Changes in relative histone abundance and heterochromatin in αA-crystallin and αB-crystallin knock-in mutant mouse lenses

Abstract

Objective Understanding the mechanisms of cataract formation is important for age-related and hereditary cataracts caused by mutations in lens protein genes. Lens proteins of the crystallin gene families α-, β-, and γ-crystallin are the most abundant proteins in the lens. Single point mutations in crystallin genes cause autosomal dominant cataracts in multigenerational families. Our previous proteomic and RNAseq studies identified genes and proteins altered in the early stages of cataract formation in mouse models. Histones H2A, H2B, and H4 increase in abundance in αA- and αB-crystallin mutant mouse lenses and in cultured cells expressing the mutant form of αA-crystallin linked with hereditary cataracts. Results In this study of histones in mutant lenses, we extracted histones from adult mouse lenses from cryaa-R49C and cryab-R120G mutant knock-in mice. We characterized the histones using matrix-assisted laser desorption/ionization time of flight (MALDI-TOF)-mass spectrometric analysis and gel electrophoresis and characterized the lens nucleus morphology using electron microscopy (EM). The relative abundance of histone H3 protein decreased in lenses from cryaa-R49C mutant mice and the relative abundance of histone H2 increased in these lenses. Electron microscopy of nuclei from cryaa-R49C-homozygous mutant mouse lenses revealed a pronounced alteration in the distribution of heterochromatin.

Single-Cell RNA Sequencing Analysis of the Early Postnatal Mouse Lens Epithelium

“… 61 In crystallin-deficient lenses, the relative ratios of histones H2A/H2B and H3/H4 are altered, suggesting a synergistic relationship between crystallins and histones. 62 However, the relative abundance and roles of these histones in LEC subpopulations have yet to be established. Cluster 3 also displayed expression of Pclaf , which plays an essential role in cell proliferation but has not yet been described in the lens.…”