Hypomethylation of alphoid DNA and classical satellite DNA on chromosome 1, 9, 16 and Y in extraembryonic tissue

The pattern of DNA methylation can be analyzed on methaphase chromosomes wi th fluorescein labeled antibodies against 5-methylcytosine. In human extrae mbryonic tissue lower overall intensity of immunofluorescence in centromeri c chromosomal regions correspond to hypomethylation of the DNA when compare d with normal human lymphocytes. Pericentromeric regions an chromosomes 1,9 ,16 and heterochromatin on chromosome Y, which reveal lower levels of immun ofluorescence, are rich in classical satellite DNA type II and III. In our experiment methylation-sensitive restriction enzymes, alphoid and classical satellite DNA probes specific for chromosomes 1,9,16 and Y were used. Sout hern blot analysis on cells ham extraembryonic tissue revealed different ex tent of hypomethylation in different chromosomal regions. Our results confi rm overall and sequence-specific hypomethylation of DNA in cells from extra embryonic tissue in comparison with somatic cells.