Generation of mice deficient for Lbx2, a gene expressed in the urogenital system, nervous system, and Pax3 dependent tissues.

Lbx2 is a member of the ladybird family of homeobox genes. The first murine ortholog identified, Lbx1, is required for hypaxial musculature and dorsal spinal cord neuron development. The second murine ortholog, Lbx2, is expressed in the developing urogenital and nervous systems. To elucidate the function of Lbx2, we generated a gene-targeted allele of Lbx2 in mice. Lbx2 deficiency did not impair mouse development, and Lbx2 null mice appeared healthy and fertile. Replacement of Lbx2 by the lacZ gene provides a valuable histological marker for Lbx2-expressing cells. Given the important role of Pax3 in neural crest, we intercrossed our Lbx2 deficient mice with Splotch Pax3 mutant mice to determine if Pax3 affects Lbx2 expression. There was reduced Lbx2 expression in dorsal root ganglia and cranial nerve ganglia with Pax3 deficiency, but not in the genital tubercle. This suggested that Pax3 is required for Lbx2 expression in affected neural crest-derived tissues.