Rupp R A, Snider L, Weintraub H
Hutchinson Cancer Research Center, Howard Hughes Medical Institute, Seattle, Washington 98104.
Genes Dev. 1994 Jun 1;8(11):1311-23. doi: 10.1101/gad.8.11.1311.
Injection of Xenopus myoD mRNA into Xenopus embryos leads to only a modest activation of myogenic markers. In contrast, we show that injected mouse myoD mRNA leads to a potent activation. We postulate that XMyoD is under negative control in frog embryos, but because of slight sequence differences, mouse MyoD fails to see the negative signal. Whereas mMyoD is constitutively nuclear, XMyoD is largely cytoplasmic except in a region of the embryo that includes the location where mesoderm induction occurs; there, it is nuclear. At MBT, endogenous XmyoD mRNA is expressed ubiquitously in the frog embryo. Our results suggest that this expression would lead to cytoplasmic XMyoD protein. Among other events, muscle induction might remove this negative regulation, allow MyoD to enter the nucleus, and establish an autoregulatory loop that could commit cells to myogenesis.
将非洲爪蟾肌分化蛋白（Xenopus myoD）mRNA注射到非洲爪蟾胚胎中仅能引起生肌标记物适度激活。相比之下，我们发现注射小鼠肌分化蛋白（mouse myoD）mRNA能引发强效激活。我们推测非洲爪蟾肌分化蛋白（XMyoD）在蛙胚胎中受到负调控，但由于序列存在细微差异，小鼠肌分化蛋白（mMyoD）无法识别该负信号。小鼠肌分化蛋白（mMyoD）持续定位于细胞核，而非洲爪蟾肌分化蛋白（XMyoD）主要位于细胞质中，不过在胚胎中包括中胚层诱导发生位置的区域除外，在此区域它位于细胞核中。在中囊胚转换（MBT）时，内源性非洲爪蟾肌分化蛋白（XmyoD）mRNA在蛙胚胎中普遍表达。我们的结果表明这种表达会产生细胞质中的非洲爪蟾肌分化蛋白（XMyoD）。在其他事件中，肌肉诱导可能会消除这种负调控，使肌分化蛋白（MyoD）进入细胞核，并建立一个能使细胞定向分化为肌细胞的自动调节环。
