Fig. 1. Unaltered distribution of Lhx2 expression and lack of OR expression in OE of Lhx2 ^-/- embryos. (A-C) Double-immunohistochemical analysis of Lhx2 and TubIII expression in OE of E15.5 mouse embryo is shown. (A) Nuclear Lhx2 immunoreactivity in the neuronal cell layer (N) and in a fraction of cells in the basal progenitor cell layer (P). No Lhx2-positive cells are present in the sustentacular cell layer (S) and the lamina propria (l.p.). (B) TubIII immunoreactivity in neuronal soma and neuronal processes. (C) Images in A and B combined, showing that Lhx2 and TubIII are co-expressed in OSNs. A limited number of TubIII-negative Lhx2-positive cells are present in the progenitor cell layer (arrows in C). (D-I) In-situ hybridization analyses of serial OE sections from control (left panel) and Lhx2^-/- embryos (right panel) with Dig-labeled cRNA probes that hybridize to Lhx2 and mutated Lhx2 transcripts (Lhx2^m) (D,E), and OR genes (K21, L45, M50 and A16) (F-I). (J) Autoradiographs of in-situ hybridization analyses with a ³⁵S-labeled cRNA probe specific to the OR gene K20. Scattered cells expressing the different OR genes are present in control mice. The zones in which each the OR gene is expressed is indicated, i.e. dorsomedial (dm), the middle (m) or the ventrolateral (vl) zone. In Lhx2 ^-/- mice, there are no cells expressing ORs in any epithelial region (representative results are shown).