The mSin3A Chromatin-Modifying Complex Is Essential for Embryogenesis and T-Cell Development

Abstract

The corepressor mSin3A is the core component of a chromatin-modifying complex that is recruited by multiple gene-specific transcriptional repressors. In order to understand the role of mSin3A during development, we generated constitutive germ line as well as conditional msin3A deletions. msin3A deletion in the developing mouse embryo results in lethality at the postimplantation stage, demonstrating that it is an essential gene. Blastocysts derived from preimplantation msin3A null embryos and mouse embryo fibroblasts (MEFs) lacking msin3A display a significant reduction in cell division. msin3A null MEFs also show mislocalization of the heterochromatin protein, HP1α, without alterations in global histone acetylation. Heterozygous msin3A^+/− mice with a systemic twofold decrease in mSin3A protein develop splenomegaly as well as kidney disease indicative of a disruption of lymphocyte homeostasis. Conditional deletion of msin3A from developing T cells results in reduced thymic cellularity and a fivefold decrease in the number of cytotoxic (CD8) T cells, while helper (CD4) T cells are unaffected. We show that CD8 development is dependent on mSin3A at a step downstream of T-cell receptor signaling and that loss of mSin3A specifically decreases survival of double-positive and CD8 T cells. Thus, msin3A is a pleiotropic gene which, in addition to its role in cell cycle progression, is required for the development and homeostasis of cells in the lymphoid lineage.

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://mcb.asm.org/.

ACKNOWLEDGMENTS

We thank Philippe Soriano for advice and encouragement throughout the course of this work, Elizabeth Wayner for technical expertise in the generation of P1E7 monoclonal antibody, and Piper Treuting for assistance with photos of H&E-stained slides, Mark Tsang for analysis of apoptotic thymocytes, and the FHCRC Histology Core for the processing, embedding, and H&E staining of tissue samples. We also thank Ron DePinho for communicating results prior to publication. We are very grateful for the kind gifts of antibodies from Don Ayer (anti-mSDS3; Huntsman Institute, Salt Lake City, UT) and Yoram Groner (anti-Runx3; Weizmann Institute, Rehovot, Israel).

This work was supported by postdoctoral fellowships from the Rett Syndrome Research Foundation (to S.M.C.) and the American Cancer Society (to S.M.M.) and by grants to R.N.E. (NIH/NCI RO1CA57138), B.I. (R01AI0535468 from the NIAID and University of Washington Royalty Research Fund), and to H.D.L. (5RO1HD18184 and 5RO1JL65898). R.N.E. is an American Cancer Society Research Professor.