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Changes of glycoprotein patterns in rat placenta during early pregnancy caused by the demethylating agent 5-azacytidine

DNA methylation is an important mechanism for regulation of gene expression during development. It can be changed by 5-azacytidine (5-azaC), a demethylating agent capable of incorporation into DNA instead of cytosine. During placentation the expression of different glycoproteins is crucial for normal development of placenta. DNA demethylation caused by 5-azaC might influence the normal expression of glycoproteins during placentation. The single dose of 5-azacytidine (5 mg/kg body weight) was administered to pregnant rats on day 8 of pregnancy. The animals were sacrificed on day 20 of pregnancy and placentas were measured and histologicaly analyzed. Glycoproteins were detected by Western-blot method using lectins: SNA, DBA, PHA-E and UEA-I. In treated animals significantly smaller placentas were found. Histological analysis demonstrated reduced labyrinthine layer in treated placentas, compared to controls. Comparison of glycosylation patterns of placental proteins between treated and control placentas have shown significant differences. Differences in glycosylation between cytosol and membrane proteins was found. Lectin UEA-I detected the cytosol glycoprotein GP 70, which was absent from control samples. PHA-E identified cytosol GP 70 only in the experimental sample. Comparing the samples of membrane proteins we found two glycoproteins GP 50 and GP 35 only in treated samples. These results support our hypothesis that proper methylation pattern of olygosaccharide genes is crucial for their regular expression and normal development of rat placenta. The demethylating agent 5-azacytidine disturbs this normal pattern, allowing in treated samples some new glycoproteins to appear in cytosol and membrane protein extracts.

DNA methylation; 5-azacytidine; glycoproteins; rat placenta

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