Program Nr: 553 for the 2006 ASHG Annual Meeting

Candidate genes for congenital diaphragmatic hernia from animal models: Mutation screening of FOG2, SIX1 and PDGFRA in 96 patients reveals rare variants. S.B. Bleyl1, A. Moshrefi2, G. Shaw3, Y. Saijoh1, G.C. Schoenwolf1, L. Pennacchio4, A.M. Slavotinek2. 1) Dept Pediatrics, Dept Neurbiol Anat Univ Utah, Salt Lake City, UT; 2) Dept Pediatrics, UCSF, San Francisco, CA; 3) California Birth Defects Monitoring Program, Berkely, CA; 4) Genomics Division, Lawrence Berkley National Laboratory, Berkley, CA.
   Congenital diaphragmatic hernia (CDH) is a life threatening birth defect that can be isolated or occur with other anomalies. Although isolated CDH is usually sporadic, recent reports have implicated chromosome deletions at 15q26, 8p23.1, 4p16.3-4pter, and 1q41-1q42.1 in CDH patients, but no causative genes have been identified from these studies. We selected three candidate genes involved in diaphragm formation from animal models - FOG2, SIX1 and PDGFRA - and hypothesized that mutations in these genes could cause CDH in humans. Mice homozygous for a hypomorphic fog2 allele have diaphragmatic eventration, a defect related to CDH. Homozygous null mice for Six1 have selective loss of muscles including the diaphragm and limbs. Null and conditionally inactivated alleles of Pdgfra in mice result in diaphragmatic defects and other anomalies resembling Fryns syndrome. We therefore sequenced FOG2, SIX1 and PDGFRA in 96 patients with CDH of which 53 (55.2%) had isolated CDH, 36 (37.5%) had CDH and additional anomalies and 7 (7.3%) had CDH and known chromosome aberrations. For FOG2, we identified novel sequence alterations predicting p.M703L and p.T843A that were absent in more than 100 control chromosomes in two patients with isolated CDH. These altered amino acids are highly conserved, but we were not able to determine if they were de novo. For PDGFRA, we found an alteration predicting p.L221F in two patients, one with isolated CDH and the other with CDH and preauricular tags. SIX1 sequencing did not reveal any novel alterations. In conclusion, our data found no evidence that CDH commonly results from mutations in these three candidate genes. We did identify rare variants of unknown significance in both FOG2 and PDGFRA that could play a role in the pathogenesis of isolated CDH and further evaluation of these variants is proceeding.