5-Azacytidine- and Hoechst-induced aneuploidy in Indian muntjac.

Hoechst 33258 (bis-benzimidazole) and 5-azacytidine (5-AC) cause decondensation of the pericentric heterochromatin in mouse and aberrations in the sequence of centromere separation apparently by different mechanisms. We treated the male Indian muntjac cells (2n=7), which do not undergo decondensation of the pericentric heterochromatin, to study if these chemicals would result in induction of aneuploidy limited to the Y(2) chromosome. This paper reports that both agents result in aneuploidy primarily limited to one chromosome, the Y(2). It is likely that other chromosomes are not tolerated in aneuploid condition because every chromosome carries some household genes including those essential for mitotic progression. The loss/gain of the Y(2) chromosome is tolerated because it is the smallest chromosome and is almost entirely composed of constitutive heterochromatin. Since Indian muntjac has only three pairs of large chromosomes comprising its basic genome, which can be clearly viewed under high dry objective, these cells are very suitable for the preliminary analysis of aneuploidy-inducing ability of various chemicals.