Left-Right Asymmetry of the Developing Diencephalon

描述（由申请人提供）：人们早就知道，人类大脑的左右半球在解剖学和功能上是不同的，但皮层不对称是如何产生的，或者在神经系统疾病中是如何受到干扰的，人们知之甚少。相比之下，在揭示内脏器官不对称发育的分子遗传基础方面取得了重大进展。在调节内脏不对称中起作用的节点信号通路的成分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。缺乏不对称基因表达的鱼后来显示成熟松果体茎的左右定位随机化。低等脊椎动物间脑的其他不对称包括左侧顶骨旁器官和左侧和右侧束核之间的形态差异。这项提议的总体目标是确定斑马鱼大脑中间脑不对称是如何产生的。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，松果体旁果皮来源于松果体。命运图将直接解决顶骨旁的细胞起源。顶骨旁似乎影响相邻背链的转录，造成链基因表达的左右差异。在AIM II中，一个合作项目将导致在间脑幼虫中发现新的分子不对称性。顶骨旁调节小梁偏侧的假设将通过检测左右模式改变的突变体中小梁标记物的表达来验证，或者在选择性切除顶骨旁后。在AIM III中，重点基因筛选将确定影响间脑不对称形成的新的enu诱导突变。在试点筛选中分离的两个突变失去了habenular不对称性，将在AIM IV中进一步表征。总之，拟议的实验将提供对脊椎动物前脑左右专门化的遗传机制的更好理解。

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.