To ensure appropriate dosage compensation, female cells selectively inactivate one of their two X chromosomes in a process called X chromosome inactivation (XCI), a form of epigenetic regulation. In early female mouse embryos, somatic cells of the inner cell mass inactivate their paternal or maternal X chromosomes with equal probability. Thus, cells in somatic female tissues display a random XCI pattern. The mammary gland represents a prime object to investigate genetic pathways that control the specification, proliferation, differentiation, survival and death of cells. Cellular survival and cell death decisons are critically regulated by the ubiquitin proteasome system (UPS). In particular, RING finger ubiquitin ligases act as key components in cell death signaling cascades. The functions of these enzymes for cell survival/death often rely on their RING finger-dependent ubiquitin ligase activity as well as their cellular localizations. We have generated a conditional KO mouse model for the RING finger ubiquitin ligase RLIM which is encoded by the X-linked gene Rnf12. Our preliminary results indicate that knockout (KO) of Rnf12 in female mammary glands inhibits alveolar differentiation and milk production upon pregnancy. We find that alveolar cells lacking RLIM undergo apoptosis as they differentiate from mammary epithelia. Our results suggest further that these functions are mediated primarily by the paternal Rnf12 allele due to nonrandom XCI in mammary epithelial cells which primarily silence their maternal X chromosomes. We hypothesize 1) that RLIM is crucially involved in alveolar cell survival pathways and is key for triggering involution, and 2) sex-specific epigenetic regulation of mammary gland biology by the paternal X chromosome. The proposed project will test these hypotheses and identify underlying molecular mechanisms in three specific aims.
Aim 1 will establish RLIM as triggering weaning-induced alveolar cell death/involution and test the involvement of the UPS system.
Aim 2 will connect RLIMs survival functions with nucleo- cytoplasmic shuttling, while Aim 3 establishes and examines mechanisms to establish the non-random XCI pattern in mammary precursor cells. Combined our results will establish RLIM as a novel paradigm in regulating alveolar cell survival/death pathways. Moreover, the results of our research will show that mammary gland biology is decisively controlled by sex-specific epigenetic mechanisms with profound implications for development, differentiation, evolution and disease.

Public Health Relevance

Our preliminary results provide strong evidence that paternal Rnf12/RLIM is required for alveolar morphogenesis in the mouse mammary gland, serves as a critical regulator of alveolar cell survival/cell death decision and likely triggers involution. Th proposed project will establish these functions in vivo and expected results will unravel the underlying molecular, cellular and epigenetic mechanisms for the sex-specific Rnf12/RLIM functions in mammary glands.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
2R01CA131158-06
Application #
8439608
Study Section
Development - 2 Study Section (DEV2)
Program Officer
Mietz, Judy
Project Start
2007-12-01
Project End
2018-03-31
Budget Start
2013-04-01
Budget End
2014-03-31
Support Year
6
Fiscal Year
2013
Total Cost
$334,872
Indirect Cost
$133,597
Name
University of Massachusetts Medical School Worcester
Department
Genetics
Type
Schools of Medicine
DUNS #
603847393
City
Worcester
State
MA
Country
United States
Zip Code
01655
Shin, JongDae; Wallingford, Mary C; Gallant, Judith et al. (2014) RLIM is dispensable for X-chromosome inactivation in the mouse embryonic epiblast. Nature 511:86-9
Jiao, Baowei; Taniguchi-Ishigaki, Naoko; Gungor, Cenap et al. (2013) Functional activity of RLIM/Rnf12 is regulated by phosphorylation-dependent nucleocytoplasmic shuttling. Mol Biol Cell 24:3085-96
Jiao, Baowei; Ma, Hong; Shokhirev, Maxim N et al. (2012) Paternal RLIM/Rnf12 is a survival factor for milk-producing alveolar cells. Cell 149:630-41
Zhong, Zhen; Ma, Hong; Taniguchi-Ishigaki, Naoko et al. (2011) SSDP cofactors regulate neural patterning and differentiation of specific axonal projections. Dev Biol 349:213-24
Shin, Jongdae; Bossenz, Michael; Chung, Young et al. (2010) Maternal Rnf12/RLIM is required for imprinted X-chromosome inactivation in mice. Nature 467:977-81
Johnsen, Steven A; Gungor, Cenap; Prenzel, Tanja et al. (2009) Regulation of estrogen-dependent transcription by the LIM cofactors CLIM and RLIM in breast cancer. Cancer Res 69:128-36