Comparative spatiotemporal analysis of Hox gene expression in early stages of intermediate mesoderm formation

Background : Hox genes are key players in AP patterning of the vertebrate body plan and are necessary for organogenesis. Several studies provide evidence for the role Hox genes play during kidney development and especially regarding metanephros initiation and formation. However, the role Hox genes play during early stages of kidney development is largely unknown. A recent study in our lab revealed the role Hoxb4 plays in conferring the competence of intermediate mesodermal cells to respond to kidney inductive signals and express early kidney regulators. Results : As a first step in understanding the role Hox genes play in setting the formation of the pronephros morphogenetic field and the expression of early regulators of kidney development, we studied in detail the expression pattern of 10 Hox genes in relation to the 6th somite axial level, the anterior sharp border of the kidney field. Despite the idea of spatial co‐linearity as exemplified in the Hox gene expression pattern in late developmental stages, a very dynamic spatio‐temporal expression of these genes was found in early stages. Conclusions : Since mesodermal patterning occurs at gastrula stages, the relevance of a “Hox code” at early stages is questioned in this study. Developmental Dynamics 241:1637–1649, 2012. © 2012 Wiley Periodicals, Inc.