[The relationship between HCY-2 gene and congenital heart teratogenesis in early chick embryos].

OBJECTIVE

To explore the relationship between novel gene (HCY-2), homocysteine and congenital heart defects, and to study their biological mechanisms.

METHODS

The teratogenic test of chick embryos which were treated with D.L-homocysteine (0.16 micromol/embryo) was used to observe the developmental toxicity of homocysteine per se. The eukaryotic expressing vector containing whole-length HCY-2 cDNA (2 014 bp) was microinjected into fertile eggs with lipofect AMINE(TM) reagent; then the effects of HCY-2 gene on cardiovascular damages of embryos, the expression and distribution of HCY-2 gene coding product were investigated with the techniques of Western blot, immunohistochemistry, light and electron microscopy.

RESULTS

Apparently teratogenic action of homocysteine on developing heart was observed in the critical stage of organogenesis and the damages were concentration dependent (P < 0.05). 10 approximately 20 microgram HCY-2 gene could cause dysmorphogenesis of the cardiovascular system. The congenital heart defect rates were 16.7% and 24.0% respectively. The abnormal forms were ectopic cardis extrathoracic heart and hypoplastic heart. Western blot and immunohistochemical staining showed that HCY-2 protein was largely expressed in the abnormal embryos, with stronger staining at the sites of embryonic heart and brain as compared with controls. Under light and electron microscope, it was seen that HCY-2 gene resulted in structure disturbance, endocardial cushion defect and hypoplasia of heart.

CONCLUSION

Homocysteine/HCY-2 gene may be a new heart-developing cytotoxic/genotoxic factor, and HCY-2 gene may play a very important role in the mechanisms of congenital heart defects of chick, and probably humans as well.