Hereditary hypotrichosis is a rare autosomal recessive disorder characterized by sparse hair on scalp and rest of the body of affected individuals. Two forms of such hypotrichosis LAH and AH have been mapped on chromosome 18q12.1 and 3q27, respectively. Mutations in desmogelin 4 (DSG4) gene have been reported to underlie LAH. Recently, a deletion mutation in Lipase H (LIPH) gene, located at AH locus, has been identified in two ethnic groups of Russian population. In the present study, a four generation Pakistani family with AH phenotype has been mapped to chromosome 3q27. Sequence analysis of candidate gene LIPH revealed a novel five base pair deletion mutation (c.346-350delATATA) in exon 2 of the gene leading to frameshift and downstream premature termination codon. The mutation reported in the family, presented here, is the second mutation identified in LIPH gene. The identification of a genetic defect in LIPH suggests that this enzyme regulates hair growth.
Human autosomal recessive primary microcephaly (MCPH) is a rare genetic disorder in which affected individuals are born with reduced brain size. MCPH is genetically heterogeneous, with six loci and four genes reported to date. Mutations in the ASPM gene at the MCPH5 locus appear to be the most common cause of MCPH. For this study, 33 Pakistani families with primary microcephaly were enrolled. Genotyping using microsatellite markers linked to the six known MCPH loci showed the linkage of 18 families to the MCPH5 locus, two to the MCPH2 locus, two to the MCPH4 locus, and one to the MCPH6 locus. The remaining ten families were not linked to any of the known loci. Families linked to the MCPH5 locus were further subjected to screening of the ASPM gene with direct DNA sequencing. Two previously reported variants, 3978G>A (W1326X) and 9557C>G (S3186X), were observed in five Pakistani families. Four novel nonsynonymous sequence variants, 9118insCATT, 9238A>T (L3080X), 9539A>C (Q3180P), and 1260delTCAAGTC, were found to segregate within four families, but were not observed in 200 Pakistani control chromosomes. One of the variants, 9539A>C (Q3180P), occurred in the IQ 79 domain, but its functional significance awaits definition.
Hereditary hearing impairment (HI) displays extensive genetic heterogeneity. To date, 67 autosomal recessive nonsyndromic hearing impairment (ARNSHI) loci have been mapped, and 24 genes have been identified. This report describes three large consanguineous ARNSHI Pakistani families, all of which display linkage to marker loci located in the genetic interval of DFNB49 locus on chromosome 5q13. Recently, Riazuddin et al. (Am J Hum Genet 2006; 79:1040-1051 reported that variants within the TRIC gene, which encodes tricellulin, are responsible for HI due to DFNB49. TRIC gene sequencing in these three families led to the identification of a novel mutation (IVS4 + 1G [ A) in one family and the discovery of a previously described mutation (IVS4 + 2T [ C) in two families. It is estimated that 1.06% (95% confidence interval 0.02-3.06%) of families with ARNSHI in Pakistan manifest HI due to mutations in the TRIC gene.
Autosomal recessive hypotrichosis (LAH3) is a rare hair disorder characterized by sparse hair on scalp and the rest of the body of affected individuals. Recently mutations in a G protein-coupled receptor gene, P2RY5, located at LAH3 locus, have been reported in several families with autosomal recessive hypotrichosis simplex and woolly hair. For the present study, 22 Pakistani families with autosomal recessive hypotrichosis were enrolled. Genotyping using microsatellite markers linked to three autosomal recessive forms of hypotrichosis (LAH1, LAH2, LAH3) showed the linkage of 2 families to the LAH2 locus and 14 to the LAH3 locus. The remaining 6 families were not linked to any of the three loci. Families linked to LAH3 locus were further subjected to screening of the P2RY5 gene with direct DNA sequencing. Three previously reported variants, c.69insCATG (p.24insHfs52), c.188A > T (p.D63V) and c.565G > A (p.E189K) were observed in eight families. Four novel nonsynonymous sequence variants, c.8G > C (p.S3T), c.36insA (p.D13RfsX16), c.160insA (p.N54TfsX58) and c.436G > A (p.G146R) were found to segregate within six families.
Ectodermal-dysplasia-syndactyly syndrome (EDSS1) is a rare form of ectodermal dysplasia (ED), affecting skin and its appendages mainly hair, teeth and nails. In the present study, we have investigated a large consanguineous Pakistani family with 10 individuals showing features of EDSS1. Human genome was screened using highly polymorphic microsatellite markers to identify the gene causing EDSS1. The disease locus for EDSS1 was assigned to chromosome 1q23.1-q23.3. This region corresponds to 5.63 Mb according to the sequenced based physical map (Build 36.2) of the human genome and flanked by markers D1S1653 and D1S1677. A maximum two-point LOD score of 5.05 was obtained with the marker D1S484. Sequence analysis revealed a homozygous missense mutation (c.635C4G; p.Pro212Arg) in the recently reported PVRL4 gene causing EDSS1. The involvement of mutant nectin-4 in causing EDSS1 may open up interesting prospectives into the role of cell adhesion molecules in causing syndromic forms of EDs.
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