S. Hoyer-fender et al., The murine heterochromatin protein M31 is associated with the chromocenterin round spermatids and is a component of mature spermatozoa, EXP CELL RE, 254(1), 2000, pp. 72-79
In mature sperm the normal nucleosomal packaging of DNA found in somatic an
d meiotic cells is transformed into a highly condensed form of chromatin wh
ich consists mostly of nucleoprotamines. Although sperm DNA is highly conde
nsed it is nevertheless packaged into a highly defined nuclear architecture
which may be organized by the heterochromatic chromocenter, One major comp
onent of heterochromatin is the heterochromatin protein 1 which is involved
in epigenetic gene silencing. In order to investigate the possible involve
ment of heterochromatin protein in higher order organization of sperm DNA w
e studied the localization of the muring homologue of heterochromatin prote
in 1, M31, during chromatin reorganization in male germ cell differentiatio
n. Each cell type in the testis showed a unique distribution pattern of M31
, Colocalization to the heterochromatic regions were found in Sertoli cells
, in midstage pachytene spermatocytes, and in round spermatids in which M31
localizes to the centromeric chromocenter. M31 cannot be detected in elong
ated spermatids or mature spermatozoa immunocytologically, but could be det
ected in mature spermatozoa by Western blotting, We suggest that M31, a nuc
lear protein involved in the organization of chromatin architecture, is inv
olved in higher order organization of sperm DNA (C) 2000 Academic Press.