Developmentally regulated linker histone H1c promotes heterochromatin condensation and mediates structural integrity of rod photoreceptors in mouse retina

J Biol Chem. 2013 Jun 14;288(24):17895-907. doi: 10.1074/jbc.M113.452144. Epub 2013 May 3.

Abstract

Mature rod photoreceptor cells contain very small nuclei with tightly condensed heterochromatin. We observed that during mouse rod maturation, the nucleosomal repeat length increases from 190 bp at postnatal day 1 to 206 bp in the adult retina. At the same time, the total level of linker histone H1 increased reaching the ratio of 1.3 molecules of total H1 per nucleosome, mostly via a dramatic increase in H1c. Genetic elimination of the histone H1c gene is functionally compensated by other histone variants. However, retinas in H1c/H1e/H1(0) triple knock-outs have photoreceptors with bigger nuclei, decreased heterochromatin area, and notable morphological changes suggesting that the process of chromatin condensation and rod cell structural integrity are partly impaired. In triple knock-outs, nuclear chromatin exposed several epigenetic histone modification marks masked in the wild type chromatin. Dramatic changes in exposure of a repressive chromatin mark, H3K9me2, indicate that during development linker histone plays a role in establishing the facultative heterochromatin territory and architecture in the nucleus. During retina development, the H1c gene and its promoter acquired epigenetic patterns typical of rod-specific genes. Our data suggest that histone H1c gene expression is developmentally up-regulated to promote facultative heterochromatin in mature rod photoreceptors.

Keywords: Development; Heterochromatin; Histone H1c; Histones; Photoreceptors; Retina; Retina Development; Rod Photoreceptor.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Cell Nucleus / metabolism
  • Chromatin Assembly and Disassembly*
  • Epigenesis, Genetic
  • Female
  • Gene Expression Regulation, Developmental*
  • Gene Knockout Techniques
  • Heterochromatin / metabolism*
  • Histones / genetics*
  • Histones / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Nucleosomes / metabolism
  • Repetitive Sequences, Nucleic Acid / genetics
  • Retina / cytology
  • Retina / growth & development
  • Retinal Rod Photoreceptor Cells / metabolism*
  • Transcription, Genetic

Substances

  • H1c protein, mouse
  • Heterochromatin
  • Histones
  • Nucleosomes