Temporal change in mKIAA gene expression during the early stage of retinoic acid-induced neurite outgrowth.

mKIAA genes are mouse counterparts of human KIAA genes, which were isolated in our cDNA project and were functionally unknown at the time they were sequenced. Because KIAA/mKIAA genes were isolated mainly from cDNA libraries derived from brain tissues, they are thought to be important for the organization and function of the brain. To investigate the participation of mKIAA genes in neuronal phenomena, we analyzed retinoic acid-induced neurite outgrowth using an mKIAA oligonucleotide microarray. Focusing on the early stage of this outgrowth phenomenon, we analyzed temporal gene expression changes 1-24 h after treatment with retinoic acid and found several change patterns in 38 mKIAA genes. Among them, six were upregulated at 3 h and subsequently returned to the steady state. Supposing that these genes had important roles, we performed semi-quantitative RT-PCR analysis and confirmed the existence of temporal expression patterns in two genes (mKIAA0182 and mKIAA1039). Further computational analysis of the 38 genes enabled us to find the cellular pathway associated with 6 of them with high confidence. These results indicate that some mKIAA genes are apparently relevant to retinoic acid-induced neurite outgrowth.