title: c-Myb inhibits myoblast fusion.
abstract: Satellite cells represent a heterogeneous population of stem and progenitor cells responsible for muscle growth, repair and regeneration. We investigated whether c-Myb could play a role in satellite cell biology because our previous results using satellite cell-derived mouse myoblast cell line C2C12 showed that c-Myb was expressed in growing cells and downregulated during differentiation. We detected c-Myb expression in activated satellite cells of regenerating muscle. c-Myb was also discovered in activated satellite cells associated with isolated viable myofiber and in descendants of activated satellite cells, proliferating myoblasts. However, no c-Myb expression was detected in multinucleated myotubes originated from fusing myoblasts. The constitutive expression of c-Myb lacking the 3' untranslated region (3' UTR) strongly inhibited the ability of myoblasts to fuse. The inhibition was dependent on intact c-Myb transactivation domain as myoblasts expressing mutated c-Myb in transactivation domain were able to fuse. The absence of 3' UTR of c-Myb was also important because the expression of c-Myb coding region with its 3' UTR did not inhibit myoblast fusion. The same results were repeated in C2C12 cells as well. Moreover, it was documented that 3' UTR of c-Myb was responsible for downregulation of c-Myb protein levels in differentiating C2C12 cells. DNA microarray analysis of C2C12 cells revealed that the expression of several muscle-specific genes was downregulated during differentiation of c-Myb-expressing cells, namely: ACTN2, MYH8, TNNC2, MYOG, CKM and LRRN1. A detailed qRT-PCR analysis of MYOG, TNNC2 and LRRN1 is presented. Our findings thus indicate that c-Myb is involved in regulating the differentiation program of myogenic progenitor cells as its expression blocks myoblast fusion.
authors.affiliation: Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague 4, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Kaspar
authors.forename: Kristina
authors.initials: K
authors.lastname: Ilencikova
authors.forename: Martina
authors.initials: M
authors.lastname: Zikova
authors.forename: Ondrej
authors.initials: O
authors.lastname: Horvath
authors.forename: Vladimir
authors.initials: V
authors.lastname: Cermak
authors.forename: Petr
authors.initials: P
authors.lastname: Bartunek
authors.forename: Hynek
authors.initials: H
authors.lastname: Strnad
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D000818:Animals; D054715:Cardiotoxins / Q000494:pharmacology; D002454:Cell Differentiation / Q000235:genetics*; D002459:Cell Fusion; D002460:Cell Line; D002478:Cells, Cultured; D005260:Female; D020869:Gene Expression Profiling; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000378:metabolism; D018482:Muscle, Skeletal / Q000187:drug effects / Q000503:physiopathology; D032446:Myoblasts / Q000166:cytology / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D020598:Proto-Oncogene Proteins c-myb / Q000235:genetics* / Q000378:metabolism; D012038:Regeneration / Q000187:drug effects / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D032496:Satellite Cells, Skeletal Muscle / Q000166:cytology / Q000378:metabolism*
chemical_list: D020413:3' Untranslated Regions; D054715:Cardiotoxins; D020598:Proto-Oncogene Proteins c-myb