Lineage & Development of the Midbrain & Hindbrain

描述（由申请人提供）：脊椎动物的脑来源于吻侧神经管，其首先表现为一系列称为神经节的形态学收缩，其描绘了脑的主要亚部。神经节的组织特异性模式导致成人高度专业化的解剖和功能单位。完成这些显著的发育事件的一种方法是使用图案化的组合机制，其涉及谱系限制边界的形成，伴随着指示特定位置信息和邻近组织的命运的“组织者”的出现。这一机制已被证明是模式果蝇翅膀的成虫盘以及小鸡和小鼠的肢体，但尚未大脑。中脑（mes）和后脑（met）彼此相对，是明显不同的形态结构。在早期发展的MES，表达Otx 2和Wnt 1，和MET，表达Gbx 2和Fgf 8，并置在一个明确的收缩沿前后轴定义为峡部。差异表达的MES/MET基因指定区域身份，并可能将两个群体的细胞分离到假定的隔室中。有趣的是，峡部已被证明是一个组织者使用经典的移植研究，并出现通过一个复杂的遗传级联启动的形态Fgf 8介导的教学活动。分泌因子Wnt 1可能在维持MES/MET边界完整性方面发挥作用，但该机制尚未得到深入研究。该提案将调查MES/MET并置是否是谱系限制边界，并解决Wnt 1在MES/MET边界形成或维持中的作用。我建议解决这些问题，通过遗传标记和命运映射Wnt 1表达细胞的MES和Gbx 2表达细胞的MET使用两个诱导型Cre/loxP系统。为了解决Wnt 1是否在建立和/或维持MES/MET界面中发挥作用，我将产生一个条件Wnt 1突变等位基因，并评估在不同发育阶段Wnt 1功能丧失的表型后果。

DESCRIPTION (provided by applicant): The vertebrate brain is derived from the rostral neural tube, which first appears as a series of morphological constrictions termed neuromeres that delineate the major subdivisions of the brain. Tissue specific patterning of neuromeres results in highly specialized anatomical and functional units in the adult. One method to accomplish these remarkable developmental events is with a combinatorial mechanism of patterning that involves the formation of a lineage restriction boundary concomitant with the emergence of an 'organizer' that instructs specific positional information and fates on adjacent tissue. This mechanism has been shown to pattern Drosophila wing imaginal disks as well as chick and mouse limb but not as of yet brain. The mesencephalon (mes) and metencephalon (met) are opposed to each other and are clearly distinct morphological structures. During early development the mes, which expresses Otx2 and Wnt1, and the met, which expresses Gbx2 and Fgf8, are juxtaposed at a well-defined constriction along the anteroposterior axis defined as the isthmus. The differentially expressed mes/met genes specify regional identity and potentially segregate two populations of cells into presumptive compartments. Interestingly, the isthmus has been shown to be an organizer using classical transplantation studies and appears to mediate instructional events through a complex genetic cascade initiated by the morphogen Fgf8. The secreted factor Wnt1 may play a role in maintaining mes/met boundary integrity, though this mechanism has not been closely studied. This proposal will investigate whether the mes/met juxtaposition is a lineage restriction boundary and addresses the role of Wnt1 in mes/met boundary formation or maintenance. I propose to address these questions by genetically marking and fate mapping Wnt1 expressing cells of the mes and Gbx2-expressing cells of the met using two inducible Cre/loxP systems. To address whether Wnt1 plays a role in establishing and/or maintaining the mes/met interface, I will generate a conditional Wnt1 mutant allele and assess the phenotypic consequences of loss of Wnt1 function at different developmental stages.