The regulation of myogenin gene expression during the embryonic development of the mouse.

Abstract

The myogenic program can be activated in cultured cells by each of four basic-helix-loop-helix (bHLH) transcription factors, the expression of which is strictly controlled, both temporally and spatially, during embryonic development. To begin to understand the mechanisms by which these regulators ~re regulated themselves, we have used transgenic animals to define the minimal sequences required for the complete recapitulation of the temporal and spatial expression pattern of the myogenin gene during embryogenesis. We show that this can be achieved with only 133 bp of 5'-flanking DNA and identify two essential motifs, which are consensus binding sites for the bHLH proteins and for the proteins of the RSRF family. We show further that these sequences, when juxtaposed to a heterologous promoter, are capable of imposing the myogenin expression pattern. We conclude that the proper regulation of myogenin requires a bHLH protein, most probably Myf-5, the only myogenic bHLH factor known to be present in the embryo at the time that myogenin is activated, and an RSRF-Iike binding activity. Furthermore, the expression pattern of a mutant myogenin promoter lacking the RSRF site reveals the existence of at least two populations of cells within the myotomes and of novel rostrocaudal gradients of expression.

An evolutionarily conserved three-dimensional structure in the vertebrate Irx clusters facilitates enhancer sharing and coregulation

“…Th e PCR fragments were subcloned in PCR8 / GW / TOPO vector and, using Gateway technology, transferred to the corresponding destination vectors for transgenesis in mouse, Xenopus tropicalis or zebrafi sh. For the generation of transgenic mice, the genomic fragments were transferred into a vector containing the human minimal β -globin promoter, lacZ and a SV40 polyadenylation signal 41 . Vectors were subsequently linearized, the vector backbone removed and the construct microinjected into one-cell mouse embryos.…”

Oncostatin M inhibits myoblast differentiation and regulates muscle regeneration

“…To understand mechanistically how OSM inhibits myoblast differentiation, we first examined the expression levels of MEF2 and MyoD that are known to be involved in regulating myogenin gene expression [54,55]. While OSM did not affect the expression of MyoD, it clearly reduced the expression of MEF2 in both primary myoblasts and C2C12 cells ( Figure 4A).…”

“…This prompted us to test whether STAT1 could also physically interact with key transcription factors (e.g., MEF2 and MyoD) involved in regulating myogenin gene expression [54,55].…”

Loss of procollagen IIA from the anterior mesendoderm disrupts the development of mouse embryonic forebrain

“…E8.0-E8.5 wild-type and mutant embryos were fixed briefly in 4% paraformaldehyde (PFA) in phosphate buffered saline (PBS) and stained in the dark at 37 C with X-gal reagents prepared essentially as described (Yee and Rigby, 1993). To assay cell death, X-gal stained embryos were post-fixed and permeabilized for 10 min in PBS buffer containing 0.1% Triton X-100, 0.1% Tween-20, and 0.1% sodium citrate.…”