Transcriptional Regulation of Myogenesis

确定细胞命运决定的基因表达级联是理解由于错误调节引起的发育和疾病的关键因素。 全基因组微阵列的可用性，加上几乎纯的细胞类型群体的分离，允许人们开始定义与特定细胞命运相关的转录组。 由于肌肉细胞易于分离和培养以及它们在人类病理学中的重要性，它们一直是成熟动物中此类研究的有吸引力的靶点。 然而，要确定早期体内胚胎肌源性基因的表达模式，从而深入了解肌肉发育的调控，则更为困难。 为此，我们已经做了基因表达的发育概况，并确定了关键的转录调控因子。 我们继续研究由生肌调节因子HLH-1（脊椎动物MyoD家族的同源物）激活的体内靶基因。 我们先前已经证明，hlh-1在早期C. elegans胚胎足以将大多数卵裂球转化为体壁肌肉样的命运。 为了确定HLH-1的转录靶点，即肌细胞命运的指定和分化的基础，我们使用染色质免疫沉淀（ChIP），然后探测全基因组tilling微阵列（Chip），或者与Reinke实验室合作，对ChIP样品进行下一代测序。 结果表明，这种转录因子的体内结合位点在整个基因组中广泛存在，与最近在小鼠中报道的相似。 这有力地表明，这些肌生成的主要调节因子不仅控制下游靶基因的激活，还可能参与染色质组织。

Defining the gene expression cascade underlying cell fate determination is a key element in understanding development and diseases that arise due to mis-regulation. The availability of whole genome microarrays, coupled with the isolation of nearly pure cell type populations, allows one to begin to define the transcriptome associated with specific cell fates. Muscle cells have been attractive targets for such studies in mature animals due to their ease of isolation and_or culture and their importance in human pathologies. It has been more difficult, however, to determine early in vivo embryonic myogenic gene expression patterns that would give insights into the regulation of muscle development. To this end, we have done a developmental profile of gene expression and identified key transcriptional regulators. We continue to study the in vivo target genes activated by the myogenic regulator, HLH-1,a homolog of the vertebrate MyoD family. We have previously shown that ectopic expression of hlh-1 in early C. elegans embryos is sufficient to convert most blastomeres to a body wall muscle like fate. To define the transcriptional targets of HLH-1 that underlie muscle cell fate specification and differentiation, we have use chromatin immunoprecipitation (ChIP) followed by probing whole genome tilling microarrays (Chip) or, in collaboration with the Reinke lab, ChIPed samples are subjected to next generation sequencing. The results reveal that the in vivo binding sites for this transcription factor are widespread throughout the genome, similar to what has recently been reported in the mouse. This strongly suggests that these master regulators of myogenesis are acting to control more than just downstream target gene activation, perhaps being also involved in chromatin organization.