The genetic basis of early-onset hereditary ataxia in Iran: results of a national registry of a heterogeneous population.

BACKGROUND: To investigate the genetics of early-onset progressive cerebellar ataxia in Iran, we conducted a study at the Children's Medical Center (CMC), the primary referral center for pediatric disorders in the country, over a three-year period from 2019 to 2022. In this report, we provide the initial findings from the national registry. METHODS: We selected all early-onset patients with an autosomal recessive mode of inheritance to assess their phenotype, paraclinical tests, and genotypes. The clinical data encompassed clinical features, the Scale for the Assessment and Rating of Ataxia (SARA) scores, Magnetic Resonance Imaging (MRI) results, Electrodiagnostic exams (EDX), and biomarker features. Our genetic investigations included single-gene testing, Whole Exome Sequencing (WES), and Whole Genome Sequencing (WGS). RESULTS: Our study enrolled 162 patients from various geographic regions of our country. Among our subpopulations, we identified known and novel pathogenic variants in 42 genes in 97 families. The overall genetic diagnostic rate was 59.9%. Notably, we observed PLA2G6, ATM, SACS, and SCA variants in 19, 14, 12, and 10 families, respectively. Remarkably, more than 59% of the cases were attributed to pathogenic variants in these genes. CONCLUSIONS: Iran, being at the crossroad of the Middle East, exhibits a highly diverse genetic etiology for autosomal recessive hereditary ataxia. In light of this heterogeneity, the development of preventive strategies and targeted molecular therapeutics becomes crucial. A national guideline for the diagnosis and management of patients with these conditions could significantly aid in advancing healthcare approaches and improving patient outcomes.

Neurofibromatosis-Noonan syndrome and growth deficiency in an Iranian girl due to a pathogenic variant in NF1 gene.

BACKGROUND: Mutations in NF1 gene could cause allelic disorders with clinical spectrum of Neurofibromatosis type 1 to Noonan syndrome. Here, a 7-year-old Iranian girl is described with Neurofibromatosis-Noonan syndrome due to a pathogenic variant in NF1 gene. METHODS: Clinical evaluations were performed along with genetic testing using whole exome sequencing (WES). The variant analysis including pathogenicity prediction was also done using bioinformatics tools. RESULTS: The chief compliant of the patient was short stature and lack of proper weight gain. Other symptoms were developmental delay, learning disability, inadequate speech skill, broad forehead, hypertelorism, and epicanthal folds, low set ears and webbed neck. A small deletion, c.4375-4377delGAA, was found in NF1 gene using WES. This variant was classified as pathogenic according to ACMG. CONCLUSIONS: NF1 variants may show variable phenotypes among the patients; identifying such variants is helpful in therapeutic management of the disease. WES is considered as an appropriate test to diagnose Neurofibromatosis-Noonan syndrome.

COLQ-related congenital myasthenic syndrome: An integrative view.

Congenital myasthenic syndromes are inherited disorders caused by mutation in components of the neuromuscular junction and manifest early in life. Mutations in COLQ gene result in congenital myasthenic syndrome. Here, we present the analysis of data from 209 patients from 195 unrelated families highlighting genotype-phenotype correlation. In addition, we describe a COLQ homozygous variant a new patient and discuss it utilizing the Phyre2 and I-TASSER programs. Clinical, molecular genetics, imaging (MRI), and electrodiagnostic (EEG, EMG/NCS) evaluations were performed. Our data showed 89 pathogenic/likely pathogenic variants including 35 missenses, 21 indels, 14 nonsense, 14 splicing, and 5 large deletions variants. Eight common variants were responsible for 48.46% of those. Weakness in proximal muscles, hypotonia, and generalized weakness were detected in all individuals tested. Apart from the weakness, extensive clinical heterogeneity was noted among patients with COLQ-related patients based on their genotypes-those with variants affecting the splice site exhibited more severe clinical features while those with missense variants displayed milder phenotypes, suggesting the role of differential splice variants in multiple functions within the muscle. Analyses and descriptions of these COLQ variants may be helpful in clinical trial readiness and potential development of novel therapies in the setting of established structure-function relationships.

High genetic heterogeneity of leukodystrophies in Iranian children: the first report of Iranian Leukodystrophy Registry.

Leukodystrophies (LDs) are a heterogeneous group of progressive neurological disorders and characterized by primary involvement of white matter of the central nervous system (CNS). This is the first report of the Iranian LD Registry database to describe the clinical, radiological, and genomic data of Persian patients with leukodystrophies. From 2016 to 2019, patients suspicious of LDs were examined followed by a brain magnetic resonance imaging (MRI). A single gene testing or whole-exome sequencing (WES) was used depending on the neuroradiologic phenotypes. In a few cases, the diagnosis was made by metabolic studies. Based on the MRI pattern, diagnosed patients were divided into cohorts A (hypomyelinating LDs) versus cohort B (Other LDs). The most recent LD classification was utilized for classification of diagnosed patients. For novel variants, in silico analyses were performed to verify their pathogenicity. Out of 680 registered patients, 342 completed the diagnostic evaluations. In total, 245 patients met a diagnosis which in turn 24.5% were categorized in cohort A and the remaining in cohort B. Genetic tests revealed causal variants in 228 patients consisting of 213 variants in 110 genes with 78 novel variants. WES and single gene testing identified a causal variant in 65.5% and 34.5% cases, respectively. The total diagnostic rate of WES was 60.7%. Lysosomal disorders (27.3%; GM2-gangliosidosis-9.8%, MLD-6.1%, KD-4.5%), amino and organic acid disorders (17.15%; Canavan disease-4.5%, L-2-HGA-3.6%), mitochondrial leukodystrophies (12.6%), ion and water homeostasis disorders (7.3%; MLC-4.5%), peroxisomal disorders (6.5%; X-ALD-3.6%), and myelin protein disorders (3.6%; PMLD-3.6%) were the most commonly diagnosed disorders. Thirty-seven percent of cases had a pathogenic variant in nine genes (ARSA, HEXA, ASPA, MLC1, GALC, GJC2, ABCD1, L2HGDH, GCDH). This study highlights the most common types as well as the genetic heterogeneity of LDs in Iranian children.

Genome sequencing identifies coding and non-coding variants for non-syndromic hearing loss.

Hearing loss (HL) is a common heterogeneous trait that involves variants in more than 200 genes. In this study, we utilized exome (ES) and genome sequencing (GS) to effectively identify the genetic cause of presumably non-syndromic HL in 322 families from South and West Asia and Latin America. Biallelic GJB2 variants were identified in 58 probands at the time of enrollment these probands were excluded. In addition, upon review of phenotypic findings, 38/322 probands were excluded based on syndromic findings at the time of ascertainment and no further evaluation was performed on those samples. We performed ES as a primary diagnostic tool on one or two affected individuals from 212/226 families. Via ES we detected a total of 78 variants in 30 genes and showed their co-segregation with HL in 71 affected families. Most of the variants were frameshift or missense and affected individuals were either homozygous or compound heterozygous in their respective families. We employed GS as a primary test on a subset of 14 families and a secondary tool on 22 families which were unsolved by ES. Although the cumulative detection rate of causal variants by ES and GS is 40% (89/226), GS alone has led to a molecular diagnosis in 7 of 14 families as the primary tool and 5 of 22 families as the secondary test. GS successfully identified variants present in deep intronic or complex regions not detectable by ES.

Clinical and Molecular Findings of Autosomal Recessive Spastic Ataxia of Charlevoix Saguenay: an Iranian Case Series Expanding the Genetic and Neuroimaging Spectra.

Autosomal recessive spastic ataxia of Charlevoix Saguenay (ARSACS) is now increasingly identified from all countries over the world, possibly rendering it one of the most common autosomal recessive ataxias. Here, we selected patients harboring SACS variants, the causative gene for ARSACS, in a large cohort of 137 patients with early-onset ataxia recruited from May 2019 to May 2021 and were referred to the ataxia clinic. Genetic studies were performed for 111 out of 137 patients (81%) which led to a diagnostic rate of 72.9% (81 out of 111 cases). Ten patients with the molecular diagnosis of ARSACS were identified. We investigated the phenotypic and imaging spectra of all confirmed patients with ARSACS. We also estimated the frequency of ARSACS in this cohort and described their clinical and genetic findings including seven novel variants as well as novel neuroimaging findings. While the classic clinical triad of ARSACS is progressive cerebellar ataxia, spasticity, and sensorimotor polyneuropathy, it is not a constant feature in all patients. Sensorimotor axonal-demyelinating neuropathy was detected in all of our patients, but spasticity and extensor plantar reflex were absent in 50% (5/10). In all patients, brain magnetic resonance imaging (MRI) showed symmetric linear hypointensities in the pons (pontine stripes) and anterior superior cerebellar atrophy as well as a hyperintense rim around the thalami (thalamic rim). Although infratentorial arachnoid cyst has been reported in ARSACS earlier, we report anterior temporal arachnoid cyst in two patients for the first time, indicating that arachnoid cyst may be an associated imaging feature of ARSACS. We also extended molecular spectrum of ARSACS by presenting 8 pathogenic and one variant of unknown significance (VUS) sequence variants, which 7 of them have not been reported previously. MetaDome server confirmed that the identified VUS variant was in the intolerant regions of sacsin protein encoded by SACS.

Determinants of perivascular adipose tissue stranding as a novel imaging marker and its relation to inflammatory biomarker high-sensitivity C-reactive protein.

Purpose: This study aimed to examine the relationship of perivascular adipose tissue (PVAT) stranding in coronary computed tomography angiography (CCTA) with high-sensitivity C-reactive protein (hsCRP) and the determinants of PVAT stranding in coronary artery disease (CAD) patients. Material and methods: This retrospective cross-sectional study was done by collecting data from CAD patients who were referred to Rajaie Cardiovascular Centre between January 2018 and September 2020, with CCTA and hsCRP test 72 hours apart from the CCTA. PVAT stranding was defined as irregular obscuration of PVAT adjacent to the coronary arteries. An attempt was made to find a correlation between included variables and PVAT stranding by comparing them between 2 groups: patients with and without PVAT stranding. Results: From 92 patients, 31 participants had PVAT stranding, and statistically significant higher levels of hsCRP were detected in them (p = 0.007). We demonstrated significantly higher prevalence of history of hyperlipidaemia (OR = 3.83, p = 0.029), high-risk plaque features (OR = 11.80, p = 0.015), and obstructive coronary luminal stenosis (OR = 3.25, p = 0.025) in patients with PVAT stranding. Also, significantly higher PVAT attenuation was detected in patients with PVAT stranding (p < 0.001) independently from mean attenuation of epicardial fat. Conclusion: PVAT stranding could be used as a novel non-invasive marker in CCTA of CAD patients. More studies focusing on patient outcomes are required to better evaluate the reliability and prognostic value of this marker.

Nonsyndromic Early-Onset Epileptic Encephalopathies: Two Novel KCTD7 Pathogenic Variants and a Literature Review.

Early-onset epileptic encephalopathies (EOEE) affect cognitive, sensory, and motor development. Genetic variations are among the identifiable primary causes of these syndromes. However, some patients have been reported to be affected by EOEE without any other clinical symptoms and signs. We study the genotype and phenotype of patients with nonsyndromic early-onset epileptic encephalopathy (NSEOEE) and report 2 novel patients from Iran. A comprehensive search was conducted in PubMed, John Willy, Springer, Elsevier, and Google Scholar databases to collect related information of all the previously reported cases with KCTD7 mutations. Fifty-four patients (from 40 families) were investigated. Using trio-whole-exome sequencing (trio-WES) and Sanger sequencing, the possible genetic causes of the disorder were checked. The probable impacts of the identified variants on the KCTD7 protein structure and function were predicted. This study provided a detailed overview of all published KCTD7 mutations and 2 de novo ones. We identified 2 novel homozygous variants of uncertain significance, c.458 G > A p. Arg153His and c.529C > T (p.Arg177Cys), in KCTD7 (NM_153033.4) (Chr7(GRCh37)). There is a significant wide distribution of the KCTD7 gene causing NSEOEE among different populations. In conclusion, KCTD7 mutations demonstrate a diverse geographical distribution alongside a wide range of ethnicities. This highlights the importance of careful consideration in the WES data analysis. Mutations of this gene may be a common cause of NSEOEE. Also, this study imprints targeted therapeutic opportunities for potassium channelepsies such as KCTD7-related NSEOEE.

Novel cases of pediatric sudden cardiac death secondary to TRDN mutations presenting as long QT syndrome at rest and catecholaminergic polymorphic ventricular tachycardia during exercise: The TRDN arrhythmia syndrome.

TRDN mutations cause catecholaminergic polymorphic ventricular tachycardia (CPVT) but may present with abnormal electrocardiogram (ECG) findings provoking a diagnosis of long QT syndrome (LQTS). We report two novel cases of sudden cardiac death in children due to mutations of TRDN, providing further insight into this rare and aggressive inherited arrhythmia syndrome. Whole exome sequencing (WES) was performed in two unrelated children who experienced cardiac arrest during exercise and were negative for targeted testing of LQTS. WES identified a novel homozygous splice-site mutation in both patients, denoted c.22+1G>T, absent from gnomAD and suggesting a founder variant in the Iranian population. We now summarize the genetic architecture of all reported TRDN-related patients, including 27 patients from 21 families. The average age-onset was 30 months (range 1-10) for all cases. Adrenergic-mediated cardiac events were common, occurring in 23 of 27 cases (85%). LQTS was diagnosed in 10 cases (37%), CPVT in 10 (37%) cases, and in 7 cases. No phenotypic diagnosis was provided. Five cases (15%) had evidence for associated skeletal myopathy. Four missense TRDN variants (24%) were observed in diseased cases, while the remaining variants reflect putative loss-of-function (LOF) mutations. No disease phenotype was reported in 26 heterozygous carriers. In conclusion, TRDN mutations cause a rare autosomal recessive arrhythmia syndrome presenting with adrenergic-mediated arrhythmic events, but with ECG abnormalities leading to a diagnosis of LQTS in a proportion of cases. Heterozygous carriers are free of disease manifestations.

A novel de novo dominant mutation of NOTCH1 gene in an Iranian family with non-syndromic congenital heart disease.

BACKGROUND: Congenital heart disease (CHD) is the most common birth defect which can arises from different genetic defects. The genetic heterogeneity of this disease leads to restricted success in candidate genes screening method. Emerging approaches such as next-generation sequencing (NGS)-based genetic analysis might provide a better understating of CHD etiology in the patients who are left undiagnosed. To this aim, in this study, we survived the causes of CHD in an Iranian family who was consanguineous and had two affected children. METHODS: Affected individuals of this family were checked previously by PCR-direct sequencing for six candidate genes (NKX2-5, ZIC3, NODAL, FOXH1, GJA1, GATA4) and had not revealed any reported CHD causative mutations. Whole-exome sequencing (WES) was performed on this family probond to determine the underlying cause of CHD, and the identified variants were confirmed and segregated by Sanger sequencing. RESULTS: We identified one heterozygous missense mutation, c.T6797C (p.Phe2266Ser), in the NOTCH1 gene, which seems to be the most probably disease causing of this family patients. This mutation was found to be novel and not reported on 1000 Genomes Project, dbSNP, and ExAC. CONCLUSION: Worldwide, mutations in NOTCH1 gene are considered as one of the most known causes of CHD. The found NOTCH1 variant in this family affected individuals was the first report from Iran. Yet again, this result indicates the importance of NOTCH1 screening in CHD patients.

Hypomyelinating Leukodystrophy with Spinal Cord Involvement Caused by a Novel Variant in RARS: Report of Two Unrelated Patients.

Leukodystrophies are heterogeneous group of genetic white matter disorders with a wide range of neurologic and systemic manifestations. Defects in genes encoding aminoacyl tRNA (transfer ribonucleic acid) synthetase enzymes (aaRSs) are recently identified as the etiology of some leukodystrophies. Herein, we described two unrelated children referred to Children's Medical Center, Tehran, Iran, with developmental delay, nystagmus, seizures, psuedo-bulbar palsy and dystonia. Whole exome sequencing (WES) in both patients identified a homozygous (c.2T > C) variant in exon one of RARS gene, encoding cytoplasmic arginyl-tRNA synthetase. Our finding was confirmed by segregation analysis. In silico analyses of the c.2T > C variant showed its possible pathogenic role due to the absence of the start codon. Severe hypomyelination was the common neuroimaging finding of both cases. Spinal cord involvement was found in one of our patients which was not previously reported in studies. We, therefore, showed that RARS-related hypomyelination might affect spinal cord.

Mosaic trisomy 22 in a 4-year-old boy with congenital heart disease and general hypotrophy: A case report.

BACKGROUND: Trisomy 22 mosaicism is a rare autosomal anomaly with survival compatibility. Recognition of the complete trisomy 22 which is incompatible with life from the mosaic form is critical for genetic counseling. Affected mosaic cases have prevalent clinical presentations such as webbed neck, developmental delay, abnormal ears, cardiac disorders, and microcephaly. Phenotype of these patients is milder than full chromosomal aneuploidy, and the severity of the phenotype depends on the count of trisomic cells. We describe a 4-year-old boy with mosaic trisomy 22 from healthy parents and no family history of any genetic disorders in the pedigree. METHOD AND RESULTS: The patient had determined dysmorphic clinical features including facial asymmetry, cleft palate, gastroenteritis, hydronephrosis, developmental delay, genital anomalies, dysplastic toenails, flattened nasal bridge, congenital heart defect, hearing loss, cryptorchidism, and hypotonic muscle. He is the first reported with hypothyroidism and larynx wall thickness in worldwide and the first with atrial septal defect (ASD) from Iran. Chromosomal analyses using G-banding indicated a de novo Mos 47,XY,+22(6)/46,XY(44) karyotype with no other chromosomal structural changes. CONCLUSIONS: Our observations confirm the importance of cytogenetic analyses for determining the cause of congenital anomalies and provide a useful genetic counseling. In addition, due to the fact that some of mosaic trisomy 22 features are unavoidable such as CHD and general hypotrophy, we suggest including echocardiography test for early diagnosis during the clinical assessment.

GATA4 screening in Iranian patients of various ethnicities affected with congenital heart disease: Co-occurrence of a novel de novo translocation (5;7) and a likely pathogenic heterozygous GATA4 mutation in a family with autosomal dominant congenital heart disease.

BACKGROUND: Congenital heart disease (CHD) is the most common birth defect and a major health problem around the world. However, its exact etiology has remained unclear. Among various genetic contributing factors, GATA4 transcription factor plays a significant role in the CHD pathogenesis. In this study, GATA4 coding sequence was screened in Iranian patients of various ethnicities. METHODS: Sixty six individuals with familial CHD referred to our center were recruited in this study. After receiving written informed consent from each individual or their parents, chromosomal analyses and GATA4 variant screening were performed. Pathogenicity of the suspected variants was evaluated using available online software tools: CADD, Mutation Taster, SIFT, and PolyPhen-2. RESULTS: A total of twelve GATA4 variants were detected including five intronic, 2 exonic and 3 polymorphisms as well as 2 missense mutations, the c.1220C>A and c.1309G>A. Unlike the c.1220C>A, the likely pathogenic heterozygous c.1309G>A has not been previously associated with any phenotype. Here, we not only report, for the first time, a c.1309G>A-related CHD, but also report a novel de novo balanced translocation, 46,XY,t(5;7)(qter13;qter11), in the same patient which may have influenced the disease severity. CONCLUSION: From screening GATA4 sequence in 66 Iranian patients of various ethnicities, we conclude that cytogenetic analysis and PCR-direct sequencing of different candidate genes may not be the best approach for genetic diagnosis in CHD. Applying novel approaches such as next-generation sequencing (NGS) may provide a better understating of genetic contributing factors in CHD patients for whom conventional methods could not reveal any genetic causative factor.

Genotypic effect of a mutation of the MYBPC3 gene and two phenotypes with different patterns of inheritance.

BACKGROUND: MYBPC3 mutations have been described in dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM). A mutation, c.3373G>A, has been reported to cause autosomal recessive form of HCM. Here, we report that this mutation can cause autosomal dominant form of DCM. METHODS: Next-generation sequencing using targeted panel of a total of 23 candidate genes and following Sanger sequencing was applied to detect causal mutations of DCM. Computational analyses were also performed using available software tools. In silico structural and functional analyses including protein modeling and prediction were done for the mutated MYBPC3 protein. RESULTS AND CONCLUSION: Targeted sequencing showed one variant c.3373G>A (p.Val1125Met) in the studied family following autosomal dominant inheritance. Computational programs predicted a high score of pathogenicity. Secondary structure of the region surrounding p.Val1125 was changed to a shortened beta-strand based on prediction of I-TASSER and Phyre2 servers with high confidence value for the mutation. cMyBP-C protein was modeled to 3dmkA. Our findings suggest that one single mutation of MYBPC3 may have different effects on the cellular mechanisms based of its zygosity. Various factors might be considered for explaining this phenomenon. This gene may have an important role in Iranian DCM and HCM patients.

A novel PKP2 mutation and intrafamilial phenotypic variability in ARVC/D.

Background: Arrhythmogenic ventricular cardiomyopathy (AVC) is an inherited cardiac disorder affecting 1 in 1000 individuals worldwide. The mean diagnosed age of disease is 31 years. In this article, an Iranian family reported that they were affected by ARVC due to a novel PKP2 mutation. Methods: Clinical evaluations, 12-lead ECG, CMR, and signal-averaged ECG were performed. After DNA extraction, genetic testing was done, and PCR-sequencing was applied to find causal mutations. Segregation analysis was also performed for the family. Results: ARVC criteria were documented in the patients. Genetic testing revealed a novel chain termination mutation (p.Tyr168Ter) in PKP2 gene; this mutation was transmitted from the mother to her 23-year-old son, but only the son was affected with ARVC. Conclusion: Modifier genes were indicated using interactome analysis of Plakophilin 2 protein (PKP2); they might have led to phenotypic variability through cellular mechanisms, such as nonsense-mediated mRNA decay. At least, 9 proteins were identified that might have affected Plakophilin 2 protein function, and consequently, rationalizing this intrafamilial phenotypic variability. This study highlighted the role of modifier genes involved in ARVC as well as the major role of PKP2 mutation in developing the disease in our population.

Autosomal Recessive Nonsyndromic Arrhythmogenic Right Ventricular Cardiomyopathy without Cutaneous Involvements: A Novel Mutation.

The arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is a genetic disease frequently associated with desmosomal mutations, mainly attributed to dominant mutations in the Plakophilin-2 (PKP2) gene. Naxos and Carvajal are the syndromic forms of ARVD/C due to recessive mutations. Herein, we report an autosomal recessive form of nonsyndromic ARVD/C caused by a mutation in the PKP2 gene. After examination and implementation of diagnostic modalities, the definite diagnosis of ARVD/C was confirmed by detection of ventricular tachycardia with a left bundle branch configuration and a superior axis, T-wave inversion in right precordial leads (i.e., V1-V3) in a 12-lead electrocardiogram, and a right ventricle outflow tract dilatation. Neither cutaneous involvement nor other abnormalities were observed. Genetic testing was performed during which an intronic mutation of c.2577+1G>T in the PKP2 gene was observed homozygously. The c.2577+1G>T disrupts PKP2 mRNA splicing and causes a nonsyndromic form of ARVD/C.

Construction, expression, and activity of a novel immunotoxin comprising a humanized antiepidermal growth factor receptor scFv and modified Pseudomonas aeruginosa exotoxin A.

Overexpression of epidermal growth factor receptor (EGFR) plays a significant role in the development and metastasis of many solid tumors. Strategies based on anti-EGFR immunotoxins have shown promising results in several studies, but immunogenicity of antibody and toxin moieties is a limitation of this type of therapeutics. In the present study, a novel humanized anti-EGFR immunotoxin (huscFv-PE25) was developed by genetic fusing of a humanized anti-EGFR single-chain variable fragment (huscFv) with a modified Pseudomonas aeruginosa exotoxin A (PE25KDEL). The reactivity and toxicity of this immunotoxin with tumor cells were assessed by dot-blot, enzyme-linked immunosorbent assay, and MTT procedures. Results of enzyme-linked immunosorbent assay and dot-blot assay indicated that the immunotoxin recognizes and efficiently binds to EGFR-overexpressing tumor cells. MTT assay showed a specific growth-inhibitory effect of huscFv-PE25 on EGFR-overexpressing A431 cells, without any inhibitory effect on EGFR-negative cells. In conclusion, the results of this study indicated that huscFv-PE25 can recognize and exert an inhibitory effect on EGFR-overexpressing cancer cells, despite its smaller size and lower immunogenicity. This may provide a basis for the development of novel clinical therapeutic agents against EGFR-overexpressing tumor cells.

The Frequency of HBB Mutations Among ß-Thalassemia Patients in Hamadan Province, Iran.

ß-Thalassemia (ß-thal) caused by mutations on the HBB gene is the most common single-gene disorder in the world. In this study, the HBB gene mutation was investigated in Hamadan province, Iran. Forty-one patients referred to a referral hospital were admitted to the study. DNA samples were extracted from peripheral blood. The HBB gene was sequenced in all recruited patients. Eleven mutations and eight polymorphisms were found in the studied patients. IVS-II-1 (G>A) (HBB: c.315+1 G>A) was the most common mutation, accounting for 25.61% of mutant alleles. Other mutations included codon 8 (-AA) (HBB: c.25-26delAA); IVS-I-110 (G>A) (HBB: c.93-21 G>A); codons 8/9 (+G) (HBB: c.27-28insG); IVS-I-1 (G>A) (HBB: c.92 G>A); codon 44 (-C) (HBB: c.135delC); codons 25/26 (+T) (HBB: c.78-79insT); IVS-I-130 (G>C) (HBB: c.93-1 G>C); -28 (A>C) (HBB: c.-78 A>C); codons 36/37 (-T) (HBB: c.112delT) and IVS-I-6 (T>C) (HBB: c.92+6 T>C). According to our findings, the IVS-II-1 mutation has the highest prevalence in Hamadan Province. It was found that the total frequency of the IVS-II-1, codons 25/26 (+T), codons 8/9 (+G), IVS-I-110 and IVS-I-1 mutations was 82.92%. Therefore, given these findings, it is recommended that these five mutations are screened for as a first step in laboratories without sequencing instruments, and that the rest of the gene is subsequently examined.

Comprehensive analysis via exome sequencing uncovers genetic etiology in autosomal recessive nonsyndromic deafness in a large multiethnic cohort.

PURPOSE: Autosomal recessive nonsyndromic deafness (ARNSD) is characterized by a high degree of genetic heterogeneity, with reported mutations in 58 different genes. This study was designed to detect deafness-causing variants in a multiethnic cohort with ARNSD by using whole-exome sequencing (WES). METHODS: After excluding mutations in the most common gene, GJB2, we performed WES in 160 multiplex families with ARNSD from Turkey, Iran, Mexico, Ecuador, and Puerto Rico to screen for mutations in all known ARNSD genes. RESULTS: We detected ARNSD-causing variants in 90 (56%) families, 54% of which had not been previously reported. Identified mutations were located in 31 known ARNSD genes. The most common genes with mutations were MYO15A (13%), MYO7A (11%), SLC26A4 (10%), TMPRSS3 (9%), TMC1 (8%), ILDR1 (6%), and CDH23 (4%). Nine mutations were detected in multiple families with shared haplotypes, suggesting founder effects. CONCLUSION: We report on a large multiethnic cohort with ARNSD in which comprehensive analysis of all known ARNSD genes identifies causative DNA variants in 56% of the families. In the remaining families, WES allows us to search for causative variants in novel genes, thus improving our ability to explain the underlying etiology in more families.Genet Med 18 4, 364-371.