The function of microRNAs (miRNAs) is translational repression or mRNA cleavage of target genes by binding to 3'-UTRs of target mRNA. In this study, we investigated the functions and the target genes of microRNA124a (miR124a), and imaged the miR124a-mediated repression of chromosome 14 open reading frame24 (c14orf24, unknown function) during neurogenesis, using noninvasive luciferase systems. The expression and functions of miR124a were investigated in neuronal differentiation of P19 cells (P19 is a mouse embryonic carcinoma cell line) by qRT-PCR and RT-PCR. The predicted target genes of miR124a were found by searching a bioinformatics database and confirmed by RT-PCR analysis. Remarkable repression of c14orf24 by miR124a was detected during neurogenesis, and was imaged using in vitro and in vivo luciferase systems. The expression of miR124a was highly upregulated during neuronal differentiation. Overexpression of miR124a in P19 cells resulted in a preneuronal gene expression pattern. MicroRNA124a-mediated repression of c14orf24 was successfully monitored during neuronal differentiation. Also, c14orf24 showed molecular biological characteristics as follows: dominant expression in the cytoplasm; a high level of expression in proliferating cells; and gradually decreased expression during neurogenesis. Our noninvasive luciferease system was used for monitoring the functions of miRNAs, to provide imaging information on miRNA-related neurogenesis and the miRNA-regulated molecular network in cellular metabolism and diseases.