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PubMed1996

Evidence of genetic heterogeneity of Leber's congenital amaurosis (LCA) and mapping of LCA1 to chromosome 17p13.

Leber's congenital amaurosis (LCA) is an autosomal recessive disease responsible for congenital blindness. It is the earliest and most severe inherited retinal dystrophy in human and its genetic heterogeneity has long been recognised. We have recently reported on the first localisation of a disease gene (LCA1) to the short arm of chromosome 17 by homozygosity mapping in five families of North African origin. Here, we refine the genetic mapping of LCA1 to chromosome 17p13 between loci D17S938 and D17S1353 and provide strong support for the genetic heterogeneity of this condition (maximum likelihood for heterogeneity, 17.20 in InL; heterogeneity versus homogeneity, P = 0.0002, heterogeneity versus no linkage, P < 0.0001)

Blindness↗
PubMed1993

[Genetic heterogeneity of certain sporadic colorectal cancers].

Intratumoral heterogeneity provides information concerning the timing of genetic events which occur during colorectal carcinogenesis. In a series of 14 colorectal adenocarcinomas, the following genetic alterations were characterized: loss of heterozygosity on chromosomes 17 p, 1 p, 18 q, 5 q and 22 q, point mutations on TP53 and K-RAS genes, change in DNA index. Six of the 14 initial samples were investigated for putative genetic heterogeneity. In two cases, variations in genetic alterations on chromosome 17 p and gene TP53 were demonstrated. These events seem to occur at a late stage in colorectal carcinogenesis.

Adenocarcinoma↗
PubMed1997

Genetic heterogeneity of autosomal dominant polycystic kidney disease in Argentina.

Autosomal dominant polycystic kidney disease (ADPKD) is an inherited disorder with genetic heterogeneity. Up to three loci are involved in this disease, PKD1 on chromosome 16p13.3, PKD2 on 4q21, and a third locus of unknown location. Here we report the existence of locus heterogeneity for this disease in the Argentinian population by performing linkage analysis on 12 families of Caucasian origin. Eleven families showed linkage to PKD 1 and one family showed linkage to PKD2. Two recombinants in the latter family placed the locus PKD2 proximal to D4S1563, in agreement with data recently published on the cloning of this gene. Analysis of clinical data suggests a milder ADPKD phenotype for the PKD2 family.

Adolescent↗
PubMed2000

Genetic heterogeneity of hypervariable region 1 of the hepatitis C virus (HCV) genome and sensitivity of HCV to alpha interferon therapy.

Hepatitis C virus (HCV) populations persist in vivo as a mixture of heterogeneous viruses called quasispecies. The relationship between the genetic heterogeneity of these variants and their responses to antiviral treatment remains to be elucidated. We have studied 26 virus strains to determine the influence of hypervariable region 1 (HVR-1) of the HCV genome on the effectiveness of alpha interferon (IFN-alpha) therapy. Following PCR amplification, we cloned and sequenced HVR-1. Pretreatment serum samples from 13 individuals with chronic hepatitis C whose virus was subsequently eradicated by treatment were compared with samples from 13 nonresponders matched according to the major factors known to influence the response, i.e., sex, genotype, and pretreatment serum HCV RNA concentration. The degree of virus variation was assessed by analyzing 20 clones per sample and by calculating nucleotide sequence entropy (complexity) and genetic distances (diversity). Types of mutational changes were also determined by calculating nonsynonymous substitutions per nonsynonymous site (K(a)) and synonymous substitutions per synonymous site (K(s)). The paired-comparison analysis of the nucleotide sequence entropy and genetic distance showed no statistical differences between responders and nonresponders. By contrast, nonsynonymous substitutions were more frequent than synonymous substitutions (P </= 0.05) in responders, but there was no significant difference in nonresponders. Nonsynonymous substitutions tended to be more frequent than synonymous substitutions in women (P = 0.06) but not in men. Nucleotide entropy and genetic distances were significantly related to serum RNA concentration (P </= 0.01). Our findings suggest that after controlling for the major determinants of interferon response, neither complexity nor diversity of the HVR-1 region is associated per se with virus eradication. Because a higher proportion of nonsynonymous substitutions than synonymous substitutions was found only in responders, host anti-HCV-specific immune response rather than viral factors may be playing an important role in the interferon response.

Adult↗
PubMed1999

Familial high myopia: evidence of an autosomal dominant mode of inheritance and genetic heterogeneity.

High myopia, defined as a refractive error inferior to -6 diopters, often appears as a familial disease. In order to precise its genetic background, we performed a segregation analysis on 32 French families (320 subjects including 120 individuals with clinical data) containing at least one high myopic person in their genealogy. Under the assumption of a two-alleles single gene model, the autosomal dominant transmission mode showed a much greater likelihood than the autosomal recessive mode, which therefore was rejected. From the segregation model obtained, a two-point linkage analysis was made on 18 families (107 subjects), among the 32 used for the segregation analysis. Different candidate loci were tested: collagen genes including Stickler syndrome types 1 and 2, proteoglycan genes, Marfan 1 syndrome and a Marfan like disorder localised in 3p24.2-p25. No evidence of linkage was found with any of the studied markers. In addition, the absence of linkage with chromosome 18p11.31 markers, a locus linked to familial high myopia in 6 North American families and 1 family of Chinese descent, demonstrated the genetic heterogeneity of the disease.

Alleles↗
PubMed1989

[Study of the genetic heterogeneity of gangliosidoses in humans].

A study of genetic heterogeneity of GM1 and GM2 gangliosidoses was performed using a wide set of cultured fibroblast lines of patients with leukodystrophies. In addition to commonly used methods for enzyme diagnosis and for isozyme fractionating, following assays were developed for locus and allele differentiation: loading tests with 3H-GM1 and 3H-GM2, analytical chromatofocusing and activity determination of activator protein for GM2.

Alleles↗
PubMed1999

A new locus for autosomal dominant "pure" hereditary spastic paraplegia mapping to chromosome 12q13, and evidence for further genetic heterogeneity.

Autosomal dominant pure hereditary spastic paraplegia (ADPHSP) is clinically characterized by slowly progressive lower-limb spasticity. The condition is genetically heterogeneous, and loci have been mapped at chromosomes 2p, 8q, 14q, and 15q. We have performed a genomewide linkage screen on a large family with ADPHSP, in which linkage to all four previously known loci was excluded. Analysis of markers on chromosome 12q gave a peak pairwise LOD score of 3.61 at D12S1691, allowing us to assign a new locus for ADPHSP (a locus that we have designated "SPG10") to this region. Haplotype construction and analysis of recombination events narrowed the SPG10 locus to a 9.2-cM region between markers D12S368 and D12S83. In addition, our data strongly suggest that there are at least six ADPHSP loci, since we describe a further family in which linkage to all five known ADPHSP loci has been excluded.

Adolescent↗
PubMed2002

CFEOM1, the classic familial form of congenital fibrosis of the extraocular muscles, is genetically heterogeneous but does not result from mutations in ARIX.

BACKGROUND: To learn about the molecular etiology of strabismus, we are studying the genetic basis of 'congenital fibrosis of the extraocular muscles' (CFEOM). These syndromes are characterized by congenital restrictive ophthalmoplegia affecting muscles in the oculomotor and trochlear nerve distribution. Individuals with the classic form of CFEOM are born with bilateral ptosis and infraducted globes. When all affected members of a family have classic CFEOM, we classify the family as a CFEOM1 pedigree. We have previously determined that a CFEOM1 gene maps to the FEOM1 locus on chromosome 12cen. We now identify additional pedigrees with CFEOM1 to determine if the disorder is genetically heterogeneous and, if so, if any affected members of CFEOM1 pedigrees or sporadic cases of classic CFEOM harbor mutations in ARIX, the CFEOM2 disease gene. RESULTS: Eleven new CFEOM1 pedigrees were identified. All demonstrated autosomal dominant inheritance, and nine were consistent with linkage to FEOM1. Two small CFEOM1 families were not linked to FEOM1, and both were consistent with linkage to FEOM3. We screened two CFEOM1 families consistent with linkage to FEOM2 and 5 sporadic individuals with classic CFEOM and did not detect ARIX mutations. CONCLUSIONS: The phenotype of two small CFEOM1 families does not map to FEOM1, establishing genetic heterogeneity for this disorder. These two families may harbor mutations in the FEOM3 gene, as their phenotype is consistent with linkage to this locus. Thus far, we have not identified ARIX mutations in any affected members of CFEOM1 pedigrees or in any sporadic cases of classic CFEOM.

Female↗
PubMed1981

XY gonadal dysgenesis: genetic heterogeneity based upon clinical observations, H-Y antigen status and segregation analysis.

Clinical observations and segregation analysis indicate that XY gonadal dysgenesis is characterized by genetic heterogeneity. In addition to the type inherited in X-linked recessive fashion, segregation analysis of other families suggested another type by revealing that the proportion of affected sibs did not differ from that expected on the basis of a male-limited autosomal recessive inheritance. Further heterogeneity may be deduced on the basis of coexisting campomelic dwarfism or possibly also renal parenchymal abnormalities. These observations of genetic heterogeneity must be considered when interpreting studies in which individuals with XY gonadal dysgenesis may or may not show H-Y antigen.

Alleles↗
PubMed2003

Familial atrial fibrillation is a genetically heterogeneous disorder.

OBJECTIVES: The aims of this study were to identify and characterize familial cases of atrial fibrillation (AF) in our clinical practice and to determine whether AF is genetically heterogeneous. BACKGROUND: Atrial fibrillation is not generally regarded as a heritable disorder, yet a genetic locus for familial AF was previously mapped to chromosome 10. METHODS: Of 2,610 patients seen in our arrhythmia clinic during an 18-month study period, 914 (35%) were diagnosed with AF. Familial cases were identified by history and medical records review. Four multi-generation families with autosomal dominant AF (FAF 1 to 4) were tested for linkage to the chromosome 10 AF locus. RESULTS: Fifty probands (5% of all AF patients; 15% of lone AF patients) were identified with lone AF (age 41 +/- 9 years) and a positive family history (1 to 9 additional relatives affected). In FAF 1 to 3, AF was associated with rapid ventricular response. In contrast, AF in FAF-4 was associated with a slow ventricular response and, with progression of the disease, junctional rhythm and cardiomyopathy. Genotyping of FAF 1 to 4 with deoxyribonucleic acid markers spanning the chromosome 10q22-q24 region excluded linkage of AF to this locus. In FAF-4, linkage was also excluded to the chromosome 3p22-p25 and lamin A/C loci associated with familial AF, conduction system disease, and dilated cardiomyopathy. CONCLUSIONS: Familial AF is more common than previously recognized, highlighting the importance of genetics in disease pathogenesis. In four families with AF, we have excluded linkage to chromosome 10q22-q24, establishing that at least two disease genes are responsible for this disorder.

Adult↗
PubMed1998

Evidence of genetic heterogeneity in a BALB/c mouse colony as determined by DNA fingerprinting.

A genetic monitoring of the BALB/c mouse foundation colony in our animal facility was carried out. The techniques of choice were skin grafting, coat colour test, flow cytometric analysis for H2 antigens (loci H2-D and H2-A), electrophoretic analysis of isoenzymes (loci Idh1, Pep3, Es3 and Mod1), PCR-amplified microsatellites (loci Igh-V, Ngfg, Plau, Crp, Igh, D16Mit5, D3Mit49 and D17Mit16) and DNA fingerprinting (multilocus probes 33.6, 33.15 and (CAC)5). No evidence of genetic contamination was found, ruling out the possibility of an outcross with AKR, the other albino strain maintained at the facility. Nevertheless, DNA fingerprint patterns revealed evidence of genetic heterogeneity in four out of nine lines of the nucleus colony, interpreted as minisatellite mutations favoured for a single line system with more than 40 generations of separation from the ancestral pair. These mice are mainly used in cancer and immunological research within the institute.

Animals↗
PubMed1994

Genetic heterogeneity of hepatitis C virus.

There are four hierarchical strata in the genetic heterogeneity of hepatitis C virus (HCV): group above subgroup above isolates above quasispecies. The entire genome sequence has so far been reported for 16 isolates which are classifiable into 3 groups and 6 subgroups. Provisional classification of HCV is also possible using a partial sequence of the HCV genome. With the E1 region sequence for example, the present collection of HCV isolates can be classified into 9 groups and 23 subgroups. The rationale for these classifications and the epidemiological and clinical implications of genotyping HCV are reviewed.

Amino Acid Sequence↗
PubMed1998

Paget's disease of bone: evidence for a susceptibility locus on chromosome 18q and for genetic heterogeneity.

Paget's disease of bone is a common condition characterized by bone pain, deformity, pathological fracture, and an increased incidence of osteosarcoma. Genetic factors play a role in the pathogenesis of Paget's disease but the molecular basis of the disease remains unclear. Previous genetic linkage studies have mapped the rare Paget's disease-like bone dysplasia familial expansile osteolysis (FEO) to chromosome 18q21-22, and recent work has shown evidence of linkage between this locus and Paget's disease in one family. Here we studied the relationship between the 18q21-22 locus and Paget's disease in eight large multiplex families from diverse ethnic backgrounds with inherited Paget's disease. Paget's disease was inherited as an autosomal dominant trait in all families, with high penetrance by the sixth decade. Analysis of seven highly polymorphic markers from chromosome 18q21-22 showed positive summated two-point log10 odds ratio (lodscores) of +2.97 with the marker D18S42 at a recombination fraction (theta) = 0.05, and of +2.95 with the marker D18S60 at theta = 0.00, values which are close to the cut-off of +3.0, which is generally accepted as evidence of linkage. Segregation analysis of the haplotypes and formal statistical analysis using the HOMOG program provided evidence for genetic heterogeneity, however, with evidence for linkage in five families and against linkage in the remaining three families (chi square 8.82; df = 2; p < 0.025). Multipoint linkage analysis in the five linked families showed lodscores of above +3.5 across the whole susceptibility region and a maximum summated lodscore of 3.89 at the marker D18S465. In the three nonlinked families, negative multipoint results were obtained for the whole region, with lodscores below -2.0 in one family, excluding this as a candidate locus for the disease. Our studies demonstrate the importance of hereditary factors in the pathogenesis of Paget's disease and confirm evidence of linkage between Paget's disease and chromosome 18q21-22 in some families. This raises the possibility that Paget's disease and FEO may share a common molecular basis, perhaps due to different mutations in the same gene or family of genes. Data from three families did not support evidence of linkage to 18q21-22 however, indicating that Paget's disease is genetically heterogeneous and suggests the presence of at least one additional locus which remains to be discovered.

Chromosome Aberrations↗
PubMed1998

Evidence for genetic heterogeneity in X-linked congenital stationary night blindness.

X-linked congenital stationary night blindness (CSNB) is a nonprogressive retinal disorder characterized by disturbed or absent night vision; its clinical features may also include myopia, nystagmus, and impaired visual acuity. X-linked CSNB is clinically heterogeneous, and it may also be genetically heterogeneous. We have studied 32 families with X-linked CSNB, including 11 families with the complete form of CSNB and 21 families with the incomplete form of CSNB, to identify genetic-recombination events that would refine the location of the disease genes. Critical recombination events in the set of families with complete CSNB have localized a disease gene to the region between DXS556 and DXS8083, in Xp11.4-p11.3. Critical recombination events in the set of families with incomplete CSNB have localized a disease gene to the region between DXS722 and DXS8023, in Xp11.23. Further analysis of the incomplete-CSNB families, by means of disease-associated-haplotype construction, identified 17 families, of apparent Mennonite ancestry, that share portions of an ancestral chromosome. Results of this analysis refined the location of the gene for incomplete CSNB to the region between DXS722 and DXS255, a distance of 1.2 Mb. Genetic and clinical analyses of this set of 32 families with X-linked CSNB, together with the family studies reported in the literature, strongly suggest that two loci, one for complete (CSNB1) and one for incomplete (CSNB2) X-linked CSNB, can account for all reported mapping information.

Female↗
PubMed2000

Genetic heterogeneities and phenotypic characteristics of strains of the genus Abiotrophia and proposal of Abiotrophia para-adiacens sp. nov.

The genus Abiotrophia represents a heterogeneous group of fastidious cocci that show a dependence on pyridoxal hydrochloride analogs for growth. The genetic heterogeneity in the genus Abiotrophia was examined by DNA-DNA hybridization, PCR assay of genomic DNA sequences, and restriction fragment length polymorphism and sequence homology analyses of the PCR-amplified 16S rRNA gene. Nine type or reference strains of Abiotrophia defectiva, Abiotrophia adiacens, and Abiotrophia elegans and 36 oral Abiotrophia isolates including the ones presumptively identified as Gemella morbillorum by the rapid ID32 STREP system were divided into four groups: A. defectiva (genotype 1), A. adiacens (genotype 2), A. elegans (genotype 4), and a fourth species (genotype 3) which we propose be named Abiotrophia para-adiacens sp. nov. A PCR assay specific for detection and identification of the novel Abiotrophia species was developed. A. para-adiacens generally produced beta-glucosidase but did not produce alpha- or beta-galactosidase or arginine dihydrolase, did not ferment, trehalose, pullulan, or tagatose, and was serotype IV, V, or VI. Thus, it was distinguished phenotypically from A. adiacens, A. elegans, and A. defectiva as well as, apparently, from the recently described species Abiotrophia balaenopterae sp. nov., which produces arginine dihydrolase and which ferments pullulan but not sucrose (P. A. Lawson et al., Int. J. Syst. Bacteriol. 49:503-506, 1999). Strain ATCC 27527, currently listed as G. morbillorum, was a member of the species A. para-adiacens.

Bacteremia↗
PubMed1992

Confirmation of genetic heterogeneity in limb-girdle muscular dystrophy: linkage of an autosomal dominant form to chromosome 5q.

Limb-girdle muscular dystrophy (LGMD) is a clinically and genetically heterogenous group of disorders, with both recessive and dominant forms reported. Recently, a series of recessive LGMD families were linked to chromosome 15q. We report herein the results of our linkage studies in a previously reported large autosomal dominant family. The LGMD gene in this family was localized to chromosome 5q22.3-31.3 by using a series of CA(n) microsatellite repeat markers. Linkage to 15q was excluded. These findings confirm genetic heterogeneity in this clinically diverse syndrome.

Cell Line, Transformed↗
PubMed1993

Genetic heterogeneity of oncogenic human papillomavirus type 5 (HPV5) and phylogeny of HPV5 variants associated with epidermodysplasia verruciformis.

Variants of oncogenic human papillomavirus type 5 (HPV5), specifically associated with epidermodysplasia verruciformis, were recognized on the basis of the genetic heterogeneity of the E6 open reading frame (ORF). To further evaluate the genetic heterogeneity of HPV5, we sequenced the long control region (LCR), the E7 ORF, and the terminal parts of the E2 ORF of five previously characterized HPV5 variants and compared the data with the published HPV5a1 and HPV5b sequences. Alignment of the variants showed 140 (7.6%) variable nucleotides of 1,854 sequenced. Nucleotide substitution rates varied from 3.6% in the E7 ORF to 11% in the E6 ORF. By sequencing the variable region encompassing the LCR 3' part and the E6 ORF of isolates from six additional epidermodysplasia verruciformis patients, we identified three new variants and three already known variants, indicating the stability of HPV5 variants. This stability was further demonstrated by the identity of isolates obtained years later from benign and malignant lesions of three patients. Phylogenetic analysis of the 10 HPV5 variants distributed them into three groups, tentatively defining subtypes a, b, and c. The phylogenetic grouping shows no geographical dependence, a fact that may be related to the host restriction that characterizes HPV5 infections. No differences in the enhancer potential of the LCR or in the transactivating properties of the E2 protein assayed in vitro were observed among HPV5 variants. Whether HPV5 variants possess distinct biological properties in vivo remains to be determined.

Base Sequence↗
PubMed2001

Phenotypic and genetic heterogeneity of familial hyperkalaemic hypertension (Gordon syndrome).

1. Familial hyperkalaemic hypertension (FHH), also called pseudohypoaldosteronism type II (PHA2) or Gordon syndrome, is a rare Mendelian-form of low-renin hypertension. The first cases of FHH were reported approximately 30 years ago and they described the peculiar biochemical abnormalities (i.e. hyperkalaemia and hyperchloraemic acidosis despite a normal glomerular filtration rate). 2. Since then, more than 90 single cases and families have been reported in the literature. These various reports show marked differences in phenotype. 3. Our group has now collected 14 unrelated pedigrees originating from different parts of France and Europe. We confirm the large variations in the age of discovery and in the severity of the biochemical abnormalities from one individual to another and from one family to another one. 4. Blood pressure levels have no significant relationship with hyperkalaemia or hyperchloraemia, but there is a positive relationship with age, as in the normal population. 5. Analyses of clinical features and Mendelian segregation in our families demonstrate autosomal-dominant inheritance, as expected from the literature. 6. Efforts have been made in the past years to unravel the gene responsible for the disease. Until now, a primary responsibility of the gene encoding the thiazide-sensitive Na-Cl cotransporter (SLC12A3) has been excluded in PHA2 families. Three loci have been identified on chromosomes 1 (PHA2A), 17 (PHA2B) and 12 (PHA2C). 7. More recently, analysis of three additional pedigrees, including 10 affected subjects, with over 25 members allowed us to demonstrate further genetic heterogeneity and the existence of at least a fourth locus. 8. The genetic heterogeneity of this syndrome, and thus the variety of molecular defects, suggests the role of either several new components of the same pathway, multiple aldosterone- regulated effectors or direct or indirect partners of the Na-Cl cotransporter.

Adolescent↗