A susceptibility locus for bipolar affective disorder on chromosome 4q35.

Bipolar affective disorder (BAD) affects approximately 1% of the population and shows strong heritability. To identify potential BAD susceptibility loci, we undertook a 15-cM genome screen, using 214 microsatellite markers on the 35 most informative individuals of a large, statistically powerful pedigree. Data were analyzed by parametric two-point linkage methods under several diagnostic models. LOD scores >1.00 were obtained for 21 markers, with four of these >2.00 for at least one model. The remaining 52 individuals in the family were genotyped with these four markers, and LOD scores remained positive for three markers. A more intensive screen was undertaken in these regions, with the most positive results being obtained for chromosome 4q35. Using a dominant model of inheritance with 90% maximum age-specific penetrance and including bipolar I, II, schizoaffective/mania, and unipolar individuals as affected, we obtained a maximum two-point LOD score of 2.20 (theta = .15) at D4S1652 and a maximum three-point LOD score of 3.19 between D4S408 and D4S2924. Nonparametric analyses further supported the presence of a locus on chromosome 4q35. A maximum score of 2.62 (P=.01) was obtained between D4S1652 and D4S171 by use of the GENEHUNTER program, and a maximum score of 3.57 (P=.0002) was obtained at D4S2924 using the affected pedigree member method. Analysis of a further 10 pedigrees suggests the presence of this locus in at least one additional family, indicating a possible predisposing locus and not a pedigree-specific mutation. Our results suggest the presence of a novel BAD susceptibility locus on chromosome 4q35.     

Duplication of HRAS1, INS, and IGF2 is not a common event in Beckwith-Wiedemann syndrome

A few cases of Beckwith-Wiedemann syndrome (BWS) have in common a duplication of 11p15. Among the genes located in 11p15, c-Ha-ras 1 (HRAS1), insulin (INS), and insulin-like growth factor II (IGF2) may account for the clinical features and the increased risk for malignancy. Using eight 11p15 markers including HRAS1, INS and IGF2 we have studied eight sporadic and hereditary cases of BWS whether or not associated with a nephroblastoma. By gene dosage determination and family studies, we have shown the following: the eight patients examined had an apparent diploid representation of all of the eight markers studied, thus indicating that a microduplication of these markers or of the region characterized by these markers is not a common event in BWS; in a family with three affected sibs the genes for HRAS1 and INS/IGF2 did not cosegregate with BWS and therefore may not participate in the pathogenic processes here observed.     

The D4 dopamine receptor (DRD4) maps to distal 11p close to HRAS.

Dopaminergic pathophysiology is important in several psychiatric illnesses. The recently cloned D4 dopamine receptor gene (DRD4) shows considerable homology to the D2 and D3 dopamine receptors (DRD2 and DRD3); pharmacologically, its affinity for the atypical antipsychotic clozapine is much higher than that of these other dopamine receptors. Probe pB28 for this locus recognizes an informative HincII polymorphism. We typed this polymorphism on several large reference families (a total of about 271 individuals) to place DRD4 in the genetic linkage map. Pairwise linkage analysis (using ILINK) provided evidence for close linkage to the distal 11p loci tyrosine hydroxylase (TH) and the Harvey ras oncogene (HRAS). We used our version of LINKMAP adapted to run under distributed parallel processing (Linda-LINKMAP) for an analysis moving DRD4 across a fixed map with HRAS set 3.8 cM distal to TH. This localized DRD4 close to HRAS, with no crossovers observed between those loci and a maximum lod score of 19.9 (2 cM distal to HRAS). The one LOD unit support interval extends from about 1 cM proximal to HRAS to 8 cM distal to HRAS. Crossovers identified in one kindred place DRD4 distal to TH, providing further evidence for its location close to HRAS, making DRD4 one of the most telomeric of 11p markers. (This also places DRD4 in band 11p15.5.)     

BRCA1 maps proximal to D17S579 on chromosome 17q21 by genetic analysis

Previous studies have demonstrated linkage between early-onset breast cancer and ovarian cancer and genetic markers on chromosome 17q21. These markers define the location of a gene (BRCA1) which appears to be inherited as an autosomal dominant susceptibility allele. We analyzed five families with multiple affected individuals for evidence of linkage to the BRCA1 region. Two of the five families appear to be linked to BRCA1. One apparently linked family contains critical recombinants, suggesting that the gene is proximal to the marker D17S579 (Mfd188). These findings are consistent with the maximum-likelihood position estimated by the Breast Cancer Linkage Consortium and with recombination events detected in other linked families. Linkage analysis was greatly aided by PCR-based analysis of paraffin-embedded normal breast tissue from deceased family members, demonstrating the feasibility and importance of this approach. One of the two families with evidence of linkage between breast cancer and genetic markers flanking BRCA1 represents the first such family of African-American descent to be reported in detail.     

Mapping eight new polymorphisms in 11q13 in the vicinity of multiple endocrine neoplasia type 1: identification of a new distal recombinant

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder that predisposes affected individuals to neoplasms of the parathyroid glands, endocrine pancreas, anterior pituitary, and carcinoids. The MEN1 locus has been localized by family studies to 11q13, flanked by markers PGA and D11S97. Eight new polymorphisms located in three separate radiation-reduced somatic cell hybrid segregation groups were developed. The order of the new markers, within the context of previously described loci, was determined by linkage analysis on the Venezuelan reference pedigree. Four independent MEN1 families, consisting of 57 affected individuals, and 70 individuals at-risk for the disease were genotyped. Sixteen people inherited a chromosome that shows recombination between a linked marker and the disease. The nearest proximal and distal markers that show recombination with the disease are D11S822 and GSTP1, respectively, thereby narrowing the candidate region for MEN1 by 50% on the distal side. Using these loci in haplotype analysis, an accurate presymptomatic molecular diagnostic test has been developed. These new markers in 11q13 linked to MEN1 also facilitate the genetic and physical characterization of this very gene-rich region.     

Tyrosine hydroxylase maps to the short arm of chromosome 11 proximal to the insulin and HRAS1 loci

Tyrosine hydroxylase (TH) is the rate-limiting enzyme for catecholamine biosynthesis and a candidate gene for manic-depressive illness. The TH locus was typed for a BglII RFLP using a cDNA clone Ty7 in four large kindreds. Pairwise analyses and multipoint analyses were carried out to map the TH locus more precisely in the region of the linked markers: D11S12, INS, and HRAS1 on 11p. Results confirm the close linkage between TH with these previously mapped markers and support a most likely ordering which places TH on the side of INS where the centromere lies.     

Exclusion of linkage between hypokalemic periodic paralysis (HOKPP) and three candidate loci.

Hypokalemic periodic paralysis (HOKPP) is an autosomal dominant neuromuscular disorder characterized by flaccid paralysis accompanied by lowered serum potassium levels. We have tested polymorphic markers linked to the adult skeletal muscle sodium channel (SCN4A) locus at 17q23-q25, the T-cell receptor beta (TCRB) locus at 7q35, and the H-Ras cellular proton-cogene locus (HRAS) at 11p15.5 for linkage with the affected phenotype in a single multigenerational pedigree. No evidence for genetic linkage to HOKPP was found at any of the candidate loci.     

Localization of the mutation in an extended family with Charcot-Marie-Tooth neuropathy (HMSN I).

Hereditary motor and sensory neuropathy type I (HMSN I) or Charcot-Marie-Tooth (CMT) disease is an autosomal dominant peripheral neuropathy. In some CMT families linkage has been reported with either the Duffy blood group or the APOA2 gene, both located on chromosome 1q. More recently, linkage has been found in six CMT families with two chromosome 17p markers. We extensively analyzed a multi-generation Charcot-Marie-Tooth family by using molecular genetic techniques in order to localize the CMT gene defect. First, we constructed a continuous linkage group of 11 chromosome 1 markers and definitely excluded chromosome 1 as the site of mutation. Second, we analyzed the family for linkage with chromosome 17. The two-point lod scores obtained with D17S58 and D17S71 proved that this Charcot-Marie-Tooth family is linked to chromosome 17. Moreover, multipoint linkage results indicated that the mutation is most likely located on the chromosome 17p arm, distal of D17S71.     

Evidence for locus heterogeneity in human autosomal dominant split hand/split foot malformation.

Split hand/split foot (SHSF; also known as ectrodactyly) is a human developmental disorder characterized by missing central digits and other distal limb malformations. An association between SHSF and cytogenetically visible rearrangements of chromosome 7 at bands q21-q22 provides compelling evidence for the location of a causative gene at this location, and the locus has been designated SHFD1. In the present study, marker loci were localized to the SHFD1 critical region through the analysis of somatic cell hybrids derived from individuals with SHSF and cytogenetic abnormalities involving the 7q21-q22 region. Combined genetic and physical data suggest that the order of markers in the SHFD1 critical region is cen-D7S492-D7S527-(D7S479-D7S491)-SHFD1-++ +D7S554-D7S518-qter. Dinucleotide repeat polymorphisms at three of these loci were used to test for linkage of SHSF to this region in a large pedigree that demonstrates autosomal dominant SHSF. Evidence against linkage of the SHSF gene to 7q21-q22 was obtained in this pedigree. Therefore, combined molecular and genetic data provide evidence for locus heterogeneity in autosomal dominant SHSF. We propose the name SHSF2 for this second locus.     

Mitotic deletions of 11p15.5 in two different tumors indicate that the CALCA locus is distal to the PTH locus

We have compared the constitutional and tumor genotypes in two patients with Wilms tumor and adrenocortical carcinoma. The allelic distribution of chromosome 11-specific markers spanning chromosome 11 from pter to qter (HRAS1-HBB-[CALCA/PTH]-FSHB-CAT-APOA1) and an approach combining RFLP analysis and gene copy number determination showed that a mitotic deletion had occurred in both tumors. The loss of one copy of the gene for alpha-calcitonin-gene-related polypeptide (CALCA), together with that of a more distal marker (HRAS1 or HBB), indicates that CALCA is distal to the gene for parathyroid hormone (PTH), which was not deleted in either tumor. These results suggest that mitotic deletion mapping may be as useful as meiotic deletion or recombination mapping in ordering closely linked markers, such as CALCA and PTH, for which other approaches, including physical mapping and multipoint linkage analysis, have failed to accurately identify the gene order.     

Multipoint linkage analysis of the short arm of chromosome 11 in non-insulin dependent diabetes including maturity onset diabetes of youth

Summary Members of three families with maturity onset diabetes of youth (MODY) and seven with common type 2 diabetes were typed for six DNA markers (H-RAS, INS, HBBC, PTH, CALC1, CAT) on the short arm of chromosome 11. Using conventional pairwise linkage analysis, close linkage in the MODY families was excluded for all six markers. By multipoint analysis and a genetic map of the short arm of chromosome 11, MODY was excluded from a region of at least 35 and up to 60 centiMorgans (cM) on the short arm of chromosome 11. Multipoint analysis in the type 2 families also excludes linkage to the INS, H-RAS region of at least 3 and up to 30 cM. This study using multipoint linkage analysis in non-insulin dependent diabetes provides strong evidence against a role for mutations in or around the insulin gene in the causation of MODY or type 2 diabetes in the families studied.     

Diagnosis of susceptibility to malignant hyperthermia with flanking DNA markers.

OBJECTIVE--To define the region on human chromosome 19 carrying the gene for malignant hyperthermia susceptibility and to evaluate the use of flanking DNA markers in diagnosing susceptibility. DESIGN--Prospective molecular genetic linkage studies in a large malignant hyperthermia pedigree. SETTING--Irish malignant hyperthermia testing centre. SUBJECTS--A large Irish malignant hyperthermia pedigree. MAIN OUTCOME MEASURES--Routine diagnosis of susceptibility to malignant hyperthermia with in vitro contracture test on muscle biopsy specimens and genetic linkage between susceptibility and polymorphic DNA markers in a malignant hyperthermia family. RESULTS--Genetic typing of polymorphic DNA markers in a large Irish malignant hyperthermia pedigree generated a lod score of greater than 3 for the marker D19S9 and showed that the gene for susceptibility is flanked by the markers D19S9 and D19S16. These tightly linked flanking markers allowed non-invasive presymptomatic diagnosis of susceptibility in five untested subjects in the large pedigree with an accuracy of greater than 99.7%. CONCLUSIONS--DNA markers flanking the gene for susceptibility to malignant hyperthermia can be used with high accuracy to diagnose susceptibility in subjects in large known malignant hyperthermia pedigrees and may replace the previous in vitro contracture test for diagnosing this inherited disorder in large families with malignant hyperthermia.     

Linkage of Paget Disease of Bone to a Novel Region on Human Chromosome 18q23

Paget disease of bone (PDB) is characterized by increased osteoclast activity and localized abnormal bone remodeling. PDB has a significant genetic component, with evidence of linkage to chromosomes 6p21.3 (PDB1) and 18q21-22 (PDB2) in some pedigrees. There is evidence of genetic heterogeneity, with other pedigrees showing negative linkage to these regions. TNFRSF11A, a gene that is essential for osteoclast formation and that encodes receptor activator of nuclear factor-kappa B (RANK), has been mapped to the PDB2 region. TNFRSF11A mutations that segregate in pedigrees with either familial expansile osteolysis or familial PDB have been identified; however, linkage studies and mutation screening have excluded the involvement of RANK in the majority of patients with PDB. We have excluded linkage, both to PDB1 and to PDB2, in a large multigenerational pedigree with multiple family members affected by PDB. We have conducted a genomewide scan of this pedigree, followed by fine mapping and multipoint analysis in regions of interest. The peak two-point LOD scores from the genomewide scan were 2.75, at D7S507, and 1.76, at D18S70. Multipoint and haplotype analysis of markers flanking D7S507 did not support linkage to this region. Haplotype analysis of markers flanking D18S70 demonstrated a haplotype segregating with PDB in a large subpedigree. This subpedigree had a significantly lower age at diagnosis than the rest of the pedigree (51.2+/-8.5 vs. 64.2+/-9.7 years; P=.0012). Linkage analysis of this subpedigree demonstrated a peak two-point LOD score of 4.23, at marker D18S1390 (straight theta=0), and a peak multipoint LOD score of 4.71, at marker D18S70. Our data are consistent with genetic heterogeneity within the pedigree and indicate that 18q23 harbors a novel susceptibility gene for PDB.     

Genetic linkage mapping of multiple epiphyseal dysplasia to the pericentromeric region of chromosome 19.

Multiple epiphyseal dysplasia (MED) is an inherited chondrodystrophy that results in deformity of articular surfaces and in subsequent degenerative joint disease. The disease is inherited as an autosomal dominant trait with high penetrance. An MED mutation has been mapped by genetic linkage analysis of DNA polymorphisms in a single large pedigree. Close linkage of MED to 130 tested chromosomal markers was ruled out by discordant inheritance patterns. However, strong evidence for linkage of MED to markers in the pericentromeric region of chromosome 19 was obtained. The most closely linked marker was D19S215, with a maximum LOD score of 6.37 at theta = .05. Multipoint linkage analysis indicated that MED is located between D19S212 and D19S215, a map interval of 1.7 cM. Discovery of the map location of MED in this family will facilitate identification of the mutant gene. The closely linked DNA polymorphisms will also provide the means to determine whether other inherited chondrodystrophies have underlying defects in the same gene.     

Localization of the muscular dystrophy AM locus using a chicken linkage map constructed with the Kobe University resource family

A chicken linkage map, constructed with the Kobe University (KU) resource family, was used to locate the genetic locus for muscular dystrophy of abnormal muscle type (AM). The KU resource family is a backcross pedigree with 55 offspring produced from the mating of a White Leghorn F-line (WL-F) male and a hybrid female produced from a cross between the WL-F male and a female of the Fayoumi OPN line who was homozygous for the AM gene. In total, 872 loci were genotyped on the pedigree; 749 (86%) were informative and mapped to 38 linkage groups. These informative loci included 649 AFLPs, 93 MS, three functional genes, the AM locus, sex phenotype, and two red blood cell loci. The remaining 123 markers were unlinked. Nineteen of the 38 KU linkage groups were assigned to macrochromosomes 1-8 and 11 microchromosomes including chromosome W, while 19 linkage groups were unassigned. The total map was 3569 cM in length, with an average marker interval of 4.8 cM. The AM locus was mapped 130 cM from the distal end of chromosome 2q.     

Linkage analysis of von Recklinghausen neurofibromatosis to DNA markers on chromosome 17

Several recent studies indicate that the von Recklinghausen neurofibromatosis (NF1) gene is located near the centromere of chromosome 17 in some families. However, variable expressivity and a very high mutation rate suggest that defects at several different loci could result in phenotypes categorized as NF1. In order to assess this possibility and to map the NF1 gene more precisely, we have used two polymorphic DNA markers from chromosome 17 to screen several pedigrees for linkage to NF1. We ascertained a large Caucasian pedigree (33 individuals sampled, 17 NF1 affected) as well as eight smaller pedigrees and nuclear families (50 individuals sampled, 30 NF1 affected). Here, we report strong evidence of linkage of NF1 to the centromeric marker D17Z1 (maximum lod = 4.42) and a weaker suggestion of linkage to the ERBA1 oncogene (maximum lod = 0.57), both at a recombination fraction of zero. Since obligate cross-overs with NF1 were not observed for either marker in any of the informative families tested, the possibility of NF1 locus heterogeneity is not supported.     

Linkage analysis of autosomal dominant atrio ventricular canal defects: exclusion of chromosome 21

The association between trisomy 21 and a high incidence of atrioventricular canal defects (AVCDs) indicates that a locus on chromosome 21 is involved in this congenital heart defect. We have investigated whether a genetic locus on chromosome 21 is also involved in familial nonsyndromic AVCDs. Short tandem repeat polymorphisms (STRPs) from chromosome 21 were used for linkage analysis of a family having multiple members affected with AVCDs. In this family, the gene for AVCDs is transmitted as an autosomal dominant with incomplete penetrance. The affected family members are nonsyndromic and have normal karyotypes. Two-point and multipoint linkage analyses produced significantly negative LOD scores for all informative markers. A comparison of the overlapping exclusion distances obtained for each marker at LOD equal -2.0 with the 1000:1 consensus genetic map of the markers, excludes chromosome 21 as the genetic location for AVCDs in this family. The exclusion of chromosome 21 indicates that another gene, not located on chromosome 21, is involved in atrioventricular canal defect formation.     

A second locus for familial high myopia maps to chromosome 12q.

Myopia, or nearsightedness, is the most common eye disorder worldwide. "Pathologic" high myopia, or myopia of <=-6.00 diopters, predisposes individuals to retinal detachment, macular degeneration, cataract, or glaucoma. A locus for autosomal dominant pathologic high myopia has been mapped to 18p11.31. We now report significant linkage of high myopia to a second locus at the 12q21-23 region in a large German/Italian family. The family had no clinical evidence of connective-tissue abnormalities or glaucoma. The average age at diagnosis of myopia was 5.9 years. The average spherical-component refractive error for the affected individuals was -9.47 diopters. Markers flanking or intragenic to the genes for the 18p locus, Stickler syndromes type I and II (12q13.1-q13.3 and 6p21.3), Marfan syndrome (15q21.1), and juvenile glaucoma (chromosome 1q21-q31) showed no linkage to the myopia in this family. The maximum LOD score with two-point linkage analysis in this pedigree was 3.85 at a recombination fraction of .0010, for markers D12S1706 and D12S327. Recombination events identified markers D12S1684 and D12S1605 as flanking markers that define a 30.1-cM interval on chromosome 12q21-23, for the second myopia gene. These results confirm genetic heterogeneity of myopia. The identification of this gene may provide insight into the pathophysiology of myopia and eye development.     

一个先天性眼球震颤家系致病基因的初步定位

为确定一个X染色体显性遗传先天性眼球震颤家系的致病基因与X染色体的连锁关系, 选用X染色体上的DXS1214、DXS1068、DXS993、DXS8035、DXS1047、DXS8033、DXS1192和DXS1232共8个微卫星DNA标记对该家系进行基因扫描与基因分型,并利用LINKAGE等软件包对基因分型结果进行分析,探讨该家系致病基因与X染色体的连锁关系。 两点连锁分析时X染色体短臂4个基因座最大LOD值均小于-1,不支持与该家系致病基因连锁; X染色体长臂4个基因座中最大LOD值达到2,提示存在较大的连锁可能性。该家系的致病基因可初步定位于X染色体长臂,且提示Xq26-Xq28区间附近可能是先天性眼球震颤一个共同的致病基因座,但区间范围仍较大,仍须进一步选择合适的微卫星标记进行精确的定位以缩小候选基因的筛查范围。Abstract： To investigate the relationship between X chromosome and obligatory gene of a pedigree with congenital nystagmus,we used the following markers: DXS1214、DXS1068、DXS993、DXS8035、DXS1047、DXS8033、DXS1192 and DXS1232.Genome screening and genotyping were conducted in this pedigree of congenital nystagmus, and linkage analysis by LINKAGE package was used to determine the potential location. The linkage was not found on the Xp ( All LOD score <-1) but on Xq (the maximum LOD score=2). The related gene of this pedigree was located on the long arm of X chromosome. We demonstrate that Xq26-Xq28 is a common locus for CMN. It bring us closer to the identification of a gene responsible for X-linked CMN.