Expression of Pbx1b during mammalian organogenesis

Mammalian Pbx genes (Pbx1-3) encode a family of TALE homeodomain proteins t hat function as transcriptional regulators in numerous cell types (Curr. Op in. Genet. Dev. 8 (1998) 423). The present study highlights distinctive fea tures of Pbx1b expression during mouse embryonic development as a framework to understand its biological functions. Immunohistochemical analyses demon strate extensive expression of Pbx1b throughout post-implantation developme nt, with highest levels observed during early to mid-gestation. Its initial distribution is predominantly associated with condensing mesoderm, however , Pbx1b displays dynamic expression patterns in derivatives of all principa l germ layers. In particular, Pbx1b localizes to sites of mesenchymal-epith elial interactions during periods of active morphogenesis in tissues such a s the lung, kidney, tooth buds and vibrissae follicles. Furthermore, BrdU l abeling studies reveal that Pbx1b expression domains partially overlap with regions of cellular proliferation. Taken together, these data suggest that Pbx1b contributes to multiple cellular processes during embryogenesis, whi ch may include roles in cell-autonomous regulation as well as in the mediat ion of tissue interactions. (C) 2001 Elsevier Science Ireland Ltd. All righ ts reserved.