The Microphthalmia (Mi) gene encodes one of the oldest recognized factors critical to osteoclast development and function. Mi is also required for development of the melanocyte lineage. The recently cloned Mi gene encodes a HLH-ZIP transcription factor, and is unique in its highly restricted tissue distribution. We have defined protein and DNA interactions of MI and found it to bind and potentially activate transcription off promoters containing its recognition element. We have recently examined an unusual rat mutant which displays severe osteoporosis which resolves with aging and shown that this results from a large deletion within Mi. We also discovered 3 dimerization partners of Mi (TFEB, TFEC, and TFE3) collectively called the """"""""MiT"""""""" family. At least one of these other factors is present in the Mi-deficient osteoclasts of this rat strain, suggesting a general a general role of this family in osteoclast function and maturation. Our studies in melanocytes have also revealed that Mi is strongly activated by MAP kinase phosphorylation following cytokine stimulation. c-Kit signaling operates through activation of Mi in this fashion. We now also know that the mechanism of this activation is phospho-Mi selective recruitment of the transcriptional co-activators p300/CBP. Importantly, our current results suggest that Mi is similarly phosphorylated in response to cytokine signaling in osteoclasts, and this response (to factors such as interleukin 6 and M-CSF) could lie critically within a major pathway of osteoclast activation. The understanding of such pathways is clearly central to future goals of modulating osteoclast function in conditions such as osteoporosis. To further enhance our understanding of this factor and extend our analysis of its actions within osteoclasts, this grant proposes to: 1) systematically examine Mi'T protein temporal expression patterns in osteoclasts throughout development and aging, 2) derive viral vectors permitting up- or down-regulation of endogenous MiT factors in osteoclasts, and examine their consequences on osteoclast development and function, 3) define mechanistic relationships between Mi and osteoclast signaling pathways of importance in bone homeostasis including other genes implicated in osteopetrosis and cytokines of functional importance, and 4) identify transcriptional target genes for Mi in osteoclasts by testing """"""""rational"""""""" candidates identified through sequence analysis of known promoters as well as a highly stringent differential display which requires up-regulation by wild type Mi, down- regulation by dominant negative Mi, as well as cytokine-mediated Mi induction in the presence of cycloheximide. Through these studies we hope to gain insight into osteoclast biology through an understanding of Mi's central role.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR045662-03
Application #
6375177
Study Section
General Medicine B Study Section (GMB)
Program Officer
Sharrock, William J
Project Start
1999-06-01
Project End
2003-05-31
Budget Start
2001-06-01
Budget End
2002-05-31
Support Year
3
Fiscal Year
2001
Total Cost
$292,406
Indirect Cost
Name
Dana-Farber Cancer Institute
Department
Type
DUNS #
149617367
City
Boston
State
MA
Country
United States
Zip Code
02215
Nguyen, Nhu T; Fisher, David E (2018) MITF and UV responses in skin: From pigmentation to addiction. Pigment Cell Melanoma Res :
Sullivan, Ryan J; Fisher, David E (2014) Understanding the biology of melanoma and therapeutic implications. Hematol Oncol Clin North Am 28:437-53
Chen, Hongxiang; Weng, Qing Y; Fisher, David E (2014) UV signaling pathways within the skin. J Invest Dermatol 134:2080-2085
Chin, Lynda; Garraway, Levi A; Fisher, David E (2006) Malignant melanoma: genetics and therapeutics in the genomic era. Genes Dev 20:2149-82
Miller, Arlo J; Levy, Carmit; Davis, Ian J et al. (2005) Sumoylation of MITF and its related family members TFE3 and TFEB. J Biol Chem 280:146-55
Hershey, Christine L; Fisher, David E (2004) Mitf and Tfe3: members of a b-HLH-ZIP transcription factor family essential for osteoclast development and function. Bone 34:689-96
So, Hongseob; Rho, Jaerang; Jeong, Daewon et al. (2003) Microphthalmia transcription factor and PU.1 synergistically induce the leukocyte receptor osteoclast-associated receptor gene expression. J Biol Chem 278:24209-16
McGill, Gael G; Horstmann, Martin; Widlund, Hans R et al. (2002) Bcl2 regulation by the melanocyte master regulator Mitf modulates lineage survival and melanoma cell viability. Cell 109:707-18
Weilbaecher, K N; Motyckova, G; Huber, W E et al. (2001) Linkage of M-CSF signaling to Mitf, TFE3, and the osteoclast defect in Mitf(mi/mi) mice. Mol Cell 8:749-58