Downstream of homeotic genes: in the heart of Hox function.

A functional organ is constituted of diverse cell types. Each one occupies a distinct position and is associated to specific morphological and physiological functions. The identification of the genetic programs controlling these elaborated and highly precise features of organogenesis is crucial to understand how a mature organ works under normal conditions, and how pathologies can develop. Recently, a number of studies have reported a critical role for Hox genes in one example of organogenesis: cardiogenesis in Drosophila. Beyond the interest in understanding the molecular basis of functional cardiogenesis, this system might provide a model for proposing new paradigms of how Hox genes achieve their action throughout development.