Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Genetic Heterogeneity”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12Linked to original sources
PubMed2000

Influence of viral load and alanine aminotransferase on viral genetic heterogeneity in patients with chronic hepatitis C virus infection.

BACKGROUND/AIM: Hepatitis C virus (HCV) populations in vivo consist of genetically different heterogeneous mixtures defined as 'quasispecies', which vary in the hypervariable region 1 (HVR1) mostly. To further address the role of quasispecies diversity in hepatitis C infection, this study aimed to evaluate the influence of ALT, viral load and genotypes on quasispecies heterogeneity in patients with HCV infection. METHODS: Thirty-six chronic hepatitis C patients with high levels of alanine aminotransferase (ALT) were studied. None of them received any antiviral therapy. HCV RNA serum levels, genotype and genetic heterogeneity were determined by branched-chain DNA assay, restriction fragment length patterns and RT-PCR single-strand conformational polymorphism analysis of HVR1, respectively. RESULTS: Twenty-eight patients had genotype 1b (28/36; 78%), 6 patients had genotype 1a (6/36; 17%), 1 patient was 2a (1/36; 3%) and genotype could not be determined in 1 patient. The patients were categorized into two groups according to the number of bands representing the dominant strains in the circulation: group A with 2 bands having 1 strain (14/36 patients; 39%) and group B with more than 2 bands indicating more than 1 strain (22/36 patients; 61%). The serum viremia and ALT levels for these groups were 11 +/- 8.8 and 5.3 +/- 4.6 mEq/ml (p < 0.05), and 79 +/- 20, and 127 +/- 80 IU/l (p < 0.05), respectively. CONCLUSION: The results of this study suggest that hepatitis C patients having 1 dominant strain in the circulation may show a relatively weaker immune response resulting in lower ALT and higher viremia levels, whereas patients with high degrees of virus quasispecies diversity have higher ALT levels and a more active immune response causing the selection of new genome variants and depressing viral replication partly.

Adult↗
PubMed1996

Evidence for genetic heterogeneity in the carbohydrate-deficient glycoprotein syndrome type I (CDG1).

We have analyzed a series of polymorphic markers on chromosome 16p13 in 17 families with carbohydrate-deficient glycoprotein syndrome type I (CDG1). First, linkage to the region between D16S406 and D16S500 is confirmed. The telomeric border of the candidate region is now definitively placed proximal to D16S406 by crossovers observed in 2 families. Second, in 1 family with 2 affected siblings, the disease is not linked to chromosome 16p. Genetic heterogeneity has not been previously reported for CDG1, and this observation has implications for prenatal diagnosis. Third, allelic associations suggest that the disease locus is localized close to D16S414/D16S497. This places the region of interest centromeric of its published localization.

Chromosomes, Human, Pair 16↗
PubMed1995

Genetic heterogeneity of the hepatitis C virus.

Hepatitis C virus (HCV) is an important etiological agent in the development of chronic liver diseases such as chronic hepatitis, cirrhosis, and hepatocellular carcinoma (HCC). The virus, identified only recently, contains a single-stranded RNA genome of positive polarity, is distantly related to pestiviruses and flaviviruses, and has been classified as the first member of a third genus within the family Flaviviridae. Extensive analysis of HCV genomic sequences demonstrated that this virus possesses significant genetic heterogeneity. Different regions of the viral genome demonstrate a varying degree of heterogeneity; the regions coding for the putative envelope proteins are the most variable sites between different isolates. Furthermore, HCV circulates as a quasispecies in the host. During the course of acute and chronic infection, the sequence composition of the HCV population in one patient has been found to change sequentially with an extremely high rate of nonconserved nucleotide changes in the hypervariable region I (HVR1) of HCV. Such sequence changes alter the antigenicity of the epitopes coded within HVR1 so that these are not always recognized by preexisting antibodies. It has been suggested that this could represent one mechanism by which HCV evades host immune surveillance and may account for the high rate of chronicity observed in such infections. Continuous viral replication may, in turn, lead to the development of chronic liver disease, including HCC, in infected individuals. To date, at least nine major genetic groups (genotypes 1-9) and more than 30 subgroups of HCV have been recognized based on genetic differences. A distinct difference has been observed in the genotype distribution in Africa compared with other continents. Recent data have suggested a difference in pathogenesis and in the outcome of interferon therapy in individuals infected with HCV of certain genotypes. For example, genotype 1b (II) seems to be associated with more severe liver disease, including HCC, and with a poorer response to interferon therapy. The extensive genetic heterogeneity of HCV may have serious implications for the diagnosis, treatment and prevention of hepatitis C as well as in understanding the biology of infection by this important human pathogen.

Genome, Viral↗
PubMed1994

Genetic heterogeneity of familial hemiplegic migraine.

Familial hemiplegic migraine (FHM) is an autosomal dominant variety of migraine with aura. We previously mapped a gene responsible for this disorder to the short arm of chromosome 19, within a 30-cM interval bracketed by D19S216 and D19S215. Linkage analysis conducted on two large pedigrees did not show any evidence of heterogeneity, despite their clinical differences due to the presence, in one family, of cerebellar ataxia and nystagmus. Herein we report linkage data on seven additional FHM families including another one with cerebellar ataxia. Analysis was conducted with a set of seven markers spanning the D19S216-D19S215 interval. Two-point and multipoint lod score analyses as well as HOMOG testing provided strong evidence for genetic heterogeneity. Strong evidence of linkage was obtained in two families and of absence of linkage in four families. The posterior probability of being of the linked type was > .95 in the first two families and < .01 in four other ones. It was not possible to draw any firm conclusion for the last family. Thus, within the nine families so far tested, four were linked, including those with associated cerebellar ataxia. We could not find any clinical difference between the pure FHM families regardless of whether they were linked. In addition to the demonstration of genetic heterogeneity of FHM, this study also allowed us to establish that the most likely location of the gene was within an interval of 12 cM between D19S413 and D19S226.

Ataxia↗
PubMed1997

Mutations in the gene encoding the inwardly-rectifying renal potassium channel, ROMK, cause the antenatal variant of Bartter syndrome: evidence for genetic heterogeneity. International Collaborative Study Group for Bartter-like Syndromes.

Inherited renal tubular disorders associated with hypokalemic alkalosis (Bartter-like syndromes) can be subdivided into at least three clinical phenotypes: (i) the hypocalciuric-hypomagnesemic Gitelman variant; (ii) the classic variant; and (iii) the antenatal hypercalciuric variant (also termed hyperprostaglandin E syndrome). Mutations in the Na-Cl cotransporter (NCCT) underlie the pathogenesis of the Gitelman variant and mutations in the Na-K-2Cl cotransporter (NKCC2) have recently been identified in the antenatal hypercalciuric variant. We now describe mutations in the gene encoding the inwardly-rectifying potassium channel, ROMK, in eight kindreds with the antenatal variant of Bartter syndrome. These findings indicate that antenatal Bartter syndrome is genetically heterogeneous and provide new insights into the molecular pathogenesis of Bartter-like syndromes.

Amino Acid Sequence↗
PubMed1997

Genetic heterogeneity of Borrelia burgdorferi in the United States.

To examine in detail Borrelia burgdorferi strain diversity in the United States, 186 isolates from human, tick, and rodent sources were analyzed from multiple distinct geographic regions of the United States and abroad. Strains were characterized by genomic macrorestriction analysis and ospA and 23S rDNA gene sequencing followed by phylogenetic analysis. Results indicate that spirochetal isolates from the United States fall into two major divisions and nine or more subdivisions; human isolates fell into five of these subdivisions. Greater genetic diversity was observed among B. burgdorferi isolates from moderate climatic regions, consistent with increased tick vector and reservoir diversity. All of the Borrelia isolates were reactive by ospA polymerase chain reaction except for Borrelia hermsii controls and several tick isolates from the Northeast, which were shown to lack the 49-kb plasmid encoding outer surface protein A (OspA). The data suggest that US B. burgdorferi isolates demonstrate substantial genetic heterogeneity, with regional differences in spirochete populations.

Animals↗
PubMedDate not supplied

Genetic heterogeneity in skeletal dysplasias.

Certain skeletal dysplasias represent excellent examples of genetic heterogeneity. Clinical recognition of their individual characteristics is a fundamental prerequisite for an understanding of their pathogenetic mechanisms and for the identification of their basic molecular defects.

Achondroplasia↗
PubMed1989

Autoimmune thyroid phenomena are not evidence for human lymphocyte antigen-genetic heterogeneity in insulin-dependent diabetes.

It is well established that there is genetic heterogeneity between a human lymphocyte antigen (HLA)-DR3-associated allele and an HLA-DR4-associated allele in insulin-dependent diabetes mellitus (IDDM). Equally well established are the association of DR3 with Graves' disease and other autoimmune disorders in nondiabetics and the increased prevalence of autoimmune thyroid disease in IDDM. Perhaps in large part because of these facts, it has been postulated that there are two major forms of classical IDDM--one form characterized by coexistent autoimmune disease, such as autoimmune thyroid disease which is associated with DR3, and another form not associated with additional autoimmune disorders, which is associated with DR4. Several studies have repudiated the idea of specific clinical findings in IDDM being associated exclusively with DR4. However, the DR3-thyroid association in IDDM has not been investigated carefully. Therefore, in order to study this putative association, we divided a group of diabetic children into overlapping subgroups based on thyroid enlargement, antithyroid microsomal antibodies, acquired hypothyroidism, and no evidence of thyroid disease. The distributions of HLA-DR3 and -DR4 among these subgroups did not differ from each other; nor did the distribution of the HLA alleles differ from those of randomly selected IDDM individuals. These results suggest that thyroid autoimmunity in IDDM is part of the IDDM "syndrome" and is associated with DR3 and DR4 to the same extent that IDDM without thyroid disease is associated with these two antigens. Thus, although genetic studies are consistent with the heterogeneity between DR3 and DR4 in IDDM, there is no HLA-thyroid disease association to support this heterogeneity.

Diabetes Mellitus, Type 1↗
PubMed1995

Genetic heterogeneity within the coding regions of E2 and NS3 in strains of bovine viral diarrhea virus.

We have amplified and sequenced parts of the genomes of eleven laboratory strains of bovine viral diarrhea (BVD) virus originating from North America, New Zealand and Europe. The cumulative nucleotide (nt) sequence heterogeneity of the amplified fragments located in the analysed region of the gene encoding the nonstructural protein NS3 (P80) was 24% as compared to 47% for E2 (Gp53). The nt substitutions in the E2 region resulted in replacements in 42% of amino acid (aa) positions, while the deduced aa sequence of all BVD virus strains remained identical in NS3 and differed from the corresponding region of classical swine fever viruses. This makes possible the differentiation of bovine and porcine pestiviruses. It is suggested that genetic heterogeneity results from passage in transiently infected animals.

Amino Acid Sequence↗
PubMed2002

Genetic heterogeneity of FG syndrome: a fourth locus (FGS4) maps to Xp11.4-p11.3 in an Italian family.

FG syndrome (FGS, MIM 305450) is a rare X-linked recessive disorder comprising mental retardation and multiple malformations. Various families have been described to date, increasing our knowledge of the phenotype variability and making the clinical diagnosis complex, especially in sporadic patients. The first locus for FG syndrome (FGS1) was linked to chromosome region Xq12-q21.31, but other families have been excluded from this locus. The genetic heterogeneity of FG syndrome has been confirmed by analysis of an X chromosome inversion [inv(X)(q11q28)] in an affected boy and in his mentally retarded maternal uncle, suggesting that an additional locus for FG syndrome (FGS2, MIM 300321) is located at either Xq11 or Xq28. Recently, a third locus (FGS3) has been mapped to Xp22.3. We have identified and clinically characterized an Italian FG family, including 31 members with three affected males in two generations and two obligate carriers. We have excluded linkage to known FGS loci, whereas an extensive study of the whole X chromosome has yielded a maximum LOD score (Z(max)) of 2.66 (recombination fraction=0) for markers between DXS8113 and sWXD805. This new locus for FG syndrome corresponds to a region of approximately 4.6 Mb on the X chromosome.

Abnormalities, Multiple↗
PubMed1997

Autosomal recessive long-QT syndrome (Jervell Lange-Nielsen syndrome) is genetically heterogeneous.

Jervell Lange-Nielsen syndrome (JLNS) is a recessive disorder with congenital deafness and long-QT syndrome (LQTS 1). Mutations in the potassium-channel gene KVLQT1 (LQTS 1) have been identified in JLNS and in autosomal-dominant LQTS as well. We performed haplotype analysis with microsatellite markers in a Lebanese family with JLNS, but failed to detect linkage at LQTS 1. Moreover, using this approach, we excluded two other ion-channel genes involved in autosomal-dominant LQTS, HERG (LQTS 2) and SCN5A (LQTS 3). Our findings indicate that JLNS is genetically heterogeneous and that, in this family, an unknown LQTS gene causes the disease.

Cation Transport Proteins↗
PubMed2002

Clinical and genetic heterogeneity of Seckel syndrome.

Seckel syndrome is a rare autosomal recessive condition belonging to the group of osteodysplastic primordial "dwarfism" and characterized by the association of 1) severe pre- and postnatal growth retardation, 2) microcephaly with mental retardation, and 3) specific dysmorphic features. Recently, two disease loci have been mapped to chromosomes 3q22.1-q24 and 18p11.31-q11.2, respectively, by homozygosity mapping in consanguineous families. Here, we report on the exclusion of these loci in five consanguineous and one multiplex nonconsanguineous Seckel syndrome families and in two consanguineous families presenting type II osteodysplastic primordial dwarfism. These results support the view that Seckel syndrome is a clinically and genetically heterogeneous condition.

Abnormalities, Multiple↗
PubMed2006

Further evidence of the clinical and genetic heterogeneity of recessive transgressive PPK in the Mediterranean region.

Transgressive palmoplantar keratoderma (PPK) is the phenotypic hallmark of Mal de Meleda (MDM, MIM 24300). It is characterized by erythema and hyperkeratosis that extend to the dorsal face of the hands and feet. The disease is distributed worldwide and includes the Mediterranean population. The gene responsible for MDM, ARS (component B) mapped on chromosome 8qter, encodes for the SLURP-1 protein (Ly-6/uPAR related protein-1). A variety of mutations within the ARS gene have been shown to underlie MDM in different populations. Genetic heterogeneity of MDM is suspected. We have recently shown that three different homozygous mutations (82delT, C77R, C99Y) were responsible for MDM in 17 patients from Northern Tunisia belonging to eight unrelated consanguineous families. We report here a Tunisian family with three siblings presenting with recessive transgressive PPK closely resembling the MDM phenotype that excludes linkage to the ARS gene.

Adult↗
PubMed1984

Osteogenesis imperfecta type II delineation of the phenotype with reference to genetic heterogeneity.

A group of fetuses with a perinatally lethal variety of osteogenesis imperfecta (O.I. type II) is characterized by short limbs, and clinical and roentgenological evidence of severe osseous fragility and defective ossification. Forty-eight cases were reviewed and can be subdivided into 3 groups on the basis of small but probably significant differences in clinical and radiographic findings. Group A (38 cases): short, broad, "crumpled" long bones, angulation of tibiae and continuously beaded ribs. Group B (6 cases): short, broad, crumpled femora, angulation of tibiae but normal ribs or ribs with incomplete beading. Group C (4 cases): long, thin, inadequately modelled, rectangular long bones with multiple fractures and thin beaded ribs. Consistency of findings within sibships suggests the groups reflect genetic heterogeneity. An increased frequency of parental consanguinity, sib occurrence with normal parents, and normal mean paternal age at birth, suggest that most cases of O.I. type II represent autosomal recessive traits. Some previously reported cases and the biochemical findings in one case suggest still further genetic heterogeneity.

Consanguinity↗
PubMed1997

Molecular genetic analysis of two families with keratosis follicularis spinulosa decalvans: refinement of gene localization and evidence for genetic heterogeneity.

X-linked keratosis follicularis spinulosa decalvans (KFSD) is a rare disorder affecting both skin and eyes. In the two extended KFSD families analysed to date, the gene was mapped to Xp22.13-p22.2. By analyzing several new markers in this region, we were able to narrow the candidate region to a 1-Mb interval between DXS7161 and (DXS7593, DXS7105) in the large Dutch pedigree. In addition, we analyzed 23 markers in Xp21.2-p22.2 in a German family with KFSD. Haplotype and recombination analysis positioned the KFSD gene in this family most likely outside the candidate region on Xp22.13-p22.2. This finding is suggestive for genetic heterogeneity: in this pedigree there is either another locus on the X-chromosome, or KFSD is transmitted here as an autosomal dominant trait with variable expression.

Child, Preschool↗
PubMed1994

Linkage of a human brain malformation, familial holoprosencephaly, to chromosome 7 and evidence for genetic heterogeneity.

Holoprosencephaly (HPE) is a common malformation of the developing forebrain and midface characterized by incomplete penetrance and variable expressivity. Familial HPE has been reported in many families with autosomal dominant inheritance in some and apparent autosomal recessive inheritance in others. We have examined 125 individuals from nine families with autosomal dominant HPE. Expression in gene carriers varied from alobar HPE and cyclopia through microforms such as microcephaly or single central incisor to normal phenotype. We performed linkage studies by either Southern blot or polymerase chain reaction analyses with DNA markers (D7S22, D7S550, and D7S483) that are deleted from some patients with sporadic HPE and flank a translocation breakpoint in 7q36 associated with HPE. The strongest support for linkage was with D7S22, which was linked with no recombination to autosomal dominant HPE in eight of nine families with a combined logarithm of odds score of 6.4 with an affected-only model-free analysis and 8.2 with a reduced-penetrance model and all phenotypes. Close linkage to this region could be excluded in one family, and there was significant evidence of genetic heterogeneity. These results show that a gene for autosomal dominant HPE is located in a chromosomal region (7q36) known to be involved in sporadic HPE with visible cytogenetic deletions. They also demonstrate genetic heterogeneity in familial HPE. We hypothesize that mutations of a gene in 7q36, designated HPE3, are responsible for both sporadic HPE and a majority of families with autosomal dominant HPE.

Adolescent↗
PubMed1998

Linkage of cytokine genes to rheumatoid arthritis. Evidence of genetic heterogeneity.

OBJECTIVE: To investigate linkage of candidate disease susceptibility genes to rheumatoid arthritis (RA) in affected sibling pair families stratified for specific clinical features. METHOD: Two hundred RA affected sibling pair families were genotyped for informative microsatellite markers mapping within or less than 3cM from: INF alpha, INF gamma, INF beta, IL1 alpha, IL1 beta, IL1R, IL2, IL6, IL5R, IL8R, BCL2, CD40L, NOS3, NRAMP, alpha 1 anti-trypsin, and alpha 1 anti-chymotrypsin, using fluorescence based automated technology. Linkage was examined by defining allele sharing sibling pairs. This was assessed by maximum likelihood-inheritance by descent methods. RESULTS: An increase in allele sharing was seen for IL5R in female sibling pairs (LOD 0.91, p = 0.03), for INF gamma in sibling pairs with an affected male (LOD 0.96, p = 0.03) and most significantly for IL2 in sibling pairs where one or both were persistently seronegative (LOD 1.05, p = 0.02). CONCLUSION: Weak evidence of linkage of RA to IL5R, IFN gamma, and IL2 has been detected in clinical subsets of sibling pairs suggesting that RA is a genetically heterogeneous disease.

Arthritis, Rheumatoid↗
PubMed1997

An extension of the admixture test for the study of genetic heterogeneity in hereditary multiple exostoses.

Hereditary multiple exostoses (EXT) is an autosomal dominant disorder characterized by the presence of multiple cartilage-capped exostoses in the juxta-epiphyseal regions of the long bones. EXT is heterogeneous with at least three different locations currently having been identified on chromosomes 8, 11 and 19. We have tested a series of 29 EXT families for possible linkage to the three disease loci and estimated the probability of linkage of the disease to each locus in our series, by using an extension of the admixture test, which makes modelling of heterogeneous monogenic disease feasible. The maximum likelihood was obtained for proportions of 44%, 28% and 28% of families being linked to chromosome 8, 11 and 19, respectively. The a posteriori probability of linkage of the disease to EXT1, EXT2 and EXT3 was greater than 80% for 8/29, 5/29 and 3/29 families, respectively, and did not give evidence of a fourth locus for the disease. The present approach can be generalized to the investigation of genetic heterogeneity in other monogenic diseases, as it simultaneously estimates the location of each disease gene and the proportion of families linked to each locus.

Chromosomes, Human, Pair 11↗