Neuromuscular Biology & Disease Group, Boston Biomedical Research Institute, Watertown, Massachusetts, United States of America.
PLoS One. 2010 Apr 1;5(4):e9951. doi: 10.1371/journal.pone.0009951.
Multiple types of fast and slow skeletal muscle fibers form during early embryogenesis in vertebrates. In zebrafish, formation of the earliest slow myofibers in fin muscles requires expression of the zinc-finger transcriptional repressor Prdm1 (also known as Blimp1). To further understand how the role of Prdm1 in early myogenesis may vary through evolution and during development, we have now analyzed Prdm1 expression in the diverse types of myotubes that form in culture from somitic, embryonic, and fetal chicken myoblasts.
In cultures of somitic, embryonic limb, and fetal limb chicken cells, we found that Prdm1 was expressed in all of the differentiated muscle cells that formed, including those that expressed only fast myosin heavy chain isoforms, as well as those that co-expressed both fast and slow myosin heavy chain isoforms. Prdm1 was also expressed in Pax7-positive myoblasts, as well as in non-myogenic cells in the cultures. Furthermore, though all differentiated cells in control somite cultures co-expressed fast and slow myosin heavy chains, antisense knockdown of Prdm1 expression inhibited the formation of these co-expressing cells in somite cultures.
In chicken myogenic cell cultures, Prdm1 was expressed in most Pax7-positive myoblasts and in all differentiated muscle cells, irrespective of the developmental stage of cell donor or the pattern of fast and slow myosin heavy chains expressed in the differentiated cells that were formed. Thus, Prdm1 was expressed in myogenic cells prior to terminal differentiation; and, after differentiation, Prdm1 expression was not limited to cells that expressed slow myosin heavy chain isoforms. In addition, Prdm1 appeared to be required for differentiation of the somitic myocytes, which are the earliest myocytes to form in the avian embryo.
在脊椎动物的早期胚胎发生过程中，会形成多种类型的快肌和慢肌纤维。在斑马鱼中，鳍肌中最早的慢肌纤维的形成需要锌指转录抑制因子 Prdm1（也称为 Blimp1）的表达。为了进一步了解 Prdm1 在早期肌发生中的作用如何在进化和发育过程中发生变化，我们现在分析了来自体节、胚胎和胎儿鸡成肌细胞的培养中形成的各种类型的肌管中 Prdm1 的表达。
在体节、胚胎肢和胎儿肢鸡细胞的培养中，我们发现 Prdm1 在形成的所有分化肌肉细胞中均有表达，包括仅表达快肌球蛋白重链同工型的细胞，以及共表达快肌球蛋白重链同工型和慢肌球蛋白重链同工型的细胞。Prdm1 也在 Pax7 阳性成肌细胞以及培养物中的非成肌细胞中表达。此外，尽管对照体节培养物中的所有分化细胞均共表达快肌球蛋白重链和慢肌球蛋白重链，但 Prdm1 表达的反义敲低抑制了体节培养物中这些共表达细胞的形成。
在鸡成肌细胞培养物中，Prdm1 在大多数 Pax7 阳性成肌细胞和所有分化的肌肉细胞中表达，而与细胞供体的发育阶段或形成的分化细胞中快肌球蛋白重链同工型的表达模式无关。因此，Prdm1 在成肌细胞终末分化之前表达；并且，分化后，Prdm1 的表达不仅限于表达慢肌球蛋白重链同工型的细胞。此外，Prdm1 似乎是体节肌细胞分化所必需的，体节肌细胞是鸡胚胎中最早形成的肌细胞。
