noun, plural: myoblasts
Myoblasts are the embryonic precursors of myocytes (also called muscle cells). Myoblasts differentiate into muscle cells through a process called myogenesis. During myogenesis, the myoblasts fuse into multi-nucleated myotubes, which later become the muscle fibers.1 During the early embryonic development, the myoblasts may either divide into other myoblasts or differentiate into myotubes. In vitro studies show that most myoblasts will divide mitotically when there is a sufficient concentration of growth factors. In contrast, an insufficient amount of growth factors lead to the cessation of cell division of myoblasts. This eventually results in the differentiation of myoblasts into myotubes. During the differentiation stage, certain genes (e.g. striated alpha-actin genes) are expressed and the myoblasts align with one another. The myoblasts, then, fuse with the recruitment of actin to the plasma membrane.2
Myoblasts may be classified as skeletal muscle myoblasts, smooth muscle myoblasts, and cardiac muscle myoblasts depending on the type of muscle cell that they will differentiate into.
Word origin: Ancient Greek mûs (mouse; muscle) + Ancient Greek blastós (germ, sprout)
1 Birbrair, Alexander; Zhang, Tan; Wang, Zhong-Min; Messi, Maria Laura; Enikolopov, Grigori N.; Mintz, Akiva; Delbono, Osvaldo (2013). "Role of Pericytes in Skeletal Muscle Regeneration and Fat Accumulation". Stem Cells and Development 22 (16): 2298–314.
2 Yaffe, David; Feldman, Michael (1965). "The formation of hybrid multinucleated muscle fibers from myoblasts of different genetic origin". Developmental Biology 11 (2): 300.