Exome sequencing reveals the first intragenic deletion in ABCA5 underlying autosomal recessive hypertrichosis.

BACKGROUND: Hereditary hypertrichosis (HH) is characterized by excessive hair growth on various body areas, which is independent of the individual's age. This rare hair disorder has been classified by its origin (genetic or acquired), age of onset, breadth of hair distribution (universal or localized) and the affected body areas. HH is often linked to several additional congenital abnormalities involving teeth, heart and bones. Human HH is associated with heterozygous genomic duplications and deletions in the chromosomal region 17q24.2-q24.3, containing genes such as ABCA5, ABCA6, ABCA10 and MAP2K6. Recently, a homozygous splice-site variant in ABCA5 has been reported to cause autosomal recessive congenital generalized hypertrichosis terminalis (CGHT; OMIM 135400). AIM: To investigate the clinical and genetic basis of autosomal recessive hypertrichosis in a large consanguineous Pakistani family. METHODS: In the present study, we characterized a family of Pakistani origin segregating CGHT in an autosomal recessive pattern, using whole exome sequencing followed by Sanger sequencing. RESULTS: We identified a novel 2-bp intragenic deletion [NM_172232.4(ABCA5);c.977_978delAT] causing a frameshift variant (p.His326ArgfsTer5) in ABCA5. CONCLUSIONS: To our knowledge, this is the first intragenic deletion in ABCA5 underlying CGHT. The findings further validate the involvement of ABCA5 in hair development. The study will facilitate genetic counselling of families carrying CGHT-related features in Pakistani and other populations.

Wolfram-like syndrome with bicuspid aortic valve due to a homozygous missense variant in CDK13.

BACKGROUND: Wolfram syndrome (WFS) is characterized by deafness, diabetes mellitus, and diabetes insipidus along with optic atrophy. WFS has an autosomal recessive mode of inheritance and is due to variants in WFS1 and CISD2. METHODS: We evaluated the underlying molecular etiology of three affected members of a consanguineous family with hearing impairment, bicuspid aortic valve, diabetes mellitus and insipidus, clinodactyly, and gastrointestinal tract abnormalities via exome sequencing approach. We correlated clinical and imaging data with the genetic findings and their associated phenotypes. RESULTS: We identified a homozygous missense variant p.(Asn1097Lys) in CDK13, a gene previously associated with autosomal dominant congenital heart defects, dysmorphic facial features, clinodactyly, gastrointestinal tract abnormalities, intellectual developmental disorder, and seizures with variable phenotypic features. CONCLUSION: We report a homozygous variant in CDK13 and suggest that this gene causes an autosomal recessive disorder with hearing impairment, bicuspid aortic valve, diabetes mellitus and insipidus, clinodactyly, and gastrointestinal tract abnormalities.

ß2 Integrin Gene (ITGB2) mutation spectra in Pakistani families with leukocyte adhesion deficiency type 1 (LAD1).

Leukocyte adhesion deficiency I (LADI) is an autosomal recessive type of primary immunodeficiency characterized by occurrence of repeated bacterial infections, impaired pus formation and wound healing. Genetic variations in the ß-2 integrin subunit encoding gene ITGB2 have been implicated in causing the disorder. In the present study, we have investigated twelve patients presenting LAD1 features. After collecting clinical and family history, flow cytometry was used to determine levels of CD18 in the patients. Clinical history revealed that umbilical cord separation occurred mostly after 19 days in the patients. Recurrent skin infections were found in seven patients. Eight patients had at least one elder sibling who died due to repeated infections. All patients had marked neutrophilia with only 0.77% of neutrophils expressing CD18. Total 12 patients suffering from LAD1 were Sanger sequenced for ITGB2 gene. Five variants, including a novel p.(Cys286Phe) and four previously reported [p.(Gly273Arg), p.(Asp128Tyr), p.(Cys62*), IVS7 + 1G > A] were identified in 8 cases, while no pathogenic variant was observed in remaining four cases. This study represents the first comprehensive clinical and genetic characterization of LAD1 in Pakistani population. This will facilitate diagnosis and genetic counselling of patients with immunodeficiency disorders in Pakistani population.

Relationship of S/R warfarin ratio with CYP2C9 genotypes in Pakistani population.

Warfarin is administered as a racemic preparation of R- and S-enantiomers. S-warfarin is more potent than R-warfarin, so changes in blood levels of S-warfarin affect the anticoagulant response. This study was carried out to determine the effect of CYP2C9*2 and CYP2C9*3 polymorphisms on S/R warfarin ratio. A single blood sample was collected 12-16 hours after drug administration from 170 stable patients fulfilling the criteria. Genotyping of the CYP2C9 polymorphisms was done by polymerase chain reaction-restriction fragment length polymorphism assay. S- and R-warfarin enantiomers extraction from plasma was accomplished by a validated HPLC method. The concentration of S-warfarin was significantly different among CYP2C9 genotypes (p =0.018) whereas there was no effect on R-warfarin (p =0.134). There was statistically significant effect of different CYP2C9 genotypes on S/R warfarin ratio (p=0.000). It is concluded that CYP2C9 polymorphisms influence CYP2C9 enzymatic activity in turn affecting S-warfari levels but not R-warfarin, thus leading to different S/R warfarin enantiomers ratio among different CYP2C9 genotypes.

Identification of CACNA1D variants associated with sinoatrial node dysfunction and deafness in additional Pakistani families reveals a clinical significance.

Sinoatrial node dysfunction and deafness (SANDD) syndrome is rare and characterized by a low heart beat and severe-to-profound deafness. Additional features include fatigue, dizziness, and episodic syncope. The sinoatrial node (SAN) drives heart automaticity and continuously regulates heart rate. The CACNA1D gene encoding the Cav1.3 protein expressed in inner hair cells, atria and SAN, induces loss-of-function in channel activity and underlies SANDD. To date, only one variant c.1208_1209insGGG:p.(G403_V404insG) has been reported for SANDD syndrome. We studied five Pakistani families with SANDD and characterized a new missense variant p.(A376V) in CACNA1D in one family, and further characterized the founder variant p.(G403_V404insG) in four additional pedigrees. We show that affected individuals in the four families which segregate p.(G403_V404insG) share a 1.03 MB haplotype on 3p21.1 suggesting they share a common distant ancestor. In conclusion, we identified new and known variants in CACNA1D in five Pakistani families with SANDD. This study is of clinical importance as the CACNA1D founder variant is only observed in families from the Khyber Pakhtunkhwa (KPK) province, in Pakistan. Therefore, screening patients with congenital deafness for SAN dysfunction in this province could ensure adequate follow-up and prevent cardiac failure associated with SAN.

Molecular and in silico analyses validates pathogenicity of homozygous mutations in the NPR2 gene underlying variable phenotypes of Acromesomelic dysplasia, type Maroteaux.

Homozygous and/or heterozygous loss of function mutations in the natriuretic peptide receptor B (NPR2) have been reported in causing acromesomelic dysplasia, type Maroteaux with variable clinical features and idiopathic short stature with nonspecific skeletal deformities. On the other hand, gain of function mutations in the same gene result in overgrowth disorder suggesting that NPR2 and its ligand, natriuretic peptide precursor C (CNP), are the key players of endochondral bone growth. However, the precise mechanism behind phenotypic variability of the NPR2 mutations is not fully understood so far. In the present study, three consanguineous families of Pakistani origin (A, B, C) with variable phenotypes of acromesomelic dysplasia, type Maroteaux were evaluated at clinical and molecular levels. Linkage analysis followed by Sanger sequencing of the NPR2 gene revealed three homozygous mutations including p.(Leu314 Arg), p.(Arg371*), and p.(Arg1032*) in family A, B and C, respectively. In silico structural and functional analyses substantiated that a novel missense mutation [p.(Leu314 Arg)] in family A allosterically affects binding of NPR2 homodimer to its ligand (CNP) which ultimately results in defective guanylate cyclase activity. A nonsense mutation [p.(Arg371*)] in family B entirely removed the transmembrane domain, protein kinase domain and guanylate cyclase domains of the NPR2 resulting in abolishing its guanylate cyclase activity. Another novel mutation [p.(Arg1032*)], found in family C, deteriorated the guanylate cyclase domain of the protein and probably plundered its guanylate cyclase activity. These results suggest that guanylate cyclase activity is the most critical function of the NPR2 and phenotypic severity of the NPR2 mutations is proportional to the reduction in its guanylate cyclase activity.

Role of gut microbiota against calcium oxalate.

Nephrolithiasis is a condition marked by the presence or formation of stones in kidneys. Several factors contribute to kidney stones development such as environmental conditions, type of dietary intake, gender and gastrointestinal flora. Most of the kidney stones are composed of calcium phosphate and calcium oxalate, which enter in to the body through diet. Both sources of oxalates become dangerous when normal flora of gastrointestinal tract is disturbed. Oxalobacter and Lactobacillus species exist symbiotically in the human gut and prevent stone formation by altering some biochemical pathways through production of specific enzymes which help in the degradation of oxalate salts. Both Oxalobacter and Lactobacillus have potential probiotic characteristics for the prevention of kidney stone formation and this avenue should be further explored.

Autosomal-Recessive Hearing Impairment Due to Rare Missense Variants within S1PR2.

The sphingosine-1-phosphate receptors (S1PRs) are a well-studied class of transmembrane G protein-coupled sphingolipid receptors that mediate multiple cellular processes. However, S1PRs have not been previously reported to be involved in the genetic etiology of human traits. S1PR2 lies within the autosomal-recessive nonsyndromic hearing impairment (ARNSHI) locus DFNB68 on 19p13.2. From exome sequence data we identified two pathogenic S1PR2 variants, c.323G>C (p.Arg108Pro) and c.419A>G (p.Tyr140Cys). Each of these variants co-segregates with congenital profound hearing impairment in consanguineous Pakistani families with maximum LOD scores of 6.4 for family DEM4154 and 3.3 for family PKDF1400. Neither S1PR2 missense variant was reported among ∼120,000 chromosomes in the Exome Aggregation Consortium database, in 76 unrelated Pakistani exomes, or in 720 Pakistani control chromosomes. Both DNA variants affect highly conserved residues of S1PR2 and are predicted to be damaging by multiple bioinformatics tools. Molecular modeling predicts that these variants affect binding of sphingosine-1-phosphate (p.Arg108Pro) and G protein docking (p.Tyr140Cys). In the previously reported S1pr2(-/-) mice, stria vascularis abnormalities, organ of Corti degeneration, and profound hearing loss were observed. Additionally, hair cell defects were seen in both knockout mice and morphant zebrafish. Family PKDF1400 presents with ARNSHI, which is consistent with the lack of gross malformations in S1pr2(-/-) mice, whereas family DEM4154 has lower limb malformations in addition to hearing loss. Our findings suggest the possibility of developing therapies against hair cell damage (e.g., from ototoxic drugs) through targeted stimulation of S1PR2.

Disease causing homozygous variants in the human hairless gene.

BACKGROUND: Atrichia with papular lesions (APL) is a rare irreversible form of complete hair loss inherited in autosomal recessive manner. Hair loss is often followed by the appearance of multiple keratin-filled cysts or papules on exterior parts of the body. This phenotype results due to mutations in the human hairless gene (HR) mapped on chromosome 8p21.3. The present study was aimed to search for disease-causing sequence variants in the HR gene in five consanguineous families exhibiting features of APL. METHODS: Linkage in five Pakistani lineal consanguineous families, displaying features of APL, was tested using microsatellite markers flanking the HR gene on chromosome 8p21.3. After constructing the haplotypes, variants in the gene HR were searched by dideoxy-chain termination sequencing. RESULTS: Haplotype analysis established linkage in all five families to the HR gene located on chromosome 8p.21.3. Subsequently, sequencing HR identified a novel homozygous nonsense variant (c.2541G>A, p.Trp847*) in one and previously reported two pathogenic variants (p.Cys690*, p.Pro1157Arg) in the other four families. CONCLUSION: Mutations identified extend the spectrum of mutations in the HR gene resulting in APL. Characterizing the clinical spectrum resulting from the disease-causing homozygous variants in the HR gene will direct clinical care of the family members.

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 homozygous missense variant in type I keratin KRT25 causes autosomal recessive woolly hair.

BACKGROUND: Woolly hair (WH) is a hair abnormality that is primarily characterised by tightly curled hair with abnormal growth. METHODS: In two unrelated consanguineous Pakistani families with non-syndromic autosomal recessive (AR) WH, homozygosity mapping and linkage analysis identified a locus within 17q21.1-q22, which contains the type I keratin gene cluster. A DNA sample from an affected individual from each family underwent exome sequencing. RESULTS: A homozygous missense variant c.950T>C (p.(Leu317Pro)) within KRT25 segregated with ARWH in both families, and has a combined maximum two-point LOD score of 7.9 at Ï´=0. The KRT25 variant is predicted to result in disruption of the second α-helical rod domain and the entire protein structure, thus possibly interfering with heterodimerisation of K25 with type II keratins within the inner root sheath (IRS) of the hair follicle and the medulla of the hair shaft. CONCLUSIONS: Our findings implicate a novel gene involved in human hair abnormality, and are consistent with the curled, fragile hair found in mice with Krt25 mutations, and further support the role of IRS-specific type I keratins in hair follicle development and maintenance of hair texture.

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.

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 recessive mutation in the gene ELOVL4 causes a neuro-ichthyotic disorder with variable expressivity.

BACKGROUND: A rare neuro-ichthyotic disorder characterized by ichthyosis, spastic quadriplegia and intellectual disability and caused by recessive mutations in ELOVL4, encoding elongase-4 protein has recently been described. The objective of the study was to search for sequence variants in the gene ELOVL4 in three affected individuals of a consanguineous Pakistani family exhibiting features of neuro-ichthyotic disorder. METHODS: Linkage in the family was searched by genotyping microsatellite markers linked to the gene ELOVL4, mapped at chromosome 6p14.1. Exons and splice junction sites of the gene ELOVL4 were polymerase chain reaction amplified and sequenced in an automated DNA sequencer. RESULTS: DNA sequence analysis revealed a novel homozygous nonsense mutation (c.78C > G; p.Tyr26*). CONCLUSIONS: Our report further confirms the recently described ELOVL4-related neuro-ichthyosis and shows that the neurological phenotype can be absent in some individuals.

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.

Cut-off values of anthropometric indices to determine insulin resistance in Pakistani adults.

OBJECTIVE: To determine the cut-off values of anthropometric indices to indicate insulin resistance and correlation of these indices with insulin resistance in Pakistani adults. METHODS: The cross-sectional study was conducted at the Military Hospital and Army Medical College, Rawalpindi, Pakistan, from June 2010 to November 2011. The study measured 209 adults for body mass index, waist circumference, waist-to-hip ratio, waist-to-height ratio and conicity index. Receiver operating characteristics curve analyses were done to determine the predictive values of these anthropometric measures and their cut-off values for insulin resistance by triglyceride/high density lipoprotein ratio. RESULTS: Overall mean age was 51.5 +/- 1.16 years (range: 28-73) and there were 136 (65%) males and 73 (35%) females. Body mass index had the maximum predictive value for insulin resistance followed by waist circumference and waist-to-height ratio in males (p < 0.0001), sensitivity and specificity being 68% and 62% respectively with cut-off value of 25.04 kg/m2. ROC curve analyses showed the maximum predictive value of conicity index for insulin resistance followed by waist circumference and waist-to-height ratio in females (p < 0.08), sensitivity and specificity being 65% and 50% respectively with cut-off value of 1.39. CONCLUSION: In Pakistani male adults, BMI is the best indicator of insulin resistance, while in female adults, conicity index is the best indicator.This is the first study in Pakistan reporting predictive values of anthropometric indices as a non-invasive method in determining insulin resistance.

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.

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

Autosomal 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.