Human Molecular Genetics Advance Access published online on December 8, 2008
Human Molecular Genetics, 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), Baylor College of Medicine, Houston, Texas 77030 2 Children's & Women's Health Centre, Vancouver BC V6H 3V4 3 Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030 4 Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, Ohio 45229
* Address correspondence to: Stephanie M. Ware, M.D., Ph.D. Cincinnati Children's Hospital Medical Center 240 Albert Sabin Way, MLC 7020 Cincinnati, OH 45229 Ph: 513-636-9427 FAX: 513-636-5958 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 roles 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 patterning defects. Therefore, NODAL, a member of TGF-β superfamily of developmental regulators, is a strong candidate to be functionally involved in congenital left right 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 to 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 left right patterning defects.