Abstract
ObjectiveUnderstanding 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.ResultsIn 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.
Highlights
The ocular lens consists of a single layer of lens epithelial cells on its anterior surface that overlay the lens fiber cells
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
Summary
We reported the effects of these mutations on lens opacification and observed prominent opacities in the lens nucleus, and morphology changes in lens epithelial and fiber cells [10, 23, 24]. In cryaa-R49C-homo lens histone extracts, histone H2 was the most abundant followed by histone H4 (Fig. 2). In the cryab-R120G-het lens histone extracts, histone H4 was the most abundant followed by histone H3 and H2 (Fig. 2 and Additional files 2: Table S2, 4: Figure S2). Histone H3 was the most abundant in the cryab-R120G-homo lenses, followed by H4 and H2 (Additional file 5: Figure S3). Histones extracted from lenses obtained from 3- to 4-month-old WT and cryaa-R49C-het mice were analyzed (Additional file 6: Figure S4). Compared with WT or cryaaR49C-het mice, the nuclei in cryaa-R49C-homo lens epithelial cells had markedly increased heterochromatin in a thin ring at the nuclear periphery and one or two condensations in the inner nucleus.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
