09-P039 vHNF1 functions in distinct regulatory circuits to control ureteric bud morphogenesis and early nephrogenesis

and differentiation into lens fiber cells as well as for cell survival. Surprisingly, Pax6 loss did not appear to affect the expression of crystallin genes at later developmental stages. We show that Pax6 regulates the Wnt antagonist Sfrp2 in the lens, and that Sox2 expression is upregulated in the Pax6-deficient lenses. Our finding revealed that the failed differentiation following loss of Pax6 is independent of Sox2 or Wnt/b-catenin activity. These findings reveal a pivotal role for Pax6 in the initiation of the lens fiber differentiation program in mammals.