The winged helix gene, Foxb1, controls development of mammary glands and regions of the CNS that regulate the milk-ejection reflex

The ability to lactate is a process restricted to mammals and is necessary for the survival of nonhuman mammals. Female mice carrying a null mutation in the winged helix transcription factor Foxb1 (previously Mf3/ Fkh5/TWH) h ave lactation defects on inbred genetic backgrounds. To determine the cellu lar basis of the Foxb1 lactation defect we have inserted a tau-lacZ lineage marker into the locus to follow the fate of Foxb1 expressing cells. This a pproach has revealed that Foxb1 is expressed in epithelial cells of develop ing and adult mammary glands as well as previously described regions of the central nervous system. Mammary glands from C57BL/6 Foxb1(-/-) mice have i ncomplete lobuloavelor development. In addition, the tau-lacZ lineage label was used to determine that the mammillothalamic tract was lost in all Foxb 1(-/-) mice. Finally, morphological defects in the inferior colliculi of th e midbrain in Foxb1(-/-) mice correlate with the inability to lactate, sugg esting that the midbrain defect, but not the loss of the mammillothalamic t ract, may be responsible for the lactation defect, genesis 29:60-71, 2001. (C) 2001 Wiley-Liss, Inc.