 morphogenesis during development is fundamental to the differentiation of several cell types . as neurite outgrowth marks neuritogenesis , formation of filopodia precede the formation of dendrites and axons . 
 while the structure of filopodia is well - known , the initiation of filopodia during neurite outgrowth is not clear . 
 sh2b1 is known to promote neurite outgrowth of pc12 cells , hippocampal and cortical neurons . as a signaling adaptor protein , 
 sh2b1 interacts with several neurotrophin receptors , and regulates signaling as well as gene expression . 
 our recent findings suggest that sh2b1 can be recruited to the plasma membrane and f - actin fractions by irsp53 . 
 irsp53 bends plasma membrane and facilitates actin bundling to set the stage for filopodium formation . 
 we further demonstrate that sh2b1-irsp53 complexes enhance the formation of filopodia , dendrites and dendritic branches of hippocampal and cortical neurons . 
 while the molecular mechanism underlying filopodium initiation is not clear , we propose that sh2b1-neurotrophin interacting sites may mark the putative sites of filopodium initiation . 
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