Developmental Gene Expression In C elegans

线虫的发育基因表达

• 批准号: 9148779
• 负责人: Michael Krause
• 金额: $ 73.06万
• 依托单位: NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/9148779
• 关键词: Address; Alleles; Anatomy; Animals; Anterior; Area; Baltimore; Biological Models; Caenorhabditis elegans; Cell Fate Control; Cell Lineage; Cells; Collaborations; Control Animal; County; Development; Developmental Gene; Embryo; Event; Gene Expression; Gene Targeting; Genes; Genetic; Human; Human Development; Knowledge; Laboratories; Life; Logic; Malignant Neoplasms; Mediating; Membrane; Mesoderm; Microarray Analysis; Mus; Muscle; Muscle Development; Mutation; MyoD Protein; Myogenin; Nematoda; Pathway interactions; Pattern; Phenotype; Play; Process; Proteins; Role; Signal Pathway; Signal Transduction; Signaling Protein; Staging; Striated Muscles; System; Tissues; Transcriptional Regulation; Universities; Vertebrates; Work; beta catenin; blastomere structure; bone; cell fate specification; cell motility; cell type; differential expression; embryo stage 2; interest; mutant; myogenesis; novel strategies; overexpression; research study; response; stem cell division; transcription factor

One of our main focus areas over the years is muscle development. In mice, striated muscle development requires the function of the MRFs, a set of four closely related factors (MyoD, Myf-5, MRF-4, Myogenin) that regulated muscle specification and differentiation. C. elegans has a single MRF-related factor called CeMyoD (HLH-1). One of the puzzling aspects of C. elegans myogenesis was the observation that muscles could be formed in the absence of CeMyoD, as demonstrated in mutant animals. To further define the exact role of this transcription factor, we ectopically expressed HLH-1/MyoD in the early nematode embryo and found that it was sufficient to convert all early blastomeres to a muscle-like fate. The sufficiency of HLH-1/MyoD alone to direct cells into the muscle lineage illustrated its potency and revealed a level of evolutionary conservation in function that had not previously been appreciated. Moreover, these experiments revealed a remarkable degree of plasticity of the early embryonic cells to be reprogrammed with regards to cell fate choice. Using genetic deletion alleles of three genes, we showed that muscle could form when at least one of these factors was present. However, elimination of all three gene products blocked muscle differentiation in the embryo. These results defined this trio of transcription factors as the key regulators of C. elegans muscle, explaining why muscle could form in the absence of HLH-1/MyoD. This past year, we have focused on the factors regulating anterior mesoderm specification and bodywall muscle development. Captializing on the defined cell lineage of C. elegans, we have defined a hierarchy of transcription factors involved regulating muscle development at the single cell level. This has allowed us to tease apart multiple pathways all leading to the eventual activation of HLH-1/MyoD and UNC-120/SRF, the common set of drivers for bodywall muscle fate specification and differentiation. Our results also revealed an unexpected evolutionary conservation of pathway components with anterior muscle development in vertebrates. In on-going collaboration with Dr. Eisenmann (Univ of MD, Baltimore County) we have explored gene expression regulated by Wnt signaling. The Wnt signaling pathway plays a fundamental role during metazoan development, where it regulates diverse processes, including cell fate specification, cell migration, and stem cell renewal. Activation of the beta-catenin-dependent/canonical Wnt pathway up-regulates expression of Wnt target genes to mediate a cellular response. In the nematode Caenorhabditis elegans, a canonical Wnt signaling pathway regulates several processes during larval development; however, few target genes of this pathway have been identified. To address this deficit, we used a novel approach of conditionally activated Wnt signaling during a defined stage of larval life by overexpressing an activated beta-catenin protein, then used microarray analysis to identify genes showing altered expression compared with control animals. We identified 166 differentially expressed genes, of which 104 were up-regulated. A subset of the up-regulated genes was shown to have altered expression in mutants with decreased or increased Wnt signaling; we consider these genes to be bona fide C. elegans Wnt pathway targets. In a collaboration with Dr. Liu (Cornell University) we capitalized on the genetics of C. elegans to identify a role of Bone Morphogentic Protein (BMP) in signaling developmental events in the postembryonic mesoderm. This work further revealed a role for membrane tetraspanins to modulate BMP signaling, providing a possible mechanism underlying their previously defined role in cancer development.

多年来，我们主要关注的领域之一是肌肉的发展。在小鼠中，横纹肌的发育需要mrf的功能，这是一组四个密切相关的因子（MyoD, Myf-5, MRF-4, Myogenin），它们调节肌肉的规格和分化。秀丽隐杆线虫有一个单一的mrf相关因子，称为CeMyoD （HLH-1）。秀丽隐杆线虫肌肉发生的一个令人困惑的方面是观察到肌肉可以在没有CeMyoD的情况下形成，正如在突变动物中所证明的那样。为了进一步确定该转录因子的确切作用，我们在早期线虫胚胎中异位表达HLH-1/MyoD，发现它足以将所有早期卵裂球转化为肌肉样命运。仅HLH-1/MyoD就足以引导细胞进入肌肉谱系，这说明了它的效力，并揭示了以前未被认识到的功能进化保护水平。此外，这些实验揭示了早期胚胎细胞在细胞命运选择方面具有显著的可塑性。利用三个基因的基因缺失等位基因，我们发现当这些因素中至少有一个存在时，肌肉可以形成。然而，消除这三个基因产物会阻碍胚胎中的肌肉分化。这些结果将这三个转录因子定义为秀丽隐杆线虫肌肉的关键调节因子，解释了为什么肌肉可以在缺乏HLH-1/MyoD的情况下形成。