Unexpected segregation of chromosome and common fragile site expression induced by 5-Azacytidine exposure in human lymphocytes of Down's syndrome patients

Abstract

Preferential breakge of chromosomes at specific sites are known as chromosomal fragile sites are distributed all over the mammalian genome. The 5-Azacytidine (5-AZC) induced expression of "common fragile sites" and other chromosomal changes were evaluated in prometaphase/ metaphase chromosomes obtained from peripheral blood lymphocytes from clinically diagnosed Down's syndrome patients. The present study possibly for the first time reveals significantly (p<0.001) high incidence of common fragile sites expression (12%), centromere breakage (6%) and more then 3% of premature condensation (PMC) of chromosomes in cell poplution when compared with controls, suggesting that high incidencec of common fragile sites expression due to demethylation action of DNA by 5 - AZC could reveal differential gene activity in mentally retarted patients.