A Japanese Family of Spinocerebellar Ataxia Type 21: Clinical and Neuropathological Studies.

Cerebellum. 2018 Apr 23;:

Authors: Yahikozawa H, Miyatake S, Sakai T, Uehara T, Yamada M, Hanyu N, Futatsugi Y, Doi H, Koyano S, Tanaka F, Suzuki A, Matsumoto N, Yoshida K

Abstract
Spinocerebellar ataxia type 21 (SCA21) is a rare subtype of autosomal dominant cerebellar ataxias, which was first identified in a French family and has been reported almost exclusively in French ancestry so far. We here report the first Japanese family with SCA21, in which all affected members examined carried a heterozygous c.509C > T:p.Pro170Leu variant in TMEM240. Their clinical features were summarized as a slowly progressive ataxia of young-adult onset (5-48 years) associated with various degree of psychomotor retardation or cognitive impairment. The MR images revealed atrophy in the cerebellum, but not in the cerebrum or brainstem. These clinical findings were consistent with those in the original French families with SCA21. Neuropathological findings in one autopsied patient showed a prominent decrease of cerebellar Purkinje cells, but no specific abnormalities outside the cerebellum.

PMID: 29687291 [PubMed - as supplied by publisher]

Analysis of Downs syndrome with molecular techniques for future diagnoses.

Saudi J Biol Sci. 2018 Mar;25(3):558-562

Authors: Al-Nbaheen MS

Abstract
Down syndrome (DS) is a genetic disorder appeared due to the presence of trisomy in chromosome 21 in the G-group of the acrocentric region. DS is also known as non-Mendelian inheritance, due to the lack of Mendel's laws. The disorder in children is identified through clinical symptoms and chromosomal analysis and till now there are no biochemical and molecular analyses. Presently, whole exome sequencing (WES) has largely contributed in identifying the new disease-causing genes and represented a significant breakthrough in the field of human genetics and this technique uses high throughput sequencing technologies to determine the arrangement of DNA base pairs specifying the protein coding regions of an individual's genome. Apart from this next generation sequencing and whole genome sequencing also contribute for identifying the disease marker. From this review, the suggestion was to perform the WES is DS children to identify the marker region.

PMID: 29686519 [PubMed]

Multiomics biomarkers for the prediction of nonalcoholic fatty liver disease severity.

World J Gastroenterol. 2018 Apr 21;24(15):1601-1615

Authors: Pirola CJ, Sookoian S

Abstract
This review intends to uncover how information from large-scale genetic profiling (whole genome sequencing, and whole exome sequencing) of nonalcoholic fatty liver disease (NAFLD), as well as information from circulating transcriptomics (cell-free miRNAs) and metabolomics, contributes to the understanding of NAFLD pathogenesis. A further aim is to address the question of whether OMICs information is ready to be implemented in the clinics. The available evidence suggests that any new knowledge pertaining to molecular signatures associated with NAFLD and nonalcoholic steatohepatitis should be promptly translated into the clinical setting. Nevertheless, rigorous steps that must include validation and replication are mandatory before utilizing OMICs biomarkers in diagnostics to identify patients at risk of advanced disease, including liver cancer.

PMID: 29686467 [PubMed - in process]

Novel founder intronic variant in SLC39A14 in two families causing Manganism and potential treatment strategies.

Mol Genet Metab. 2018 Apr 06;:

Authors: Rodan LH, Hauptman M, D'Gama AM, Qualls AE, Cao S, Tuschl K, Al-Jasmi F, Hertecant J, Hayflick SJ, Wessling-Resnick M, Yang ET, Berry GT, Gropman A, Woolf AD, Agrawal PB

Abstract
Congenital disorders of manganese metabolism are rare occurrences in children, and medical management of these disorders is complex and challenging. Homozygous exonic mutations in the manganese transporter SLC39A14 have recently been associated with a pediatric-onset neurodegenerative disorder characterized by brain manganese accumulation and clinical signs of manganese neurotoxicity, including parkinsonism-dystonia. We performed whole exome sequencing on DNA samples from two unrelated female children from the United Arab Emirates with progressive movement disorder and brain mineralization, identified a novel homozygous intronic mutation in SLC39A14 in both children, and demonstrated that the mutation leads to aberrant splicing. Both children had consistently elevated serum manganese levels and were diagnosed with SLC39A14-associated manganism. Over a four-year period, we utilized a multidisciplinary management approach for Patient 1 combining decreased manganese dietary intake and chelation with symptomatic management of dystonia. Our treatment strategy appeared to slow disease progression, but did not lead to a cure or reversal of already established deficits. Clinicians should consider testing for noncoding mutations in the diagnosis of congenital disorders of manganese metabolism and utilizing multidisciplinary approaches in the management of these disorders.

PMID: 29685658 [PubMed - as supplied by publisher]

The role of monogenic disease in children with very early onset inflammatory bowel disease.

Curr Opin Pediatr. 2017 Oct;29(5):566-571

Authors: Kelsen JR, Baldassano RN

Abstract
PURPOSE OF REVIEW: Inflammatory bowel disease (IBD) is a multifactorial disease caused by dysregulated immune responses to commensal or pathogenic intestinal microbes, resulting in chronic intestinal inflammation. Patients diagnosed with IBD occurring before the age of 5 are a unique population, known as very early onset (VEO)-IBD and can be phenotypically and genetically distinct from older-onset IBD. We aim to review the clinical presentation of children with VEO-IBD and recent discoveries that point to genomic drivers of disease that may impact our therapeutic decisions.
RECENT FINDINGS: VEO-IBD is increasing in incidence and is associated with more severe disease, aggressive progression and poor response to most conventional therapies. This article will review the advances in sequencing technology that have led to identification of novel gene variants associated with disease and potentially new targeted therapeutic options.
SUMMARY: Children with VEO-IBD may present with a different phenotype and more severe disease than older children and adults. Identification of the causal gene or pathways, these children may allow for true precision medicine with targeted therapy and improved disease course.

PMID: 28700415 [PubMed - indexed for MEDLINE]

Diagnosis of Chronic Intestinal Pseudo-obstruction and Megacystis by Sequencing the ACTG2 Gene.

J Pediatr Gastroenterol Nutr. 2017 Oct;65(4):384-387

Authors: Milunsky A, Baldwin C, Zhang X, Primack D, Curnow A, Milunsky J

Abstract
OBJECTIVES: The diagnosis of chronic intestinal pseudo-obstruction has depended on clinical features, manometry, and imaging. This report aimed to determine the efficacy of sequencing the actin γ-2 (ACTG2) gene for diagnosis. In addition, the goal was to determine how often a mutation would be found in our randomly collected cohort of probands and those probands published previously.
METHODS: Whole exome sequencing was performed in 4 probands with chronic intestinal pseudo-obstruction. Subsequently, only the ACTG2 gene was sequenced in another 24 probands (total 28). We analyzed published data of 83 probands and our 28 (total 111) and determined how many had pathogenic variants and the precise genotype.
RESULTS: Whole exome and Sanger sequencing revealed a pathogenic variant in the ACTG2 gene in 4 out of 28 of our probands and in 45 out of 83 published probands (49/111 [44.1%]). Moreover, a mutational hotspot in the ACTG2 gene was recognized. Genetic heterogeneity is evident.
CONCLUSIONS: Pooled gene sequencing results from 1 individual in each of 111 families enabled a precise diagnosis of an ACTG2 mutation in 49 (44%). The benefit to patients and families of early confirmation of a motility disorder not only helps avoid unnecessary intervention, but also enables institution of appropriate treatments and avoidance of secondary disorders such as malnutrition and poor growth. Knowledge of a pathogenic variant in a parent, with a 50% risk of recurrence, provides an opportunity for genetic counseling.

PMID: 28422808 [PubMed - indexed for MEDLINE]

Whole Exome Sequencing and Molecular Modeling of a Missense Variant in TNFAIP3 That Segregates with Disease in a Family with Chronic Urticaria and Angioedema.

Case Rep Genet. 2018;2018:6968395

Authors: Harris AL, Blackburn PR, Richter JE, Gass JM, Caulfield TR, Mohammad AN, Atwal PS

Abstract
Chronic urticaria is a common condition characterized by recurrent hives lasting several weeks or months and is usually idiopathic. Approximately half of the individuals with chronic urticaria will present with episodes of angioedema that can be severe and debilitating. In this report, we describe a 47-year-old Hispanic male who presented initially for an evaluation of chronic hives following hospitalization due to hive-induced anaphylaxis. The individual had a history significant for urticaria and angioedema beginning in his early 30s. Interestingly, both the individual's 41-year-old sister and 12-year-old daughter were also affected with chronic urticaria and severe angioedema. Whole exome sequencing of the proband and several family members revealed a heterozygous variant of uncertain significance in exon 2 of TNFAIP3, denoted as c.65G>A (p.R22Q), in all affected members. Variants in TNFAIP3 have been associated with multiple autoimmune diseases, susceptibility to allergy and asthma, and periodic fever syndromes, suggesting that this variant could potentially play a role in disease.

PMID: 29682366 [PubMed]

Early onset flecked retinal dystrophy associated with new compound heterozygous RPE65 variants.

Mol Vis. 2018;24:286-296

Authors: Katagiri S, Hosono K, Hayashi T, Kurata K, Mizobuchi K, Matsuura T, Yoshitake K, Iwata T, Nakano T, Hotta Y

Abstract
Purpose: To report genetic and clinical features of two unrelated Japanese patients with early onset flecked retinal dystrophy.
Methods: Patients underwent comprehensive ophthalmic examinations that included electroretinography (ERG) after 30 min and 24 h of dark adaptation (DA). Disease-causing gene variants were identified with whole exome sequencing (WES), with identified candidates confirmed with direct sequencing.
Results: WES identified compound heterozygous RPE65 variants in both patients. Variants in patient 1 included c.1543C>T (p.R515W) and c.683A>C (p.Q228P), while patient 2 exhibited c.1028T>A (p.L343*) and c.683A>C (p.Q228P). Although variants p.R515W and p.L343* have been previously reported as pathogenic, variant p.Q228P was reported as uncertain significance. Each unaffected parent carried the variant heterozygously. Both patients had similar ophthalmic findings, including decreased visual acuity with early onset night blindness, numerous dense white dots/flecks occurring mainly outside the vascular arcades, a diffuse and/or disrupted ellipsoid line as shown with optical coherence tomography, and non-recordable rod and combined responses along with decreased cone responses after 30 min of DA. After 24 h of DA, both patients exhibited marked or partial recovery of the combined responses.
Conclusions: The results indicate that the recovery of combined or residual cone responses might be associated with a mild form of RPE65-related early onset flecked retinal dystrophy with new compound heterozygous variants.

PMID: 29681726 [PubMed - in process]

Functional mRNA analysis reveals aberrant splicing caused by novel intronic mutation in WDR45 in NBIA patient.

Am J Med Genet A. 2018 May;176(5):1049-1054

Authors: Willoughby J, Duff-Farrier C, Desurkar A, Kurian M, Raghavan A, DDD Study, Balasubramanian M

Abstract
WDR45 gene-associated neurodegeneration with brain iron accumulation (NBIA), referred to as beta-propeller protein-associated neurodegeneration (BPAN), is a rare disorder that presents with a very nonspecific clinical phenotype in children constituting global developmental delay. This case report illustrates the power of a combination of trio exome sequencing, in silico splicing analysis, and mRNA analysis to provide sufficient evidence for pathogenicity of a relatively intronic variant in WDR45, and in so doing, find a genetic diagnosis for a 6-year-old patient with developmental delay and seizures, a diagnosis which may otherwise have only been found once the characteristic MRI patterns of the disease became more obvious in young adulthood.

PMID: 29681108 [PubMed - in process]

Lethal persistent pulmonary hypertension of the newborn in Bohring-Opitz syndrome.

Am J Med Genet A. 2018 May;176(5):1245-1248

Authors: Kibe M, Ibara S, Inagaki H, Kato T, Kurahashi H, Ikeda T

Abstract
Bohring-Opitz syndrome (BOS) is a rare disease with a number of characteristic features, including hypertelorism, prominent metopic suture, exophthalmos, cleft palate, abnormal posture, and developmental retardation. Here, we report a BOS patient presenting with lethal persistent pulmonary hypertension of the newborn (PPHN) and inspiratory respiratory failure. The female infant was treated with nitric oxide and vasodilator, which did not improve her condition. The inspiratory respiratory failure required management with deep sedation. She died on postnatal day 60 due to progressed heart failure. Whole exome sequencing revealed de novo mutation in the ASXL1 gene, c.1934dupG, p.Gly646TrpfsTer12.

PMID: 29681105 [PubMed - in process]

A neurodegenerative mitochondrial disease phenotype due to biallelic loss-of-function variants in PNPLA8 encoding calcium-independent phospholipase A2γ.

Am J Med Genet A. 2018 May;176(5):1232-1237

Authors: Shukla A, Saneto RP, Hebbar M, Mirzaa G, Girisha KM

Abstract
Animal studies have demonstrated the critical roles of the patatin-like protein family plays in cellular growth, lipid homeostasis, and second messenger signaling the nervous system. Of the nine known calcium-independent phospholipase A2γ, only PNPLA2, PNLPA6, PNPLA9 and most recently a single patient with PNPLA8 are associated with mitochondrial-related neurodegeneration. Using whole exome sequencing, we report two unrelated individuals with variable but similar clinical features of microcephaly, severe global developmental delay, spasticity, lactic acidosis, and progressive cerebellar atrophy with biallelic loss-of-function variants in PNPLA8.

PMID: 29681094 [PubMed - in process]

LIPT1 deficiency presenting as early infantile epileptic encephalopathy, Leigh disease, and secondary pyruvate dehydrogenase complex deficiency.

Am J Med Genet A. 2018 May;176(5):1184-1189

Authors: Stowe RC, Sun Q, Elsea SH, Scaglia F

Abstract
Lipoic acid is an essential cofactor for the mitochondrial 2-ketoacid dehydrogenase complexes and the glycine cleavage system. Lipoyltransferase 1 catalyzes the covalent attachment of lipoate to these enzyme systems. Pathogenic variants in LIPT1 gene have recently been described in four patients from three families, commonly presenting with severe lactic acidosis resulting in neonatal death and/or poor neurocognitive outcomes. We report a 2-month-old male with severe lactic acidosis, refractory status epilepticus, and brain imaging suggestive of Leigh disease. Exome sequencing implicated compound heterozygous LIPT1 pathogenic variants. We describe the fifth case of LIPT1 deficiency, whose phenotype progressed to that of an early infantile epileptic encephalopathy, which is novel compared to previously described patients whom we will review. Due to the significant biochemical and phenotypic overlap that LIPT1 deficiency and mitochondrial energy cofactor disorders have with pyruvate dehydrogenase deficiency and/or nonketotic hyperglycinemia, they are and have been presumptively under-diagnosed without exome sequencing.

PMID: 29681092 [PubMed - in process]

Anticipation in a family with primary familial brain calcification caused by an SLC20A2 variant.

Neurol Neurochir Pol. 2018 Apr 11;:

Authors: Konno T, Blackburn PR, Rozen TD, van Gerpen JA, Ross OA, Atwal PS, Wszolek ZK

Abstract
AIM OF THE STUDY: To describe a family with primary familial brain calcification (PFBC) due to SLC20A2 variant showing possible genetic anticipation.
MATERIALS AND METHODS: We conducted historical, genealogical, clinical, and radiologic studies of a family with PFBC. Clinical evaluations including neurological examination and head computed tomography (CT) scans of a proband and her father were performed. They provided additional information regarding other family members. To identify a causative gene variant, we performed whole-exome sequencing for the proband followed by segregation analysis in other affected members using direct sequencing.
RESULTS: In this family, nine affected members were identified over four generations. The proband suffered from chronic daily headache including thunderclap headache. We identified an SLC20A2 (c.509delT, p.(Leu170*)) variant in three affected members over three generations. Interestingly, the age of onset became younger as the disease passed through successive generations, suggestive of genetic anticipation.
CONCLUSIONS AND CLINICAL IMPLICATIONS: For clinical purpose, it is important to consider thunderclap headache and genetic anticipation in PFBC caused by SLC20A2 variants. Further investigation is required to validate our observation.

PMID: 29680161 [PubMed - as supplied by publisher]

KIR2DL5 mutation and loss underlies sporadic dermal neurofibroma pathogenesis and growth.

Oncotarget. 2017 Jul 18;8(29):47574-47585

Authors: Anastasaki C, Dahiya S, Gutmann DH

Abstract
Dermal neurofibromas (DNFs) are benign peripheral nerve sheath tumors thought to originate from Schwann cell progenitors. These tumors represent one of the hallmarks of the neurofibromatosis type 1 (NF1) tumor predisposition syndrome, where they can number in the thousands. While NF1-DNFs arise due to mutations in the NF1 gene, the vast majority of DNFs occur sporadically (sp-DNFs), where the genetic etiology is currently unknown. Herein, we employed whole-exome sequencing of sp-DNFs to identify a recurrent mutation in the KIR2DL5 gene, which codes for a protein suppressor of natural killer (NK) cell activity. While the function of KIR2DL5 outside of the immune system is unknown, we identified a KIR2DL5N173D mutation in three of nine sp-DNFs, resulting in loss of KIR2DL5 protein expression. In contrast, two of these subjects had unrelated tumors, which retained KIR2DL5 protein expression. Moreover, loss of KIR2DL5 expression was demonstrated in 15 of 45 independently-identified sp-DNFs. Consistent with its potential role as a negative growth regulator important for neurofibroma maintenance, ectopic KIR2DL5N173D expression in normal human Schwann cells resulted in reduced KIR2DL5 expression and increased cell proliferation. Similarly, KIR2DL5 short hairpin RNA knockdown (KD) decreased KIR2DL5 protein levels and increased cell proliferation, as well as correlated with PDGFRβ and downstream RAS/AKT/mTOR hyperactivation. Importantly, inhibition of PDGFRβ or AKT/mTOR activity in KIR2DL5-KD human Schwann cells reduced proliferation to control levels. Collectively, these findings establish KIR2DL5 as a new Schwann cell growth regulator relevant to sp-DNF pathogenesis, which links sporadic and NF1-associated DNFs through RAS pathway hyperactivation.

PMID: 28548933 [PubMed - indexed for MEDLINE]

Novel magnetic resonance imaging findings in a patient with short chain acyl CoA dehydrogenase deficiency.

Metab Brain Dis. 2017 Aug;32(4):967-970

Authors: Chiplunkar S, Bindu PS, Nagappa M, Panikulam BB, Arvinda HR, Govindaraj P, Srinivas Bharath MM, Gayathri N, Jessiena Ponmalar JN, Mathuranath PS, Sinha S, Taly AB

Abstract
Reports on magnetic resonance imaging findings in patients with short chain acyl -Coenzyme A dehydrogenase (SCAD) deficiency, an autosomal recessive disorder caused by mutations in the acyl-Coenzyme A dehydrogenase (ACADS), are limited. Many asymptomatic carriers of ACAD variants have also been described necessitating careful evaluation of clinical and biochemical findings for an accurate diagnosis. Here we report a an infant with short chain acyl -Coenzyme A dehydrogenase (SCAD) deficiency diagnosed based on the characteristic biochemical findings and confirmed by genetic testing. He presented with refractory seizures and neuro regression at 4 months of age. His metabolic work up revealed elevated butyryl carnitine in plasma and ethyl malonic acid in urine. Magnetic resonance imaging of the brain showed cortical and basal ganglia signal changes with cortical swelling. Serial scans showed progression of the lesions resulting in cystic leukomalacia with brain atrophy. Exome sequencing revealed a novel homozygous nonsense variation, c.1146C > G (p.Y382Ter) in exon ten of ACADS which was further validated by Sanger sequencing. Both parents were heterozygous carriers. Follow up at 15 months showed gross psychomotor retardation and refractory seizures despite being on optimal doses of anti-epileptic medications, carnitine and multivitamin supplementation. This report expands the phenotypic and genotypic spectrum of SCAD deficiency.

PMID: 28374236 [PubMed - indexed for MEDLINE]

Deleterious coding variants in multi-case families with non-syndromic cleft lip and/or palate phenotypes.

Sci Rep. 2016 07 26;6:30457

Authors: Pengelly RJ, Arias L, Martínez J, Upstill-Goddard R, Seaby EG, Gibson J, Ennis S, Collins A, Briceño I

Abstract
Nonsyndromic Cleft Lip and/or Palate (NSCLP) is regarded as a multifactorial condition in which clefting is an isolated phenotype, distinguished from the largely monogenic, syndromic forms which include clefts among a spectrum of phenotypes. Nonsyndromic clefting has been shown to arise through complex interactions between genetic and environmental factors. However, there is increasing evidence that the broad NSCLP classification may include a proportion of cases showing familial patterns of inheritance and contain highly penetrant deleterious variation in specific genes. Through exome sequencing of multi-case families ascertained in Bogota, Colombia, we identify 28 non-synonymous single nucleotide variants that are considered damaging by at least one predictive score. We discuss the functional impact of candidate variants identified. In one family we find a coding variant in the MSX1 gene which is predicted damaging by multiple scores. This variant is in exon 2, a highly conserved region of the gene. Previous sequencing has suggested that mutations in MSX1 may account for ~2% of NSCLP. Our analysis further supports evidence that a proportion of NSCLP cases arise through monogenic coding mutations, though further work is required to unravel the complex interplay of genetics and environment involved in facial clefting.

PMID: 27456059 [PubMed - indexed for MEDLINE]

CAPN1 mutations broadening the hereditary spastic paraplegia/spinocerebellar ataxia phenotype.

Pract Neurol. 2018 Apr 20;:

Authors: Lambe J, Monaghan B, Munteanu T, Redmond J

Abstract
Increasing availability of next-generation sequencing technologies has revealed several limitations of diagnosis-driven traditional clinicogenetic disease classifications, particularly among patients with an atypical or mixed phenotype. Hereditary spastic paraplegia (HSP) and spinocerebellar ataxia (SCA) are two such disease entities with an often overlapping presentation, in which next generation exome sequencing has played a key role in identification of genes causing disease along a continuum of ataxia and spasticity. We describe a patient who presented with features of both ataxia and spasticity, in whom initial diagnostic testing was inconclusive. Ultimately next generation exome sequencing identified homozygosity for a pathogenic variant in exon 13 of the CAPN1 gene c.1534C>T(p.Arg512Cys). This case supports consideration of a less discriminatory classification system among such patients, potentially allowing for more expedient diagnosis through testing of a larger gene panel along the 'ataxia-spasticity spectrum'.

PMID: 29678961 [PubMed - as supplied by publisher]

Use of Genetic Testing for Primary Immunodeficiency Patients.

J Clin Immunol. 2018 Apr 19;:

Authors: Heimall JR, Hagin D, Hajjar J, Henrickson SE, Hernandez-Trujillo HS, Tan Y, Kobrynski L, Paris K, Torgerson TR, Verbsky JW, Wasserman RL, Hsieh EWY, Blessing JJ, Chou JS, Lawrence MG, Marsh RA, Rosenzweig SD, Orange JS, Abraham RS

Abstract
Genetic testing plays a critical role in diagnosis for many primary immunodeficiency diseases. The goals of this report are to outline some of the challenges that clinical immunologists face routinely in the use of genetic testing for patient care. In addition, we provide a review of the types of genetic testing used in the diagnosis of PID, including their strengths and limitations. We describe the strengths and limitations of different genetic testing approaches for specific clinical contexts that raise concern for specific PID disorders in light of the challenges reported by the clinical immunologist members of the CIS in a recent membership survey. Finally, we delineate the CIS's recommendations for the use of genetic testing in light of these issues.

PMID: 29675737 [PubMed - as supplied by publisher]

Auto-immune disorders in a child with PIK3CD variant and 22q13 deletion.

Eur J Med Genet. 2018 Apr 16;:

Authors: Kiyota K, Yoshiura KI, Houbara R, Miyahara H, Korematsu S, Ihara K

Abstract
22q13 deletion syndrome is a genetic disorder caused by the deletion or disruption of the segment of the long arm of chromosome 22. The characteristic clinical features of this syndrome include delayed expressive speech, autistic behavior and hypotonia, and clinically severe complications associated with autoimmunity are rarely reported. We herein report a girl with 22q13 deletion syndrome complicated with multiple inflammatory and autoimmune diseases during early childhood. We performed whole-exome sequencing to identify the genes responsible for her autoimmune diseases and identified the de novo variant p.R512W in the phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit delta (PIK3CD) gene. We suspected it to be the disease-causing variant at the conserved residue in PIK(3)C p110δ. Alternatively, haplo-insufficiency of SHANK3 or other genes by 22q13 deletion and the PIK3CD variant might have synergistically contributed to the onset of the distinctive clinical manifestations in this patient.

PMID: 29673649 [PubMed - as supplied by publisher]

In silico prediction of the pathogenic effect of a novel variant of BCKDHA leading to classical maple syrup urine disease identified using clinical exome sequencing.

Clin Chim Acta. 2018 Apr 16;:

Authors: Fernández-Lainez C, Aláez-Verson C, Ibarra-González I, Enríquez-Flores S, Carrillo-Sanchez K, Flores-Lagunes L, Guillén-López S, Belmont-Martínez L, Vela-Amieva M

Abstract
Maple syrup urine disease (MSUD) is a metabolic disorder caused by mutations in three of the branched-chain α-keto acid dehydrogenase complex (BCKDC) genes. Classical MSUD symptom can be observed immediately after birth and include ketoacidosis, irritability, lethargy, and coma, which can lead to death or irreversible neurodevelopmental delay in survivors. The molecular diagnosis of MSUD can be time-consuming and difficult to establish using conventional Sanger sequencing because it could be due to pathogenic variants of any of the BCKDC genes. Next-generation sequencing-based methodologies have revolutionized the molecular diagnosis of inborn errors in metabolism and offer a superior approach for genotyping these patients. Here, we report an MSUD case whose molecular diagnosis was performed by clinical exome sequencing (CES), and the possible structural pathogenic effect of a novel E1α subunit pathogenic variant was analyzed using in silico analysis of α and β subunit crystallographic structure. Molecular analysis revealed a new homozygous non-sense c.1267C>T or p.Gln423Ter variant of BCKDHA. The novel BCKDHA variant is considered pathogenic because it caused a premature stop codon that probably led to the loss of the last 22 amino acid residues of the E1α subunit C-terminal end. In silico analysis of this region showed that it is in contact with several residues of the E1β subunit mainly through polar contacts, hydrogen bonds, and hydrophobic interactions. CES strategy could benefit the patients and families by offering precise and prompt diagnosis and better genetic counseling.

PMID: 29673582 [PubMed - as supplied by publisher]