Wong T S, Ordahl C P
Department of Anatomy and Cardiovascular Research Institute, University of California, San Francisco, San Francisco, California, 94143-0452, USA.
Dev Biol. 1996 Dec 15;180(2):732-44. doi: 10.1006/dbio.1996.0342.
Myogenesis involves a conserved program of muscle gene isoform switching requiring the synchronized induction and repression of numerous muscle-specific gene family members. Central to understanding the regulation of this process are questions related to the origin and transmission of regulatory signals to the myofiber. We show here that troponin T gene switching can be precociously initiated by extrinsic blood-borne components but also requires other mechanisms that are regulated locally, intrinsically, or posttranscriptionally. We established a chimeric blood circulation by parabiosis between fetal chicks and quails to determine whether signals inducing earlier troponin T mRNA isoform switching in quails could be transduced to chick partners through the serum. While quail fetuses were unaffected by parabiosis, quail serum caused premature troponin T iso-mRNA switching in chick muscle, although initiation remained later than in quails. The onset of repression of a known innervation-dependent acetylcholine receptor mRNA did not coincide with the initiation of troponin T iso-mRNA switching and was not affected by parabiosis. These results support serum-borne factor regulation of isoform switching as an important and distinct mechanism relevant to understanding how extrinsic and intrinsic cues are integrated during muscle differentiation and development.
肌生成涉及一个保守的肌肉基因亚型转换程序，该程序需要同步诱导和抑制众多肌肉特异性基因家族成员。理解这一过程调控的核心问题是与调控信号向肌纤维的起源和传递相关的问题。我们在此表明，肌钙蛋白T基因转换可由外在的血液传播成分过早启动，但也需要其他在局部、内在或转录后水平受到调控的机制。我们通过将胎鸡和鹌鹑联体建立了嵌合血液循环，以确定诱导鹌鹑中更早的肌钙蛋白T mRNA亚型转换的信号是否能通过血清传递给鸡伙伴。虽然鹌鹑胎儿不受联体影响，但鹌鹑血清导致鸡肌肉中肌钙蛋白T同工型mRNA过早转换，尽管起始时间仍比鹌鹑晚。已知的神经支配依赖性乙酰胆碱受体mRNA抑制的起始与肌钙蛋白T同工型mRNA转换的起始不一致，且不受联体影响。这些结果支持血清传播因子对亚型转换的调控是一种重要且独特的机制，这与理解外在和内在线索在肌肉分化和发育过程中如何整合相关。
