HOXC8 Initiates an Ectopic Mammary Program by Regulating FGF10 and TBX3 Expression, and Wnt/β-Catenin Signaling

The study investigated the role of the Hoxc8 gene in the development of mammary glands and hair follicles in mice. Researchers found that Hoxc8 had a strong, early expression in the ventrolateral surface ectoderm at E10.5. By conditionally misexpressing Hoxc8, they expanded the thoracic identity domain in mutant embryos, leading to the formation of ectopic mammary placodes in the cervical region. These placodes expressed markers such as Wnt10b and Tbx3 and were associated with upregulated Fgf10 expression. Ablation of Tbx3 eliminated both normal and ectopic mammary placodes. The findings suggested that Hoxc8 plays a crucial role in the initiation of mammary placode morphogenesis and potentially other cutaneous accessory organs.