Sumaira Kanwal

A cohort study of MFN2 mutations and phenotypic spectrums in Charcot–Marie–Tooth disease 2A patients

Charcot–Marie–Tooth disease 2A (CMT2A) is the most common axonal form of peripheral neuropathy caused by a defect in the mitofusin 2 (MFN2) gene, which encodes an outer mitochondrial membrane GTPase. MFN2 mutations result in a large range of phenotypes. This study analyzed the prevalence of MFN2 mutation in Korean families with their assorted phenotypes (607 CMT families and 160 CMT2 families). Direct sequencing of the MFN2 coding exons or whole‐exome sequencing has been applied to identify causative mutations. A total of 21 mutations were found in 36 CMT2 families. Comparative genotype–phenotype correlations impacting severity, onset age, and specific symptoms were assessed. Most mutations were seen in the GTPase domain (∼86%). A deletion mutation found in the transmembrane helices is reported for the first time, as well as five novel mutations at other domains. MFN2 mutations made up 5.9% of total CMT families, whereas 22.9% in CMT2 families, of which 27.8% occurred de novo. Interestingly, patient phenotypes ranged from mild to severe even for the same mutation, suggesting other factors influenced phenotype and penetrance. This CMT2A cohort study will be useful for molecular diagnosis and treatment of axonal neuropathy.

Phylogenetic analysis of mitochondrial DNA control region in the swimming crab, portunus trituberculatus

Abstract The control region of mitochondrial DNA (13516–14619) is located between srRNA and tRNAlle gene in swimming crab, Portunus trituberculatus. The present study was investigated the genetic polymorphisms of the control region in samples of P. trituberculatus collected at coastal waters of the Yellow Sea in Korea. A total of 300 substitution and indel polymorphic sites were identified. In addition to SNPs and indel variation, a hypervariable microsatellite motif was also identified at position from 14358 to 14391, which exhibited 10 alleles including 53 different suballeles. When the hypervariable microsatellite motif was removed from the alignment, 95 haplotypes were identified (93 unique haplotypes). The nucleotide and haplotype diversities were ranged from 0.024 to 0.028 and from 0.952 to 1.000, respectively. The statistically significant evidence for geographical structure was not detected from the analyses of neighbor‐joining tree and minimum‐spanning network, neither. This result suggest that population of P. trituberculatus are capable of extensive gene flow among populations. We believed that the polymorphisms of the control region will be used for informative markers to study phylogenetic relationships of P. trituberculatus.

Adaptive evolution and elucidating the potential inhibitor against schizophrenia to target DAOA (G72) isoforms

Schizophrenia (SZ), a chronic mental and heritable disorder characterized by neurophysiological impairment and neuropsychological abnormalities, is strongly associated with D-amino acid oxidase activator (DAOA, G72). Research studies emphasized that overexpression of DAOA may be responsible for improper functioning of neurotransmitters, resulting in neurological disorders like SZ. In the present study, a hybrid approach of comparative modeling and molecular docking followed by inhibitor identification and structure modeling was employed. Screening was performed by two-dimensional similarity search against selected inhibitor, keeping in view the physiochemical properties of the inhibitor. Here, we report an inhibitor compound which showed maximum binding affinity against four selected isoforms of DAOA. Docking studies revealed that Glu-53, Thr-54, Lys-58, Val-85, Ser-86, Tyr-87, Leu-88, Glu-90, Leu-95, Val-98, Ser-100, Glu-112, Tyr-116, Lys-120, Asp-121, and Arg-122 are critical residues for receptor–ligand interaction. The C-terminal of selected isoforms is conserved, and binding was observed on the conserved region of isoforms. We propose that selected inhibitor might be more potent on the basis of binding energy values. Further analysis of this inhibitor through site-directed mutagenesis could be helpful for exploring the details of ligand-binding pockets. Overall, the findings of this study may be helpful in designing novel therapeutic targets to cure SZ.

Association of miR-149 polymorphism with onset age and severity in Charcot–Marie–Tooth disease type 1A

Charcot-Marie-Tooth disease type 1A (CMT1A) is caused by 1.5-fold increased dosage of the PMP22; however, onset age and severity vary considerably among patients. The exact reason behind these phenotypic heterogeneities has rarely been discovered yet. Because miRNAs are the key regulators of gene expression, we speculated that variants of miRNAs might be the genetic modifiers for CMT1A. This study noticed a common single nucleotide polymorphism (n.86Tu2009>u2009C, rs2292832) in the miR-149 which was predicted to target several CMT causing genes including PMP22. The rs2292832 was located near the 3 end of the precursor microRNA of the miR-149. We performed an association study between the rs2292832 polymorphism and clinical phenotypes of CMT1A in subjects consisting of 176 unrelated Korean CMT1A patients and 176 controls. From this study, we observed that rs2292832 was closely associated to the onset age and severity of CMT1A. Particularly, the TC and CC genotypes were significantly associated with late onset and mild symptom. Therefore, we suggest that the rs2292832 variant in the miR-149 is a potential candidate as a genetic modifier which affects the phenotypic heterogeneity of CMT1A. This study may provide the first evidence that polymorphism in the miR gene is associated with the CMT1A phenotype.

A Novel Nonsense Mutation in Leucine-Rich, Glioma-Inactivated-1 Gene as the Underlying Cause of Familial Temporal Lobe Epilepsy

Dear Editor, Epilepsy constitutes a group of chronic neurological disorders that can be diagnosed at all ages and is characterized by recurrent seizures in which abnormal electrical activity causes altered perception or behavior. The prevalence of epilepsy varies between countries and ethnic groups, and generally ranges from 0.1% to 0.5%, but this increases to more than 1% in underdeveloped countries. Multiple factors such as genetic and environmental factors are associated with the etiology of epilepsy. Epilepsy is genetically highly heterogeneous and shows a weak genotype-phenotype correlation.1 More than 100 genes have been reported to be implicated in the seizure phenotype. As the environmental factors, infection, brain tumor, cerebrovascular disease, degenerative brain disease, trauma, and impairment of the cerebral cortex are suggested to be associated. Autosomal dominant lateral temporal lobe epilepsy (ADLTE or ETL1; MIM 600512) is a specific form of temporal lobe epilepsy characterized by partial seizures. ADLTE is caused by dominant mutations in the leucine-rich, glioma-inactivated-1 (LGI1) gene on chromosome 10q22-q24.2,3 Many LGI1 mutations have been reported as causes of ADLTE and sporadic epilepsy.4 LGI1 protein is strongly expressed in the lateral temporal lobe, and it is known to form the LGI1-ADAM22 epilepsy-related ligand-receptor complex that plays important roles in synaptic transmission and brain excitability.5 More than two million people in Pakistan suffer from epilepsy, which constitutes around 5% of the epilepsy patients worldwide. However, genetic tests for epilepsy have rarely been performed in Pakistan. This study examined a large Pakistani autosomal dominant epilepsy family (family ID: EF-23) comprising seven siblings: five affected and two unaffected individuals (Fig. 1A). The five affected family members had a history of complex partial seizures. All of them had experienced auditory auras or ictal aphasia followed by secondarily generalized tonic-clonic seizures (SGTCs), and one individual (II-1) additionally had visual symptoms followed by SGTCs. The ages at seizure onset ranged from 5 to 15 years (10.8±3.7 years, mean±SD). Both the seizure semiology and the neuropsychological findings pointed to lateral temporal lobe dysfunction in this ADLTE family. This study was approved by the IRB of Kongju National University (IRB No. KNU-IRB-2015-67-2) and Samsung Medical Center (IRB No. SMC 2015-08-057-002). Exome sequencing of the proband (II-6) revealed a novel c.988C>T (p.R330X) nonsense mutation in LGI1. Sanger sequencing showed complete cosegregation of the mutation, with the five affected individuals in the EF-23 pedigree (Fig. 1A and B). The LGI1 mutation was located in the highly conserved third leucine-rich glioma-inactivated epitempin protein repeat domain (Fig. 1C and D). The p.R330X mutation was not reported in several global human genome databases, including the 1,000 Genomes Project (http://www.1000genomes.org/), Sumaira Kanwal Da Hye Yoo Shahzad Tahir Su Jung Lee Min Hee Lee Byung-Ok Choi Ki Wha Chung

BAG3 mutation in a patient with atypical phenotypes of myofibrillar myopathy and Charcot–Marie–Tooth disease

Bcl2-associated athanogene 3 (BAG3) mutations have been reported to cause the myofibrillar myopathy (MFM) which shows progressive limb muscle weakness, respiratory failure, and cardiomyopathy. Myopathy patients with BAG3 mutation are very rare. We described a patient showing atypical phenotypes. We aimed to find the genetic cause of Korean patients with sensory motor polyneuropathy, myopathy and rigid spine. We performed whole exome sequencing (WES) with 423 patients with sensory motor polyneuropathy. We found BAG3 mutation in one patient with neuropathy, myopathy and rigid spine syndrome, and performed electrophysiological study, whole body MRI and muscle biopsy on the patient. A de novo heterozygous p.Pro209Leu (c.626C>T) mutation in BAG3 was identified in a female myopathy. She first noticed a gait disturbance and spinal rigidity at the age of 11, and serum creatine kinase levels were elevated ninefolds than normal. She showed an axonal sensory-motor polyneuropathy like Charcot–Marie–Tooth disease (CMT), myopathy, rigid spine and respiratory dysfunction; however, she did not show any cardiomyopathy, which is a common symptom in BAG3 mutation. Lower limb MRI and whole spine MRI showed bilateral symmetric fatty atrophy of muscles at the lower limb and paraspinal muscles. When we track traceable MRI 1xa0year later, the muscle damage progressed slowly. As far as our knowledge, this is the first Korean patient with BAG3 mutation. We described a BAG3 mutation patient with atypical phenotype of CMT and myopathy, and those are expected to broaden the clinical spectrum of the disease and help to diagnose it.

In silico identification of novel Apolipoprotein E4 inhibitor for Alzheimer’s disease therapy

INTRODUCTIONnApolipoprotein E4 (ApoE) is a major genetic factor for developing Alzheimers disease (AD). It plays a vital role in brain to maintain a constant supply of neuronal lipids for rapid and dynamic membrane synthesis. Aggregation of beta amyloid plaques (Aβ) and neurofibrillary tangles in brain are responsible for onset of AD. The current study is designed to predict a drug against over activity of apoE4. 22 natural compounds (marine, microorganism and plant derivative) were used in current study.nnnMETHODSnThese compounds were used as inhibitors to target apoE4 protein activity. Moreover, six synthetic compounds were docked with target protein to compare and analyze the docking results with natural compounds. S-Allyl-L-Cysteine, Epicatechin Gallate and Fulvic acid showed highest binding affinity (-7.1, - 7 and -7 kcal /mol respectively). Analysis of the docked complex showed that Epicatechin Gallate bonded with Gln156 and Asp35. Furthermore, Fulvic Acid showed hydrogen bonding with Glu27. Among synthetic compound, Tideglusib had highest binding affinity with target protein but did not show hydrogen bonding with any amino acid residue. Moreover, a natural compound S-Allyl-LCysteine also showed highest binding affinity but did not show hydrogen bonding with any amino acid residue.nnnRESULTS AND CONCLUSIONnOur study highlighted Epicatechin Gallate as a potential lead compound on the basis of binding affinity and hydrogen bonding to inhibit the progression of AD.

Wide phenotypic variations in Charcot-Marie-Tooth 1A neuropathy with rare copy number variations on 17p12

Abstract Charcot-Marie-Tooth disease (CMT) is clinically heterogeneous hereditary motor and sensory neuropathies with genetic heterogeneity, age-dependent penetrance, and variable expressivity. Rare copy number variations by nonrecurrent rearrangements have recently been suggested to be associated with Charcot-Marie-Tooth 1A (CMT1A) neuropathy. In our previous study, we found three Korean CMT1A families with rare copy number variations (CNVs) on 17p12 by nonrecurrent rearrangement. Careful clinical examinations were performed in all the affected individuals with rare CNVs (n=19), which may be the first full study of a subject from a large CMT1A family with nonrecurrent rearrangement. The clinical phenotype showed no significant difference compared with common CMT1A patients, but with variable phenotypes. In particular, a broad intrafamilial phenotypic spectrum was observed within the same family, which may suggest the existence of a genetic modifier. This study may broaden the understanding of the role of CNVs in the pathogenesis of CMT.