Papers by Nyamkhishig Sambuughin
Molecular genetics and metabolism reports, 2018
Exertional rhabdomyolysis is a metabolic event characterized by the release of muscle content int... more Exertional rhabdomyolysis is a metabolic event characterized by the release of muscle content into the circulation due to exercise-driven breakdown of skeletal muscle. Recurrent exertional rhabdomyolysis has been associated with metabolic myopathies and mitochondrial disorders, a clinically and genetically heterogeneous group of predominantly autosomal recessive, monogenic conditions. Although genetics factors are well recognized in recurrent rhabdomyolysis, the underlying causes and mechanisms of exercise-driven muscle breakdown remain unknown in a substantial number of cases. We present clinical and genetic study results from seven adult male subjects with recurrent exertional rhabdomyolysis. In all subject, whole exome sequencing identified multiple heterozygous variants in genes associated with monogenic metabolic and/or mitochondrial disorders. These variants consisted of known pathogenic and/or new likely pathogenic variants in combination with other rare deleterious alleles. ...
Genetics, 1996
High levels of mitochondrial DNA (mtDNA) diversity were determined for Mongolian populations, rep... more High levels of mitochondrial DNA (mtDNA) diversity were determined for Mongolian populations, represented by the Mongol-speaking Khalkha and Dariganga. Although 103 samples were collected across Mongolia, low levels of genetic substructuring were detected, reflecting the nomadic lifestyle and relatively recent ethnic differentiation of Mongolian populations. mtDNA control region I sequence and seven additional mtDNA polymorphisms were assayed to allow extensive comparison with previous human population studies. Based on a comparative analysis, we propose that indigenous populations in east Central Asia represent the closest genetic link between Old and New World populations. Utilizing restriction/deletion polymorphisms, Mongolian populations were found to carry all four New World founding haplogroups as defined by WALLACE and coworkers. The ubiquitous presence of the four New World haplogroups in the Americas but narrow distribution across Asia weakens support for GREENBERG and cowo...
Molecular Genetics & Genomic Medicine, 2014
Whole exome sequencing (WES) was used to determine the primary cause of muscle disorder in a fami... more Whole exome sequencing (WES) was used to determine the primary cause of muscle disorder in a family diagnosed with a mild, undetermined myopathy and malignant hyperthermia (MH) susceptibility (MHS). WES revealed the compound heterozygous mutations, p.Ile235Asn and p.Glu982Lys, in ATP2A1, encoding the sarco(endo)plasmic reticulum Ca 2+ ATPase type 1 (SERCA1), a calcium pump, expressed in fast-twitch muscles. Recessive mutations in ATP2A1 are known to cause Brody myopathy, a rare muscle disorder characterized by exercise-induced impairment of muscle relaxation and stiffness. Analyses of affected muscles showed the absence of SERCA1, but SERCA2 upregulation in slow and fast myofibers, suggesting a compensatory mechanism that partially restores the diminished Ca 2+ transport in Brody myopathy. This compensatory adaptation to the lack of SERCA1 Ca 2+ pumping activity within the muscle explains, in part, the mild course of disease in our patient. Diagnosis of MHS in this family was secondary to a loss of SERCA1 due to disease-associated mutations. Although there are obvious differences in clinical expression and molecular mechanisms between MH and Brody myopathy, a feature common to both conditions is elevated myoplasmic Ca 2+ content. Prolonged intracellular Ca 2+ elevation is likely to have led to MHS diagnosis in vitro and postoperative MHlike symptoms in Brody patient.
Acta Neuropathologica, 2003
Synemin is a member of the intermediate protein superfamily. Previous studies in avian and rodent... more Synemin is a member of the intermediate protein superfamily. Previous studies in avian and rodent skeletal and cardiac muscles have demonstrated that synemin localises at the Z-band, where it associates with desmin and α-actinin. In the present study, the distribution of synemin was examined using immunohistochemistry in muscle biopsy specimens from patients suffering from myofibrillar myopathy (MM, n=6), dermatomyositis (DM,
Journal of the Neurological Sciences, 2004
Ten Spanish patients from six unrelated families diagnosed with desmin-related myopathy (DRM) wer... more Ten Spanish patients from six unrelated families diagnosed with desmin-related myopathy (DRM) were studied. The pattern of DRM inheritance was autosomal dominant in three families, autosomal recessive in one, and there was no family history in two cases. The disease onset was in early adulthood. Cardiac myopathy was the initial presentation in two patients, respiratory insufficiency in one, and lower limb weakness in all others. Cardiac involvement was observed in four patients. Lens opacities were found in four. CK level was normal or slightly elevated, and electrophysiological examination was consistent with myopathy. Muscle biopsies identified intracytoplasmic desminimmunoreactive inclusions. In addition to desmin, synemin, actin, gelsolin, ubiquitin, aB-crystallin and amyloid hA4 were also present in the deposits. Ultrastructural examination revealed areas of myofibrillary disruption, abnormal electron-dense structures and accumulations of granulofilamentous material.
Journal of the Neurological Sciences, 2000
Twelve cases of adult-onset progressive muscular atrophy variant of amyotrophic lateral sclerosis... more Twelve cases of adult-onset progressive muscular atrophy variant of amyotrophic lateral sclerosis (PMA /ALS) were studied in a small rural population of 1500 in the Republic of Belarus (former Soviet Union). The patients were members of three apparently related kindreds, each showing autosomal dominant pattern of disease inheritance. The average age at clinical onset ranged from 26 to 57 years (mean, 40 years). Each patient suffered from skeletal muscle weakness and wasting, starting in the limbs and spreading to the trunk and neck, with very limited bulbar and no upper motor neuron involvement. Death from respiratory failure occurred from 13 to 48 months (mean, 28 months) after first symptoms. Dramatically decreased number of spinal motor neurons was the most characteristic neuropathologic feature in two autopsied cases. Most of the remaining degenerating neurons contained intracytoplasmic hyaline inclusion bodies. A D101N mutation in exon 4 of the SOD1 gene was identified in a PMA /ALS patient and in one of her three unaffected children. Our data support the view that some subtypes of familial ALS associated with SOD1 mutations may present as PMA. Diagnostic criteria of ALS should be accordingly modified to include the PMA variant of familial ALS.
Journal of the Neurological Sciences, 1998
International Journal of Cardiology, 2007
According to the predominant view, desmin mutations cause dilated cardiomyopathy (DCM). We evalua... more According to the predominant view, desmin mutations cause dilated cardiomyopathy (DCM). We evaluated a family with restrictive cardiomyopathy (RCM) associated with a novel desmin mutation and reviewed recent reports regarding the frequency of RCM in patients with desmin myopathy. Cardiovascular examination was performed in three affected and five at-risk members of a family from Poland, histopathologic study of skeletal muscle biopsy was done in a single patient, and functional analysis of mutant desmin protein was carried out in cultured cells. Cardiovascular assessment led to the diagnosis of RCM in affected family members. Histopathological study of skeletal muscle biopsy revealed features characteristic of desmin myopathy. A novel desmin E413K mutation was identified in each affected family member, but not unrelated controls. The pathogenicity of the E413K mutation was confirmed in transfected cell cultures showing inability of mutant desmin to form a cellular filamentous network or support a pre-existing network formed by other intermediate filaments. Three-dimensional modeling and electrostatic calculations indicated that the E413K mutation located in a functionally unique domain of desmin molecule potentially disrupts intramolecular interactions. Analysis of previously reported observations indicates that RCM in desminopathy patients may be as frequent as DCM. A novel E413K mutation in desmin caused autosomal dominant RCM rather than DCM. The location of the E413K mutation at a highly conserved end of the alpha-helical rod domain may be related to the phenotypic differences from the previously described DCM-associated desmin mutations. Functional and structural analyses of mutant desmin allowed to identify likely pathogenic mechanisms.
Human Genetics, 2003
Enzymes encoded by two gene families, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALD... more Enzymes encoded by two gene families, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH), mediate alcohol metabolism in humans. Allelic variants have been identified that alter metabolic rates and influence risk for alcoholism. Specifically, ADH1B*47His (previously ADH2-2) and ALDH2-2 have been shown to confer protection against alcoholism, presumably through accumulation of acetaldehyde in the blood and a resultant 'flushing response' to alcohol consumption. In the current study, variants at ADH1B(previously ADH2), ADH1C (pre-viously ADH3), and ALDH2 were assayed in DNA extracts from participants belonging to a Southwest American Indian tribe (n=490) with a high prevalence of alcoholism. Each subject underwent a clinical interview for diagnosis of alcohol dependence, as well as evaluation of intermediate phenotypes such as binge drinking and flushing response to alcohol consumption. Detailed haplotypes were constructed and tested against alcohol dependence and related intermediate phenotypes using both association and linkage analysis. ADH and ALDH variants were also assayed in three Asian and one African population (no clinical data) in order to provide an evolutionary context for the haplotype data. Both linkage and association analysis identified several ADH1C alleles and a neighboring microsatellite marker that affected risk of alcohol dependence and were also related to binge drinking. These data strengthen the support for ADH as a candidate locus for alcohol dependence and suggest further productive study.
European Journal of Human Genetics, 2009
Myofibrillar myopathies (MFMs) are an expanding and increasingly recognized group of neuromuscula... more Myofibrillar myopathies (MFMs) are an expanding and increasingly recognized group of neuromuscular disorders caused by mutations in DES, CRYAB, MYOT, and ZASP. The latest gene to be associated with MFM was FLNC; a p.W2710X mutation in the 24th immunoglobulin-like repeat of filamin C was shown to be the cause of a distinct type of MFM in several German families. We studied an International cohort of 46 patients from 39 families with clinically and myopathologically confirmed MFM, in which DES, CRYAB, MYOT, and ZASP mutations have been excluded. In patients from an unrelated family a 12-nucleotide deletion (c.2997_3008del) in FLNC resulting in a predicted in-frame four-residue deletion (p.Val930_Thr933del) in the seventh repeat of filamin C was identified. Both affected family members, mother and daughter, but not unrelated control individuals, carried the p.Val930_Thr933del mutation. The mutation is transcribed and, based on myopathological features and immunoblot analysis, it leads to an accumulation of dysfunctional filamin C in the myocytes. The study results suggest that the novel p.Val930_Thr933del mutation in filamin C is the cause of MFM but also indicate that filamin C mutations are a comparatively rare cause of MFM.
Clinical Genetics, 2002
Malignant hyperthermia (MH) is an autosomal dominant disorder that predisposes susceptible indivi... more Malignant hyperthermia (MH) is an autosomal dominant disorder that predisposes susceptible individuals to a potentially life-threatening crisis when exposed to commonly used anesthetics. Mutations in the skeletal muscle calcium release channel, ryanodine receptor (RYR1) are associated with MH in over 50% of affected families. Linkage analysis of the RYR1 gene region at 19q13 was performed in a large Brazilian family and a distinct disease co-segregating haplotype was revealed in the majority of members with diagnosis of MH. Subsequent sequencing of RYR1 mutational hot spots revealed a nucleotide substitution of C to T at position 7062, causing a novel amino acid change from Arg2355 to Cys associated with MH in the family. Haplotype analysis of the RYR1 gene area at 19q13 in the family with multiple MH members is an important tool in identification of genetic cause underlying this disease.
Clinical Genetics, 2009
It has been suggested that exertional rhabdomyolysis (ER) and malignant hyperthermia (MH) are rel... more It has been suggested that exertional rhabdomyolysis (ER) and malignant hyperthermia (MH) are related syndromes. We hypothesize that patients with unexplained ER harbor mutations in the ryanodine receptor gene type 1 (RYR1), a primary gene implicated in MH, and therefore ER patients are at increased risk for MH. Although there are reported cases of MH in individuals of African descent, there are no data available on molecular characterization of these patients. We analyzed RYR1 in six, unrelated African American men with unexplained ER, who were subsequently diagnosed as MH susceptible (MHS) by the Caffeine Halothane Contracture Test. Three novel and two variants, previously reported in Caucasian MHS subjects, were found in five studied patients. The novel variants were highly conserved amino acids and were absent among 230 control subjects of various ethnic backgrounds. These results emphasize the importance of performing muscle contracture testing and RYR1 mutation screening in patients with unexplained ER. The MHS-associated variant Ala1352Gly was identified as a polymorphism predominant in individuals of African descent. Our data underscore the need for investigating RYR1 across different ethnic groups and will contribute to interpretation of genetic screening results of individuals at risk for MH.
Brazilian Journal of Medical and Biological Research, 2009
Brain, 2006
Essential tremor (ET) is the most prevalent adult-onset movement disorder showing evidence of non... more Essential tremor (ET) is the most prevalent adult-onset movement disorder showing evidence of non-random accumulation in some families. ET has previously been mapped to genetic loci on chromosomes 2p and 3q, but no causative genes identified. We conducted genomewide linkage screening with subsequent fine mapping in seven large North American families comprising a total of 325 genotyped individuals that included 65 patients diagnosed as definite ET. Linkage analysis was based on methodology implemented in SimWalk2 and LINKAGE programs. A multigenerational family revealed suggestive linkage to a locus on chromosome 6p23 with maximal nonparametric linkage (NPL) multipoint score 3.281 (P = 0.0005) and parametric multipoint log of the odds (LOD) score 2.983. A second family showed positive linkage to the same 6p23 region with a maximal NPL score 2.125 (P = 0.0075) and LOD score 1.265. Haplotype analysis led to the identification of a 600 kb interval shared by both families. Sequencing of coding regions of 15 genes located in the linked region detected numerous sequence variants, some of them predicting a change of the encoded amino acid, but each was also found in controls. Our findings provide evidence for linkage to a novel susceptibility locus on chromosome 6p23. Analysis of additional ET-affected families is needed to confirm linkage and identify the underlying gene.
Biophysical Journal, 2011
Biochemical and Biophysical Research Communications, 2012
Autosomal dominant mutations in BTB and Kelch domain containing 13 protein (KBTBD13) are associat... more Autosomal dominant mutations in BTB and Kelch domain containing 13 protein (KBTBD13) are associated with a new type of Nemaline Myopathy (NEM). NEM is a genetically heterogeneous group of muscle disorders. Mutations causing phenotypically distinct NEM variants have previously been identified in components of muscle thin filament. KBTBD13 is a muscle specific protein composed of an N terminal BTB domain and a C terminal Kelch-repeat domain. The function of this newly identified protein in muscle remained unknown. In this study, we show that KBTBD13 interacts with Cullin 3 (Cul3) and the BTB domain mediates this interaction. Using ubiquitination assays, we determined that KBTBD13 participates in the formation of a Cul3 based RING ubiquitin ligase (Cul3-RL) capable of ubiquitin conjugation. Confocal microscopy of transiently expressed KBTBD13 revealed its co-localization with ubiquitin. Taken together, our results demonstrate that KBTBD13 is a putative substrate adaptor for Cul3-RL that functions as a muscle specific ubiquitin ligase, and thereby implicate the ubiquitin proteasome pathway in the pathogenesis of KBTBD13-associated NEM.
Annals of Neurology, 1999
X-linked adrenoleukodystrophy (ALD) usually presents in childhood as severe cerebral demyelinatio... more X-linked adrenoleukodystrophy (ALD) usually presents in childhood as severe cerebral demyelination accompanied by axonal loss or in adults as a progressive spinal cord syndrome (adrenomyeloneuropathy). Rarely, patients present with adult onset spinocerebellar ataxia. We performed mutation analysis in a family with several members who had this rare phenotype and identified a single nucleotide deletion in exon 2 of the ALD gene. This is the first mutation analysis to be reported in this unusual phenotypic variant of ALD and the first deletion to be reported in exon 2.
Anesthesiology, 2004
Malignant hyperthermia (MH) is a pharmacogenetic disorder of skeletal muscle, manifested as a lif... more Malignant hyperthermia (MH) is a pharmacogenetic disorder of skeletal muscle, manifested as a life-threatening hypermetabolic crisis after exposure to anesthetics. Type I ryanodine receptor 1 is the primary gene responsible for susceptibility to MH as well as central core disease, a congenital myopathy that predisposes susceptibility to MH. More than 40 mutations in the RyR1 gene cluster in three coding regions: the N-terminus, central, and C-terminus regions. However, the frequency of mutations in each region has not been studied in the North American MH-susceptible population. The authors tested 124 unrelated patients with MH susceptibility for the presence of mutations in the N-terminus (exons 2, 6, 9, 11, 12, and 17), central (exons 39, 40, 44, 45, and 46), and C-terminus (exons 95, 100, 101, and 102) regions. Fourteen mutations have been identified in 29 of 124 MH-susceptible patients (23%). Approximately 70% of the mutations, which include a novel mutation, Ala 2437Val, were in the central region. In 8 patients (28%), mutations were identified in the N-terminus region. Screening the C-terminus region yielded a novel mutation, Leu4824Pro, in a single patient with a diagnosis of central core disease. The detection rate for mutations is only 23% by screening mutations (or exons) listed in the 2002 North American consensus panel. The implications from this study suggest that testing the central region first is currently the most effective screening strategy for the North American population. Screening more exons in the three hot spots may be needed to find an accurate frequency of mutations in the RyR1 gene.
Anesthesiology, 2001
Malignant hyperthermia (MH) is a disorder of skeletal muscle manifested as a life-threatening hyp... more Malignant hyperthermia (MH) is a disorder of skeletal muscle manifested as a life-threatening hypermetabolic crisis in susceptible individuals after exposure to inhalational anesthetics and depolarizing muscle relaxants. Mutations in the gene encoding the skeletal muscle ryanodine receptor (RYR1) are considered a common cause of the disorder, and, to date, more than 20 RYR1 mutations have been reported in European and Canadian families. Some studies suggest that differences may exist in the frequencies and distribution of mutations in the RYR1 gene between European and North American MH families the frequency and distribution of mutations in the RYR1 gene. Skeletal muscle samples from 73 unrelated individuals diagnosed as MH susceptible according to the North American MH caffeine-halothane contracture test were studied. Genomic DNA of MH-susceptible patients was investigated by polymerase chain reaction-based restriction fragment length polymorphism, single-strand conformation polymorphism, and sequencing analysis. The majority of known RYR1 mutations were analyzed using the restriction fragment length polymorphism method, whereas new mutations were searched by single-strand conformation polymorphism in exons 12, 15, 39, 40, 44, 45, and 46 of the gene. Seven known RYR1 mutations (Arg163Cys, Gly248Arg, Arg614Cys, Val2168Met, Thr2206Met, Gly2434Arg, and Arg2454His) were detected at frequencies of 2.7, 1.4, 1.4, 1.4, 1.4, 5.5, and 4.1%, respectively. In addition, three novel amino acid substitutions (Val2214Ile, Ala2367Thr, and Asp2431Asn) were detected at frequency of 1.4% each. These 10 mutations account for 21.9% of the North American MH-susceptible population. Three novel candidate mutations in the RYR1 gene were identified in these MH patients. The frequency and distribution of RYR1 mutations observed in this North American MH population was markedly different from that previously identified in Europe. Larger-scale studies are necessary to clarify the type and frequency of mutations in RYR1 associated with MH in North American families.
Uploads
Papers by Nyamkhishig Sambuughin