Sostdc1 Defines the Size and Number of Skin Appendage Placodes

The study investigated the role of Sostdc1 in the development of mammary glands and hair follicles in mice, revealing that Sostdc1-null mice had increased numbers and sizes of vibrissae and other muzzle hair follicles, as well as larger primary hair placodes. Sostdc1 was crucial for preventing hair follicle formation in the normally hairless nipple epidermis, leading to extra nipple-like protrusions in its absence. The findings suggested that Sostdc1 primarily functioned by attenuating Wnt/β-catenin signaling, thereby regulating the spatial organization and number of skin appendages.