Alterations of DNA methylation patterns in germ cells and Sertoli cells from developing mouse testis

Abstract

In situ alterations of DNA methylation were studied between 14 d postcoitum and 4 d postpartum in Sertoli cells and germ cells from mouse testis, using anti-5-methylcytosine antibodies. Compared to cultured fibroblasts, Sertoli cells display strongly methylated juxtacentromeric heterochromatin, but hypomethylated chromatids. Germ cells always possess hypomethylated heterochromatin, whereas their euchromatin passes from a demethylated to a strongly methylated status between days 16 and 17 postcoitum. This hypermethylation occurs in the absence of DNA replication, germ cells being blocked in the G₀-G₁ phase from day 15 postcoitum to birth. The DNA hypermethylation of germ cells is maintained until birth and could be visualized on both chromatids of metaphase chromosomes at the first postpartum cell division. Subsequently, the DNA hypermethylation is lost semiconservatively, being replaced by a methylation pattern recalling the typical fibroblast pattern. These alterations of DNA methylation follow a strict chronology, are chromosome structure and cell-type dependent, and may underlie profound changes of genome function.

The paternal methylation imprint of the mouse H19 locus is acquired in the gonocyte stage during foetal testis development

“…In the male germline, the partial paternal methylation is overlaid with full methylation during foetal, and also postnatal (Davis et al 1999) development. This de novo methylation mainly occurs in mitotically arrested gonocytes, coincident with the methylation of euchromatic regions of mouse chromosomes (Cof®gny et al 1999) and of intracisternal A particle retroviruses dispersed in the mouse genome (Walsh et al 1998). As to the exact timings of the complete demethylation in the female germline and the initiation of methylation in the male germline, the results obtained with the¯ow-sorted cells were slightly different from those obtained with the cells isolated by conventional procedures.…”

Gamete imprinting: setting epigenetic patterns for the next generation

“…In the male germ line, increases in DNA methylation, as measured by staining with an antibody to methylated cytosine, are first seen by immunocytochemistry in gonocytes between 15.5 and 18.5 days of gestation (Coffigny et al 1999). Methylation analysis of individual genes yields similar results.…”

Conservation of methylation reprogramming in mammalian development: Aberrant reprogramming in cloned embryos

“…Genome-wide demethylation can be examined comprehensively with the use of immunostaining with a 5-methyl cytosine antibody (10,13,24). Here we used immunostaining of interphase nuclei in mammalian preimplantation embryos.…”