,3). Genetic heterogeneity of BFNC has been observed. Two loci, EBN1 and EBN2, have been mapped by linkage analysis to chromosome 20q13 (refs 5,6) and chromosome 8q24 (refs 7,8), respectively. By positional cloning, we recently identified the gene for EBN1 as KCNQ2 (ref. 9). This gene, a voltage-gated potassium channel, based on homology, is a member of the KQT-like family. Here we describe an additional member, KCNQ3. We mapped this new gene to chromosome 8, between markers D8S256 and D8S284 on a radiation hybrid map. We screened KCNQ3 for mutations in the large BFNC family previously linked to chromosome 8q24 in the same marker interval. We found a missense mutation in the critical pore region in perfect co-segregation with the BFNC phenotype. The same conserved amino acid is also mutated in KVLQT1 (KCNQ1) in an LQT patient. KCNQ2, KCNQ3 and undiscovered genes of the same family of K+ channels are strong candidates for other IGEs.

A novel potassium channel gene, KCNQ2, is mutated in an inherited epilepsy of newborns

Idiopathic generalized epilepsies account for about 40% of epilepsy up to age 40 and commonly have a genetic basis. One type is benign familial neonatal convulsions (BFNC), a dominantly inherited disorder of newborns. We have identified a sub-microscopic deletion of chromosome 20q13.3 that co-segregates with seizures in a BFNC family. Characterization of cDNAs spanning the deleted region identified one encoding a novel voltage-gated potassium channel, KCNQ2, which belongs to a new KQT-like class of potassium channels. Five other BFNC probands were shown to have KCNQ2 mutations, including two transmembrane missense mutations, two frameshifts and one splice-site mutation. This finding in BFNC provides additional evidence that defects in potassium channels are involved in the mammalian epilepsy phenotype.

Genetic linkage of Paget disease of the bone to chromosome 18q

Paget disease is a common bone disease characterized by abnormal osteoclasts that are large, multinucleated, and overactive and that contain paramyxovirus-like nuclear inclusions. There is evidence for a major genetic component to Paget disease, with up to 40% of patients having affected first-degree relatives; however, the locus (loci) and gene(s) involved are unknown. Another bone disorder, familial expansile osteolysis (FEO), although extremely rare, also is characterized by similar osteoclast abnormalities but has an earlier age at onset and a more aggressive clinical progression. The causative gene for FEO has been localized to a region of human chromosome 18q. On the basis of the presence of similar clinical findings and of viral-like nuclear inclusions in osteoclasts, we hypothesized that FEO and Paget disease are allelic versions of the same locus. Therefore, a large kindred with a high incidence of Paget disease was examined to determine if Paget disease was linked to genetic markers in the same region of chromosome 18 as that for FEO. Our analysis yielded a two-point LOD score of 3.40, with the genetic marker D18S42, a marker tightly linked to the FEO locus. This demonstrates that the gene(s) responsible for FEO and that for Paget disease are either closely linked or the same locus.

Growth hormone insufficiency associated with haploinsufficiency at 18q23

Growth hormone insufficiency is a common cause of growth failure in children with the 18q- syndrome. Individuals with this syndrome have a deletion as large as 36 Mb from the long arm of chromosome 18. We have evaluated 33 children with this syndrome for growth hormone production and have identified a region of approximately 2 Mb, which is deleted in every growth hormone insufficient patient. Two genes contained in this region, myelin basic protein, and the galanin receptor, are candidate genes for the growth hormone insufficiency phenotype.

Magnetic resonance imaging demonstrates incomplete myelination in 18q- syndrome: evidence for myelin basic protein haploinsufficiency

Magnetic resonance imaging (MRI) and MRI relaxometry were used to investigate disturbed brain myelination in 18q- syndrome, a disorder characterized by mental retardation, dysmorphic features, and growth failure. T1-weighted and dual spin-echo T2-weighted MR images were obtained, and T1 and T2 parametric image maps were created for 20 patients and 12 controls. MRI demonstrated abnormal brain white matter in all patients. White matter T1 and T2 relaxation times were significantly prolonged in patients compared to controls at all ages studied, suggesting incomplete myelination. Chromosome analysis using fluorescence in situ hybridization techniques showed that all patients with abnormal MRI scans and prolonged white matter T1 and T2 relaxation times were missing one copy of the myelin basic protein (MBP) gene. The one patient with normal-appearing white matter and normal white matter T1 and T2 relaxation times possessed two copies of the MBP gene. MRI and molecular genetic data suggest that incomplete cerebral myelination in 18q- is associated with haploinsufficiency of the gene for MBP.

Ameloblastin gene (AMBN) maps within the critical region for autosomal dominant amelogenesis imperfecta at chromosome 4q21

Amelogenesis imperfecta (AI) is a broad group of hereditary enamel defects that is characterized by a high degree of clinical diversity. Recently, the local hypoplastic form of autosomal dominant AI (AIH2) has been mapped to human chromosome 4q in a 17.6-cM region. This locus has been further refined to a 4-Mb interval between D4S2421 and Albumin. Recently, a cDNA clone for an enamel matrix protein, ameloblastin (AMBN), has been isolated. In this report, we have isolated a PAC human genomic clone containing the human AMBN gene. The AMBN was mapped by two color fluorescence in situ hybridization using two P1 genomic clones for sequence tagged site (STS) markers, D4S400 and D4S409, which flank the critical AIH2 region. Our results place AMBN at 4q21 between D4S409 (4q13) and D4S400 (4q21). Furthermore, the AMBN PAC genomic clone was shown to contain three STS markers, D4S2604, D4S2670, and D4S2609, which are contained within the critical region defined by six Swedish families with AIH2. AMBN is therefore a strong candidate gene for AIH2.

Preferential loss of the paternal alleles in the 18q- syndrome

Individuals with the 18q- syndrome have variable deletions from the long arm of chromosome 18. They also exhibit a highly variable phenotype. To correlate genotype with phenotype accurately, extensive molecular and phenotypic analyses are needed on each affected individual. As a part of this analysis, we have determined the parental origin of the deleted chromosome in 34 individuals with the 18q- syndrome. We have found that 85% of the de novo deletions are paternal in origin. The percentage of fathers of individuals with paternally derived deletions who were > 30 years old was (not significantly) greater than that of the general population. The mothers of individuals with maternally derived deletions were near an average age for childbearing compared to the general population. Individuals with maternally derived terminal deletions had breakpoints as varied as those with paternally derived deletions. These results are consistent with the hypothesis that the reduced incidence of maternally derived deletions is not due to reduced viability, since individuals with large maternally derived deletions of chromosome 18q were found. We hypothesize that the prevalence of paternally derived deletions is due to an increased frequency of chromosome breakage in male germ cells. These results are consistent with results observed in other segmental aneusomies in which there is a high incidence of paternally derived deletions.

Growth hormone deficiency associated in the 18q deletion syndrome

The 18q- syndrome is one of the commonest deletion syndromes. Clinical characteristics are variable but may include: hypotonia, tapered digits, "carp-like" mouth, mental retardation, and hearing impairment. Growth failure (GF; both weight and height < 3%) was reported in 80% of affected individuals. We evaluated growth hormone (GH) sufficiency in 5 18q- syndrome patients, 3 of whom had growth failure (< 3% weight and height); the remaining 2 had normal growth parameters. Laboratory evaluation of growth included measurement of IGF-1, IGFBP-3, bone ages and GH response to pituitary provocative agents. Three patients failed to produced adequate GH following stimulation testing. Of 3 patients with inadequate GH production, 1 had normal growth (above 3%). Only 1 of 5 patients had normal GH production and normal growth parameters. Our findings to date suggest that GH deficiency is common in individuals with the 18q- syndrome. The pathogenesis of this finding is unknown. We postulate that a gene(s) on 18q is involved in GH production.

New variants of the human and rat nuclear hormone receptor, TR4: expression and chromosomal localization of the human gene

TR4 is a new member of the nuclear hormone receptor family. This receptor is highly conserved in rat and human, but an in-frame insertion of 19 amino acid residues in the amino-terminal (A/B) region was found in the human homolog, which we refer to as hTR4alpha1. By reverse transcription-PCR (RT-PCR) we have identified a human TR4 mRNA (hTR4alpha2) that is analogous in size and sequence to the reported rat TR4. RT-PCR analysis using total RNA derived from various rat tissues revealed a new rat TR4 transcript, referred to as rTR4alpha1, which is homologous to hTR4alpha1 since it contains the extra 19 amino acids in the A/B region. The two rat transcripts showed a differential tissue distribution. Analysis of the exon-intron organization of the hTR4 A/B region showed that the 19-amino-acid peptide insert in hTR4alpha1 was encoded by a separate exon, indicating that hTR4alpha1 and hTR4alpha2 transcripts were produced by the differential usage of the exon. RT-PCR analysis revealed that both hTR4alpha1 and hTR4alpha2 were detectable in brain, placenta, and ovary. In contrast, the human ovarian cancer cell line, PA1, failed to express hTR4alpha1. By fluorescence in situ hybridization, we have mapped the hTR4 gene to 3p25, a region deleted in some forms of cancer.

1,25-Dihydroxyvitamin D3 and transforming growth factor-beta act synergistically to override extinction of liver/bone/kidney alkaline phosphatase in osteosarcoma hybrid cells

In this study, a somatic cell genetic approach was used to study the regulation of liver/bone/kidney alkaline phosphatase (ALPL) gene expression in osteoblasts. ALPL plays an important role in skeletal mineralization and serves as a good index of bone formation. A series of intertypic hybrids constructed by fusion of the human osteosarcoma TE-85 with the mouse fibrosarcoma La-t- demonstrated a 10-fold reduction of ALPL steady-state mRNA and enzyme activity, a phenomenon termed extinction. Hybrid subclones which reexpressed ALPL contained reduced numbers of fibroblast chromosomes compared to earlier passages. This suggests that a trans-acting negative regulatory factor expressed from the fibroblast genome regulates ALPL expression. Two factors known to influence ALPL expression are 1,25-dihydroxyvitamin D3 (1,25D3) and transforming growth factor-beta1 (TGFbeta1). 1,25D3 is involved in mobilizing bone calcium stores and TGFbeta1 plays a critical role in bone remodeling. The extinguished hybrids were exposed to 1,25D3, TGFbeta1, and a combination of these factors. For two hybrids, the combination induced reexpression of ALPL activity to levels comparable to the TE-85 parent, indicating a competition between the factors and the extinguisher(s). Neither factor alone could induce ALPL reexpression to the levels observed with the combination. In only one hybrid, the combination of factors synergistically increased ALPL expression. These data help define the cis sequence element(s) in the ALPL promoter which are involved in the negative regulation of this gene.

Evidence of a third locus for benign familial convulsions

Two autosomal dominant forms of benign idiopathic epilepsy of early life have been described: benign neonatal familial convulsions and benign infantile familial convulsions. Herein we describe a pedigree with familial convulsions in which the age of onset is intermediate between that seen in these two disorders. Two genes responsible for benign neonatal familial convulsions have been mapped to chromosome 20q and to chromosome 8q. Previously, the chromosome 20q benign neonatal familial convulsions locus had been excluded in this pedigree. Further linkage analysis in our laboratory revealed that the chromosome 8 benign neonatal familial convulsions locus also is not responsible for seizures in this pedigree. These results indicate that there are at least three loci responsible for autosomal dominant benign epilepsies of early life.

Suppression of the malignant phenotype of human prostate cancer cell line PPC-1 by introduction of normal fragments of human chromosome 10

Numerous studies have detected frequent losses of heterozygosity at polymorphic loci on chromosomal arms 10p and 10q in human prostate cancers. To confirm the presence of tumor suppressor genes in these chromosomal regions, fragments of normal human chromosome 10 tagged with a neomycin resistance gene were transferred into cells from a human prostate cancer cell line. PPC-1, by microcell-mediated chromosome transfer. Two of the six hybrid clones obtained showed decreased tumorigenicity in athymic nude mice and decreased efficiency of colony formation in soft agar compared with PPC-1; the other four retained fully malignant phenotypes. Analysis of polymorphic loci on chromosome 10 in these hybrid clones suggested that a tumor suppressor gene associated with prostate cancer is located within a 17-cM region at distal 10p.

Localization of a gene for a glutamate binding subunit of a NMDA receptor (GRINA) to 8q24

A glutamate binding subunit gene, GRINA, has been previously mapped to human chromosome 8. A form of inherited epilepsy, benign familial neonatal convulsions (BFNC), has also been localized to chromosome 8. As NMDA receptors have been implicated in the pathogenesis of epilepsy, we were interested in determining whether GRINA mapped to the same region of chromosome 8 as BFNC. Fluorescence in situ hybridization localized GRINA to band 8q24, distal to the thyroglobulin gene. The strongest signal was seen at 8q24.3. A panel of 97 radiation hybrids (RH) was used to verify the localization. The RH mapping results placed GRINA as the most telomeric marker on our map of 8q24, distal to the interval defined for BFNC.

Regional Mapping Strategies Utilizing Microcell Hybrids

Microcell hybrids are useful resources for the mapping of human chromosomes. The procedure of microcell-mediated chromosome transfer often causes fragmentation of the donor chromosome. These fragment-containing microcell hybrids frequently contain a limited region around the locus used in selecting for retention of the chromosome in the hybrids, as well as other fragments from the donor chromosome. Monochromosomal microcell hybrids are useful as the donor cell line for creation of radiation-reduced hybrids. In contrast to fragment-containing microcell hybrids, radiation-reduced hybrids can be used to construct maps of regions of chromosomes that lack selectable markers. For both fragment-containing hybrids and radiation-reduced hybrids, the presence or absence of chromosome-specific sequences can be determined and used to construct a linear map of the chromosome. A protocol and general overview outlining the key concepts in the construction and analysis of a radiation-reduced hybrid panel is presented.