Figure 4.

Olfactory Precursor Cells of Foxg1-Cre^+/−; Dicer^loxP/loxP Mutants Display Normal Specification but Do Not Fully Differentiate

(A) Number of differentiating and postmitotic cells in olfactory placodes was quantified by neuroD (mean ± SEM, WT 41.71 ± 2.10, n = 5; mutant 34.33 ± 1.60, n = 4, p < 0.01, Student's t test) and Hu-C/D (mean ± SEM, WT 45.82 ± 2.57, n = 3; mutant 31.32 ± 2.09, n = 3, p < 0.01, Student's t test) expression, respectively, in Foxg1-Cre^+/−; Dicer^loxP/loxP and control E10.5 embryos. Only moderate reduction in the number of precursor cells and postmitotic neurons is observed in the mutant at this stage. Cell counts were derived from sections spanning the entire nasal pit of several animals per genotype and normalized to 0.03 mm²; the average MOE in a given section.

(B) In situ hybridization on E13.5 olfactory epithelium fails to detect OMP expression in Foxg1-Cre^+/−; Dicer^loxP/loxP olfactory placodes, suggesting the failure of olfactory terminal differentiation in the absence of Dicer function.