Syed Irfan Raza

A mutation in the lipase H (LIPH) gene underlie autosomal recessive hypotrichosis

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.

Mutations in TBC1D24, a gene associated with epilepsy, also cause nonsyndromic deafness DFNB86.

Inherited deafness is clinically and genetically heterogeneous. We recently mapped DFNB86, a locus associated with nonsyndromic deafness, to chromosome 16p. In this study, whole-exome sequencing was performed with genomic DNA from affected individuals from three large consanguineous families in which markers linked to DFNB86 segregate with profound deafness. Analyses of these data revealed homozygous mutation c.208G>T (p.Asp70Tyr) or c.878G>C (p.Arg293Pro) in TBC1D24 as the underlying cause of deafness in the three families. Sanger sequence analysis of TBC1D24 in an additional large family in which deafness segregates with DFNB86 identified the c.208G>T (p.Asp70Tyr) substitution. These mutations affect TBC1D24 amino acid residues that are conserved in orthologs ranging from fruit fly to human. Neither variant was observed in databases of single-nucleotide variants or in 634 chromosomes from ethnically matched control subjects. TBC1D24 in the mouse inner ear was immunolocalized predominantly to spiral ganglion neurons, indicating that DFNB86 deafness might be an auditory neuropathy spectrum disorder. Previously, six recessive mutations in TBC1D24 were reported to cause seizures (hearing loss was not reported) ranging in severity from epilepsy with otherwise normal development to epileptic encephalopathy resulting in childhood death. Two of our four families in which deafness segregates with mutant alleles of TBC1D24 were available for neurological examination. Cosegregation of epilepsy and deafness was not observed in these two families. Although the causal relationship between genotype and phenotype is not presently understood, our findings, combined with published data, indicate that recessive alleles of TBC1D24 can cause either epilepsy or nonsyndromic deafness.

A novel deletion mutation in CENPJ gene in a Pakistani family with autosomal recessive primary microcephaly

AbstractAutosomal recessive primary microcephaly (MCPH) is a rare human genetic disorder in which the head circumference is reduced because of abnormality in fetal brain growth. To date, six loci and four genes have been identified for this condition. Our study of primary MCPH led to the identification of 33 Pakistani families with different ethnic backgrounds. Most of these families showed linkage to MCPH5 locus on chromosome 1q31. Only one family with Pashtoon origin from a remote region in Pakistan linked to MCPH6 locus on chromosome 13q12.12-q12.13. Sequence analysis of exon 11 of CENPJ gene, located at MCPH6 locus, revealed a novel four base pair deletion mutation, which is predicted to be protein truncating.

A novel deletion mutation in the phospholipase H (LIPH) gene in a consanguineous Pakistani family with autosomal recessive hypotrichosis (LAH2)

To date, seven isolated forms of hair loss have been reported and mapped on different human chromosomes. These include congenital atrichia at 8q12, hypotrichosis simplex at 6p21.3, Marie Unna hereditary hypotrichosis at 8p21, three similar forms of localized hereditary hypotrichosis, LAH1 at 18q12.1, LAH2 at 3q26.33 and LAH3 at 13q14.11-q21.32, and autosomal recessive hypotrichosis simplex at 13q14.11-q21.33. All these conditions have been described at the molecular level and causative genes including hairless (HR, MIM 602302) for congenital atrichia, corneodesmosin (CDSN, MIM 602593) for hypotrichosis simplex, desmoglein 4 (DSG4, MIM 607892) for LAH1, LIPH (MIM 607365) for LAH2 and P2RY5 (MIM 609239) for autosomal recessive hypotrichosis simplex have been identified. The LIPH gene contains 10 exons and is expressed in several tissues including prostate, testis, ovary, colon, pancreas, kidney, lung, spleen, brain, heart and hair follicle. To date only three mutations (all deletions) in the LIPH gene have been reported. The first deletion mutation encompassing exon 4 and the flanking intronic sequences of the LIPH gene was reported by Kazantseva et al. in a large number of affected individuals in two populations from the Volga-Ural region of Russia. Our group previously reported two novel deletion mutations, c.346-350delATATA and c.659-660delTA in exon 2 and 5 of the LIPH gene, respectively. In this study we have identified the fourth novel deletion mutation of a single base pair (c.682delT) in exon 5 of the LIPH gene in a consanguineous Pakistani family, which showed linkage to the LAH2 locus on chromosome 3q26.33. Approval for the study was obtained from the Institutional Review Board of Quaid-i-Azam University, Islamabad, Pakistan. Informed consent was obtained from all participating subjects of the family.

In silico analysis of SIGMAR1 variant (rs4879809) segregating in a consanguineous Pakistani family showing amyotrophic lateral sclerosis without frontotemporal lobar dementia

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder affecting upper motor neurons in the brain and lower motor neurons in the brain stem and spinal cord, resulting in fatal paralysis. It has been found to be associated with frontotemporal lobar degeneration (FTLD). In the present study, we have described homozygosity mapping and gene sequencing in a consanguineous autosomal recessive Pakistani family showing non-juvenile ALS without signs of FTLD. Gene mapping was carried out in all recruited family members using microsatellite markers, and linkage was established with sigma non-opioid intracellular receptor 1 (SIGMAR1) gene at chromosome 9p13.2. Gene sequencing of SIGMAR1 revealed a novel 3′-UTR nucleotide variation c.672*31A>G (rs4879809) segregating with disease in this family. The C9ORF72 repeat region in intron 1, previously implicated in a related phenotype, was excluded through linkage, and further confirmation of exclusion was obtained by amplifying intron 1 of C9ORF72 with multiple primers in affected individuals and controls. In silico analysis was carried out to explore the possible role of 3′-UTR variant of SIGMAR1 in ALS. The Regulatory RNA motif and Element Finder program revealed disturbance in miRNA (hsa-miR-1205) binding site due to this variation. ESEFinder analysis showed new SRSF1 and SRSF1-IgM-BRCA1 binding sites with significant scores due to this variation. Our results indicate that the 3′-UTR SIGMAR1 variant c.672*31A>G may have a role in the pathogenesis of ALS in this family.

A novel deletion mutation in the DSG4 gene underlies autosomal recessive hypotrichosis with variable phenotype in two unrelated consanguineous families.

Autosomal recessive hypotrichosis is a rare human hereditary disorder presenting as sparse scalp hair or as woolly hair occurring on various parts of the body. Various forms of isolated hypotrichosis have been reported to date. Mutations in at least 11 genes have been reported to cause hypotrichosis.

In Silico Analysis of Missense Mutations in LPAR6 Reveals Abnormal Phospholipid Signaling Pathway Leading to Hypotrichosis

Autosomal recessive hypotrichosis is a rare genetic irreversible hair loss disorder characterized by sparse scalp hair, sparse to absent eyebrows and eyelashes, and sparse axillary and body hair. The study, presented here, established genetic linkage in four families showing similar phenotypes to lysophosphatidic acid receptor 6 (LPAR6) gene on chromosome 13q14.11-q21.32. Subsequently, sequence analysis of the gene revealed two previously reported missense mutations including p.D63V in affected members of one and p.I188F in three other families. Molecular modeling and docking analysis was performed to investigate binding of a ligand oleoyl-L-alpha-lysophosphatidic acid (LPA) to modeled protein structures of normal and mutated (D63V, G146R, I188F, N248Y, S3T, L277P) LPAR6 receptors. The mutant receptors showed a complete shift in orientation of LPA at the binding site. In addition, hydropathy analysis revealed a significant change in the membrane spanning topology of LPAR6 helical segments. The present study further substantiated involvement of LPAR6-LPA signaling in the pathogenesis of hypotrichosis/woolly hair and provided additional insight into the molecular mechanism of hair development.

A novel WDR62 mutation causes primary microcephaly in a Pakistani family

Autosomal recessive primary microcephaly (MCPH) is a heterogeneous disorder which mainly affects neurodevelopment. Generally, MCPH patients exhibit mild brain structural anomalies and simplified cerebral cortex, but few recently identified genes are associated with severe brain malformations. Here, we report a five generation Pakistani family with three affected individuals presenting primary microcephaly, intellectual disability, schizencephaly and hypoplasia of corpus callosum. The comparison of available clinical information led to candidate gene mapping and sequencing of WD repeat domain 62 (WDR62) gene which is mostly associated with severe brain malformations. A homozygous deletion mutation c.1143delA was detected in exon 9 of WDR62 gene, in all affected individuals, which resulted in frameshift and protein truncation (p.H381PfsX48). This study supports the frequent involvement of WDR62 in patients with gross brain malformations.

A novel missense mutation in the gene FZD6 underlies autosomal recessive nail dysplasia

Background  Inherited isolated nail anomaly manifesting with onychauxis and onycholysis is a rare condition, caused by mutations in the gene FZD6, encoding membrane‐bound Wnt receptor protein.

A Novel Homozygous Nonsense Mutation in the PVRL4 Gene and Expansion of Clinical Spectrum of EDSS1

Ectodermal dysplasias (EDs) belong to a group of genetic diseases which result from alterations in ectoderm‐derived appendages including hair, nail, teeth and sweat glands. Ectodermal dysplasia syndactyly syndrome (EDSS1) is one of the rare forms of ED caused by mutations in nectin‐4, encoded by the PVRL4 gene. The present study described clinical investigation of the EDSS1 identified in a large consanguineous family. Furthermore, DNA sequence analysis revealed a novel homozygous nonsense mutation (181C>T, p.Asp61*) in the PVRL4 gene.