SRY-box containing gene 11 (Sox11) transcription factor is required for neuron survival and neurite growth

The transcription factor Sox11 is expressed at high levels in developing sensory neurons and injured adult neurons but little is known about its transcriptional targets and function. In this study we examined the role of Sox11 using Neuro2a neuroblastoma cells and cultured mouse dorsal root ganglia (DRG) neurons. Results show Sox11 has an essential role in regulation of neuron survival and neurite outgrowth in Neuro2a cells and primary sensory neurons. Neuro2a cells increase expression of Sox11 as they differentiate in culture. Following addition of 20 microM retinoic acid (RA), a stimulus for differentiation that enhances neurite growth and differentiation, Sox11 level rises. RNAi-mediated knockdown of Sox11 in RA-differentiated Neuro2a cells caused a decrease in neurite growth and an increase in the percent of apoptotic cells. RNA expression analysis showed that Sox11 knockdown modulated the level of mRNAs encoding several genes related to cell survival and death. Further validation in the Neuro2a model showed Sox11 knockdown increased expression of the pro-apoptotic gene BNIP3 (BclII interacting protein 1 NIP3) and decreased expression of the anti-apoptotic gene TANK (TNF receptor-associated factor family member-associated NFkappaB activator). Cultured primary DRG neurons also express Sox11 and treatment with Sox11 small interfering RNA (siRNA) caused a significant decrease in neurite growth and branching and a decrease in mRNA encoding actin-related protein complex 3 (Arpc3), an actin organizing protein that may be involved in axon growth. The percent of apoptotic neurons also increased in cultures of DRG neurons treated with Sox11 siRNA. Similar to Neuro2a cells, a decrease in TANK gene expression occurred, suggesting at least some overlap in Sox11 transcriptional targets in Neuro2a and DRG neurons. These data are consistent with a central role for Sox11 in regulating events that promote neurite growth and neuron survival.