An avian muscle factor related to MyoD1 activates muscle-specific promoters in nonmuscle cells of different germ-layer origin and in BrdU-treated myoblasts.

Abstract

We isolated the cDNA encoding a myogenic [actor expressed in embryonic chick breast muscle by virtue of its weak hybridization to the mouse MyoD1 clone. Nucleotide sequence analysis and amino acid comparison define this clone, CMD1, as encoding a protein similar to mouse MyoD1. CMD1 encodes a polypeptide smaller than MyoD1, 298 versus 318 amino acids, respectively, and is 80% concordant by amino acid sequence overall. The basic and myc domains required for myogenic conversion of mouse 10TI/2 'fibroblasts' to myoblasts with MyoD1 are completely conserved in CMD1. CMD1 is just as efficient as the mouse homolog in myogenic conversion of 10TV2 cells and coactivates the endogenous mouse MyoD1 gene in the process. The efficiency of myoblast conversion depends on the levels of CMD 1 expression and suggests that the cellular concentration of CMD1 plays a role in the onset of myogenesis. Transient expression of CMD1 in a variety of nonmuscle cells from different germ-layer origins activates both cotransfected muscle-specific promoters and, in some cases, endogenous muscle-specific genes. 5-Bromodeoxyuridine (BrdU) treatment of chicken and mouse myoblasts reduces the expression of CMD1 and MyoD1, respectively, and may explain how this thymidine analog inhibits myogenesis and the activity of transfected muscle-specific promoters in BrdU-treated myoblasts. Transient expression of CMD 1 in BrdU-treated myoblasts reactivates cotransfected muscle-specific promoters. CMD1 activates muscle-specific promoters in cotransfections regardless of cell type, whereas 'housekeeping' or constitutive promoters can be activated moderately, unaffected, or repressed, depending on the promoter and cell background. The rate and degree of myogenic conversion may be more restricted by cell phenotype than by germ-layer origin.

Tbx1 regulation of myogenic differentiation in the limb and cranial mesoderm

“…Whole-mount and 35 S-labeled in situ hybridization to tissue sections was performed as described by FrancisWest et al (1994) using antisense ribroprobes prepared as described: Myf5 (Pownall and Emerson, 1992), MyoD (Lin et al, 1989), Tbx1 (Garg et al, 2001). The capsulin and MyoR cDNAs were obtained by reverse transcriptase-polymerase chain reaction (RT-PCR) using primers derived from sequences in the chick expressed sequence tag database.…”

Tissue-specific Isoforms of Chicken Myomesin Are Generated by Alternative Splicing

“…For the negative control, a 1500-bp RNA probe derived from a full-length cDNA clone, CMD1, of chicken MyoD1 (Lin et al, 1989) was used. The construct was linearized by KpnI/BamHI-digestion and transcribed by T3 RNA polymerase, yielding a probe of 1500 bp identical to the mRNA.…”

A myogenic factor from sea urchin embryos capable of programming muscle differentiation in mammalian cells.

“…Although much can be learned about myogenesis from mouse embryos (8) and from other vertebrate embryos such as chicken (9), quail (10), and frog (11)(12)(13), several investigators have turned to invertebrates for comparative purposes. In particular, the invariant cell lineages of Caenorhabditis elegans, the genetic techniques of Drosophila, and the localized determinants of ascidians make these embryos attractive systems in which to study muscle differentiation (14)(15)(16).…”