Eya1 and Eya2 gene expression is down-regulated during somitic myogenesis in the cadmium-induced omphalocele chick model

PurposeThe molecular mechanisms underlying omphalocele are still largely unknown. Recently, established cadmium (Cd)-induced omphalocele chick model has been used to investigate the pathogenesis of omphalocele. The earliest histologic changes in this model has been observed in somites 4 hours posttreatment, leading us to hypothesize that disruption of migration of somite-derived cells ventrally may cause omphalocele phenotype. Eyes absent (Eya) genes are expressed in the somite (dermomyotome) and play a key role in somitic myogenesis. We designed this study to investigate the hypothesis that Eya1 and Eya2 gene expression is down-regulated during the critical period of early embryogenesis in the Cd-induced omphalocele chick model.MethodsAfter 60 hours of incubation, chicks were exposed to either chick saline or Cd and divided into control and Cd (n = 24 for each group). Chicks were then harvested 1 hour, 4 hours, and 8 hours posttreatment. Real-time quantitative polymerase chain reaction was performed to evaluate gene expression levels of Eya1 and Eya2 in the chick embryo, and they were statistically analyzed. Immunofluorescence confocal microscopy was also performed to evaluate protein expression and distribution pattern of Eya1 and Eya2.ResultsAt 4 hours posttreatment, the relative messenger RNA expression levels of Eya1 and Eya2 were significantly down-regulated in the Cd group compared with controls (P < .05). The intensity of Eya1 and Eya2 immunofluorescence was also markedly diminished at 4 hours in the Cd-treated embryos, whereas in control embryos, strong intensity of immunofluorescence of them was expressed in the dermomyotomal cells.ConclusionDown-regulation of Eya genes during the critical period of early embryogenesis may contribute to omphalocele phenotype in the Cd chick model, interfering with migration of embryonic body wall ventrally.