Mauthner Cell Development in the Zebrafish Mutant

神经细胞数量的精确调控是神经系统正常工作的必要条件。在离散细胞群中表现出多余神经元的突变体对于研究神经元产生的遗传控制是有用的。此外，具有额外神经元的突变体为分析神经回路形成的可塑性提供了机会。我们已经在斑马鱼身上分离出一种突变，松散的末端（爱），导致多余的毛纳细胞。野生型斑马鱼后脑菱形体4中线两侧各有一对毛纳细胞。相比之下，爱的突变体在中线两侧平均有5个毛纳细胞。通过克隆爱的基因，我们将揭示导致这种缺陷的分子的身份。为此，我们将把爱放在斑马鱼基因组的遗传图谱上，以确定它是否与已知基因相对应。如果没有发现已知的基因，我们将对爱进行位置克隆。我们还将利用爱情增加毛纳细胞的事实来探究这些额外细胞的存在如何影响逃逸反应回路的形成。逃逸反应回路包括感觉输入到毛特纳细胞和毛特纳细胞输入到初级运动神经元。我们将描述爱突变体的突触前和突触后接触，以阐明由于额外的毛特纳细胞的存在，电路是如何组织不同的。

The precise regulation of neuronal cell number is essential for proper nervous system function. Mutants exhibiting excess neurons in discreet cell populations are useful for studying the genetic control of neuronal production. Moreover, mutants with extra neurons offer an opportunity to analyze the plasticity of neural circuit formation. We have isolated a mutation in zebrafish, loose ends (loe), that results in supernumerary Mauthner cells. Wild-type zebrafish have a bilateral pair of Mauthner cells on either side of the midline in hindbrain rhombomere 4. In contrast, loe mutants have on average five Mauthner cells on either side of the midline. By cloning the loe gene, we will reveal the identity of the molecule causing this defect. To this end, we will place loe on the genetic map of the zebrafish genome to determine whether it corresponds to a known gene. If a known gene is not revealed, we will positionally clone loe. We will also exploit the fact that loe has an increase in Mauthner cells to ask how the presence of these extra cells affects the formation of the escape response circuit. The escape response circuit involves sensory input onto Mauthner cells and Mauthner cell input onto primary motoneurons. We will characterize both the pre- and post-synaptic contacts in loe mutants to elucidate and how the circuit is organized differently due to the presence of extra Mauthner cells.