鸡骨骼肌发育过程生肌素的表达

The Expression of Myogenin during Chicken Myogenesis

ＭｙｏＤ家族生肌因子ＭｙｏＤ、生肌素（ｍｙｏｇｅｎｉｎ）、ｍｙｆ－５和ｍｙｆ－６／ｈｅｒｃｕｌｉｎ对脊椎动物肌细胞分化和骨骼肌系统的发育成熟具有重要意义，其中生肌素的作用尤为突出，是肌细胞终末分化的关键因素。采用Ｎｏｒｔｈｅｒｎ和Ｗｅｓｔｅｒｎ印迹技术检测鸡胚骨骼肌发育过程中生肌素在转录水平的表达动力学，发现在胚胎发育第９ｄ已有鸡肢体骨骼肌生肌素ｍＲＮＡ表达，第１３ｄ达到高峰，第１５ｄ开始下降，第１８ｄ至出生后两周几无可检测的ｍＲＮＡ；而生肌素蛋白则在胚胎发育第１３ｄ方可被检测到，第１５～１８ｄ达到高峰，至出生后两周仍维持在一定水平，表明生肌素的表达存在翻译和翻译后水平的调控。利用鸡生肌素基因上游－２２３／＋４０调控片段为探针对发育不同时期的鸡肌肉组织细胞核抽提物进行Ｓｏｕｔｈｗｅｓｔｅｒｎ印迹分析。发现一种约３５ｋＤ的核内蛋白与探针有较强结合，结合活性第９ｄ时出现，至第１８ｄ达到峰值，出生后两周时降至难检测水平；另外有一种约１１ｋＤ的核内蛋白的ＤＮＡ结合活性恰好在转录活性下降的第１５～１８ｄ发生，按此情况两种核因子可能对生肌素的转录激活分别起正负调控作用。

The kinetic expression of myogenin at the levels of transcription and translation during chicken embryogenesis was tested, using Northern blotting and Western blotting. It was found that the expression of myogenin mRNA in chicken limb skeletal muscle was at a detectable level on day 9 in ovo, reaching maximum on day 13. After day 15 it decreased to undetectable level throughout late embryogenesis. The detectable protein of myogenin appeared on day 13 in ovo, increasing up from day 15 to day 18,and maintained a stable level until 2 weeks after birth.which suggested that myogenin expression is still under translational and post translational regulation. Using-223/+40 fragment of chicken myogenin gene as a probe. the DNA binding proteins in nuclear extracts from chicken muscle at different developing stages were analyzed. Southwestern blotting showed that a 35 kD nuclear protein strongly binding to the probe appeared on day 9 in ovo., raching maximum on day 18,and then decreased to undetectable level in two weeks after birth. A 11 kD nuclear protein with DNA binding activity occurred from day 15 to day 18 in ovo, in such time the expression of myogenin mRNA just decreased. Both nuclear factors might regulate the transcriptional activation of myogenin in positive or negative manners respectively.