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Histone modifications accompanying the onset of developmental commitment.
1Department of Chemistry, Paul M. Gross Chemical Laboratory, Duke University, Durham, North Carolina 27706.
Developmental Biology
|December 1, 1987
Summary
Early sea urchin embryos show distinct nuclear protein differences between cell types. Micromeres, the most committed cells, have altered histone H3, H2A, and H1 variants, suggesting roles in cell commitment and differentiation.
Area of Science:
- Developmental Biology
- Cell Biology
- Molecular Biology
Background:
- The 16-cell stage sea urchin embryo (Strongylocentrotus purpuratus) consists of three distinct cell types: micromeres, macromeres, and mesomeres.
- Understanding the molecular differences between these cell types is crucial for deciphering early developmental commitment and differentiation pathways.
Purpose of the Study:
- To analyze and compare the newly synthesized nuclear proteins, specifically histones, in the three distinct cell types at the 16-cell stage embryo.
- To investigate potential correlations between observed histone modifications and the degree of cell commitment.
Main Methods:
- Analysis of newly synthesized nuclear proteins in isolated micromeres, macromeres, and mesomeres from 16-cell stage sea urchin embryos.
- Electrophoretic separation and comparison of histone variants (H3, H2A, H1) across the different cell types.
Main Results:
- Micromeres exhibited a lack of triply modified and reduced levels of doubly modified histone H3, with an enrichment of unmodified, unacetylated histone H3.
- Differences in histone H2A variants were observed, with micromeres showing a higher alpha-stage to cleavage-stage (CS) H2A ratio and depletion of CS-H2A.
- Micromeres displayed distinct H1 histone profiles, including a faster-migrating cleavage-stage H1 and reduced levels of H1 alpha a compared to macromeres and mesomeres.
Conclusions:
- Newly synthesized chromatin proteins, particularly histones, differ significantly among sea urchin blastomere types by the 16-cell stage.
- Variations in histone subtypes and the activity of chromatin-modifying enzymes (e.g., acetylases, phosphorylases) may play a role in cell commitment and differentiation.