Suppression of Sox6 in P19 cells leads to failure of neuronal differentiation by retinoic acid and induces retinoic acid-dependent apoptosis.

The Sox6 gene is a member of the Sox gene family, which encodes transcription factors, and previous studies have suggested that it plays an important role in the development of the central nervous system. Aggregation of embryonic carcinoma P19 cells with retinoic acid (RA) results in the development of neurons, glia, and fibroblast-like cells. Sox6 mRNA increases rapidly in P19 cells during RA induction and then decreases during differentiation into neuronal cells. To investigate whether Sox6 expression is essential for neuronal differentiation, we established Sox6-suppressed P19 (P19[anti-Sox6]) cells by transfection of antisense-Sox6 cDNA. Most of the P19[anti-Sox6] cells showed no neurites and were not stained by the anti-MAP 2 antibody, while the suppression of Sox6 expression nearly totally blocked neuronal differentiation in P19 cells. Further, Sox6 suppression caused RA-dependent apoptosis by P19[anti-Sox6] cells: RA-treated P19[anti-Sox6] cells showed chromatin condensation, DNA fragmentation, and an increase in caspase-3-like activity. Thus, Sox6 is considered essential for neuronal differentiation and may play an important role in the early stages of neuronal differentiation or apoptosis.