Abstract
Abstract
Introduction: Rapid-onset obesity, hypoventilation, hypothalamic dysfunction and autonomic dysregulation (ROHHAD) is a rare syndrome beginning at 3-6 years of age with approximately 150 cases described. Additional features include eye abnormalities, neurobehavioral dysfunction and paraneoplastic tumors. The etiology of the complex phenotype remains unknown.
Methods: This study aims to investigate the genetic landscape of this complex phenotype by whole exome sequencing (WES) and copy number variation (CNV) analysis. We recruited 33 families (27 trios, 1 duo and 5 singletons) with a proband with ROHHAD syndrome (Ize-Ludlow 2007, Pediatrics). WES of 89 individuals was performed at the Center for Mendelian Genomics, Broad Institute. The Illumina platform with a mean coverage of ~100X (> 90% targets 20x) and Infinium Global Screening Array BeadChip 24v1.0 were used.
Results: This report includes 28 probands (female = 18, 64%) with rapid onset obesity (100%), hypoventilation (88%), hypothalamic dysfunction (69%), eye disorders (62%) and neurobehavioral abnormalities (76%). Neuroendocrine tumor, ganglioneuroblastoma, was present in 38% (n=13). No unifying causative single gene or CNV was identified, but a number of sequence variants are prioritized.
ARNT2, which encodes for a helix-loop-helix transcription factor, plays a role in the development of the hypothalamic-pituitary axis, postnatal brain growth, and visual and renal function. The de novo monoallelic missense variant was found in a 14-year old white girl (BMIz +3.25) with extreme obesity and a neurobehavioral phenotype.
OCRL1, a multi-domain protein involved in cytoskeleton-plasma membrane adhesion, endosomal trafficking and in primary cilium assembly. Mutations in this gene have also been known to cause Lowe syndrome. A hemizygous X-linked frameshift variant in a 5-year old white boy with extreme obesity (BMIz +5.48), central hypoventilation neurobehavioral dysfunction and ganglioneuroblastoma.
A monoallelic missense variant in NSD1, a transcriptional intermediary factor acting as a histone methyltransferase, was identified in a 8-year old Hispanic girl with severe obesity (BMIz +2.91), neurobehavioral disorder, pituitary and eye dysfunction and ganglioneuroblastoma. NSD1 is known to cause Sotos and Beckwith-Wiedemann.
Compound heterozygous variants in KIF7, a key component of the Hedgehog signaling pathway, were identified in a 14-year old white girl with severe obesity (BMIz +3.00), autistic behavior, pituitary dysfunction and central hypoventilation. This gene is known to cause autosomal recessive hydrolethalis and acroscallosal syndromes with mutations also noted in Bardet-Biedl, Meckel and Joubert syndromes.
Conclusion: While no unifying genetic cause has been identified in ROHHAD syndrome, it is possible that the phenotype represents a collection of complex genetic syndromes.