Altered PITX2 and LEF1 gene expression in the cadmium-induced omphalocele in the chick model.
OBJECTIVE
Although, recent studies have suggested that disruption of somitogenesis may be involved in ventral body wall (VBW) defects; the molecular mechanisms of VBW defects remain unclear. In the chick embryo, the administration of cadmium (Cd) induces VBW defects similar to the human omphalocele. In this model, the earliest histological change in the somite occurs commencing at 4 h post-Cd treatment (4 h). PITX2 is expressed in somites, and PITX2 mutants have been shown to display VBW defects. PITX2 interacts with lymphoid enhancer factor-1 (LEF1) to regulate somite myogenesis. We designed this study to investigate the hypothesis that PITX2 and LEF1 genes are downregulated during the critical period of early embryogenesis in the Cd-induced omphalocele chick model.


METHODS
Chick embryos were exposed to Cd or saline after 60 h incubation and harvested at 1, 4, and 8 h posttreatment. Chicks were then divided into two groups: control (n = 24), and Cd (n = 24). RT-PCR was performed and analyzed statistically (significant difference was accepted at p < 0.05). Immunohistochemistry was also performed to evaluate expression/distribution of those proteins.


RESULTS
The mRNA expression levels of PITX2 and LEF1 at 4 h were significantly decreased in the Cd group compared with controls, whereas there were no differences at the other time points. Immunoreactivity of those proteins at 4 h was also markedly decreased in somites in the Cd-treated embryos compared with controls.


CONCLUSIONS
Downregulation of PITX2 and LEF1 genes may interfere with ventral body wall formation in Cd chick model causing omphalocele by disrupting somite myogenesis.
National Children's Research Centre, Our Lady's Children's Hospital, Dublin 12, Ireland.
Takashi
T
Doi
Prem
P
Puri
John
J
Bannigan
Jennifer
J
Thompson
D000818:Animals; D002104:Cadmium / Q000633:toxicity; D002642:Chick Embryo; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D006554:Hernia, Umbilical / Q000139:chemically induced / Q000196:embryology / Q000235:genetics* / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D007150:Immunohistochemistry; D051821:Lymphoid Enhancer-Binding Factor 1 / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D000097577:Homeobox Protein PITX2
D002104:Cadmium; D018398:Homeodomain Proteins; D051821:Lymphoid Enhancer-Binding Factor 1; D012333:RNA, Messenger; D012097:Repressor Proteins; D014157:Transcription Factors; D000097577:Homeobox Protein PITX2; C497573:LEF1 protein, human
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