Oocyte-Specific Linker Histone in Mammalian Species

Abstract

Abstract:The linker histones constitute the major proteins bound to linker DNA, the DNA bridging nucleosome core particles. The composition of the linker histone fraction is tissue-and species-specific, as well as developmentally-regulated. As such, linker histones play a critical role in the higher order packaging of chromatin and thus, inevitably, in an impressive array of regulatory functions. Recently, we uncovered a mammalian oocyte-specific linker histone H1oo homologous to the cs-H1 of sea urchin and to the B4 of the frog in the course of a differential screening project. H1oo protein localized to the intact germinal vesicle (GV) of preovulatory oocytes, to the condensed c hro mosome s o f ovul at ed oocyt es ar re ste d a t metaphase (M) II, and to the first polar body. The pronuclei were both positive at the 1-cell stage. Nuclear staining, however, was reduced in 2-cell embryos and was no longer detectable at the 4-cell stage of embryonic development. These findings indicate oocyte-specific linker histones may play some roles in genome-wide reprogramming in vertebrate eggs.

Chromatin Remodeling with Oocyte-specific Linker Histones

“…However, following the extrusion of a second polar body, H1foo was detected in the swollen sperm head. Nuclear staining was somewhat reduced in two-cell embryos and was no longer detectable in four-cell embryos [11,18]. The expression pattern of H1foo in preimplantation embryos is developmentally regulated, like Xenopus oocyte-specific linker histone B4.…”