Human Molecular Genetics Advance Access originally published online on December 8, 2008
Human Molecular Genetics 2009 18(5):861-871; doi:10.1093/hmg/ddn411
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Identification and functional characterization of NODAL rare variants in heterotaxy and isolated cardiovascular malformations
1 Department of Pediatrics (Cardiology) 2 Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA 3 Children's & Women's Health Centre, Vancouver, BC, Canada V6H 3V4 4 Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA
* To whom correspondence should be addressed at: Cincinnati Children's Hospital Medical Center, 240 Albert Sabin Way, MLC 7020, Cincinnati, OH 45229, USA. Tel: +1 5136369427; Fax: +1 5136365958; Email: stephanie.ware{at}cchmc.org
Received November 11, 2008; Revised November 11, 2008; Accepted December 3, 2008
NODAL and its signaling pathway are known to play a key role in specification and patterning of vertebrate embryos. Mutations in several genes encoding components of the NODAL signaling pathway have previously been implicated in the pathogenesis of human left–right (LR) patterning defects. Therefore, NODAL, a member of TGF-β superfamily of developmental regulators, is a strong candidate to be functionally involved in congenital LR axis patterning defects or heterotaxy. Here we have investigated whether variants in NODAL are present in patients with heterotaxy and/or isolated cardiovascular malformations (CVM) thought to be caused by abnormal heart tube looping. Analysis of a large cohort of cases (n = 269) affected with either classic heterotaxy or looping CVM revealed four different missense variants, one in-frame insertion/deletion and two conserved splice site variants in 14 unrelated subjects (14/269, 5.2%). Although similar with regard to other associated defects, individuals with the NODAL mutations had a significantly higher occurrence of pulmonary valve atresia (P = 0.001) compared with cases without a detectable NODAL mutation. Functional analyses demonstrate that the missense variant forms of NODAL exhibit significant impairment of signaling as measured by decreased Cripto (TDGF-1) co-receptor-mediated activation of artificial reporters. Expression of these NODAL proteins also led to reduced induction of Smad2 phosphorylation and impaired Smad2 nuclear import. Taken together, these results support a role for mutations and rare deleterious variants in NODAL as a cause for sporadic human LR patterning defects.