Hair Development, Growth, and Loss 68 brain), the epidermis, and various skin appendages including hair follicles, teeth, mammary glands, sweat glands, and nails. Mesenchyme: Mesenchyme is a type of undifferentiated loose connective tissue that is derived mostly from mesoderm. Mesenchymal cells can migrate freely and differentiate into connective tissue, such as bone and cartilage, the lymphatic system, and the circulatory system. Neural crest: The neural crest is derived from the ectoderm. Neural crest cells migrate extensively and give rise to a diversity of cell lineages including (1) the neurons and glial cells (2) melanocytes and (3) craniofacial cartilage and bone tissues. Wnt/ -Catenin Signaling Pathway The vertebrate Wnt family consists of 19 secreted diffusible, cysteine-rich glycoproteins that can direct the recipient cell to proliferate, change its adhesive properties, or differentiate along a specific pathway during embryogenesis and homeostasis.98 The best-studied Wnt signaling pathway is the canonical Wnt/β- catenin signaling pathway, in which Wnt proteins bind to a frizzled receptor and a low density lipoprotein related protein (LRP) co-receptor, resulting in the inactivation of a complex of proteins that target cytoplasmic β-catenin for degradation. β-Catenin is therefore stabilized and translocates into the nucleus, where it complexes with members of the Lef/Tcf transcription factor family to activate transcription of target genes (Figure 17). Bone morphogenetic protein (Bmp): The Bmp family is a group of multi-functional growth factors that are capable of inducing the Figure 17. Schematic diagram of the canonical Wnt/ß-catenin signaling pathway