Asakura A, Tapscott S J
Division of Molecular Medicine, Fred Hutchinson Cancer Research Center, 1124 Columbia Street, Seattle, Washington, 98104, USA.
Dev Biol. 1998 Nov 15;203(2):276-89. doi: 10.1006/dbio.1998.9050.
Danforth's short-tail (Sd) mouse is a semidominant mutation that prevents completion of notochord development. In homozygous mutant mice, the notochord completely degenerates at embryonic day 9.5 (E9. 5), whereas the neural tube and somites continue to form, permitting analysis of somite development in the absence of inductive signals from the notochord and floor plate. In the somites formed after notochord degeneration, Myf5 expression initiates in a normal temporal sequence, but instead of the normal restriction to the dorsomedial somite, its expression extends into the ventral somite. MyoD, myogenin, and myosin heavy chain are normally expressed in the ventral myotome and there is normal development of hypaxial muscles. In contrast, subsequent to initial Myf5 expression, muscle gene expression was not detected in the dorsal myotome and a high level of apoptosis was observed with significantly decreased formation of epaxial muscles. The apoptosis of epaxial muscle in somites that formed after notochord degeneration is consistent with a role for the notochord in the survival and differentiation of the dorsal myotome.
丹福斯短尾（Sd）小鼠是一种半显性突变体，它会阻止脊索发育的完成。在纯合突变小鼠中，脊索在胚胎第9.5天（E9.5）时完全退化，而神经管和体节继续形成，这使得在没有来自脊索和底板的诱导信号的情况下，仍可对体节发育进行分析。在脊索退化后形成的体节中，Myf5表达按正常时间顺序启动，但与其正常情况下仅局限于背内侧体节不同，其表达扩展到了腹侧体节。MyoD、肌细胞生成素和肌球蛋白重链通常在腹侧肌节中表达，并且轴下肌发育正常。相比之下，在最初的Myf5表达之后，背侧肌节中未检测到肌肉基因表达，并且观察到高水平的细胞凋亡，轴上肌的形成明显减少。脊索退化后形成的体节中轴上肌的凋亡与脊索在背侧肌节的存活和分化中的作用一致。
