REGULATION OF HETEROCYST DIFFERENTIATION BY HETR/PATA

提出的工作使用鱼腥藻7120中的异形胞形成作为识别和表征基因的模型系统，从而确定生物体用于确定细胞命运的分子机制。 阐明细胞分化的控制对于理解细胞生长控制的丧失是至关重要的，细胞生长控制的丧失导致细胞分化状态的扰动，这可能导致人类的疾病状况，如肿瘤细胞生长和癌症。鱼腥藻7120的丝状体易于培养，具有短的世代时间，是可遗传操纵的，并且可以被诱导形成两种不同细胞类型的可预测模式。最近，已经分离出几个可以扭曲这种模式的基因。 特别是两个基因，hetR和patA似乎控制异形胞沿着营养细胞细丝的分化和图案。 hetR的额外拷贝导致营养细胞不适当地过度分化为异形胞，而hetR的缺乏阻止异形胞的形成。HetR和PatA的分子功能是未知的，因为它们的生产控制。 采用两种新的遗传选择方法分别分离HetR/PatA上下游产物的基因，并利用生物化学方法阐明HetR/PatA的功能及其相互关系。 通过解剖的hetR/patA调节级联，我们希望阐明一个控制电路，这将是有益的问题，在细菌和多细胞生物体的细胞分化和疾病，可能会导致在控制细胞命运决定的干扰。

The work proposed uses heterocyst formation in Anabaena 7120 as a model system for the identification and characterization of the genes and, consequently, the molecular mechanisms that organisms use to determine cell fate. Elucidation of the controls of cellular differentiation is critical to understanding the loss of cellular growth control that causes a perturbation of the differentiated state of the cell, which can lead to a diseased condition such as neoplastic cell growth and cancer in humans. Filaments of Anabaena 7120 are easily cultured, have a short generation time, are genetically manipulable, and can be induced to form a predictable pattern of two distinct cell types. Recently, several genes have been isolated that can distort this pattern. Two genes in particular, hetR and patA appear to control the differentiation and patterning of heterocysts along a filament of vegetative cells. Extra copies of hetR cause innappropriate excessive differentiation of vegetative cells to heterocysts, whereas lack of hetR prevents heterocyst formation. The molecular functions of HetR and PatA are unknown, as is control of their production. Two novel genetic selections will be used to separately isolate genes whose products act upstream and downstream of HetR/PatA, and biochemical methods will be used to elucidate the functions and the relationship between HetR and PatA. By dissecting the hetR/patA regulatory cascade, we hope to elucidate a control circuit that will be instructive for questions of cellular differentiation in both bacteria and multicellular organisms and the diseases that can result from a disturbance in the control of cell fate determination.