Hox genes play a fundamental role in the development of the vertebrate
central nervous system, heart, axial skeleton, limbs, gut, urogenital tract and
external genitalia. The homeobox gene HoxB1 is critical to hindbrain development
and has phenotypic features frequently observed in autism. Analysis
of expression and targeted disruption of HoxB1 demonstrates that it is also
essential for patterning progenitor cells along the entire DV axis of rhombomere
4 (r4). HoxB1 maintains this function by acting very early during hindbrain
neurogenesis to specify effectors of the Sonic hedgehog and Mash1
signaling pathways. HoxB2 is a homeodomain protein important in neural
development that is also expressed during erythropoiesis, hindbrain development
and normal human adult lung development. HoxB2 may modulate the
amount of gamma-globin mRNA expressed during development and differentiation.
In addition, HoxB2 plays an important role in the patterning of
hindbrain and pharyngeal arches in the zebrafish.