Figure 3.

Lbx1 expression depends on Pax3. (A, B, E, F) Whole mount in situ hybridisation with an Lbx1 probe of control (A, E), Pax3^Pax3-En/+ partial loss of function (B) and Pax3^PAX3-FKHR/+ gain of function embryos (F) at E9.25 (A, B) and E10.5 (E, F), showing down-regulation of Lbx1 transcripts when Pax3 activity is reduced, and some up-regulation of its expression in the presence of PAX3-FKHR in somites. In the lower panels (C, D) X-gal staining of β-galactosidase from the IresnlacZ reporter in Pax3^IresnlacZ/+ (C) or Pax3^{Pax3-En-IresnlacZ/+} (D) shows the extent of the somites, notably the hypaxial domain.