Dinucleotide repeat polymorphisms at the D11S419 and CD3D loci

Analysis of HLA class I expression in different metastases from two melanoma patients undergoing peptide immunotherapy

We characterized the HLA class I alterations in five metastases obtained from two patients with melanoma immunized with Melan A/MART-1, tyrosinase and gp100 tumor peptides. All three metastases analyzed in the first patient (NW145) showed a similar HLA class I alteration with a dual population of melanoma cells. One population was HLA class I antigen positive and the other had loss of heterozygosity (LOH) in the short arm of chromosome 6 leading to an HLA haplotype loss (A02011, B4007, Cw1). The absence of HLA-A2 antigen may explain why this patient did not develop HLA-A2 restricted, Melan A/MART-1 specificity immunization, since this HLA molecule is the restriction element for the tumor peptides used. However, this HLA-deficient population was not selected after peptide immunotherapy. The primary tumor in this patient presented LOH in region 6q, but only in the vertical growth phase of the lesion, whereas LOH at 6p was observed only in DNA from metastatic material. The second patient (NW16) also presented two metastatic lesions with an identical HLA molecular defect, i.e. HLA B locus downregulation (HLA B51011: serological B51; B1503: serological B70). One lesion expressed the tumor antigen (Melan A/ MART-1), but the other did not. Interestingly, the antigen-positive metastasis regressed after peptide immunotherapy, whereas the other progressed rapidly. These findings provide the first indication that multiple metastases generated in the same host can have identically altered HLA class I phenotypes.

Familial hyperinsulinism with apparent autosomal dominant inheritance: clinical and genetic differences from the autosomal recessive variant

We describe three families with hypoglycemia caused by familial hyperinsulinism (HI) in whom vertical transmission of the disorder occurred, suggesting autosomal dominant (AD) inheritance. We therefore examined the relationship between the apparent AD disorder and the more common autosomal recessive (AR) form of HI, which has recently been linked to the sulfonylurea receptor on chromosome 11p15.1. The clinical features of the 11 patients with AD HI were milder than those seen in 14 patients with AR HI. Hypoglycemia was readily controlled with either diet alone or with diazoxide in 10 of 11 patients with AD HI but in none of those with the AR form. In one large pedigree, analysis of genomic DNA with polymorphic simple sequence repeat markers excluded linkage of AD HI to the SUR locus in a dominant manner. The possibility of linkage to the SUR locus could not be absolutely excluded in the two smaller pedigrees. None of the published mutations of the SUR gene identified in patients with AR HI were detected in the patients with the AD form. We conclude that the AD form of hyperinsulinism is phenotypically different from the AR variant. The identification of more families with this form of HI may make it possible to locate the responsible gene by the use of linkage analysis.

Linkage analysis between manic-depressive illness and markers on the long arm of chromosome 11

The long arm of chromosome 11 is one of the most interesting regions in the search for major genes involved in the etiology of manic-depressive illness. Several candidate genes have been identified, including the gene encoding the dopamine D2 receptor, the M1 muscarinic receptor, and porfobillinogen deaminase. Furthermore, different families with co-segregation of psychiatric illness and structural chromosome abnormalities involving regions 11q21, 11q22.3, and 11q25 have been reported. Using narrow as well as broad phenotypic models, conservative genetic parameters, models with dominant or recessive modes of inheritance, and various methods to reduce misclassification, the present study did not find evidence for a major gene causing manic-depressive illness on the long arm of chromosome 11. In the broader phenotypic models multi-point analyses excluded at least 11q14 to 11q23.3, approximately 60 cM, even in one large family. Assuming homogeneity close linkage to DRD2 was excluded for all dominant models, and also in the affecteds-only analyses in the large family alone.

Immunoprinting excludes many potential susceptibility genes as predisposing to early onset pauciarticular juvenile chronic arthritis except HLA class II and TNF

DNA profiles (immunoprints) were generated for 120 patients suffering from early onset pauciarticular chronic arthritis (EOPA-JCA) and > 500 healthy controls utilizing highly polymorphic microsatellites in the vicinity of immunorelevant genes. Six T cell receptor (TCR) markers for the CD3D, TCRDVAJ, TEA, TCRBV6S1, BV6S3, BV6S7 and BV13S2 genes were analysed. Furthermore markers for the cell surface molecule CD40L, for cytokine genes (IL-1A, IL-2, IFN-alpha, FGF-alpha, TNF-alpha), the chromosomal region of the IRF2 and the cytokine receptor gene IL5RA were studied as well as two polymorphisms within the promotor region of the TNF-alpha gene. Coding region polymorphisms were evidenced indirectly by repeat length variation or they were predicted from the microsatellite distribution profiles and then confirmed by direct sequence analysis. Statistical evaluations were performed with respect to known predispositions, predominance of females (> 80%) and HLA-DR and -DQ haplotypes. Cell surface molecules (TCR, CD40L, IL5RA) as well as almost all cytokines (IL-1A, IFN alpha, FGFA, IRF2 region) were excluded as predisposing in our JCA panel. The TNF-alpha microsatellite alleles (GT)10-12 contribute considerably to manifestation of the disease, in HLA-DRB1*11(12) individuals (RR = 12.8). The TNF-alpha allele is not found in linkage disequilibrium with HLA-DRB1*11(12) and may be present on either chromosome 6. Thus, a novel susceptibility factor probably within the TNFA/TNFB gene region has been identified via linkage with the TNF-alpha microsatellite allele. Apparently complex compositions of the genetic background rather than single genes provide the precondition for manifestation of the autoimmune disease EOPA-JCA. Immunoprinting unravels the variability of the immunological genome via the semi-directed microsatellite approach efficiently.

Increased and decreased relative risk for non-insulin-dependent diabetes mellitus conferred by HLA class II and by CD4 alleles

Non-insulin-dependent diabetes mellitus has been recognized to be heterogeneous in etiology, with multiple subgroups. Several genes or chromosomal regions have been implicated in the development of the disease. In this study the association of HLA class II alleles and genotypes and the association of CD4 and CD3 polymorphisms were assessed in a large number of Belgian non-insulin-dependent diabetes mellitus patients. Furthermore, the importance of the DQ alpha 1Arg52/DQ alpha 1Arg52 and the DQ beta 1Asp57/DQ beta 1Asp57 genotypes and the combination of both genotypes were examined. Our results show that in the HLA class II genes only the DQ alpha 1Arg52+/DQ alpha 1Arg52+ genotype was significantly associated with non-insulin-dependent diabetes mellitus compared with controls (p = 0.011, RR = 2.02). We also observed that the frequency of the CD4*A4/*A8 genotype and the CD4*A7 allele was significantly increased and decreased respectively in non-insulin-dependent diabetes mellitus patients as compared with the controls (p = 0.018, RR = 2.16 and p = 0.0003, RR = 0.49 respectively). These results therefore suggest that HLA class II and CD4 genes might independently contribute to the susceptibility for non-insulin-dependent diabetes mellitus and that these alleles and genotypes might identify subgroups of patients with different susceptibilities.

Genetic linkage analysis of schizophrenia using chromosome 11q13-24 markers in Israeli pedigrees

It is generally agreed that there is a genetic component in the etiology of schizophrenia which may be tested by the application of linkage analysis to multiply-affected families. One genetic region of interest is the long arm of chromosome 11 because of previously reported associations of genetic variation in this region with schizophrenia, and because of the fact that it contains the locus for the dopamine D2 receptor gene. In this study we have examined the segregation of schizophrenia with microsatellite dinucleotide repeat DNA markers along chromosome 11q in 5 Israeli families multiply-affected for schizophrenia. The hypothesis of linkage under genetic homogeneity of causation was tested under a number of genetic models. Linkage analysis provided no evidence for significant causal mutations within the region bounded by INT and D11S420 on chromosome 11q. It is still possible, however, that a gene of major effect exists in this region, either with low penetrance or with heterogeneity.

Immunoprinting: various genes are associated with increased risk to develop rheumatoid arthritis in different groups of adult patients

To identify genes that contribute to the manifestation of rheumatoid arthritis we performed association studies via microsatellite analyses of immunorelevant loci (HLA-DRB, 5 T cell receptor loci, TNFa IL1, IL2, IL5R and CD40L). A total of 183 patients and 275 healthy controls were typed in terms of HLA and grouped according to the known predisposing HLA-DRB1 genes (DRB1*04; relative risk approx. 5; DRB1*01, relative risk approx. 2; a third group carried neither allele). Microsatellite polymorphisms characterizing the TCRBV6S3, CD3D, IL1A, IL2, and IL5R genes did not show significant associations with rheumatoid arthritis, whereas TCRBV6S1, TCRBV6S7, TNFa, and CD40L genes may influence relative protection or risk in certain groups of patients. Analysis of a microsatellite marker adjacent to the transcription element alpha (TEA) in the T cell receptor alpha delta complex indicates that in the cohort carrying neither the DRB1*04 nor the DRB1*01 allele the relative risk to acquire rheumatoid arthritis is increased (> 13) or decreased (< 0.07), depending on the inherited microsatellite allele adjacent to the TEA locus. Sequence analysis of the closely linked TEA region from patients and controls revealed a novel dimorphism. Only the newly identified TEA allele leads to binding of a nuclear protein that may be involved in the regulated expression of the TCRDA genes. Subsequent typing of rheumatoid arthritis patients and controls revealed, however, that the association of the microsatellite marker is largely independent of the TEA allele, confirming incomplete linkage in the 2 kb region of the TCRDA locus. These results are discussed in the context of hot spots of recombination in this genomic region and other linked candidate sequences that predispose to develop rheumatoid arthritis.

Study of the possible association of HLA class II, CD4, and CD3 polymorphisms with schizophrenia

In the present study the HLA-DRB and DPB1 alleles as well as CD4 and CD3 polymorphisms were tested in 100 Belgian schizophrenic patients and 204 controls. Our results indicate a significant negative association of the DPB1 0101 allele with schizophrenia (relative risk [RR] = 0.27). Furthermore a significant positive and negative association could be noticed for the CD4*A4 allele and CD4*A7/A8 genotype, respectively (RR 1.79 and 0.47, respectively). These findings suggest that some contribution of HLA class II and CD4 genes to an autoimmune-like pathogenesis in schizophrenia might exist.

Variation at the hepatic lipase and apolipoprotein AI/CIII/AIV loci is a major cause of genetically determined variation in plasma HDL cholesterol levels

Genetic factors have been shown to play an important role in determining interindividual variation in plasma HDL-C levels, but the specific genetic determinants of HDL cholesterol (HDL-C) levels have not been elucidated. In this study, the effects of variation in the genomic regions encoding hepatic lipase, apolipoprotein AI/CIII/AIV, and the cholesteryl ester transfer protein on plasma HDL-C levels were examined in 73 normotriglyceridemic, Caucasian nuclear families. Genetic factors accounted for 56.5 +/- 13% of the interindividual variation in plasma HDL-C levels. For each candidate gene, adjusted plasma HDL-C levels of sibling pairs who shared zero, one, or two parental alleles identical-by-descent were compared using sibling-pair linkage analysis. Allelic variation in the genes encoding hepatic lipase and apolipoprotein AI/CIII/AIV accounted for 25 and 22%, respectively, of the total interindividual variation in plasma HDL-C levels. In contrast, none of the variation in plasma HDL-C levels could be accounted for by allelic variation in the cholesteryl ester transfer protein. These findings indicate that a major fraction of the genetically determined variation in plasma HDL-C levels is conferred by allelic variation at the hepatic lipase and the apolipoprotein AI/CIII/AIV gene loci.

Absence of linkage between idiopathic dilated cardiomyopathy and candidate genes involved in the immune function in a large Italian pedigree

Idiopathic dilated cardiomyopathy (IDC) is a heart disease of unknown aetiology characterised by impaired ventricular function usually associated with dilatation of the cardiac chambers. In order to test the hypothesis of an immunological cause for the disease at the genetic level, we performed linkage analysis between the putative disease locus and some of the potential candidate genes involved in the immune response or coding for the targets for autoantibodies in a large multigeneration family (63 members) from southern Italy with autosomal dominant transmission of the disease. Twenty-nine polymorphic markers on 18 different chromosomal locations were investigated, including markers linked to the genes coding for the HLA antigens, the immunoglobulin heavy and light chains, the receptors for the immunoglobulin Fc fragments, the subunits of the T cell receptor and the associated CD3, CD4, CD8, and CD45 antigens, interleukins 1, 3, 4, 5, 6, 9, and 11, the interleukin 1 and 2 receptors, and the genes coding for the beta 1 adrenoreceptor, the adenine nucleotide translocator-1, and the cardiac alpha and beta myosin heavy chains. No evidence for genetic linkage to IDC was found at any of these candidate loci. These results indicate that the still unidentified IDC gene maps outside several loci involved in the regulation of immune reactivity.

Possible association of CD3 and CD4 polymorphisms with insulin-dependent diabetes mellitus (IDDM)

Population and family studies show that predisposition to type I diabetes (IDDM) is multifactorial, and that polymorphisms in the MHC region contribute substantially to the susceptibility to IDDM. In the present study the association of polymorphisms in the CD4 and the delta subunit of CD3 with IDDM were examined in a Belgian population. We observed that the frequency of the CD A4/A4 genotype and of the CD3 91 allele were significantly increased P = 0.0077) and decreased (P = 3.8 x 10(-5), respectively, in IDDM compared with controls. These results therefore suggest that CD4, CD3 or neighbouring genes might contribute to IDDM susceptibility. These results are, however, preliminary and cannot be considered as established until re-tested in a new population.

No evidence for linkage between familial hypertriglyceridemia and apolipoprotein B, apolipoprotein C-III or lipoprotein lipase genes

Familial hypertriglyceridemia has been suggested to be an autosomal dominant condition with age-dependent penetrance, but so far the underlying defective gene has not been elucidated. We examined the possible role of three candidate gene loci by linkage analysis in six Finnish families with familial clustering of hypertriglyceridemia. The probands were initially recruited from a group of hyperlipidemic outpatients after measurement of serum triglyceride concentrations exceeding 2.00 mmol/l on two occasions. Altogether, 71 subjects were included in the linkage analyses. Bi- or multiallelic DNA polymorphisms were used as markers for the apolipoprotein B gene (chromosome 2), lipoprotein lipase gene (chromosome 8), and apolipoprotein A-I/C-III/A-IV gene cluster (chromosome 11). Linkage analysis was performed by applying two alternative phenotyping models, one adopting quantitative serum triglyceride concentrations and another using qualitative classification of the subjects into hypertriglyceridemic, normotriglyceridemic, and borderline hypertriglyceridemic groups. Using either approach, the cumulative lod scores of each of the three candidate genes in the six families were less than -2.0 at the recombination fraction 0.0. These results suggest that none of the candidate genes investigated is involved in familial clustering of hypertriglyceridemia in our study.

Three tumor-suppressor regions on chromosome 11p identified by high-resolution deletion mapping in human non-small-cell lung cancer

Non-small-cell lung cancer is the leading cause of cancer death for men and women in the industrialized nations. Identification of regions for genes involved in its pathogenesis has been difficult. Data presented here show three distinct regions identified on chromosome 11p. Two regions on 11p13 distal to the Wilms tumor gene WT1 and on 11p15.5 between the markers HBB and D11S860 are described. The third region on the telomere of 11p15.5 has been previously described and is further delineated in this communication. By high-resolution mapping the size of each of these regions was estimated to be 2-3 megabases. The frequency of somatic loss of genetic information in these regions (57%, 71%, and 45%, respectively) was comparable to that seen in heritable tumors such as Wilms tumor (55%) and retinoblastoma (70%) and suggests their involvement in pathogenesis of non-small-cell lung cancer. Gene dosage analyses revealed duplication of the remaining allele in the majority of cases in the 11p13 and the proximal 11p15.5 region but rarely in the distal 11p15.5 region. In tumors with loss of heterozygosity in all three regions any combination of duplication or simple deletion was observed, suggesting that loss of heterozygosity occurs independently and perhaps at different points in time. These results provide a basis for studies directed at cloning potential tumor-suppressor genes in these regions and for assessing their biological and clinical significance in non-small-cell lung cancer.

Familial hyperinsulinism maps to chromosome 11p14-15.1, 30 cM centromeric to the insulin gene

Familial hyperinsulinism (HI) is the most common cause of persistent neonatal hyperinsulinaemic hypoglycemia. Linkage analysis in 15 families (12 Ashkenazi Jewish, 2 consanguineous Arab, 1 non-Jewish Caucasian) mapped HI to chromosome 11p14-15.1 (lod score = 9.5, theta = 0 at D11S921). Recombinants localized the disease locus to the 6.6 cM interval between D11S926 and D11S928. In Jewish families, association (p = 0.003) with specific D11S921/D11S419 haplotypes suggested a founder effect. This locus, which is important for normal glucose-regulated insulin secretion, represents a candidate gene for studies of other diseases of beta-cell dysfunction including non-insulin-dependent diabetes mellitus (NIDDM).

Functional evidence for a second tumor suppressor gene on human chromosome 17

The development and progression of human tumors often involves inactivation of tumor suppressor gene function. Observations that specific chromosome deletions correlate with distinct groups of cancer suggest that some types of tumors may share common defective tumor suppressor genes. In support of this notion, our initial studies showed that four human carcinoma cell lines belong to the same complementation group for tumorigenic potential. In this investigation, we have extended these studies to six human soft tissue sarcoma cell lines. Our data showed that hybrid cells between a peripheral neuroepithelioma (PNET) cell line and normal human fibroblasts or HeLa cells were nontumorigenic. However, hybrid cells between the PNET cell line and five other soft tissue sarcoma cell lines remained highly tumorigenic, suggesting at least one common genetic defect in the control of tumorigenic potential in these cells. To determine the location of this common tumor suppressor gene, we examined biochemical and molecular polymorphic markers in matched pairs of tumorigenic and nontumorigenic hybrid cells between the PNET cell line and a normal human fibroblast. The data showed that loss of the fibroblast-derived chromosome 17 correlated with the conversion from nontumorigenic to tumorigenic cells. Transfer of two different chromosome 17s containing a mutant form of the p53 gene into the PNET cell line caused suppression of tumorigenic potential, implying the presence of a second tumor suppressor gene on chromosome 17.

Functional evidence for a second tumor suppressor gene on human chromosome 17

The development and progression of human tumors often involves inactivation of tumor suppressor gene function. Observations that specific chromosome deletions correlate with distinct groups of cancer suggest that some types of tumors may share common defective tumor suppressor genes. In support of this notion, our initial studies showed that four human carcinoma cell lines belong to the same complementation group for tumorigenic potential. In this investigation, we have extended these studies to six human soft tissue sarcoma cell lines. Our data showed that hybrid cells between a peripheral neuroepithelioma (PNET) cell line and normal human fibroblasts or HeLa cells were nontumorigenic. However, hybrid cells between the PNET cell line and five other soft tissue sarcoma cell lines remained highly tumorigenic, suggesting at least one common genetic defect in the control of tumorigenic potential in these cells. To determine the location of this common tumor suppressor gene, we examined biochemical and molecular polymorphic markers in matched pairs of tumorigenic and nontumorigenic hybrid cells between the PNET cell line and a normal human fibroblast. The data showed that loss of the fibroblast-derived chromosome 17 correlated with the conversion from nontumorigenic to tumorigenic cells. Transfer of two different chromosome 17s containing a mutant form of the p53 gene into the PNET cell line caused suppression of tumorigenic potential, implying the presence of a second tumor suppressor gene on chromosome 17.

Absence of linkage to the ataxia telangiectasia locus in familial breast cancer

Heterozygotes for ataxia-telangiectasia (AT) are known to have an increased risk of breast cancer. The gene (or genes) responsible for almost all cases of AT has been localised to chromosome 11q by genetic linkage analysis. To examine the possibility that AT heterozygosity may account for a substantial proportion of familial breast cancer, we have typed five markers on chromosome 11q in 16 breast cancer families. We have found no evidence for linkage between breast cancer and chromosome 11q markers and conclude that the contribution of AT to familial breast cancer is likely to be minimal.

Search for a genetic event in monozygotic twins discordant for schizophrenia

When monozygotic twins are discordant for the diagnosis of schizophrenia, this discordance has been traditionally attributed to environmental factors acting upon a genome susceptible for the schizophrenia phenotype. The study presented here was designed to examine the occurrence of a genetic event, such as a postzygotic mitotic crossover, that could account for the discordance. Such a postzygotic event could affect cis-acting sequences and result in a phenotype of variable severity. We used molecular genetic methods to evaluate such an event with 94 microsatellite repeat polymorphic markers distributed on all autosomes and the X chromosome in five pairs of monozygotic twins discordant for schizophrenia. In this search, no genetic marker discordances were identified between the co-twins. The lack of a genetic difference may implicate nongenetic factors that are responsible in eliciting or suppressing the phenotype. However, the experiments performed in this study cannot eliminate the possibility that a tissue-specific mitotic crossover might have occurred in one of the discordant twins, which could not have been detected in our current study.

Analysis of a second family with hereditary non-chromaffin paragangliomas locates the underlying gene at the proximal region of chromosome 11q

The gene for autosomal, dominantly inherited, non-chromaffin paragangliomas has previously been mapped at 11q23-qter by linkage analysis of a single family. In the present study, we have used genetic markers from 11q for the analysis of two distantly related pedigrees with the same disorder. Linkage analysis and haplotyping indicate that the gene underlying the disorder in the present family is located on chromosome 11q proximal to the tyrosinase gene locus (11q14-q21). Closely linked markers are the human homologue of the murine INT2 protooncogene and the anonymous DNA marker D11S527. A maximum lod score of 5.4 (theta = 0.0) has been obtained for linkage between the disorder and the chromosomal region defined by these markers. The human INT2 gene can be regarded as a candidate for the disorder on the basis of its expression pattern during embryogenesis in the mouse. However, haplotype analysis indicates that this gene is probably not the predisposing genetic factor in the present family.

Loss of heterozygosity and amplification on chromosome 11q in human ovarian cancer

The 11q13 chromosomal region encodes oncogenes relevant to a variety of human cancers as well as a tumour suppressor gene implicated in multiple endocrine neoplasia type 1. In addition, high affinity folate receptor (FOLR1), which maps to 11q13.3-13.5, is expressed at an elevated level on the surface of over 80% of nonmucinous epithelial ovarian cancers. Further telomeric, 11q breakpoints are found in many cancers. We studied the involvement of 11q markers in ovarian cancer by looking for tumour-specific loss of heterozygosity (LOH), as well as amplification or rearrangements that might explain the overexpression of FOLR1. Twenty eight epithelial ovarian cancers, along with lymphocyte DNA from the same individual were used for Southern blotting with polymorphic probes from 11q. PCR primers from 11q23.3 were also used. The 11q13 band was amplified in four out of 28 cancers. The amplicon included the probe D11S146 as well as FGF3 (formerly INT2) and FOLR1 in one out of these four cases, thus crossing the bcl1 translocation breakpoint. LOH was seen in three out of 16 cases with FGF3 (11q13). A much higher frequency of LOH (8/12) was found at 11q23.3-qter, implying the presence of a tumour suppressor gene in this region.

A linkage study of schizophrenia with DNA markers from the long arm of chromosome 11

We report the results of a collaborative linkage study using 12 polymorphic markers (9 loci) from the long arm of chromosome 11, and 24 families multiply affected with schizophrenia and other closely related disorders. This region is of interest because several families have been reported in which balanced translocations involving 11q apparently co-segregate with psychotic illness. In addition, the dopamine D2 receptor, porphobilinogen deaminase, and tyrosinase genes map within the region studied and may be aetiologically involved in schizophrenia. We have primarily analysed genotypic data by the LOD score method using a range of single gene models. In order to minimize error due to mis-specification of genetic parameters we have analysed data from markers at candidate gene loci by the non-parametric extended sib-pair method in addition to the LOD score method. Our results suggest that most of the region can be excluded from containing a gene of major effect in the aetiology of this disease.

Localization of two genes for Usher syndrome type I to chromosome 11

The Usher syndromes (USH) are autosomal recessive diseases characterized by congenital sensorineural hearing loss and progressive pigmentary retinopathy. While relatively rare in the general population, collectively they account for approximately 6% of the congenitally deaf population. Usher syndrome type II (USH2) has been mapped to chromosome 1q (W. J. Kimberling, M. D. Weston, C. Möller, et al., 1990, Genomics 7: 245-249; R. A. Lewis, B. Otterud, D. Stauffer, et al., 1990, Genomics 7: 250-256), and one form of Usher syndrome type I (USH1) has been mapped to chromosome 14q (J. Kaplan, S. Gerber, D. Bonneau, J. Rozet, M. Briord, J. Dufier, A. Munnich, and J. Frezal, 1990. Cytogenet. Cell Genet. 58: 1988). These loci have been excluded as regions of USH genes in our data set, which is composed of 8 French-Acadian USH1 families and 11 British USH1 families. Both of these sets of families show linkage to loci on chromosome 11. Linkage analysis demonstrates locus heterogeneity between these sets of families, with the French-Acadian families showing linkage to D11S419 (Z = 4.20, theta = 0) and the British families showing linkage to D11S527 (Z = 6.03, theta = 0). Genetic heterogeneity of the data set was confirmed using HOMOG and the M test (log likelihood ratio > 10(5)). These results confirm the presence of two distinct USH1 loci on chromosome 11.

Linkage of Usher syndrome type I gene (USH1B) to the long arm of chromosome 11

Usher syndrome is the most commonly recognized cause of combined visual and hearing loss in technologically developed countries. There are several different types and all are inherited in an autosomal recessive manner. There may be as many as five different genes responsible for at least two closely related phenotypes. The nature of the gene defects is unknown, and positional cloning strategies are being employed to identify the genes. This is a report of the localization of one gene for Usher syndrome type I to chromosome 11q, probably distal to marker D11S527. Another USH1 gene had been previously localized to chromosome 14q, and this second localization establishes the existence of a new and independent locus for Usher syndrome.

The autosomal dominant familial exudative vitreoretinopathy locus maps on 11q and is closely linked to D11S533

Autosomal dominant familial exudative vitreoretinopathy (adFEVR) is a hereditary disorder characterized by the incomplete vascularization of the peripheral retina. The primary biochemical defect in adFEVR is unknown. The adFEVR locus has tentatively been assigned to 11q by linkage studies. We report the results of an extended multipoint linkage analysis of two families with adFEVR by using five markers (INT2, D11S533, D11S527, D11S35, and CD3D) from 11q13-q23. Pairwise linkage data obtained in the two families were rather similar and hence have not provided evidence for genetic heterogeneity. The highest complied two-point lod score (3.67, at a recombination fraction of .07) was obtained for the disease locus versus D11S533. Multipoint analyses showed that the adFEVR locus maps most likely, with a maximum location score of over 20, between D11S533/D11S527 and D11S35, at recombination rates of .147 and .104, respectively. Close linkage without recombination (maximum lod score 11.26) has been found between D11S533 and D11S527.

Assignment of a gene (NEMI) for autosomal dominant nemaline myopathy to chromosome I

Nemaline myopathy (NEM) is a neuromuscular disorder characterized by the presence, in skeletal muscle, of nemaline rods composed at least in part of alpha-actinin. A candidate gene and linkage approach was used to localize the gene (NEM1) for an autosomal dominant form (MIM 161800) in one large kindred with 10 living affected family members. Markers on chromosome 19 that were linked to the central core disease gene, a marker at the complement 3 locus, and a marker on chromosome 1 at the alpha-actinin locus exclude these three candidate genes. The family was fully informative for APOA2, which is localized to 1q21-q23. NEM1 was assigned to chromosome 1 by close linkage for APOA2, which is localized to 1q21-q23. NEM1 was assigned to chromosome 1 by close linkage to APOA2, with a lod score of 3.8 at a recombination fraction of 0. Recombinants with NGFB (1p13) and AT3 (1q23-25.1) indicate that NEM1 lies between 1p13 and 1q25.1. In total, 47 loci were investigated on chromosomes 1, 2, 4, 5, 7-11, 14, 16, 17, and 19, with no indications of significant linkage other than to markers on chromosome 1.