Compound heterozygous mutations in RIPPLY2 associated with vertebral segmentation defects

Hum Mol Genet. 2015 Mar 1;24(5):1234-42. doi: 10.1093/hmg/ddu534.

Aideen M McInerney-Leo ¹, Duncan B Sparrow ², Jessica E Harris ¹, Brooke B Gardiner ¹, Mhairi S Marshall ¹, Victoria C O'Reilly ³, Hongjun Shi ³, Matthew A Brown ¹, Paul J Leo ¹, Andreas Zankl ⁴, Sally L Dunwoodie ⁵, Emma L Duncan ⁶

Affiliations

1 The University of Queensland Diamantina Institute, Translational Research Institute, Princess Alexandra Hospital, Woolloongabba QLD 4102, Australia.
2 Developmental and Stem Cell Biology Division, Victor Chang Cardiac Research Institute, Sydney, Australia, St Vincent's Clinical School, Faculty of Medicine.
3 Developmental and Stem Cell Biology Division, Victor Chang Cardiac Research Institute, Sydney, Australia.
4 Discipline of Genetic Medicine, The University of Sydney, Sydney, Australia, Academic Department of Medical Genetics, Sydney Children's Hospital Network (Westmead), Sydney, Australia.
5 Developmental and Stem Cell Biology Division, Victor Chang Cardiac Research Institute, Sydney, Australia, St Vincent's Clinical School, Faculty of Medicine, School of Biotechnology and Biomolecular Sciences, Faculty of Science, University of New South Wales, Sydney, Australia.
6 The University of Queensland Diamantina Institute, Translational Research Institute, Princess Alexandra Hospital, Woolloongabba QLD 4102, Australia, Department of Endocrinology, James Mayne Building, Royal Brisbane and Women's Hospital, Butterfield Road, Herston, QLD 4029, Australia The University of Queensland, University of Queensland Centre for Clinical Research, Herston, QLD 4029, Australia e.duncan@uq.edu.au.

PMID: 25343988 DOI: 10.1093/hmg/ddu534

Abstract

Segmentation defects of the vertebrae (SDV) are caused by aberrant somite formation during embryogenesis and result in irregular formation of the vertebrae and ribs. The Notch signal transduction pathway plays a critical role in somite formation and patterning in model vertebrates. In humans, mutations in several genes involved in the Notch pathway are associated with SDV, with both autosomal recessive (MESP2, DLL3, LFNG, HES7) and autosomal dominant (TBX6) inheritance. However, many individuals with SDV do not carry mutations in these genes. Using whole-exome capture and massive parallel Sequencing, we identified compound heterozygous mutations in RIPPLY2 in two brothers with multiple regional SDV, with appropriate familial segregation. One novel mutation (c.A238T:p.Arg80*) introduces a premature stop codon. In transiently transfected C2C12 mouse myoblasts, the RIPPLY2 mutant protein demonstrated impaired transcriptional repression activity compared with wild-type RIPPLY2 despite similar levels of expression. The other mutation (c.240-4T>G), with minor allele frequency <0.002, lies in the highly conserved splice site consensus sequence 5' to the terminal exon. Ripply2 has a well-established role in somitogenesis and vertebral column formation, interacting at both gene and protein levels with SDV-associated Mesp2 and Tbx6. We conclude that compound heterozygous mutations in RIPPLY2 are associated with SDV, a new gene for this condition.

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