Synaptic Targeting in Hard-Wired Neural Circuits

神经突触的精确连接是由什么样的分子指令来实现的？ 只有对生存最关键的行为才与基因组紧密相连。 像呼吸和原始反射这样的行为是无法习得的，因此控制它们的神经回路必须使用精确的分子指令预先指定。 目前，我们对硬连线神经回路是如何形成的知之甚少。 我的长期目标是确定每一个必要的分子，并足以连接一个硬连线的神经回路。我的总体假设是，只需要少量（< 50）不同的细胞表面分子就可以产生独特的硬连线突触靶向模式。 我的实验方法将使用单个识别神经元的转录组测序，并结合参与突触靶向的细胞表面受体的系统表征。 具体来说，我们将分离出单一的神经元与刻板的硬连线突触连接和序列的RNA基因产物。 通过比较来自同一动物的不同连接的神经元对之间的基因表达模式，我们将确定预先确定其突触连接的分子。 为了了解这些分子是如何被这些神经元使用的，我们将从功能上描述创建神经元精确布线模式所需的所有细胞表面受体。 最后，我们将在另一个神经元中表达这些分子，以重新连接其突触连接，改变其功能，从而改变动物的感知和行为。 这项研究将是第一次展示精确的遗传指令，可以完全硬连线和错误连线神经回路。 通过了解细胞表面的关键分子如何产生错误的突触连接，我们可以研究纠正它的方法。我们提出的工作是理解先天行为背后的分子指令的重要的第一步。

What are the molecular instructions to hard-wire precise synaptic connections?  Only the most critical behaviours for survival are hard-wired into the genome.   Behaviours such as breathing and primitive reflexes are not learned, and so the neural circuitry that controls them must be pre-specified using precise molecular instructions.  Currently, we know very little about how hard-wired neural circuits are formed.  My long term goal is to identify every molecule necessary and sufficient to wire up a hard-wired neural circuit. My overall hypothesis is that only a small number (< 50) of different cell-surface molecules are required to generate a distinct hard-wired synaptic targeting pattern.   My experimental approach will use transcriptome sequencing of single identified neurons in concert with a systematic characterization of cell-surface receptors involved in synaptic targeting.      Specifically, we will isolate single identified neurons with stereotyped hard-wired synaptic connectivities and sequence their RNA gene products.   By comparing the gene expression patterns between pairs of differentially-connected neurons from the same animal, we will identify the molecules that pre-determine their synaptic connectivities.   To understand how these molecules are used by these neurons, we will functionally characterize all cell-surface receptors required to create the neuron's precise wiring pattern.   Finally, we will express these molecules in another neuron to re-wire its synaptic connections, alter its function, and thus alter the animal's perception and behaviour.   This research will be the first demonstration of the exact genetic instructions that can completely hardwire and mis-wire a neural circuit.   By understanding how key molecules at the cell surface can produce erroneous synaptic connections, we can investigate ways to correct it.  Our proposed work is an important first step towards understanding the molecular instructions underlying innate behaviours.