(A–O) Analysis of genes common to brachial and thoracic levels that are differentially expressed between control and PbxMNΔ mice. Panels show in situ hybridization of indicated genes in spinal cord sections of e12.5 mice. All sections are brachial except J and K, which are thoracic. Sections are derived from embryos which are Pbx1 flox/flox; Pbx3-/flox; Olig2::Cre+. (A) Mecom is downregulated in ventromedial neurons but preserved in dorsal interneurons. (B–K) Expression of Dkk3, Ebf2, Ldb2, Tmtc1, Unc5c, Hlf, Lifr, Ezr, Creb5, and Cyp26b1 is markedly decreased in MNs of Pbx mutants. (L) Megf11 is downregulated in LMC neurons but maintained in a subset of ventromedial MNs. (M) Arhgap36 expression is markedly reduced in PbxMNΔ mice. (N,O) Cpne5 and Cdkn1a are upregulated in Pbx mutants. See also Figure S6.