Phenotypic heterogeneity in monogenic diabetes: The clinical and diagnostic utility of a gene panel-based next-generation sequencing approach G. Alkorta-Aranburu a,1 , D. Carmody b,c,1 , Y.W. Cheng a , V. Nelakuditi a , L. Ma a , Jazzmyne T. Dickens b,c , S. Das a , S.A.W. Greeley b,c , D. del Gaudio a, ⁎ a Department of Human Genetics, The University of Chicago, Chicago, IL, USA b Department of Medicine, Section of Adult and Pediatric Endocrinology, Diabetes & Metabolism, The University of Chicago, Chicago, IL, USA c Department of Pediatrics, Section of Adult and Pediatric Endocrinology, Diabetes & Metabolism, The University of Chicago, Chicago, IL, USA abstract article info Article history: Received 30 July 2014 Received in revised form 17 September 2014 Accepted 18 September 2014 Available online xxxx Keywords: Next-generation sequencing Monogenic diabetes Diagnostic evaluation Targeted sequencing Single gene mutations that primarily affect pancreatic β-cell function account for approximately 1–2% of all cases of diabetes. Overlapping clinical features with common forms of diabetes makes diagnosis of monogenic diabetes challenging. A genetic diagnosis often leads to significant alterations in treatment, allows better prediction of disease prognosis and progression, and has implications for family members. Currently, genetic testing for monogenic diabetes relies on selection of appropriate individual genes for analysis based on the availability of often-limited phenotypic information, decreasing the likelihood of making a genetic diagnosis. We thus developed a targeted next-generation sequencing (NGS) assay for the detection of mutations in 36 genes known to cause monogenic forms of diabetes, including transient or permanent neonatal diabetes mellitus (TNDM or PNDM), maturity-onset diabetes of the young (MODY) and rare syndromic forms of diabetes. A total of 95 patient samples were analyzed: 19 with known causal mutations and 76 with a clinically suggestive phenotype but lacking a genetic diagnosis. All previously identified mutations were detected, validating our assay. Pathogenic sequence changes were identified in 19 out of 76 (25%) patients: 7 of 32 (22%) NDM cases, and 12 of 44 (27%) MODY cases. In 2 NDM patients the causal mutation was not expected as consanguinity was not reported and there were no clinical features aside from diabetes. A 3 year old patient with NDM diag- nosed at 3 months of age, who previously tested negative for INS, KCNJ11 and ABCC8 mutations, was found to carry a novel homozygous mutation in EIF2AK3 (associated with Wolcott–Rallison syndrome), a gene not previ- ously suspected because consanguinity, delayed growth, abnormal bone development and hepatic complications had not been reported. Similarly, another infant without a history of consanguinity was found to have a homo- zygous GCK mutation causing PNDM at birth. This study demonstrates the effectiveness of multi-gene panel anal- ysis in uncovering molecular diagnoses in patients with monogenic forms of diabetes. Published by Elsevier Inc. 1. Introduction Monogenic diabetes mellitus includes a heterogeneous group of diabetes types that are caused by mutations in one of an expanding list of genes [1]. It can be familial or sporadic and if familial, the inheri- tance can be dominant, recessive or X-linked. It is estimated that the monogenic forms of diabetes together could represent as much as 1–2% of all cases of diabetes mellitus [2]. The main phenotypes sugges- tive of an underlying monogenic cause include transient or permanent neonatal diabetes mellitus (TNDM or PNDM), maturity-onset diabetes of the young (MODY) and rare diabetes-associated syndromes. More than twenty genes highly expressed in the pancreatic beta-cell have been identified in these monogenic subtypes, and many other genes have been implicated in syndromes that often include diabetes. Several etiological mechanisms of dysfunction are involved including impair- ment of pancreatic beta-cell development and/or gene expression, fail- ure of glucose sensing, disruption of insulin synthesis, disorders of ion channels and increased endoplasmic reticulum stress leading to de- struction of the beta-cell [3–5]. Molecular Genetics and Metabolism xxx (2014) xxx–xxx Abbreviations: NGS, Next-Generation Sequencing; TNDM, Transient Neonatal Diabetes; PNDM, Permanent Neonatal Diabetes; MODY, Maturity-Onset Diabetes of the Young; NDM, Neonatal Diabetes; GATK, Genome Analysis Tool Kit; ESP, Exome Sequencing Project, GERP, Genomic Evolutionary Rate Profiling; PolyPhen-2, Polymorphism Phenotyping v2; SIFT, Sorting Intolerant from Tolerant; HGMD, Human Gene Mutation Database; VOUS, Variant of Unknown Clinical Significance; WES, Whole Exome Sequencing; WGS, Whole Genome Sequencing. ⁎ Corresponding author at: University of Chicago, 5841 S. Maryland Ave. MC.0077, Chicago, IL 60637, USA. Fax: +1 773 834 0556. E-mail address: ddelgaudio@bsd.uchicago.edu (D. del Gaudio). 1 These authors contributed equally to this work. YMGME-05809; No. of pages: 6; 4C: http://dx.doi.org/10.1016/j.ymgme.2014.09.007 1096-7192/Published by Elsevier Inc. Contents lists available at ScienceDirect Molecular Genetics and Metabolism journal homepage: www.elsevier.com/locate/ymgme Please cite this article as: G. Alkorta-Aranburu, et al., Phenotypic heterogeneity in monogenic diabetes: The clinical and diagnostic utility of a gene panel-based next-generation sequencing approach, Mol. Genet. Metab. (2014), http://dx.doi.org/10.1016/j.ymgme.2014.09.007