Rapid-Onset Obesity with Hypothalamic Dysfunction, Hypoventilation, and Autonomic Dysregulation (ROHHAD): Exome sequencing of trios, monozygotic twins and tumours

BACKGROUND: Rapid-onset Obesity with Hypothalamic Dysfunction, Hypoventilation, and Autonomic Dysregulation (ROHHAD) is thought to be a genetic disease caused by de novo mutations, though causative mutations have yet to be identified. We searched for de novo coding mutations among a carefully-diagnosed and clinically homogeneous cohort of 35 ROHHAD patients. METHODS: We sequenced the exomes of seven ROHHAD trios, plus tumours from four of these patients and the unaffected monozygotic (MZ) twin of one (discovery cohort), to identify constitutional and somatic de novo sequence variants. We further analyzed this exome data to search for candidate genes under autosomal dominant and recessive models, and to identify structural variations. Candidate genes were tested by exome or Sanger sequencing in a replication cohort of 28 ROHHAD singletons. RESULTS: The analysis of the trio-based exomes found 13 de novo variants. However, no two patients had de novo variants in the same gene, and additional patient exomes and mutation analysis in the replication cohort did not provide strong genetic evidence to implicate any of these sequence variants in ROHHAD. Somatic comparisons revealed no coding differences between any blood and tumour samples, or between the two discordant MZ twins. Neither autosomal dominant nor recessive analysis yielded candidate genes for ROHHAD, and we did not identify any potentially causative structural variations. CONCLUSIONS: Clinical exome sequencing is highly unlikely to be a useful diagnostic test in patients with true ROHHAD. As ROHHAD has a high risk for fatality if not properly managed, it remains imperative to expand the search for non-exomic genetic risk factors, as well as to investigate other possible mechanisms of disease. In so doing, we will be able to confirm objectively the ROHHAD diagnosis and to contribute to our understanding of obesity, respiratory control, hypothalamic function, and autonomic regulation. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13023-015-0314-x) contains supplementary material, which is available to authorized users

Evaluating Protocols for Embryonic Stem Cell Differentiation into Insulin-Secreting β-Cells Using Insulin II-GFP as a Specific and Noninvasive Reporter

Stable and full differentiation of pluripotent stem cells into functional β-cells offers the potential to treat type I diabetes with a theoretically inexhaustible source of replacement cells. In addition to the difficulties in directed differentiation, progress toward an optimized and reliable protocol has been hampered by the complication that cultured cells will concentrate insulin from the media, thus making it difficult to tell which, if any, cells are producing insulin. To address this, we utilized a novel murine embryonic stem cell (mESC) research model, in which the green fluorescent protein (GFP) has been inserted within the C-peptide of the mouse insulinII gene (InsulinII-GFP). Using this method, cells producing insulin are easily identified. We then compared four published protocols for differentiating mESCs into β-cells to evaluate their relative efficiency by assaying intrinsic insulin production. Cells differentiated using each protocol were easily distinguished based on culture conditions and morphology. This comparison is strengthened because all testing is performed within the same laboratory by the same researchers, thereby removing interlaboratory variability in culture, cells, or analysis. Differentiated cells were analyzed and sorted based on GFP fluorescence as compared to wild type cells. Each differentiation protocol increased GFP fluorescence but only modestly. None of these protocols yielded more than 3% of cells capable of insulin biosynthesis indicating the relative inefficiency of all analyzed protocols. Therefore, improved β-cells differentiation protocols are needed, and these insulin II GFP cells may prove to be an important tool to accelerate this process

Additional file 1: of Rapid-Onset Obesity with Hypothalamic Dysfunction, Hypoventilation, and Autonomic Dysregulation (ROHHAD): exome sequencing of trios, monozygotic twins and tumours

Low-coverage proportions of candidate genes in replication exomes. (XLSX 43 kb