Left-Right Asymmetry of the Developing Diencephalon

描述（由申请人提供）：长期以来，人们已经知道人脑的左半球和右半球在解剖学上和功能上是不同的，但是对皮质不对称是如何产生的，或者在神经系统疾病中是如何扰动的，却知之甚少。相反，在揭示内脏器官不对称发育的分子遗传学基础方面取得了重大进展。Nodal信号通路的组分，其在调节内脏不对称性中起作用，也在发育中的斑马鱼大脑的左侧特异性表达。这种短暂的左侧基因表达定位于松果体器官原基。 缺乏不对称基因表达的鱼，后来显示出一个随机化的左右定位的柄成熟的松果体。低等脊椎动物间脑的其他不对称包括左侧的松果体旁器官和左侧和右侧缰核之间的形态差异。这项建议的总体目标是确定如何间脑不对称出现在斑马鱼的大脑。在AIM I中，将使用转基因斑马鱼实时监测松果体发育。初步资料表明，松果体旁起源于松果体原基。命运映射将直接解决会阴旁的细胞起源。松果体旁似乎影响邻近背侧缰核的转录，从而在缰核基因表达中产生左右差异。在AIM II中，一个合作实验室项目将导致在幼虫间脑中发现新的分子不对称性。将通过检查左右图案改变的突变体中的缰标记物的表达，或选择性切除松果体旁，来检验松果体旁调节缰的偏侧性的假设。在AIM III中，一个集中的遗传筛选将确定新的ENU诱导的突变，影响间脑不对称的形成。在中试筛选中分离的两个突变丧失了缰不对称性，将在AIM IV中进一步表征。总之，拟议的实验将提供一个更好的理解的遗传机制，脊椎动物前脑的左右专业化。

DESCRIPTION (provided by applicant): It has long been known that the left and right hemispheres of the human brain are anatomically and functionally different, yet how cortical asymmetries are generated, or perturbed in neurological disorders, is poorly understood. In contrast, significant progress has been made towards unraveling the molecular genetic basis for asymmetric development of visceral organs. Components of the Nodal signaling pathway, that function in regulating visceral asymmetry, are also specifically expressed on the left side of the developing zebrafish brain. This transient, left-sided gene expression localizes to the pineal organ anlage. Fish lacking asymmetric gene expression later show a randomization in the left-right positioning of the stalk of the mature pineal gland. Other asymmetries in the diencephalon of lower vertebrates include the left-sided parapineal organ and morphological differences between the left and fight habenular nuclei. The overall goal of this proposal is to determine how diencephalic asymmetries arise in the zebra fish brain. In AIM I, pineal development will be monitored real-time using transgenic zebrafish. Preliminary data suggest that the parapineal is derived from the pineal anlage. Fate mapping will address the cellular origin of the parapineal directly. The parapineal appears to influence transcription in the adjacent dorsal habenula, creating a left-right difference in habenular gene expression. In AIM II, a collaboratory project will lead to the discovery of new molecular asymmetries in the larval diencephalon. The hypothesis that the parapineal regulates the laterality of the habenulae will be tested by examining expression of habenular markers in mutants with altered left-right patterning, or following selective ablation of the parapineal. In AIM III, a focused genetic screen will identify new ENU-induced mutations that affect the formation of diencephalic asymmetries. Two mutations isolated in a pilot screen that lose habenular asymmetry will be characterized further in AIM IV. Together, the proposed experiments will provide a greater understanding of the genetic mechanisms that underlie left-right specialization of the vertebrate forebrain.