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Pediatric Surgery International

, Volume 26, Issue 10, pp 1017–1023 | Cite as

HoxB2, HoxB4 and Alx4 genes are downregulated in the cadmium-induced omphalocele in the chick model

  • Takashi Doi
  • Prem Puri
  • John Bannigan
  • Jennifer Thompson
Original Article

Abstract

Purpose

In the chick embryo, administration of cadmium (Cd) induces omphalocele phenotype. HoxB2 and HoxB4, expressed in cell types that contribute to ventral body wall (VBW) formation, act together to mediate proper closure of the VBW, involving a key downstream transcription factor, Alx4. HoxB2 and HoxB4 knockout mice display VBW defects with specific downregulation of Alx4 gene expression, while homozygous Alx4 knockouts show omphalocele phenotype. Although the earliest histological changes in the Cd chick model occur commencing at 4H post treatment, the exact timing and molecular mechanism by which Cd acts is still unclear. We hypothesized that HoxB2, HoxB4 and Alx4 genes are downregulated during the critical timing of very early embryogenesis in the Cd-induced omphalocele chick model.

Methods

After 60H incubation, chick embryos were harvested at 1H, 4H and 8H after treatment with saline or Cd and divided into controls and Cd group (n = 24 for each group). RT–PCR was performed to investigate the gene expression of HoxB2, HoxB4 and Alx4 and statistically analyzed (significance was accepted at p < 0.05). Immunohistochemical staining was also performed to evaluate the protein expression/distribution of HoxB2, HoxB4 and Alx4 in the chick embryo.

Results

The expression levels of HoxB2, HoxB4 and Alx4 gene at 4H were significantly downregulated in the Cd group as compared to controls, whereas there were no significant differences at the other time points. Immunoreactivity of HoxB2, HoxB4 and Alx4 at 4H is also markedly decreased in the ectoderm and the dermomyotome in the Cd chick model as compared to controls.

Conclusion

Downregulation of HoxB2, HoxB4 and Alx4 expression during the narrow window of early embryogenesis may cause omphalocele in the Cd chick model by interfering with molecular signaling required for proper VBW formation. Furthermore, these results support the concept that HoxB2, HoxB4 and Alx4 genes work together to mediate proper VBW formation.

Keywords

Cadmium Omphalocele HoxB2 HoxB4 Alx4 

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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Takashi Doi
    • 1
    • 2
  • Prem Puri
    • 1
    • 2
  • John Bannigan
    • 2
  • Jennifer Thompson
    • 2
  1. 1.The Children’s Research CentreOur Lady’s Children’s HospitalDublin 12Ireland
  2. 2.School of Medicine and Medical Science, Conway Institute of Biomolecular and Biomedical ResearchUniversity College DublinDublinIreland

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