Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.
Dev Biol. 2011 Oct 1;358(1):240-50. doi: 10.1016/j.ydbio.2011.07.034. Epub 2011 Aug 4.
EBF proteins have diverse functions in the development of multiple lineages, including neurons, B cells and adipocytes. During Drosophila muscle development EBF proteins are expressed in muscle progenitors and are required for muscle cell differentiation, but there is no known function of EBF proteins in vertebrate muscle development. In this study, we examine the expression of ebf genes in Xenopus muscle tissue and show that EBF activity is necessary for aspects of Xenopus skeletal muscle development, including somite organization, migration of hypaxial muscle anlagen toward the ventral abdomen, and development of jaw muscle. From a microarray screen, we have identified multiple candidate targets of EBF activity with known roles in muscle development. The candidate targets we have verified are MYOD, MYF5, M-Cadherin and SEB-4. In vivo overexpression of the ebf2 and ebf3 genes leads to ectopic expression of these candidate targets, and knockdown of EBF activity causes downregulation of the endogenous expression of the candidate targets. Furthermore, we found that MYOD and MYF5 are likely to be direct targets. Finally we show that MYOD can upregulate the expression of ebf genes, indicating the presence of a positive feedback loop between EBF and MYOD that we find to be important for maintenance of MYOD expression in Xenopus. These results suggest that EBF activity is important for both stabilizing commitment and driving aspects of differentiation in Xenopus muscle cells.
EBF 蛋白在多种谱系的发育中具有多种功能，包括神经元、B 细胞和脂肪细胞。在果蝇肌肉发育过程中，EBF 蛋白在肌肉祖细胞中表达，并需要肌肉细胞分化，但在脊椎动物肌肉发育中尚未发现 EBF 蛋白的功能。在这项研究中，我们检查了 Xenopus 肌肉组织中 ebf 基因的表达情况，并表明 EBF 活性对于 Xenopus 骨骼肌发育的各个方面都是必需的，包括体节组织、轴下肌肉原基向腹侧迁移以及颌部肌肉的发育。通过微阵列筛选，我们已经确定了多个候选 EBF 活性靶标，这些靶标已知在肌肉发育中具有作用。我们已经验证的候选靶标是 MYOD、MYF5、M-Cadherin 和 SEB-4。体内过表达 ebf2 和 ebf3 基因导致这些候选靶标的异位表达，而 EBF 活性的敲低导致内源性候选靶标的表达下调。此外，我们发现 MYOD 和 MYF5 可能是直接靶标。最后，我们表明 MYOD 可以上调 ebf 基因的表达，表明 EBF 和 MYOD 之间存在正反馈回路，我们发现该回路对于维持 Xenopus 中 MYOD 表达很重要。这些结果表明，EBF 活性对于 Xenopus 肌肉细胞的稳定分化和驱动分化方面都很重要。
