Regulation of Early Development

C.后卵裂球发育。先前已显示秀丽线虫依赖于转录因子PAL-1，一种尾相关同源框蛋白。 PAL-1是必需的两个主要细胞的命运产生的后部，即皮下组织（皮肤）和体壁肌肉（横纹肌）。 为了了解PAL-1如何执行这两种命运，并确定其他转录因子的层次，我们研究了Wnt和MAP激酶信号对PAL-1功能的影响。 我们的研究表明，Wnt-MAP激酶信号，从一个不确定的来源，工作之间的皮肤与肌肉的二元命运决定的PAL-1的功能切换。 正如在C.在线虫中，该信号传导的末端效应子是TCFLEF型转录因子POP-1。 PAL-1蛋白与高水平的核POP-1的简单组合编码导致皮肤发育，而低水平的核POP-1与活性PAL-1导致肌肉发育。 为了梳理PAL-1在指导肌肉发育中的转录产物，我们集中于PAL-1编码转录因子的潜在下游靶基因。 基于其他小组先前的研究，以及我们自己的微阵列分析，我们分析了可能对肌生成重要的三个候选因子的功能; HLH-1，HLH-120和HND-1。 单独或组合使用这些基因中的遗传突变体，我们发现这三个因素的缺失是阻止肌肉发育所必需的。 我们进一步表明，这些因子都可以相互交叉调节，HLH-1积极自我调节，提供了一种分子机制，以确保一旦被PAL-1触发，这些转录因子继续发挥作用，并驱动肌肉分化和功能所需的下游基因表达。 我们现在已经扩展了这些研究，以了解不依赖PAL-1的更前谱系的肌肉发育。 这些细胞似乎使用相同的Wnt和MAP激酶途径，但依赖于尚未确定的发育因素。 利用胚胎操作和基因表达谱分析，我们已经确定了候选基因，目前正在表征它们的作用。

Posterior blastomere development in C. elegans has previously been shown to be dependent on the transcription factor PAL-1, a caudal-related homeobox protein. PAL-1 is necessary for both major cell fates arising from the posterior, namely hypodermis (skin) and body wall muscle (striated muscle). To understand how PAL-1 executes these two fates, and to identify other transcription factors in the hierarchy, we studied the effects of Wnt and MAP kinase signaling on PAL-1 function. Our studies revealed that Wnt-MAP kinase signals, from an undefined source, work to toggle the function of PAL-1 between the binary fate decisions of skin versus muscle. As seen in other early cell lineage decisions in C. elegans, the end effector for this signaling is the TCFLEF-type transcription factor POP-1. A simple combinatorial code of PAL-1 protein with high levels of nuclear POP-1 results in skin development whereas low nuclear POP-1 with active PAL-1 results in muscle development. To tease out the transcriptional output of PAL-1 in directing muscle development, we focused on potential downstream target genes of PAL-1 encoding transcription factors. Based on previous studies by other groups, and our own microarray analysis, we assayed the functions of three candidate factors that were likely important for myogenesis; HLH-1, UNC-120 and HND-1. Using genetic mutants in these genes alone, or in combination, we found that loss of all three of these factors was necessary to prevent muscle development. We further showed that these factors can both cross-regulate each other and that HLH-1 positively auto-regulates itself, providing a molecular mechanism to ensure that once triggered by PAL-1, these transcription factors continue to function and drive downstream gene expression needed for muscle differentiation and function. We have now extended these studies to understand muscle development in more anterior lineages that are not PAL-1 dependent. These cell appear to use the same Wnt and MAP Kinase pathways to, but rely on as yet undefined factors for development. Using embryo manipulation and gene expression profiling we have identified candidate genes and are currently characterizing their role.