To investigate the molecular pathways affected by a loss of Cdkl5 function in zebrafish, gene expression analysis of several neuronal associated genes known to be related to CDKL5 or Rett syndrome was performed by qPCR in WT, cdkl5+/− and cdkl5−/− mutant embryos at 5 dpf. This evidence concerns the gene CDKL5 and atypical Rett syndrome.