title: Pattern of Pax7 expression during myogenesis in the posthatch chicken establishes a model for satellite cell differentiation and renewal.
abstract: The paired-box transcription factor Pax7 plays a critical role in the specification of satellite cells in mouse skeletal muscle. In the present study, the position and number of Pax7-expressing cells found in muscles of growing and adult chickens confirm the presence of this protein in avian satellite cells. The expression pattern of Pax7 protein, along with the muscle regulatory proteins MyoD and myogenin, was additionally elucidated in myogenic cultures and in whole muscle from posthatch chickens. In cultures progressing from proliferation to differentiation, the expression of Pax7 in MyoD+ cells declined as the cells began expressing myogenin, suggesting Pax7 as an early marker for proliferating myoblasts. At all time points, some Pax7+ cells were negative for MyoD, resembling the reserve cell phenotype. Clonal analysis of muscle cell preparations demonstrated that single progenitors can give rise to both differentiating and reserve cells. In muscle tissues, Pax7 protein expression was the strongest by 1 day posthatch, declining on days 3 and 6 to a similar level. In contrast, myogenin expression peaked on day 3 and then dramatically declined. This finding was accompanied by a robust growth in fiber diameter between day 3 and 6. The distinctions in Pax7 and myogenin expression patterns, both in culture and in vivo, indicate that while some of the myoblasts differentiate and fuse into myofibers during early stages of posthatch growth, others retain their reserve cell capacity.
authors.affiliation: Department of Animal Sciences, The Hebrew University of Jerusalem, Rehovot, Israel.
authors.forename: Orna
authors.initials: O
authors.lastname: Halevy
authors.forename: Yogev
authors.initials: Y
authors.lastname: Piestun
authors.forename: Mohammed Z
authors.initials: MZ
authors.lastname: Allouh
authors.forename: Benjamin W C
authors.initials: BW
authors.lastname: Rosser
authors.forename: Yuval
authors.initials: Y
authors.lastname: Rinkevich
authors.forename: Ram
authors.initials: R
authors.lastname: Reshef
authors.forename: Israel
authors.initials: I
authors.lastname: Rozenboim
authors.forename: Monika
authors.initials: M
authors.lastname: Wleklinski-Lee
authors.forename: Zipora
authors.initials: Z
authors.lastname: Yablonka-Reuveni
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000911:Antibodies, Monoclonal / Q000276:immunology; D015415:Biomarkers; D002454:Cell Differentiation; D002455:Cell Division; D019070:Cell Lineage; D002478:Cells, Cultured; D002645:Chickens; D002999:Clone Cells; D019085:Fluorescent Antibody Technique, Direct; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000276:immunology / Q000378:metabolism*; D007150:Immunohistochemistry; D008954:Models, Biological; D024510:Muscle Development; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000276:immunology / Q000502:physiology; D017570:MyoD Protein / Q000276:immunology / Q000378:metabolism; D032446:Myoblasts / Q000378:metabolism; D018008:Myogenin / Q000276:immunology / Q000378:metabolism; D051763:PAX7 Transcription Factor; D032496:Satellite Cells, Skeletal Muscle / Q000166:cytology / Q000378:metabolism*; D013997:Time Factors
chemical_list: D000911:Antibodies, Monoclonal; D015415:Biomarkers; D018398:Homeodomain Proteins; D017570:MyoD Protein; D018008:Myogenin; D051763:PAX7 Transcription Factor