Hox genes are classically known for their roles in patterning the anterior-posterior axis of animals. Now, on , Mihaela Žigman, Cecilia Moens and colleagues uncover a new role for Hoxb1b in regulating cell shape, oriented divisions and microtubule dynamics in the developing zebrafish neural tube. The researchers first identify a zebrafish mutant that carries a point mutation in hoxb1b, a gene that shares ancestral functions with mammalian Hoxa1. These mutants, they report, exhibit classical homeotic transformations associated with Hoxa1 mutations in mice. Unexpectedly, however, these mutants also show defective neuroepithelial morphogenesis within the developing hindbrain neural tube. The researchers further show that the hoxb1b mutation does not affect apico-basal or adherens junction-based polarisation, nor the proliferation or differentiation rate of neural progenitors. Instead, Hoxb1b regulates mitotic spindle orientation and the shape of progenitor cells. This function is linked to a cell-non-autonomous role for Hoxb1b in regulating microtubule dynamics. The authors thus propose that, by regulating microtubule dynamics and cell shape, Hox genes can influence global tissue morphogenetic events.
