C-signal Perception in Myxococcus Xanthus

9304083细胞与细胞之间的相互作用对于许多生物的发育是必不可少的，粘细菌提供了一个模型系统，利用该系统可以使用遗传学方法来确定细胞间通信的生物学作用和分子机制。CsgA基因产物C-Signal是一种新型的发育调节剂，其胞外浓度在粘液黄色粘菌子实体形成过程中稳步上升，并在较高浓度下诱导发育途径的连续阶段。这些研究有望揭示C-信号是如何被发育中的细胞感知的，以表达涟漪、聚集和产孢子基因。CsgA受体基因的鉴定和克隆将采用四种方法之一：剂量抑制、构建包含不同粘液细菌物种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。推测的受体基因将被测序，并检查与已知受体的氨基酸同源性。染色体上的野生型等位基因将被中断的等位基因取代，以确定受体零突变是否会阻碍与CsgA零突变相同的点的发育。放射性标记的CsgA将用于结合研究，以确定不同发育阶段的相关常数和受体数量。CsgA受体的细胞定位将通过胶体金电子显微镜来确定。对SOCA(CsgA抑制基因)和SOCB抑制基因的遗传分析将继续进行，以了解野生型抑制基因的正常发育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，直到目前为止，这种通讯只在高等生物中为人所知。****

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. ****