前脑正常神经网络是机体执行感觉处理、运动控制、认知等高级功能的关键，调控其形成的功能基因在动物模型中陆续被发现，但它们在人胚脑发育中的作用依然不明确。通过基因敲除，我们发现Celsr3和Fzd3通过影响前脑介导细胞形成先驱“轴突桥梁”，从而导向投射神经元轴突生长、建立正常的靶向联系。为此，我们提出：CELSR3和FZD3依赖的介导细胞在人胚前脑神经联系建立过程是必需的。我们将收集6-9周流产胚胎，比较分析前脑神经元轴突投射早期形成过程经历不同“过渡区”的细胞标记物图谱、CELSR3和FZD3时空表达模式和亚细胞定位、投射神经元轴突与介导细胞的关系、介导细胞敲减CELSR3和FZD3对神经元轴突生长导向的影响、人和小鼠介导细胞生物学特性异同等。预期结果将阐明CELSR3和FZD3依赖的介导细胞调控人前脑神经网络形成的作用及其与小鼠的异同，以期望填补人胚前脑神经联系形成分子调控机制方面的空白。

The complex neural circuits in forebrain are critical for sensory processing, motor control and cognition. Using animal, mostly murine models, several genes are identified and involved in establishing neural forebrain networks. However, their role during human brain development remain elusive. Using knockout mouse models, we previously demonstrated that Celsr3 and Fzd3 play an indispensible role to regulate forming a pioneer "sling" via their expression in guidepost cells, which then steer forebrain axonal projections .These facts led us to hypothesize that CELSR3 and FZD3expressing guidepost cells are also important for establishing neural circuits in the human forebrain. To test this, we will collect WPC (post conceptual weeks) 6-9 abortion human fetuses to: i) Study the expression patterns of putative markers in intermediate targets critical for early axonal projections; ii) Analyze the distribution of CELSR3 and FZD3 mRNAs by using in situ hybridization and the sub-cellular distribution; iii) Assess their function in regulating axonal projections by knocking down their expression in guidepost cells; and iv) Compare transcriptional profiles of guidepost cells between human and mouse using FACS sorting and RNASeq. We predict that our results will shed light on the role of CELSR3 and FZD3 dependent guidepost cells in the formation of human forebrain networks and point to significant differences of gene expression between human and mouse guidepost cells. This should contribute to our basic understanding of molecular mechanisms that govern human forebrain development.