Early stages of hair follicle development: a step by step microarray identity.

Hair follicle morphogenesis requires an epithelial-mesenchymal cross-talk during development, from hair placode to hair peg, and finally hair follicle formation. During this step, factors known as activators and inhibitors allow the patterning distribution of hair follicle within the skin. Our goal was to investigate the modulation of expression of various factors already known to be part of the hair placode formation, and to identify novel factors involved during the initiation of this process. In mice, primary hair follicles arise in utero from E12.5 mouse embryos. Back skin RNA were extracted from E12.5 to E14.5 embryos to perform microarray analysis (Affymetrix). We identified four new Wnt related genes which could be involved in hair follicle initiation because of their maximum expression at E12.5, namely two activators: Wnt-2 and Zic-1 and two inhibitors: Dkk-2 and Dact-1. Real-time quantitative polymerase chain reactions confirmed their expression. Our data provide a more precise view of transcript expressions involved during induction of HF morphogenesis, particularly the hair primordium formation.