Bone is a dynamic tissue which is remodeled throughout life as a result of the biological activities of osteoblasts and osteoclasts. The production and survival of these cells as well as their metabolic activities are all highly regulated by local and systemic factors that include growth modulators, cytokines and steroid and peptide hormones. 1,25-Dihydroxyvitamin D3 (1,25(OH)2D3) together with parathyroid hormone play an integral role in many of these processes. Indeed, 1,25(OH)2D3 is known to influence the cellular activity of mature osteoblasts and to modulate the proliferation and differentiation of early precursors. Despite a general description of vitamin D action on bone, the mechanisms that permit orchestration of these activities by 1,25(OH)2D3 at the genome-wide level remain unclear. Striking technological advances have emerged which now permit such evaluations. As a consequence, we propose three specific aims.
Specific Aim 1 : To identify the 1,25(OH)2D3-independent and -dependent vitamin D receptor (VDR) cistromes and their properties in osteoblast precursors and to assess the changes that occur to these cistromes during differentiation. Genome-wide chromatin immunoprecipitation (ChIP)-DNA microarray (chip) (ChIP-chip) and gene expression techniques together with a series of bioinformatic tools will be used to identify and contrast the VDR cistromes in osteoblast precursors and in fully differentiated osteoblasts. The genome-wide properties and nature of these cistromes will be assessed.
Specific Aim 2 : To explore the molecular mechanisms associated with the regulation by VDR of selected gene targets in both osteoblast precursors and differentiated osteoblasts. DNA fragment and BAC clone analyses, together with ChIP-chip analysis using customized tiled arrays will be used to assess the role and mechanisms of action of VDR at representative classes of target genes in undifferentiated and differentiated osteoblasts.
Specific Aim 3 : To establish principles for the regulation of gene expression by 1,25(OH)2D3 and its receptor in osteoblasts at the genome-wide level. ChIP-chip approaches will be used to extend, genome-wide, the general features of VDR-mediated gene regulation identified in Aims 1 and 2 in osteoblast precursors and fully differentiated osteoblasts. The role of 1,25(OH)2D3 in the regulation of transcription factor co-recruitment, epigenetic modification and RNA polymerase II modulation will be assessed. The research proposed herein is likely to provide novel insight into the gene targets and underlying mechanisms that mediate the pleiotropic activities 1,25(OH)2D3 at the genome level in osteoblasts. The studies will also provide new information relevant to the design, development and potential therapeutic application of new vitamin D analogs.

Public Health Relevance

Vitamin D plays significant roles both in the maintenance of mineral homeostasis and in the control of cellular growth and function. The studies herein seek to enhance our understanding of the mechanisms that underlie vitamin D action in bone cells such that better and more selective medicines can be created.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK072281-08
Application #
8306852
Study Section
Skeletal Biology Structure and Regeneration Study Section (SBSR)
Program Officer
Margolis, Ronald N
Project Start
2005-09-01
Project End
2013-05-31
Budget Start
2012-06-01
Budget End
2013-05-31
Support Year
8
Fiscal Year
2012
Total Cost
$374,203
Indirect Cost
$117,342
Name
University of Wisconsin Madison
Department
Biochemistry
Type
Schools of Earth Sciences/Natur
DUNS #
161202122
City
Madison
State
WI
Country
United States
Zip Code
53715
St John, Hillary C; Meyer, Mark B; Benkusky, Nancy A et al. (2015) The parathyroid hormone-regulated transcriptome in osteocytes: parallel actions with 1,25-dihydroxyvitamin D3 to oppose gene expression changes during differentiation and to promote mature cell function. Bone 72:81-91
Lee, Seong Min; Bishop, Kathleen A; Goellner, Joseph J et al. (2014) Mouse and human BAC transgenes recapitulate tissue-specific expression of the vitamin D receptor in mice and rescue the VDR-null phenotype. Endocrinology 155:2064-76
St John, Hillary C; Bishop, Kathleen A; Meyer, Mark B et al. (2014) The osteoblast to osteocyte transition: epigenetic changes and response to the vitamin D3 hormone. Mol Endocrinol 28:1150-65
Pike, J Wesley (2014) Expression of the vitamin D receptor in skeletal muscle: are we there yet? Endocrinology 155:3214-8
Meyer, Mark B; Benkusky, Nancy A; Pike, J Wesley (2014) 1,25-Dihydroxyvitamin D3 induced histone profiles guide discovery of VDR action sites. J Steroid Biochem Mol Biol 144 Pt A:19-21
Meyer, Mark B; Benkusky, Nancy A; Pike, J Wesley (2014) The RUNX2 cistrome in osteoblasts: characterization, down-regulation following differentiation, and relationship to gene expression. J Biol Chem 289:16016-31
Meyer, Mark B; Benkusky, Nancy A; Lee, Chang-Hun et al. (2014) Genomic determinants of gene regulation by 1,25-dihydroxyvitamin D3 during osteoblast-lineage cell differentiation. J Biol Chem 289:19539-54
Lee, Seong Min; Goellner, Joseph J; O'Brien, Charles A et al. (2014) A humanized mouse model of hereditary 1,25-dihydroxyvitamin D-resistant rickets without alopecia. Endocrinology 155:4137-48
Lieben, Liesbet; Masuyama, Ritsuko; Torrekens, Sophie et al. (2012) Normocalcemia is maintained in mice under conditions of calcium malabsorption by vitamin D-induced inhibition of bone mineralization. J Clin Invest 122:1803-15
Pike, J Wesley; Meyer, Mark B (2012) Regulation of mouse Cyp24a1 expression via promoter-proximal and downstream-distal enhancers highlights new concepts of 1,25-dihydroxyvitamin D(3) action. Arch Biochem Biophys 523:2-8

Showing the most recent 10 out of 22 publications