At least seven sarcomeric myosin heavy chain (MHC) genes are expressed in mammalian skeletal muscles and these are slow type I (cardiac), embryonic (Emb), neonatal (Neo), fast-type IIa, IIx, IIb, and the extraocular (Eo). With the exception of type I MHC gene, skeletal MHC genes are clustered within -400 kilobases on chromosome 10 in the rat (17 in human) in the order Emb, IIa, IIx, IIb, Neo, and Eo (see Fig. 2). This MHC gene organization has been conserved through millions of years of evolution. We propose that the clustered organization of skeletal fast MHC genes is essential for their coordinated regulation in limb muscles. Thus, the main goal of this proposal is to establish whether the fast MHC genes are regulated as a transcriptional unit in a coordinated-fashion involving tandem gene-cross-talk (as illustrated in Fig 1), or whether they are regulated independently. To attain this goal, we will examine skeletal MHC regulation in two types of MHC transition: slow to fast MHC in inactive slow muscle (phase I), and fast to slow in overloaded fast muscles (phase II). We will test the working hypothesis that the cooperative regulation of skeletal MHC genes involves one of three mechanistic schemes: 1) a common set of transcription factors/regulatory elements that up regulates one gene while simultaneously down regulating the other (e.g., type I to IIx); 2) alternatively, a common milieu of transcription factors that are temporally controlled by the stimuli thereby affecting the target genes in an antithetical fashion (I to IIx; IIx equilibrium IIb); and 3) a unique cooperative process involving tandemly aligned genes in which the downstream (3') gene regulates the upstream one via an intergenic promoter that transcribes antisense RNA that interferes with posttranscriptional events of the 5'aligned gene (type IIa equilibrium IIx; see figure 1). For each experimental paradigm we will: a) develop a working model on the mode of MHC gene regulation in the transforming muscle using analyses of primary transcripts, antisense RNAs, and mature mRNAs of all the MHC isoforms in the target muscle; b) characterize the transcriptional regulation of the target genes, via both in silico and in vivo analyses of the IIa, IIx, and IIb promoters, including the IIa/IIx and IIx/IIb intergenic regions and c) identify transcription factors involved in this coordinated regulation and test their involvement in regulation by overexpressing them in the context of MHC gene promoter transfections. Collectively, these aims explore a new area of analyses taking advantage of new technologies and tools that were not available until recently. The results will give insight on regulatory mechanisms and cooperative regulation of the MHC gene locus. ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
2R01AR030346-22
Application #
6830633
Study Section
Special Emphasis Panel (ZRG1-MOSS-F (05))
Program Officer
Nuckolls, Glen H
Project Start
1982-07-01
Project End
2010-02-28
Budget Start
2005-03-01
Budget End
2006-02-28
Support Year
22
Fiscal Year
2005
Total Cost
$431,257
Indirect Cost
Name
University of California Irvine
Department
Physiology
Type
Schools of Medicine
DUNS #
046705849
City
Irvine
State
CA
Country
United States
Zip Code
92697
Pandorf, Clay E; Jiang, Weihua; Qin, Anqi X et al. (2012) Regulation of an antisense RNA with the transition of neonatal to IIb myosin heavy chain during postnatal development and hypothyroidism in rat skeletal muscle. Am J Physiol Regul Integr Comp Physiol 302:R854-67
Haddad, Fadia; Baldwin, Kenneth M (2010) Reverse transcription of the ribonucleic acid: the first step in RT-PCR assay. Methods Mol Biol 630:261-70
Baldwin, Kenneth M; Haddad, Fadia (2010) Research in the exercise sciences: where we are and where do we go from here--Part II. Exerc Sport Sci Rev 38:42-50
Giger, Julia M; Bodell, Paul W; Zeng, Ming et al. (2009) Rapid muscle atrophy response to unloading: pretranslational processes involving MHC and actin. J Appl Physiol (1985) 107:1204-12
Pandorf, Clay E; Jiang, Weihua H; Qin, Anqi X et al. (2009) Calcineurin plays a modulatory role in loading-induced regulation of type I myosin heavy chain gene expression in slow skeletal muscle. Am J Physiol Regul Integr Comp Physiol 297:R1037-48
McCall, Gary E; Haddad, Fadia; Roy, Roland R et al. (2009) Transcriptional regulation of the myosin heavy chain IIb gene in inactive rat soleus. Muscle Nerve 40:411-9
Pandorf, Clay E; Haddad, Fadia; Wright, Carola et al. (2009) Differential epigenetic modifications of histones at the myosin heavy chain genes in fast and slow skeletal muscle fibers and in response to muscle unloading. Am J Physiol Cell Physiol 297:C6-16
Rinaldi, Chiara; Haddad, Fadia; Bodell, Paul W et al. (2008) Intergenic bidirectional promoter and cooperative regulation of the IIx and IIb MHC genes in fast skeletal muscle. Am J Physiol Regul Integr Comp Physiol 295:R208-18
Mozaffar, Tahseen; Haddad, Fadia; Zeng, Ming et al. (2007) Molecular and cellular defects of skeletal muscle in an animal model of acute quadriplegic myopathy. Muscle Nerve 35:55-65
Pandorf, Clay E; Haddad, Fadia; Qin, Anqi X et al. (2007) IIx myosin heavy chain promoter regulation cannot be characterized in vivo by direct gene transfer. Am J Physiol Cell Physiol 293:C1338-46

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