Transcription factor Yin-Yang 2 alters neuronal outgrowth in vitro.

The Yin-Yang 2 (YY2) protein is the most recently described member of the family of YY transcription factors. Despite its high structural and functional homology with the well-characterized YY1, less is known about its role in biological processes. In previous studies, we have found differential yy2 mRNA expression levels in various cell types of the murine brain. To investigate the functional implication of yy2 in neurons, we have examined the influence of altered cellular yy2 concentrations during neuronal differentiation. Our results indicate that both the up- and down-regulation of yy2 significantly impairs the outgrowth of the major neurite of primary hippocampal neurons and the numbers of neuronal processes in proximate extensions. Moreover, enhanced expression of wild-type yy2 results in increased cell death, whereas elevated expression levels of a yy2 DNA-binding mutant have no effect on cell viability. Therefore, stringent regulation of the cellular yy2 content might be needed to ensure proper neurite outgrowth and cell vitality.