C-signal Perception in Myxococcus Xanthus

细胞间相互作用对许多生物的发育至关重要，黏菌提供了一个模型系统，利用遗传方法确定细胞间通讯的生物学作用和分子机制。CsgA基因产物c信号是一种新型的发育计时器，其胞外浓度在黄粘球菌子实体形成过程中稳步上升，并以更高的浓度诱导发育途径的连续阶段。这些研究有望揭示c信号如何被发育中的细胞感知以表达涟漪、聚集和孢子形成基因。CsgA受体基因的鉴定和克隆将使用以下四种方法中的一种：剂量抑制、构建含有不同黏菌种类成分的异源信号系统、纯化受体蛋白后的反向遗传学或分子识别。将对假定的受体基因进行测序，并检查与已知受体的氨基酸同源性。染色体野生型等位基因将被一个中断的等位基因取代，以确定受体零突变是否与csgA零突变在同一点阻断发育。放射性标记的CsgA将用于结合研究，以确定不同发展阶段的相关常数和受体数量。CsgA受体的细胞位置将通过胶体金电子显微镜确定。将继续对socA （CsgA的抑制基因）和socB抑制基因座进行遗传分析，以了解野生型抑制基因在正常发育中的作用以及突变等位基因抑制CsgA突变的机制。这项研究允许使用细菌分子遗传学技术来回答关于细胞如何分化的基本问题。Shimkets博士正在研究一种细胞间的通讯，这种通讯直到目前为止只在高等生物中被发现。＊＊＊＊

9304083 Shimkets Cell-cell interactions are essential for the development of many organisms and the myxobacteria provide a model system with which to use genetic approaches to determine the biological roles and molecular mechanisms of intercellular communication. The CsgA gene product, the C-signal, is a novel type of developmental timer whose extracellular concentration rises steadily during fruiting body formation of the myxobacterium Myxococcus xanthus and induces successive stages of the developmental pathway at successively higher concentrations. These studies are expected to reveal how the C-signal is perceived by developing cells to express rippling, aggregation, and sporulation genes. The CsgA receptor gene will be identified and cloned using one of four approaches : dosage suppression, construction of heterologous signaling systems containing components from different myxobacterial species, reverse genetics following purification of the receptor protein, or molecular recognition. Putative receptor genes will be sequenced and examined for amino acid homology with known receptors. The chromosomal wild type allele will be replaced with a disrupted allele to determine if a receptor null mutation blocks development at the same point as a csgA null mutant. Radiolabeled CsgA will be used in binding studies to determine the associate constant and receptor number during different stages of development. The cellular location of the CsgA receptor will be determined by colloidal gold electron microscopy. Genetic analysis of the socA (for suppressor of CsgA), and socB suppressor loci will continue, to learn the normal developmental roles of the wild type suppressor genes as well as the mechanisms by which the mutant alleles suppress csgA mutations. %%% This research allows the techniques of bacterial molecular genetics to be used to answer fundamental questions about how cell differentiate. Dr. Shimkets is studying a type of cell- to cell communication that up until know was only known in higher organisms. ****