COOPERATIVE FUNCTION OF POU PROTEINS AND SOX PROTEINS IN GLIAL-CELLS

Glial cells of the oligodendrocyte lineage express several highly rela ted POU proteins including Tst-1/Oct6/ SCIP and Brn-1. Tst-1/Oct6/SCIP , but not Brn-1 efficiently cooperated with Sox10, the only SRY box pr otein so far identified in oligodendrocytes, Here we show that, in add ition to Sox10, cells of the oligodendrocyte lineage contain significa nt amounts of the related SRY box proteins Sox4 and Sox11. During deve lopment, Sox11 was strongly expressed in the central nervous system. I t was first detected in neural precursors throughout the neuroepitheli um, During later stages of neural development, Sox11 was additionally expressed in areas of the brain in which neurons undergo differentiati on. In agreement with its expression in neural precursors, Sox11 level s in cells of the oligodendrocyte lineage were high in precursors and down-regulated during terminal differentiation. Outside the nervous sy stem, expression of Sox11 was also detected in the developing limbs, f ace, and kidneys, Structure function analysis revealed that Sox11 has a strong intrinsic transactivation capacity which is mediated by a tra nsactivation domain in its carboxyl-terminal part. In addition, Sox11 efficiently synergized with Brn-1. Synergy was dependent on binding of both proteins to adjacent DNA elements, and required the presence of the respective transactivation domain in each protein. Our data sugges t the existence of a specific code in which POU proteins require speci fic Sox proteins to exhibit cooperative effects in glial cells.