Role of CD164 in Skeletal Myogenesis

描述（由申请人提供）：骨骼肌谱系的确定和分化由MyoD肌源性转录因子家族控制。 这些因子，沿着MEF-2家族的转录因子，自动激活和交叉激活彼此的表达，导致维持肌原性表型的自动调节、正反馈网络。 该谱系中细胞的确定和分化也需要肌肉前体之间的细胞-细胞接触。然而，参与这种现象的细胞表面蛋白的身份，以及它们在肌发生中的特定作用，还没有很好地理解。 唾液酸粘蛋白是以粘蛋白结构域为特征的细胞表面蛋白，其是富含脯氨酸、丝氨酸和苏氨酸的区域，其上高百分比的丝氨酸和苏氨酸残基是0-糖基化的。 这些O-连接聚糖是唾液粘蛋白功能的核心，因为已知特定的唾液粘蛋白作为选择素的高亲和力配体;选择素是跨膜受体，在白细胞运输期间识别这些唾液粘蛋白上的唾液酸化碳水化合物结构。 唾液粘蛋白在白细胞运输之外的生物学作用知之甚少。 我们已经确定了Cd 164作为一个基因在增殖的C2 C12成肌细胞中表达，在分化过程中特异性上调。 CD 164编码广泛表达的细胞表面唾液粘蛋白，其参与调节细胞增殖、分化和造血前体的粘附。 Cd 164的稳定过表达增强成肌细胞分化。 用唾液酸酶或O-唾液酸糖蛋白酶（两种破坏CD 164上的功能表位的酶）处理C2 C12细胞也抑制分化。 综上所述，我们推测，CD 164是一个可能的效应器的细胞间接触的需要，在肌生成和碳水化合物为基础的细胞识别可能参与了这一过程。 具体目标是：1）鉴定CD 164的促肌生成活性的结构决定因素; 2）鉴定CD 164的反受体;和3）研究CD 164在体内肌生成中的作用。 这些实验将提供关键的信息，分子和遗传学的理解CD 164的作用，在肌发生。 因此，这项研究应该阐明骨骼肌发育的基本过程。

DESCRIPTION (provided by applicant): Determination and differentiation of the skeletal muscle lineage is controlled by the MyoD family of myogenic transcription factors. These factors, along with the MEF-2 family of transcription factors, auto-activate and cross-activate the expression of each other, resulting in an autoregulatory, positive feedback network that maintains the myogenic phenotype. Determination and differentiation of cells in this lineage also require cell-cell contact between muscle precursors. However, the identities of the cell surface proteins involved in this phenomenon, and their specific roles in myogenesis, are not well understood. Sialomucins are cell surface proteins characterized by mucin domains, which are proline-, serine-, and threonine-rich regions on which a high percentage of the serine and threonine residues are O-glycosylated. These O-linked glycans are central to sialomucin function, as specific sialomucins are known to serve as high affinity ligands for selectins; selectins are transmembrane receptors that recognize sialylated carbohydrate structures on these sialomucins during leukocyte trafficking. The biological roles of sialomucins outside of leukocyte trafficking are poorly understood. We have identified Cd164 as a gene expressed in proliferating C2C12 myoblasts that is specifically upregulated during differentiation. Cd164 encodes a widely expressed cell surface sialomucin that has been implicated in regulation of cell proliferation, differentiation and adhesion of hematopoietic precursors. Stable overexpression of Cd164 enhances myoblast differentiation. Treatment of C2C12 cells with sialidase or O-sialoglycoprotease, two enzymes which destroy functional epitopes on CD164, also inhibits differentiation. Taken together, we hypothesize that CD164 is a likely effector of the need of cell-cell contact in myogenesis and that carbohydrate-based cell recognition may be involved in this process. The Specific Aims are: 1) to identify structural determinants of the pro-myogenic activity of CD164; 2) to identify counter-receptors for CD164; and 3) to investigate the role of CD164 in myogenesis in vivo. These experiments will provide information critical to molecular and genetic understanding of CD164's role in myogenesis. This research should therefore shed light on fundamental processes by which skeletal muscles develop.