Homeobox Galore: When Reproduction Goes RHOX and Roll

Homeobox transcription factors exert essential roles in embryogenesis and are thought to govern regenerative cell differentiation. In this issue of Cell, MacLean and colleagues (MacLean et al., 2005) describe a new homeobox gene cluster composed of genes selectively expressed in reproductive tissues. Remarkably, the cluster is on the X chromosome, and the genes display a colinear pattern of expression