Molecular insight into CREBBP and TANGO2 variants causing intellectual disability.

BACKGROUND: Intellectual disability (ID) can be associated with different syndromes such as Rubinstein-Taybi syndrome (RSTS) and can also be related to conditions such as metabolic encephalomyopathic crises, recurrent,with rhabdomyolysis, cardiac arrhythmias and neurodegeneration. Rare congenital RSTS1 (OMIM 180849) is characterized by mental and growth retardation, significant and duplicated distal phalanges of thumbs and halluces, facial dysmorphisms, and an elevated risk of malignancies. Microdeletions and point mutations in the CREB-binding protein (CREBBP) gene, located at 16p13.3, have been reported to cause RSTS. By contrast, TANGO2-related metabolic encephalopathy and arrhythmia (TRMEA) is a rare metabolic condition that causes repeated metabolic crises, hypoglycemia, lactic acidosis, rhabdomyolysis, arrhythmias and encephalopathy with cognitive decline. Clinicians need more clinical and genetic evidence to detect and comprehend the phenotypic spectrum of this disorder. METHODS: Exome sequencing was used to identify the disease-causing variants in two affected families A and B from District Kohat and District Karak, Khyber Pakhtunkhwa. Affected individuals from both families presented symptoms of ID, developmental delay and behavioral abnormalities. The validation and co-segregation analysis of the filtered variant was carried out using Sanger sequencing. RESULTS: In the present study, two families (A and B) exhibiting various forms of IDs were enrolled. In Family A, exome sequencing revealed a novel missense variant (NM 004380.3: c.4571A>G; NP_004371.2: p.Lys1524Arg) in the CREBBP gene, whereas, in Family B, a splice site variant (NM 152906.7: c.605 + 1G>A) in the TANGO2 gene was identified. Sanger sequencing of both variants confirmed their segregation with ID in both families. The in silico tools verified the aberrant changes in the CREBBP protein structure. Wild-type and mutant CREBBP protein structures were superimposed and conformational changes were observed likely altering the protein function. CONCLUSIONS: RSTS and TRMEA are exceedingly rare disorders for which specific clinical characteristics have been clearly established, but more investigations are underway and required. Multicenter studies are needed to increase our understanding of the clinical phenotypes, mainly showing the genotype-phenotype associations.

Nonsense variant in a consanguineous family expands the phenotype of KPTN gene-related syndrome to include hearing impairment.

A short report with two affected siblings from consanguineous family born with intellectual disability, motor disability, language deficit, and hearing impairment and found to carry biallelic nonsense variant in KPTN gene known to be associated with KPTN gene related syndrome.

Structural and functional implications of SLC13A3 and SLC9A6 mutations: an in silico approach to understanding intellectual disability.

BACKGROUND: Intellectual disability (ID) is a condition that varies widely in both its clinical presentation and its genetic underpinnings. It significantly impacts patients' learning capacities and lowers their IQ below 70. The solute carrier (SLC) family is the most abundant class of transmembrane transporters and is responsible for the translocation of various substances across cell membranes, including nutrients, ions, metabolites, and medicines. The SLC13A3 gene encodes a plasma membrane-localized Na+/dicarboxylate cotransporter 3 (NaDC3) primarily expressed in the kidney, astrocytes, and the choroid plexus. In addition to three Na + ions, it brings four to six carbon dicarboxylates into the cytosol. Recently, it was discovered that patients with acute reversible leukoencephalopathy and a-ketoglutarate accumulation (ARLIAK) carry pathogenic mutations in the SLC13A3 gene, and the X-linked neurodevelopmental condition Christianson Syndrome is caused by mutations in the SLC9A6 gene, which encodes the recycling endosomal alkali cation/proton exchanger NHE6, also called sodium-hydrogen exchanger-6. As a result, there are severe impairments in the patient's mental capacity, physical skills, and adaptive behavior. METHODS AND RESULTS: Two Pakistani families (A and B) with autosomal recessive and X-linked intellectual disorders were clinically evaluated, and two novel disease-causing variants in the SLC13A3 gene (NM 022829.5) and the SLC9A6 gene (NM 001042537.2) were identified using whole exome sequencing. Family-A segregated a novel homozygous missense variant (c.1478 C > T; p. Pro493Leu) in the exon-11 of the SLC13A3 gene. At the same time, family-B segregated a novel missense variant (c.1342G > A; p.Gly448Arg) in the exon-10 of the SLC9A6 gene. By integrating computational approaches, our findings provided insights into the molecular mechanisms underlying the development of ID in individuals with SLC13A3 and SLC9A6 mutations. CONCLUSION: We have utilized in-silico tools in the current study to examine the deleterious effects of the identified variants, which carry the potential to understand the genotype-phenotype relationships in neurodevelopmental disorders.

Biallelic variants in WARS1 cause a highly variable neurodevelopmental syndrome and implicate a critical exon for normal auditory function.

Aminoacyl-tRNA synthetases (ARSs) are essential enzymes for faithful assignment of amino acids to their cognate tRNA. Variants in ARS genes are frequently associated with clinically heterogeneous phenotypes in humans and follow both autosomal dominant or recessive inheritance patterns in many instances. Variants in tryptophanyl-tRNA synthetase 1 (WARS1) cause autosomal dominantly inherited distal hereditary motor neuropathy and Charcot-Marie-Tooth disease. Presently, only one family with biallelic WARS1 variants has been described. We present three affected individuals from two families with biallelic variants (p.Met1? and p.(Asp419Asn)) in WARS1, showing varying severities of developmental delay and intellectual disability. Hearing impairment and microcephaly, as well as abnormalities of the brain, skeletal system, movement/gait, and behavior were variable features. Phenotyping of knocked down wars-1 in a Caenorhabditis elegans model showed depletion is associated with defects in germ cell development. A wars1 knockout vertebrate model recapitulates the human clinical phenotypes, confirms variant pathogenicity, and uncovers evidence implicating the p.Met1? variant as potentially impacting an exon critical for normal hearing. Together, our findings provide consolidating evidence for biallelic disruption of WARS1 as causal for an autosomal recessive neurodevelopmental syndrome and present a vertebrate model that recapitulates key phenotypes observed in patients.

Mutation screening of multiple Pakistani MCPH families revealed novel and recurrent protein-truncating mutations of ASPM.

Autosomal primary microcephaly (MCPH) is a heterogenetic disorder that affects brain's cerebral cortex size and leads to a reduction in the cranial vault. Along with the hallmark feature of reduced head circumference, microcephalic patients also exhibit a variable degree of intellectual disability as well. Genetic studies have reported 28 MCPH genes, most of which produce microtubule-associated proteins and are involved in cell division. Herein this study, 14 patients from seven Pashtun origin Pakistani families of primary microcephaly were analyzed. Mutation analysis was performed through targeted Sanger DNA sequencing on the basis of phenotype-linked genetic makeup. Genetic analysis in one family found a novel pathogenic DNA change in the abnormal spindle microtubule assembly (ASPM) gene (NM_018136.4:c.3871dupGA), while the rest of the families revealed recurrent nonsense mutation c.3978G>A (p.Trp1326*) in the same gene. The novel reported frameshift insertion presumably truncates the protein p.(Lys1291Glyfs*14) and deletes the N-terminus domains. Identification of novel ASPM-truncating mutation expands the mutational spectrum of the ASPM gene, while mapping of recurrent mutation c.3978G>A (p.Trp1326*) will aid in establishing its founder effect in the Khyber Pakhtunkhwa (KPK) inhabitant population of Pakistan and should be suggestively screened for premarital counseling of MCPH susceptible families. Most of the recruited families are related to first-degree consanguinity. Hence, all the family elders were counseled to avoid intrafamilial marriages.

A novel protein truncating mutation in L2HGDH causes L-2-hydroxyglutaric aciduria in a consanguineous Pakistani family.

BACKGROUND: L-2-hydroxyglutaric aciduria (L2HGA) is a rare neurometabolic disorder that occurs due to accumulation of L-2-hydroxyglutaric acid in the cerebrospinal fluid (CSF), plasma and urine. The clinical manifestation of L2HGA includes intellectual disability, cerebellar ataxia, epilepsy, speech problems and macrocephaly. METHODS: In the present study, we ascertained a multigenerational consanguineous Pakistani family with 5 affected individuals. Clinical studies were performed through biochemical tests and brain CT scan. Locus mapping was carried out through genome-wide SNP genotyping, whole exome sequencing and Sanger sequencing. For in silico studies protein structural modeling and docking was done using I-TASSER, Cluspro and AutoDock VINA tools. RESULTS: Affected individuals presented with cognitive impairment, gait disturbance, speech difficulties and psychomotor delay. Radiologic analysis of a male patient revealed leukoaraiosis with hypoattenuation of cerebral white matter, suggestive of hypomyelination. Homozygosity mapping in this family revealed a linkage region on chromosome 14 between markers rs2039791 and rs781354. Subsequent whole exome analysis identified a novel frameshift mutation NM_024884.3:c.180delG, p.(Ala62Profs*24) in the second exon of L2HGDH. Sanger sequencing confirmed segregation of this mutation with the disease phenotype. The identification of the most N-terminal loss of function mutation published thus far further expands the mutational spectrum of L2HGDH.

Novel splicing-site mutation in DCAF17 gene causing Woodhouse-Sakati syndrome in a large consanguineous family.

BACKGROUND: Woodhouse-Sakati syndrome is a rare autosomal recessive disease with endocrine and neuroectodermal aberrations with heterogeneous phenotypes and disease course. The most common phenotypes of the disease are progressive sensorineural hearing loss and alopecia, mild-to-moderate mental retardation and hypogonadism. The disease results from mutations in the DCAF17 gene. METHOD: Here, we reported a large consanguineous pedigree with multiple affected individuals with Woodhouse-Sakati syndrome phenotypes. Laboratory tests confirmed the endocrine perturbance in affected individuals. To find out the underlying genetic change, whole-exome sequencing was carried out. RESULT: Analysis of the exome data identified a splicing-site deletion NM_025000.3:c.1423-1_1425delGACA in DCAF17 gene. Sanger sequencing confirmed the co-segregation of the variant with the disease phenotypes in the family. CONCLUSION: The variant is predicted to cause aberrant splicing, i.e., exon skipping, resulting in the translation of a truncated functionless protein which results in appearance of typical phenotypic features and clinical laboratory findings of Woodhouse-Sakati syndrome in affected members of the family.

The molecular genetics of UV-Sensitive syndrome: A rare dermal anomaly.

Ultraviolet-sensitive syndrome is a rare skin disorder characterised by heterogeneous phenotypic spectrum of skin freckling, telangiectasia and acute sunburn. It usually has an autosomal recessive pattern. So far, only 18 patients from nine different families (Japanese, French, Israeli, Iranian and Pakistani) have been reported in scientific literature. Its precise prevalence is still unknown, but, according to an estimate, its prevalence ratio is 1:100,000 worldwide. Until now, only three genes have been reported to be involved in the syndrome; the Excision Repair Cross-Complementing, Group 6, the Excision Repair Cross-Complementing, Group 8 and the UV-Stimulated Scaffold Protein A (UVSSA). Among these genes, the last one is reported to be more prevalent among different ethnicities, including Pakistani. Physiologically, most of the syndrome genes are involved in the transcription-coupled nucleotide excision pathway. In order to reduce the disease severity, the patients are advised to use medicated skin moisturisers or sun-blocks, sunglasses and gloves, while going out in the sun to avoid sun exposure. The current narrative review was planned to discuss the molecular genetics and the mutational spectrum of the syndrome, and to describe the differential diagnosis of various related disorders in order to facilitate clinical researchers.

A novel nonsense variant in SLC24A4 causing a rare form of amelogenesis imperfecta in a Pakistani family.

BACKGROUND: Amelogenesis imperfecta (AI) is a highly heterogeneous group of hereditary developmental abnormalities which mainly affects the dental enamel during tooth development in terms of its thickness, structure, and composition. It appears both in syndromic as well as non-syndromic forms. In the affected individuals, the enamel is usually thin, soft, rough, brittle, pitted, chipped, and abraded, having reduced functional ability and aesthetics. It leads to severe complications in the patient, like early tooth loss, severe discomfort, pain, dental caries, chewing difficulties, and discoloration of teeth from yellow to yellowish-brown or creamy type. The study aimed to identify the disease-causing variant in a consanguineous family. METHODS: We recruited a consanguineous Pashtun family of Pakistani origin. Exome sequencing analysis was followed by Sanger sequencing to identify the pathogenic variant in this family. RESULTS: Clinical analysis revealed hypomaturation AI having generalized yellow-brown or creamy type of discoloration in affected members. We identified a novel nonsense sequence variant c.1192C > T (p.Gln398*) in exon-12 of SLC24A4 by using exome sequencing. Later, its co-segregation within the family was confirmed by Sanger sequencing. The human gene mutation database (HGMD, 2019) has a record of five pathogenic variants in SLC24A4, causing AI phenotype. CONCLUSION: This nonsense sequence variant c.1192C > T (p.Gln398*) is the sixth disease-causing variant in SLC24A4, which extends its mutation spectrum and confirms the role of this gene in the morphogenesis of human tooth enamel. The identified variant highlights the critical role of SLC24A4 in causing a rare AI type in humans.

Association of sequence variants in frizzled-6 with autosomal recessive nail dysplasia (NDNC-10) in Pashtun families.

Primitive epidermis develops the nail apparatus. Nails have a strong and inflexible nail plate at the end of each digit. Very few genes responsible for causing nonsyndromic form of nail dysplasia have been reported. In the current study, peripheral blood samples were collectedfrom three unaffected individuals and four affectedindividuals of Family A, while blood from two affected and three unaffected individuals were taken of Family B. Genotyping in both the families was performed using highly polymorphic short tandem repeat microsatellite markers. Sanger sequence of the FZD6 gene was performed and analysed for segregation analysis. A comparative modelling approach was used to predict the three-dimensional structures of FZD-6 protein using Modeller 4. Linkage analysis mapped a disease locus on chromosome 8q22.3, harbouring FZD6. Targeted Sanger sequencing of all the coding exons of FZD6 revealed a nonsense sequence variant in pedigree A, whereas a missense sequence variant in pedigree B. Finding and literature indicates the disease spectrum of Pakistani population with claw-shaped nail dysplasia, particularly in families of Pashtun origin.

Genetic studies of multiple consanguineous Pakistani families segregating oculocutaneous albinism identified novel and reported mutations.

Oculocutaneous albinism (OCA) is an autosomal-recessive disorder of a defective melanin pathway. The condition is characterized by hypopigmentation of hair, dermis, and ocular tissue. Genetic studies have reported seven nonsyndromic OCA genes, among which Pakistani OCA families mostly segregate TYR and OCA2 gene mutations. Here in the present study, we investigate the genetic factors of eight consanguineous OCA families from Pakistan. Genetic analysis was performed through single-nucleotide polymorphism (SNP) genotyping (for homozygosity mapping), whole exome sequencing (for mutation identification), Sanger sequencing (for validation and segregation analysis), and quantitative PCR (qPCR) (for copy number variant [CNV] validation). Genetic mapping in one family identified a novel homozygous deletion mutation of the entire TYRP1 gene, and a novel deletion of exon 19 in the OCA2 gene in two apparently unrelated families. In three further families, we identified homozygous mutations in TYR (NM_000372.4:c.1424G > A; p.Trp475*), NM_000372.4:c.895C > T; p.Arg299Cys), and SLC45A2 (NM_016180:c.1532C > T; p.Ala511Val). For the remaining two families, G and H, compound heterozygous TYR variants NM_000372.4:c.1037-7T > A, NM_000372.4:c.1255G > A (p.Gly419Arg), and NM_000372.4:c.1255G > A (p.Gly419Arg) and novel variant NM_000372.4:c.248T > G; (p.Val83Gly), respectively, were found. Our study further extends the evidence of TYR and OCA2 as genetic mutation hot spots in Pakistani families. Genetic screening of additional OCA cases may also contribute toward the development of Pakistani specific molecular diagnostic tests, genetic counseling, and personalized healthcare.

Variants in KIAA0825 underlie autosomal recessive postaxial polydactyly.

Postaxial polydactyly (PAP) is a common limb malformation that often leads to cosmetic and functional complications. Molecular evaluation of polydactyly can serve as a tool to elucidate genetic and signaling pathways that regulate limb development, specifically, the anterior-posterior specification of the limb. To date, only five genes have been identified for nonsyndromic PAP: FAM92A, GLI1, GLI3, IQCE and ZNF141. In this study, two Pakistani multiplex consanguineous families with autosomal recessive nonsyndromic PAP were clinically and molecularly evaluated. From both pedigrees, a DNA sample from an affected member underwent exome sequencing. In each family, we identified a segregating frameshift (c.591dupA [p.(Q198Tfs*21)]) and nonsense variant (c.2173A > T [p.(K725*)]) in KIAA0825 (also known as C5orf36). Although KIAA0825 encodes a protein of unknown function, it has been demonstrated that its murine ortholog is expressed during limb development. Our data contribute to the establishment of a catalog of genes important in limb patterning, which can aid in diagnosis and obtaining a better understanding of the biology of polydactyly.

Deleterious Variants in WNT10A, EDAR, and EDA Causing Isolated and Syndromic Tooth Agenesis: A Structural Perspective from Molecular Dynamics Simulations.

The dental abnormalities are the typical features of many ectodermal dysplasias along with congenital malformations of nails, skin, hair, and sweat glands. However, several reports of non-syndromic/isolated tooth agenesis have also been found in the literature. The characteristic features of hypohidrotic ectodermal dysplasia (HED) comprise of hypodontia/oligodontia, along with hypohidrosis/anhidrosis, and hypotrichosis. Pathogenic variants in EDA, EDAR, EDARADD, and TRAF6, cause the phenotypic expression of HED. Genetic alterations in EDA and WNT10A cause particularly non-syndromic/isolated oligodontia. In the current project, we recruited 57 patients of 17 genetic pedigrees (A-Q) from different geographic regions of the world, including Pakistan, Egypt, Saudi Arabia, and Syria. The molecular investigation of different syndromic and non-syndromic dental conditions, including hypodontia, oligodontia, generalized odontodysplasia, and dental crowding was carried out by using exome and Sanger sequencing. We have identified a novel missense variant (c.311G>A; p.Arg104His) in WNT10A in three oligodontia patients of family A, two novel sequence variants (c.207delinsTT, p.Gly70Trpfs*25 and c.1300T>G; p.Try434Gly) in EDAR in three patients of family B and four patients of family C, respectively. To better understand the structural and functional consequences of missense variants in WNT10A and EDAR on the stability of the proteins, we have performed extensive molecular dynamic (MD) simulations. We have also identified three previously reported pathogenic variants (c.1076T>C; p.Met359Thr), (c.1133C>T; p.Thr378Met) and (c.594_595insC; Gly201Argfs*39) in EDA in family D (four patients), E (two patients) and F (one patient), correspondingly. Presently, our data explain the genetic cause of 18 syndromic and non-syndromic tooth agenesis patients in six autosomal recessive and X-linked pedigrees (A-F), which expand the mutational spectrum of these unique clinical manifestations.

Genetic study of Khyber-Pukhtunkhwa resident Pakistani families presenting primary microcephaly with intellectual disability.

OBJECTIVE: To investigate the genetic factor responsible for causing microcephaly and determine allelic heterogeneity of Abnormal spindle microtubule gene. METHODS: The genetic study was conducted at the Kohat University of Science and Technology, Kohat, and Gomal University, D.I.Khan, Pakistan, during 2017-18, and comprised 5 consanguineous families from South Waziristan, Kurram Agency, Karak, Bannu and Dera Ismail Khan regions of the country's Khyber Pakhtukhwa province. Blood samples from all available and cooperative family members (including normal and affected) were obtained, and molecular analysis was carried out through whole genome single nucleotide polymorphisms genotyping, exome sequencing and Sanger sequencing. RESULTS: Of the 15 patients, 9(60%) were males and 6(40%) were females. Genetic mapping revealed linkage to the MCPH5 locus which harbours the microcephaly-associated abnormal spindle-like microcephaly gene. Mutation analysis of the gene identified missense mutation c.3978G>A (p.Trp1326*) in families A, B and C, a deletion mutation c.7782_7783delGA (p.(Lys2595Serfs*6)) in family D, and a splice site defect c.2936+5G>A in family E. CONCLUSIONS: There was suggestion of strong founder effect of mutation c.3978G>A (p.Trp1326*).

A novel mutation in the HPGD gene causing primary hypertrophic osteoarthropathy with digital clubbing in a Pakistani family.

Primary hypertrophic osteoarthropathy (PHO) is a congenital multisystemic entity characterized by three major clinical symptoms: pachydermia, periostosis, and digital clubbing. Recently it has been reported that pathogenic mutations in two genes are known to be associated with PHO: HPGD and SLCO2A1. In the present study, a five-generation consanguineous Pakistani family harboring primary hypertrophic osteoarthropathy in autosomal-recessive pattern was ascertained. Whole genome single nucleotide polymorphisms (SNPs) genotyping and sequence analysis revealed a novel homozygous missense mutation (c.577T˃C) of the human HPGD gene in all affected members of the family. The study presented here demonstrate the first case of primary hypertrophic osteoarthropathy reported in Pashtun population.

Novel candidate genes and variants underlying autosomal recessive neurodevelopmental disorders with intellectual disability.

Identification of Mendelian genes for neurodevelopmental disorders using exome sequencing to study autosomal recessive (AR) consanguineous pedigrees has been highly successful. To identify causal variants for syndromic and non-syndromic intellectual disability (ID), exome sequencing was performed using DNA samples from 22 consanguineous Pakistani families with ARID, of which 21 have additional phenotypes including microcephaly. To aid in variant identification, homozygosity mapping and linkage analysis were performed. DNA samples from affected family member(s) from every pedigree underwent exome sequencing. Identified rare damaging exome variants were tested for co-segregation with ID using Sanger sequencing. For seven ARID families, variants were identified in genes not previously associated with ID, including: EI24, FXR1 and TET3 for which knockout mouse models have brain defects; and CACNG7 and TRAPPC10 where cell studies suggest roles in important neural pathways. For two families, the novel ARID genes CARNMT1 and GARNL3 lie within previously reported ID microdeletion regions. We also observed homozygous variants in two ID candidate genes, GRAMD1B and TBRG1, for which each has been previously reported in a single family. An additional 14 families have homozygous variants in established ID genes, of which 11 variants are novel. All ARID genes have increased expression in specific structures of the developing and adult human brain and 91% of the genes are differentially expressed in utero or during early childhood. The identification of novel ARID candidate genes and variants adds to the knowledge base that is required to further understand human brain function and development.

Novel mutations in ALDH1A3 associated with autosomal recessive anophthalmia/microphthalmia, and review of the literature.

BACKGROUND: Autosomal recessive anophthalmia and microphthalmia are rare developmental eye defects occurring during early fetal development. Syndromic and non-syndromic forms of anophthalmia and microphthalmia demonstrate extensive genetic and allelic heterogeneity. To date, disease mutations have been identified in 29 causative genes associated with anophthalmia and microphthalmia, with autosomal dominant, autosomal recessive and X-linked inheritance patterns described. Biallelic ALDH1A3 gene variants are the leading genetic causes of autosomal recessive anophthalmia and microphthalmia in countries with frequent parental consanguinity. METHODS: This study describes genetic investigations in two consanguineous Pakistani families with a total of seven affected individuals with bilateral non-syndromic clinical anophthalmia. RESULTS: Using whole exome and Sanger sequencing, we identified two novel homozygous ALDH1A3 sequence variants as likely responsible for the condition in each family; missense mutation [NM_000693.3:c.1240G > C, p.Gly414Arg; Chr15:101447332G > C (GRCh37)] in exon 11 (family 1), and, a frameshift mutation [NM_000693.3:c.172dup, p.Glu58Glyfs*5; Chr15:101425544dup (GRCh37)] in exon 2 predicted to result in protein truncation (family 2). CONCLUSIONS: This study expands the molecular spectrum of pathogenic ALDH1A3 variants associated with anophthalmia and microphthalmia, and provides further insight of the key role of the ALDH1A3 in human eye development.

Whole exome sequencing identifies a novel dominant missense mutation underlying leukonychia in a Pakistani family.

Hereditary leukonychia (also known as porcelain nails or white nails) is a genetic disorder. It may exist as an isolated feature or associated with other cutaneous or systemic disorders. Although a number of genes have been described to cause leukonychia, still the underlying genetic etiologies of many cases remain unknown. Here, we report a Pakistani family presenting leukonychia and koilonychia nails in mother and five of her kids. All the affected individuals had white to pale nails in appearance exhibiting complete and partial leukonychia, respectively. Similarly, nails of finger and toe appeared brittle and concave, showing the characteristics features of koilonychia. Whole exome sequencing and subsequent Sanger sequencing identified a pathogenic novel missense mutation (c.1390G>A, p.Glu464Lys) in PLCD1, co-segregating with the disorder in an autosomal dominant pattern. In silico prediction tools supported the pathogenicity of the identified mutation. Literature review determined that mutations in PLCD1 only cause leukonychia. Therefore, our findings add another pathogenic variant to the PLCD1 mutation pool causing leukonychia that would help to understand the underlying molecular mechanism.

Molecular Characterization of ß-Thalassemia Mutations Via the Amplification Refractory Mutation System-Polymerase Chain Reaction Method at the North Waziristan Agency, Pakistan.

ß-Thalassemia (ß-thal) is a monogenic disease characterized by mutations on the HBB gene, affecting the production of globin that results in hypochromic and microcytic anemia. The aim of this study was to determine the prevalence of six common ß-thal mutations, and their frequency and inheritance pattern in affected populations of North Waziristan Agency, Pakistan. In this study, 130 blood samples from 37 unrelated ß-thalassemic families having a minimum of one transfusion-dependent child with ß-thal major (ß-TM), were retrieved either from the Thalassaemia Centre for Women and Children Hospital Bannu or their home towns situated in Noth Waziristan Agency. All samples were analyzed by the amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) using six allele-specific primers for the presence of the six ß-thal mutations common in the Pakistani population. Of the six common mutations, our study demonstrated five HBB mutations comprising HBB: c.27_28insG, HBB: c.92+5G>C, HBB: c.126_129delCTTT, HBB: c.92+1G>T and HBB: c.17_18delCT from the families studied, while mutation HBB: c.47G>A [codon 15 (G>A)] was not detected in any of the studied families. Furthermore, the HBB: c.27_28insG and HBB: c.92+5G>C were noted to be the most common with frequencies of 42.85 and 31.42%, respectively. The findings of the present study may be useful in launching carrier screening and prenatal diagnosis (PND) programs by screening analyzed and other unanalyzed affected families for the possible presence of common mutations through the ARMS-PCR technique that will help to control the disease.

A novel mutation in homeobox DNA binding domain of HOXC13 gene underlies pure hair and nail ectodermal dysplasia (ECTD9) in a Pakistani family.

BACKGROUND: Pure hair and nail ectodermal dysplasia (PHNED) is a congenital disorder of hair abnormalities and nail dysplasia. Both autosomal recessive and dominant inheritance fashion of PHNED occurs. In literature, to date, five different forms of PHNED have been reported at molecular level, having three genes known and two loci with no gene yet. METHODS: In this study, a four generations consanguineous family of Pakistani origin with autosomal recessive PHNED was investigated. Affected members exhibited PHNED phenotypes with involvement of complete hair loss and nail dysplasia. To screen for mutation in the genes (HOXC13, KRT74, KRT85), its coding exons and exons-intron boundaries were sequenced. The 3D models of normal and mutated HOXC13 were predicted by using homology modeling. RESULTS: Through investigating the family to known loci, the family was mapped to ectodermal dysplasia 9 (ECTD9) loci with genetic address of 12q13.13. Mutation screening revealed a novel missense mutation (c.929A > C; p.Asn310Thr) in homeobox DNA binding domain of HOXC13 gene in affected members of the family. Due to mutation, loss of hydrogen bonding and difference in potential energy occurs, which may resulting in alteration of protein function. CONCLUSION: This is the first mutation reported in homeodomain, while 5th mutation reported in HOXC13 gene causing PHNED.