In the present study, we sought to delineate the pathogenetic basis of the macrothrombocytopenia observed in Takenouchi-Kosaki syndrome and performed a functional analysis of p.Tyr64Cys in cdc-42 using CRISPR/Cas9-mediated gene editing and Caenorhabditis elegans. Here, CDC42 is linked to Macrothrombocytopenia.