Hardy, 56). The second step of this
two step process involves elongation and differentiation,
cells in the placode grow and differentiate into the mature
hair follicle (Oro, 575;Kashiwagi, 22-23).
During this step the final
signaling event produced by the dermal layer initiates
proliferation and differentiation of the epithelial portion
to form the hair follicle proper (Gat, 605; Hardy, 56; Oro,
576). The processes of hair follicle development are
regulated by cell-cell interactions through soluble
signaling molecules or direct cell contacts (Kashiwagi, 22).
The regulations of these processes require gene responses in
order to produce effects. Transcription factors are
molecules that cause gene effects, and thus must be involved
in the signaling pathway for gene responses to
factors are proteins that control, where, when, and how
genes are expressed by binding directly to DNA (Klug).
Transcription factors contain two domains, one that binds to
the DNA (DNA binding domain) and another that affects
transcription through protein-protein interactions (Trans-
activating domain) (Klug). TBX2 is a transcription factor
encoded by the Tbx2 mRNA, and is expressed virtually
in all areas of epithelium-mesenchyme interactions including
the mouse lung, limb, and mammary gland (Chapman 379- 381).
At 12.5 dpc
observed in the facial region (Chapman, 381-382). We predict
that Tbx2is expressed
in the 13.5 dpc whisker pad due to its location in the
facial region combined with the epithelium-mesenchyme