Bovine IgG2a antibodies to Haemophilus somnus and allotype expression

AIMS/BACKGROUND: To characterise clinically a large kindred segregating retinitis pigmentosa and sensorineural hearing impairment in an autosomal dominant pattern and perform genetic linkage studies in this family. Extensive linkage analysis in this family had previously excluded the majority of loci shown to be involved in the aetiologies of RP, some other forms of inherited retinal degeneration, and inherited deafness. METHODS: Members of the family were subjected to detailed ophthalmic and audiological assessment. In addition, some family members underwent skeletal muscle biopsy, electromyography, and electrocardiography. Linkage analysis using anonymous microsatellite markers was performed on DNA samples from all living members of the pedigree. RESULTS: Patients in this kindred have a retinopathy typical of retinitis pigmentosa in addition to a hearing impairment. Those members of the pedigree examined demonstrated a subclinical myopathy, as evidence by abnormal skeletal muscle histology, electromyography, and electrocardiography. LOD scores of Zmax = 3.75 (theta = 0.10), Zmax = 3.41 (theta = 0.10), and Zmax = 3.25 (theta = 0.15) respectively were obtained with the markers D9S118, D9S121, and ASS, located on chromosome 9q34-qter, suggesting that the causative gene in this family may lie on the long arm (q) of chromosome 9. CONCLUSIONS: These data indicate that the gene responsible for the phenotype in this kindred is located on chromosome 9 q. These data, together with evidence that a murine deafness gene is located in a syntenic area of the mouse genome, should direct the research community to consider this area as a candidate region for retinopathy and/or deafness genes.     

Genetic mapping of autosomal dominant primary open-angle glaucoma (POAG) in Sardinia

Primary open-angle glaucoma (POAG) can be subdivided into two groups according to age of onset: (1) the more prevalent middle to late-age-onset chronic open-angle glaucoma (COAG) diagnosed after age 40, and (2) the less common form, juvenile open-angle glaucoma (JOAG), which occurs between 3 years of age and early adulthood. Susceptibility to either COAG or JOAG has been found to be inherited. The discovery of several genetic markers spanning the region 1q21-q24 in genetic linkage with autosomal dominant juvenile open-angle glaucoma (adJOAG) represents a major breakthrough towards the localisation of gene(s) responsible for the disease. Linkage analysis is a powerful means of distinguishing disease loci in large families with dominant disease. However the size of the group of families may represent a crucial factor for the linkage analysis. Sardinia is an island with a relatively isolated ethnic group showing a relatively high frequency of ad JOAG and COAG (Fossarello et al, 1994) and it is genetically more homogeneous than most Western populations. Therefore it represents an ideal ethnic group to search for linkage. We identified 18 families affected by POAG in which the disease appears to be inherited as autosomic dominant trait. In all families but two, occurrence of both JOAG and COAG in the same kindred was observed. Identification of adPOAG locus was performed by linkage analysis using 9 microsatellite markers spanning the region 1q21-q24. No significant linkage was observed. Our findings provide further evidence for genetic heterogeneity in autosomal dominant primary open angle glaucoma, even in a geographic area where a relatively homogeneous genetic background exists.     

An ancestral core haplotype defines the critical region harbouring the North Carolina macular dystrophy gene (MCDR1)

Autosomal dominant North Carolina macular dystrophy (NCMD) or central areolar pigment epithelial dystrophy (CAPED) is an allelic disorder that maps to an approximately 7.2 cM interval between DNA markers at D6S424 and D6S1671 on 6q14-q16.2. The further refinement of the disease locus has been hindered by the lack of additional recombination events involving the critical region. In this study, we have identified three multigeneration families of German descent who express the NCMD phenotype. Genotyping was carried out with a series of markers spanning approximately 53 cM around the NCMD locus, MCDR1. Genetic linkage between the markers and the disease phenotype in each of the families could be shown. Disease associated haplotypes were constructed and provide evidence for an ancestral founder for the German NCMD families. This haplotype analysis suggests that a 4.0 cM interval flanked by markers at D6S249 and D6S475 harbours the gene causing NCMD, facilitating further positional cloning approaches.     

Linkage of a gene causing high bone mass to human chromosome 11 (11q12-13)

The purpose of this paper is to report the linkage of a genetic locus (designated "HBM") in the human genome to a phenotype of very high spinal bone density, using a single extended pedigree. We measured spinal bone-mineral density, spinal Z(BMD), and collected blood from 22 members of this kindred. DNA was genotyped on an Applied Biosystems model 377 (ABI PRISM Linkage Mapping Sets; Perkin Elmer Applied Biosystems), by use of fluorescence-based marker sets that included 345 markers. Both two-point and multipoint linkage analyses were performed, by use of affected/unaffected and quantitative-trait models. Spinal Z(BMD) for affected individuals (N = 12) of the kindred was 5.54 +/- 1.40; and for unaffected individuals (N = 16) it was 0.41 +/- 0.81. The trait was present in affected individuals 18-86 years of age, suggesting that HBM influences peak bone mass. The only region of linkage was to a series of markers on chromosome 11 (11q12-13). The highest LOD score (5.21) obtained in two-point analysis, when a quantitative-trait model was used, was at D11S987. Multipoint analysis using a quantitative-trait model confirmed the linkage, with a LOD score of 5.74 near marker D11S987. HBM demonstrates the utility of spinal Z(BMD) as a quantitative bone phenotype that can be used for linkage analysis. Osteoporosis pseudoglioma syndrome also has been mapped to this region of chromosome 11. Identification of the causal gene for both traits will be required for determination of whether a single gene with different alleles that determine a wide range of peak bone densities exists in this region.     

Genome-wide search for asthma susceptibility loci in a founder population. The Collaborative Study on the Genetics of Asthma

Founder populations offer many advantages for mapping genetic traits, particularly complex traits that are likely to be genetically heterogeneous. To identify genes that influence asthma and asthma-associated phenotypes, we conducted a genome-wide screen in the Hutterites, a religious isolate of European ancestry. A primary sample of 361 individuals and a replication sample of 292 individuals were evaluated for asthma phenotypes according to a standardized protocol. A genome-wide screen has been completed using 292 autosomal and three X-Y pseudoautosomal markers. Using the semi-parametric likelihood ratio chi2 test and the transmission-disequilibrium test, we identified 12 markers in 10 regions that showed possible linkage to asthma or an associated phenotype (likelihood ratio P < 0.01). Markers in four regions (5q23-31, 12q15-24.1, 19q13 and 21q21) showed possible linkage in both the primary and replication samples and have also shown linkage to asthma phenotypes in other samples; two adjacent markers in one additional region (3p24.2-22) showing possible linkage is reported for the first time in the Hutterites. The results suggest that even in founder populations with a relatively small number of independent genomes, susceptibility alleles at many loci may influence asthma phenotypes and that these susceptibility alleles are likely to be common polymorphisms in the population.     

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.     

The gene for progressive myoclonus epilepsy of the Lafora type maps to chromosome 6q

Progressive myoclonus epilepsy of the Lafora type (Lafora's disease) is an autosomal recessive disease characterized by epilepsy, myoclonus, dementia, and periodic acid-Schiff-positive intracellular inclusion bodies. The inclusion deposits consist of branched polysaccharides (polyglucosans) but the responsible biochemical defect has not been identified. Onset is during late childhood or adolescence and the disease leads to a fatal outcome within a decade of first symptoms. We studied nine families in which Lafora's disease had been proven by biopsy in at least one member. In order to locate the responsible gene, we screened the human genome with microsatellite markers spaced an average of 13 cM. We used linkage analysis in all nine families and homozygosity mapping in four consanguineous families to define the Lafora's disease gene region. Two point linkage analysis resulted in a total peak lod score of 10.54 for marker D6S311. Six additional chromosome 6q23-25 microsatellites yielded lod scores ranging from 5.92 to 9.60 at theta m = f = 0. An extended pedigree with five affected members independently proved linkage with peak lod scores over 3.8 at theta m = f = 0 for D6S292, D6S403, and D6S311. The multipoint one-lod-unit support interval covered a 2.5 cM region surrounding D6S403. Homozygosity mapping defined a 17 cM region in chromosome 6q23-25 flanked by D6S292 and D6S420 that contains the Lafora's disease gene.     

Facing the era of minimally invasive coronary grafting: current results of conventional bypass grafting for single-vessel disease

Linkage of asthma and high total serum IgE levels to chromosome 12q15-q24.1 has been recently described. To evaluate this region further in regard to total IgE responsiveness, we genotyped 52 unrelated German children with persistently "high" total serum IgE (selected from a noninterventional prospective multicenter cohort study) and their parents. We carefully defined a most extreme IgE phenotype and analyzed it as a dichotomous trait. We tested for linkage between high total IgE concentrations and nine polymorphic microsatellite markers on chromosome 12q15-q24.1 using the transmission/disequilibrium test. Evidence for linkage and allelic association for high total IgE was observed for four markers in this region. This study demonstrates the value of using extreme phenotypes in genetic analysis of a complex quantitative trait.     

The coming of age of the Delta Dental Plan of Massachusetts, 1966-1996

The finding by Straub et al. (1995) on 6p22-24 is one of the strongest reports so far in psychiatric genetics. It appears to be substantially replicated by Schwab and collaborators (1995; 1997), and to a lesser extent by Moises et al. (1995). Still, this data does not fulfill the criteria of Lander and Kruglyak (1995) for a confirmed finding in complex disease. There are a number of data sets that do not appear to show linkage. Further genotyping work needs to be done in this area and additional markers in the area would be helpful in the available data sets. It should be noted that the Straub and Kendler dataset (Straub et al., 1995, 1997; Kendler et al., 1996), with 754 affecteds, is substantially larger than any other, and should be weighted concomitant with this. Still, additional data will be necessary before the finding may be firmly accepted. Candidate gene studies have started in this area. The SCA locus is promising on theoretical grounds, but has been only weakly positive in two studies so far. The HLA locus is interesting in relation to autoimmune theories of schizophrenia. There is a long history of HLA studies in schizophrenia with mixed results. HLA is located centromeric to the major positive region identified by Straub, but perhaps not too far to be considered a candidate region. Family-based association studies will be necessary to clarify whether there is a true association in this area. The location identified by Cao et al. (1997) on 6q is promising. Straub and Kendler's data set has been partially tested in this region with negative results. Gejman and co-workers (1997) have recently reported additional positive data in this region from Levinson and Mowry. Additional studies in this area are indicated.     

Evidence for a microdeletion in 1q32-41 involving the gene responsible for Van der Woude syndrome

Van der Woude syndrome (VWS) is an autosomal dominant craniofacial disorder representing the most frequent form of syndromic cleft lip and palate. Other characteristic features are pits of the lower lip and hypodontia. The gene shows high penetrance and seems to play an important role in orofacial development determined by the tissues involved and their formation during different periods of craniofacial development. Although most individuals affected with VWS show Mendelian inheritance, one patient with a macroscopic deletion and multiple malformations including two primary features of VWS has been described in the literature, indicating hemizygosity is compatible with the VWS phenotype. We report here the allelic loss of a stable and highly polymorphic microsatellite (D1S205) from region 1q32-41 in one family with VWS. Classical manifestations of the syndrome superimposed on developmental delay in all affected members of the family, the absence of cytogenetic abnormalities, the reproducibility of the null allele with a new set of primers and close linkage of this marker in a total of 15 VWS families provide strong evidence that the first microdeletion involving the gene for VWS has been identified. Assuming 1 Mb of DNA per cM of genetic distance, the upper bound of the deletion size would amount to 4 Mb.     

The diastrophic dysplasia gene encodes a novel sulfate transporter: positional cloning by fine-structure linkage disequilibrium mapping

Diastrophic dysplasia (DTD) is a well-characterized autosomal recessive osteochondrodysplasia with clinical features including dwarfism, spinal deformation, and specific joint abnormalities. The disease occurs in most populations, but is particularly prevalent in Finland owing to an apparent founder effect. DTD maps to distal chromosome 5q and, based on linkage disequilibrium studies in the Finnish population, we had previously predicted that the DTD gene should lie about 64 kb away from the CSF1R locus. Here, we report the positional cloning of the DTD gene by fine-structure linkage disequilibrium mapping. The gene lies in the predicted location, approximately 70 kb proximal to CSF1R, and encodes a novel sulfate transporter. Impaired function of its product is likely to lead to undersulfation of proteoglycans in cartilage matrix and thereby to cause the clinical phenotype of the disease. These results demonstrate the power of linkage disequilibrium mapping in isolated populations for positional cloning.     

What significance to genotype changes have in diagnosis of malignant hyperthermia?

Malignant hyperthermia (MH) is a potentially fatal, inherited pharmacogenetic disorder characterised by a dysfunction of the intracellular calcium regulation. Linkage to DNA markers from the chromosome 19q12-13.2 region and the MHS-phenotype (MH susceptible) has been shown in about 50% of families with a history of MH. The ryanodine receptor gene encoding the human skeletal muscle ryanodine receptor has been localised to the chromosome 19q13.1-13.2 region. The ryanodine receptor, which is an intracellular calcium release channel, has been proposed to be one of the candidate structures for the MH defect. At present, eight different single point mutations have been identified in the human skeletal muscle ryanodine receptor gene in families with disposition to MH. The incidence of the various mutations has been reported as 2-10% each. A combination of different mutations within one pedigree has not been demonstrated. A few years ago, linkage of the MHS-phenotype to DNA markers from the chromosome 17q11.2-24 region was published by an American group. However, this observation has not been confirmed in any of the several European families susceptible to MH. Genes encoding for subunits of the dihydropyridine receptor and the sodium channel of the human skeletal muscle have been found to be located in the chromosome 17q11.2-24 region which, in fact, could be additional candidates for the MH defect. The dihydropyridine receptor is linked to the ryanodine receptor and involved in the calcium regulation of skeletal muscle. Very recent studies have shown linkage to DNA markers from chromosome 7q- and chromosome 3q13.1 regions and the MHS phenotype in two distinct families with history of MH. However, the relevance of this observation is so far unknown. At present, unambiguous preoperative screening of MH disposition based on molecular genetic characteristics is not available because of the enormous heterogeneity of the human MH syndrome. Thus, the halothane-caffeine in-vitro contracture test according to the standard protocol of the "European MH Group" must be performed in order to discover MH susceptibility.     

Benign recurrent intrahepatic cholestasis (BRIC): evidence of genetic heterogeneity and delimitation of the BRIC locus to a 7-cM interval between D18S69 and D18S64

Benign recurrent intrahepatic cholestasis (BRIC) is an autosomal recessive liver disease characterized by multiple episodes of cholestasis without progression to chronic liver disease. The gene was previously assigned to chromosome 18q21, using a shared segment analysis in three families from the Netherlands. In the present study we report the linkage analysis of an expanded sample of 14 BRIC families, using 15 microsatellite markers from the 18q21 region. Obligate recombinants in two families place the gene in a 7-cM interval, between markers D18S69 and D18S64. All intervening markers had significant LOD scores in two-point linkage analysis. Moreover, we identified one family in which the BRIC gene seems to be unlinked to the 18q21 region, or that represents incomplete penetrance of the BRIC genotype.     

Loss of LKB1 kinase activity in Peutz-Jeghers syndrome, and evidence for allelic and locus heterogeneity

Peutz-Jeghers syndrome (PJS) is an autosomal dominant disease characterized by mucocutaneous pigmentation and hamartomatous polyps. There is an increased risk of benign and malignant tumors in the gastrointestinal tract and in extraintestinal tissues. One PJS locus has been mapped to chromosome 19p13.3; a second locus is suspected on chromosome 19q13.4 in a minority of families. The PJS gene on 19p13.3 has recently been cloned, and it encodes the serine/threonine kinase LKB1. The gene, which is ubiquitously expressed, is composed of 10 exons spanning 23 kb. Several LKB1 mutations have been reported in heterozygosity in PJS patients. In this study, we screened for LKB1 mutations in nine PJS families of American, Spanish, Portuguese, French, Turkish, and Indian origin and detected seven novel mutations. These included two frameshift mutations, one four-amino-acid deletion, two amino-acid substitutions, and two splicing errors. Expression of mutant LKB1 proteins (K78I, D176N, W308C, and L67P) and assessment of their autophosphorylation activity revealed a loss of the kinase activity in all of these mutants. These results provide direct evidence that the elimination of the kinase activity of LKB1 is probably responsible for the development of the PJS phenotypes. In two Indian families, we failed to detect any LKB1 mutation; in one of these families, we previously had detected linkage to markers on 19q13.3-4, which suggests locus heterogeneity of PJS. The elucidation of the molecular etiology of PJS and the positional cloning of the second potential PJS gene will further elucidate the involvement of kinases/phosphatases in the development of cancer-predisposing syndromes.     

An extended panel of hamster-human hybrids for chromosome 2q

A hamster-human hybrid containing only the q arm of chromosome 2 has been used to construct a panel of hybrids bearing reduced regions of chromosome 2 using the technique of irradiation fusion gene transfer. The human chromosome 2 carried the Ecogpt gene and all hybrids were selected using this marker. The integrated Ecogpt gene was localized to the region 2q33-34, resulting in the selective retention of this region in the hybrids. These data were combined with another previously constructed panel of hybrids containing regions of 2q, which were enriched for the region 2q36-37. The combined hybrid panel is useful for the mapping of new markers to defined regions of chromosome 2 and for the cloning of genes located on 2q by a positional strategy.     

Human PEG1/MEST, an imprinted gene on chromosome 7

The mouse Peg1/Mest gene is an imprinted gene that is expressed particularly in mesodermal tissues in early embryonic stages. It was the most abundant imprinted gene among eight paternally expressed genes (Peg 1-8) isolated by a subtraction-hybridization method from a mouse embryonal cDNA library. It has been mapped to proximal mouse chromosome 6, maternal duplication of which causes early embryonic lethality. The human chromosomal region that shares syntenic homology with this is 7q21-qter, and human maternal uniparental disomy 7 (UPD 7) causes apparent growth deficiency and slight morphological abnormalities. Therefore, at least one paternally expressed imprinted gene seems to be present in this region. In this report, we demonstrate that human PEG1/MEST is an imprinted gene expressed from a paternal allele and located on chromosome 7q31-34, near D7S649. It is the first imprinted gene mapped to human chromosome 7 and a candidate for a gene responsible for primordial growth retardation including Silver-Russell syndrome (SRS).     

Tn10 transposition via a DNA hairpin intermediate

Nijmegen breakage syndrome (NBS) is a rare autosomal recessive disorder characterized by microcephaly, a birdlike face, growth retardation, immunodeficiency, lack of secondary sex characteristics in females, and increased incidence of lymphoid cancers. NBS cells display a phenotype similar to that of cells from ataxia-telangiectasia patients, including chromosomal instability, radiation sensitivity, and aberrant cell-cycle-checkpoint control following exposure to ionizing radiation. A recent study reported genetic linkage of NBS to human chromosome 8q21, with strong linkage disequilibrium detected at marker D8S1811 in eastern European NBS families. We collected a geographically diverse group of NBS families and tested them for linkage, using an expanded panel of markers at 8q21. In this article, we report linkage of NBS to 8q21 in 6/7 of these families, with a maximum LOD score of 3.58. Significant linkage disequilibrium was detected for 8/13 markers tested in the 8q21 region, including D8S1811. In order to further localize the gene for NBS, we generated a radiation-hybrid map of markers at 8q21 and constructed haplotypes based on this map. Examination of disease haplotypes segregating in 11 NBS pedigrees revealed recombination events that place the NBS gene between D8S1757 and D8S270. A common founder haplotype was present on 15/18 disease chromosomes from 9/11 NBS families. Inferred (ancestral) recombination events involving this common haplotype suggest that NBS can be localized further, to an interval flanked by markers D8S273 and D8S88.     

Linkage between markers in the vicinity of the uncoupling protein 2 gene and resting metabolic rate in humans

The recent cloning of a gene that codes for a novel uncoupling protein, UCP2, which is expressed in a wide range of adult human tissues, has raised the possibility that it may be involved in regulation of energy balance. To explore this concept we have investigated potential linkage relationships between three microsatellite markers which encompass the UCP2 gene location on 11q13 with resting metabolic rate (RMR), body mass index, percentage body fat (%FAT) and fat mass (FM) in 640 individuals from 155 pedigrees from the Québec Family Study. Using a linkage analysis strategy based on sibling, avuncular, grandparental and cousin pairs, strong evidence of linkage was found between the marker D11S911 (P = 0.000002) and RMR, with more moderate evidence for D11S916 (P = 0.006) and D11S1321 (P = 0.02). Suggestive evidence of linkage was also observed between D11S1321 and %FAT (P = 0.04) and FM (P = 0.02). It is concluded that the three markers encompassing the UCP2 locus and spanning a 5 cM region on 11q13 are linked to resting energy expenditure in adult humans. The evidence is strong enough to warrant a search for DNA sequence variation in the gene itself.     

Linkage analysis of bronchial hyperreactivity and atopy with chromosome 11q13

There are two key clinical features of asthma: allergy and bronchial hyperreactivity (BHR). Some pedigree studies of atopy have indicated linkage with the high affinity IgE receptor (Fc epsilon RI-beta) gene on chromosome 11q13, but others failed to confirm this linkage. We examined the genetic linkage of three polymorphic microsatellite markers to atopy and BHR in 120 affected sibling pairs recruited from the general community. We found no linkage to atopy at any of the three 11q13 loci studied. Our findings also do not favour linkage between BHR and loci approximately 8-9 cM either side of the Fc epsilon RI-beta gene.     

Clinical features of five pedigrees genetically linked to the juvenile glaucoma locus on chromosome 1q21-q31

BACKGROUND: Primary juvenile glaucoma is a rare form of glaucoma that typically affects individuals between 3 and 20 years of ages and is inherited as an autosomal dominant trait. One gene responsible for this condition has been localized to the 1q21-q31 region of chromosome 1. To investigate the clinical features of this form of glaucoma, the authors have examined the affected members of five pedigrees demonstrating genetic linkage to the 1q21-q31 locus. METHODS: Clinical characterization of 23 affected patients was performed. Genetic linkage to the 1q21-q31 locus was confirmed by segregation of the disease trait in each pedigree with genetic markers located in the 1q21-q31 region. RESULTS: The clinical features of affected members of the five pedigrees presented are generally homogeneous. The average age of diagnosis was 18.5 years (range, 5-30 years), and the average initial intraocular pressure was 38.5 mmHg (range, 30-53 mmHg). Eighty-seven percent of affected individuals were myopic and 83% of affected individuals required surgical treatment for glaucoma. There were no uniformly associated systemic or ocular conditions. One possible nonpenetrant carrier was identified and a difference in phenotypic expression of the presumed disease gene was observed in a pair of affected monozygotic twins. We also identified two pedigrees with juvenile glaucoma and three pedigrees affected by the pigment dispersion syndrome that are not genetically linked to the 1q21-q31 region. CONCLUSION: The form of juvenile glaucoma caused by a gene located in the q21-q31 region of chromosome 1 is generally phenotypically homogeneous. The severe elevation of intraocular pressure typically seen in affected patients suggests the product of the predisposing gene may participate in the outflow function of the eye.