Exclusion of PTEN, CTNNB1, and PTCH as candidate genes for Birt-Hogg-Dube syndrome.
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Adult↗
Biomedical subjects
J G Compton
Publications and source records attributed to J G Compton.
Mutation of a new gene causes a unique form of Hermansky-Pudlak syndrome in a genetic isolate of central Puerto Rico.
Hermansky-Pudlak syndrome (HPS) is a rare autosomal recessive disorder characterized by oculocutaneous albinism and a storage pool deficiency due to an absence of platelet dense bodies. Lysosomal ceroid lipofuscinosis, pulmonary fibrosis and granulomatous colitis are occasional manifestations of the disease. HPS occurs with a frequency of one in 1800 in north-west Puerto Rico due to a founder effect. Several non-Puerto Rican patients also have mutations in HPS1, which produces a protein of unknown function. Another gene, ADTB3A, causes HPS in the pearl mouse and in two brothers with HPS-2 (refs. 11,12). ADTB3A encodes a coat protein involved in vesicle formation, implicating HPS as a disorder of membrane trafficking. We sought to identify other HPS-causing genes. Using homozygosity mapping on pooled DNA of 6 families from central Puerto Rico, we localized a new HPS susceptibility gene to a 1.6-cM interval on chromosome 3q24. The gene, HPS3, has 17 exons, and a putative 113.7-kD product expected to reveal how new vesicles form in specialized cells. The homozygous, disease-causing mutation is a large deletion and represents the second example of a founder mutation causing HPS on the small island of Puerto Rico. We also present an allele-specific assay for diagnosing individuals heterozygous or homozygous for this mutation.
Alleles↗
Splice-site mutation in TGM1 in congenital recessive ichthyosis in American families: molecular, genetic, genealogic, and clinical studies.
Lamellar ichthyosis (LI, OMIM no. 242300) is a severe autosomal recessive genodermatosis with an estimated prevalence of 1:200,000. LI represents one end of the spectrum of congenital recessive ichthyosis (CRI). Mutations in the gene for transglutaminase-1 (TGM1) are responsible for many cases of LI and occur throughout the coding sequence of the gene. Our analyses of patients with CRI revealed a common TGM1 mutation involving loss of the intron 5 splice acceptor site leading to alternative splicing of the message. We found families in which the splice acceptor site mutation was homozygous, and families where the patients were compound heterozygotes for the splice acceptor site mutation and another TGM1 mutation. A mutation at this same site occurs in the majority of Norwegian patients as a founder effect. In our ethnically diverse patient population, none of whom have known Norwegian ancestry, haplotype analysis of the TGM1 chromosomal region also suggested the existence of a founder effect. Comparison of the common haplotype in our data with the Norwegian data showed that 2/7 of our splice acceptor site mutation chromosomes had the full reported Norwegian haplotype, and the remaining five chromosomes exhibited recombination at the most distal marker studied. History, family origins, and haplotype analysis suggested that the mutation originally arose on a German background and was introduced into Norway around 800-1000 AD. We also found a limited correlation between genotype and phenotype in our study, with the four homozygous patients having less severe disease than many of the heterozygotes, and no patient with a splice acceptor site mutation having erythroderma or a congenital ichthyosiform erythroderma phenotype.
Adolescent↗
Mutation screening using automated bidirectional dideoxy fingerprinting.
The need continues to grow for mutation identification in genetic disease in both research and clinical settings. We have developed a rapid nonradioactive bidirectional dideoxy fingerprint mutation screening procedure that is performed using an automated DNA analyzer. This technique features standardized primers and easily interpreted results from separate, but simultaneously collected, images for coding and noncoding strands. Another advantage is simplified mutation verification by sequencing using the same amplified DNA templates and also application to large multi-exon genes. We demonstrate the efficiency and reproducibility of the method in which we screen a DNA fragment encompassing exon 5 of the PTCH gene (in which mutations cause Gorlin Syndrome) in a panel of 22 patients.
Basal Cell Nevus Syndrome↗
A highly conserved lysine residue on the head domain of type II keratins is essential for the attachment of keratin intermediate filaments to the cornified cell envelope through isopeptide crosslinking by transglutaminases.
We have addressed the question of how keratin intermediate filaments are associated with the cell envelope at the periphery of cornified epidermal cells. Many peptides from human epidermal cell envelopes containing isopeptide crosslinks inserted by transglutaminases in vivo have been characterized. A major subset involves the type II keratin chains keratin 1, 2e, 5, or 6 crosslinked to several protein partners through a lysine residue located in a conserved region of the V1 subdomain of their head domains. This sequence specificity was confirmed in in vitro crosslinking experiments. Previously the causative mutation in a family with diffuse nonepidermolytic palmar-plantar keratoderma was shown to be the loss in one allele of the same lysine residue of the keratin 1 chain. Ultrastructural studies of affected palm epidermis have revealed abnormalities in the organization of keratin filaments subjacent to the cell envelope and in the shape of the cornified cells. Together, these data suggest a mechanism for the coordination of cornified cell structure by permanent covalent attachment of the keratin intermediate filament cytoskeleton to the cell envelope by transglutaminase crosslinking. Furthermore, these studies identify the essential role of a conserved lysine residue on the head domains of type II keratins in the supramolecular organization of keratin filaments in cells.
Amino Acid Sequence↗
Functional defects of Cx26 resulting from a heterozygous missense mutation in a family with dominant deaf-mutism and palmoplantar keratoderma.
Mutations in GJB2 encoding the gap junction protein connexin-26 (Cx26) have been established as the basis of autosomal recessive non-syndromic hearing loss. The involvement of GJB2 in autosomal dominant deafness has also been proposed, although the putative mutation identified in one family with both deafness and palmoplantar keratoderma has recently been suggested to be merely a non-disease associated polymorphism. We have observed a similar phenotype in an Egyptian family that segregated with a heterozygous missense mutation of GJB2, leading to a non-conservative amino acid substitution (R75W). The deleterious dominant-negative effect of R75W on gap channel function was subsequently demonstrated in the paired oocyte expression system. Not only was R75W alone incapable of inducing electrical conductance between adjacent cells, but it almost completely suppressed the activity of co-expressed wildtype protein. The Cx26 mutant W77R, which has been implicated in autosomal recessive deafness, also failed to form functional gap channels by itself but did not significantly interfere with the function of wildtype Cx26. These data provide compelling evidence for the serious functional consequences of Cx26 mutations in dominant and recessive deafness.
Amino Acid Sequence↗
Mutations in the human connexin gene GJB3 cause erythrokeratodermia variabilis.
Erythrokeratodermia variabilis (EKV, OMIM 133200) is an autosomal dominant genodermatosis with considerable intra- and interfamilial variability. It has a disfiguring phenotype characterized by the independent occurrence of two morphologic features: transient figurate red patches and localized or generalized hyperkeratosis. Both features can be triggered by external factors such as trauma to the skin. After initial linkage to the RH locus on 1p, EKV was mapped to an interval of 2.6 cM on 1p34-p35, and a candidate gene (GJA4) encoding the gap junction protein alpha-4 (connexin 31, Cx31) was excluded by sequence analysis. Evidence in mouse suggesting that the EKV region harbours a cluster of epidermally expressed connexin genes led us to characterize the human homologues of GJB3 (encoding Cx31) and GJB5 (encoding Cx31.1). GJB3, GJB5 and GJA4 were localized to a 1.1-Mb YAC in the candidate interval. We detected heterozygous missense mutations in GJB3 in four EKV families leading to substitution of a conserved glycine by charged residues (G12R and G12D), or change of a cysteine (C86S). These mutations are predicted to interfere with normal Cx31 structure and function, possibly due to a dominant inhibitory effect. Our results implicate Cx31 in the pathogenesis of EKV, and provide evidence that intercellular communication mediated by Cx31 is crucial for epidermal differentiation and response to external factors.
Amino Acid Sequence↗
A deletion mutation in COL17A1 in five Austrian families with generalized atrophic benign epidermolysis bullosa represents propagation of an ancestral allele.
Patients with generalized atrophic benign epidermolysis bullosa, a usually nonlethal form of junctional epidermolysis bullosa, have generalized blistering, nail dystrophy, patchy alopecia, and dental abnormalities. Skin fragility in most cases is due to mutations in the gene encoding type XVII collagen (COL17A1). Recently, we reported five Austrian families with generalized atrophic benign epidermolysis bullosa who share the same COL17A1 mutation. Affected individuals in three families are homozygous for 4003delTC, whereas those in two others are compound heterozygotes. To determine if the occurrence of 4003delTC in these unrelated families signifies propagation of an ancestral allele or a mutational hot spot, haplotypes were determined for polymorphisms both within and flanking COL17A1. Five intragenic polymorphisms were chosen based on their informativeness. One of these, not previously reported, was 2988 A or C that introduces a new restriction site for Eco0109 I. All the 4003delTC alleles showed the same haplotype for these five polymorphic markers. Fourteen microsatellite polymorphisms were selected based on their high heterozygosity and their location within 10q23-q25 near COL17A1. Three families shared microsatellite polymorphisms covering at most 19 cM, whereas the others shared smaller regions consistent with cross-over events during passage of this mutation through several generations. These results indicate that 4003delTC occurs on a single ancestral allele.
Alleles↗
Genomic organization and expression of the human fatty aldehyde dehydrogenase gene (FALDH).
Mutations in the fatty aldehyde dehydrogenase (FALDH) gene cause Sjögren-Larsson syndrome (SLS)-a disease characterized by mental retardation, spasticity, and congenital ichthyosis. To facilitate mutation analysis in SLS and to study the pathogenesis of FALDH deficiency, we have determined the structural organization and characterized expression of the FALDH (proposed designation ALDH10) gene. The gene consists of 10 exons spanning about 30.5 kb. A TATA-less promoter is associated with the major transcription initiation site found to be 258 bp upstream of the ATG codon. The GC-rich sequences surrounding the transcription initiation site encompassed regulatory elements that interacted with proteins in HeLa nuclear extracts and were able to promote transcription in vitro. FALDH is widely expressed as three transcripts of 2, 3.8, and 4.0 kb, which originate from multiple polyadenylation signals in the 3' UTR. An alternatively spliced mRNA was detected that contains an extra exon and encodes an enzyme that is likely to have altered membrane-binding properties. The FALDH gene lies only 50-85 kb from ALDH3, an aldehyde dehydrogenase gene that has homologous sequence and intron/exon structure.
Aldehyde Oxidoreductases↗
Sjögren-Larsson syndrome is caused by a common mutation in northern European and Swedish patients.
Sjögren-Larsson syndrome (SLS) is an autosomal recessive disorder characterized by congenital ichthyosis, mental retardation, and spastic diplegia or tetraplegia. Patients with SLS have deficient activity of fatty aldehyde dehydrogenase (FALDH), an enzyme involved in long-chain fatty alcohol oxidation. The cDNA encoding FALDH has recently been cloned and several different mutations have been found in SLS patients. We have now identified a point mutation (C943 --> T) in 7 of 19 kindreds of European descent, accounting for 24% of the SLS alleles. The C943T mutation was only found in patients of northern European ancestry from Sweden, the Netherlands, Germany, and Belgium. Haplotype analysis suggested that the patients carrying the C943T allele were distantly related. All four Swedish patients were homozygous for C943T, indicating that this mutation is probably the major cause of SLS in the inbred Swedish families. The mutation leads to the substitution of serine for the highly conserved proline 315 in the FALDH protein, and expression studies confirm that it destroys enzymatic activity. The mutation was readily detected with an MnlI restriction enzyme digestion test. The finding that C943T is a common SLS mutation in northern European and Swedish patients affords a rapid simple method for diagnosing SLS by screening patients for this mutation with DNA-based methods.
Aldehyde Oxidoreductases↗
Sjögren-Larsson syndrome is caused by mutations in the fatty aldehyde dehydrogenase gene.
Sjögren-Larsson syndrome (SLS) is an inherited neurocutaneous disorder characterized by mental retardation, spasticity and ichthyosis. SLS patients have a profound deficiency in fatty aldehyde dehydrogenase (FALDH) activity. We have now cloned the human FALDH cDNA and show that it maps to the SLS locus on chromosome 17p11.2. Sequence analysis of FALDH amplified from fibroblast mRNA and genomic DNA from 3 unrelated SLS patients reveals distinct mutations, including deletions, an insertion and a point mutation. The cloning of FALDH and the identification of mutations in SLS patients opens up possibilities for developing therapeutic approaches to ameliorate the neurologic and cutaneous symptoms of the disease.
Aldehyde Oxidoreductases↗
Genetic heterogeneity in lamellar ichthyosis.
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Genetic Variation↗
Congenital recessive ichthyosis unlinked to loci for epidermal transglutaminases.
Congenital recessive ichthyosis has a broad range of clinical presentations, which may be considered a spectrum of phenotypes with classic lamellar ichthyosis at one pole and classic congenital ichthyosiform erythroderma at the other. The identification of mutations in the transglutaminase-1 gene as a cause of lamellar ichthyosis implicates transglutaminases in other congenital recessive ichthyoses. We investigated two multiplex families with clinical manifestations between the two poles for linkage to the transglutaminase-1 locus on chromosome 14. Strongly negative lod scores prompted a search for linkage to two other epidermally expressed transglutaminases, transglutaminase-2 and transglutaminase-3, on chromosome 20. No evidence for linkage was found. These data confirm the hypothesis that the congenital recessive ichthyoses are genetically heterogeneous and in two families exclude two other transglutaminases that could be considered as candidate loci for at least some of the nonlamellar recessive ichthyoses.
Child↗
Mutations in the gene for transglutaminase 1 in autosomal recessive lamellar ichthyosis.
We recently mapped the disease locus for severe autosomal recessive lamellar ichthyosis (LI) to chromosome 14q11 and showed complete linkage with TGM1, the gene encoding transglutaminase 1. We have now identified point mutations in TGM1 in two of the multiplex LI families used in the linkage study. Each nucleotide change causes a non-conservative amino acid substitution of histidine for one of two adjacent arginine residues in exon 3 of the gene (Arg141His, Arg142His). Within the transglutaminase family, these arginines are invariant within a conserved region, distant from the catalytic site of the enzyme. We hypothesize that these mutations adversely affect formation of crosslinks essential in production of cornified cell envelopes and a normal stratum corneum layer of the skin.
Amino Acid Sequence↗
Keratin 13 point mutation underlies the hereditary mucosal epithelial disorder white sponge nevus.
Although pathogenic keratin mutations have been well characterized in inherited epidermal disorders, analogous defects in keratins expressed in non-epidermal epithelia have yet to be described. White sponge nevus (WSN) is a rare autosomal dominant disorder of non-cornifying squamous epithelial differentiation that presents clinically as bilateral white, soft, thick plaques of the oral mucosa. Less frequently the mucous membranes of the nose, esophagus, genitalia and rectum are involved. Histopathological features, including epithelial thickening, parakeratosis, extensive vacuolization of the suprabasal keratinocytes and compact aggregates of keratin intermediate filaments (KIF) in the upper spinous layers, resemble those found in epidermal disorders due to keratin defects. We analysed a multigenerational family with WSN and found cosegregation of the disease with the keratin gene cluster on chromosome 17. We identified a missense mutation in one allele of keratin 13 that leads to proline substitution for a conserved leucine. The mutation occurred within the conserved 1A region of the helical rod domain, which is critical for KIF stability and is the site of most pathogenic keratin mutations. This mutation enlarges the spectrum of keratins with disease-causing defects to include mucosally expressed keratin 13, and extends the known keratin diseases to disorders of non-cornifying stratified squamous epithelia.
Amino Acid Sequence↗
Hailey-Hailey disease maps to a 5 cM interval on chromosome 3q21-q24.
Hailey-Hailey disease (HHD) is a rare autosomal dominant genodermatosis characterized by disturbed keratinocyte adhesion. The disease has recently been mapped to a 14 cM region on chromosome 3q. We have further refined the location of the HHD gene by linkage analysis in six HHD families from Germany and Italy using 11 polymorphic microsatellite markers and found no evidence for genetic heterogeneity. We observed complete cosegregation between HHD and marker D3S1587, with a maximal lod score of 4.54. Detailed haplotype analyses allowed us to narrow the interval containing the HHD locus to 5 cM, flanked by D3S1589 and D3S1290.
Chromosome Mapping↗
Genetic homogeneity in Sjögren-Larsson syndrome: linkage to chromosome 17p in families of different non-Swedish ethnic origins.
Sjögren-Larsson syndrome (SLS) is a rare, autosomal recessive disorder that is characterized by congenital ichthyosis, mental retardation, and spastic diplegia or tetraplegia. Three United States families, three Egyptian families, and one Israeli Arab family were investigated for linkage of the SLS gene to a region of chromosome 17. Pairwise and multipoint linkage analysis with nine markers mapped the SLS gene to the same region of the genome as that reported in Swedish SLS pedigrees. Examination of recombinants by haplotype analysis showed that the gene lies in the region containing the markers D17S953, D17S805, D17S689, and D17S842. D17S805 is pericentromeric on 17p. Patients in two consanguineous Egyptian families were homozygous at the nine marker loci tested, and another patient from a third family was homozygous for eight of the nine, suggesting that within each of these families the region of chromosome 17 carrying the SLS gene is identical by descent. Linkage of the SLS gene to chromosome 17p in families of Arabic, mixed European, Native American, and Swedish descent provides evidence for a single SLS locus and should prove useful for diagnosis and carrier detection in worldwide cases.
Alleles↗
Epidermal disease: faulty keratin filaments take their toll.
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Epidermolysis Bullosa Simplex↗