A novel mutation in homeobox DNA binding domain of HOXC13 gene underlies pure hair and nail ectodermal dysplasia (ECTD9) in a Pakistani family
We examine the Hoxc12 RNA expression pattern during both hair follicle morphogenesis and cycling in direct comparison to its only upstream neighbor, Hoxc13. Expression of both genes is restricted to the epidermal part of the follicle excluding the outer root sheath and interfollicular epidermis in a distinct stage-dependent and cyclical manner. During the progressive growth phase (anagen) of developing and cycling follicles, the distinct proximo-distal expression domain of Hoxc12 overlaps only proximally, at the upper-most region of the bulb, with the more proximally restricted Hoxc13 domain. This arrangement of the expression domains of the two genes along the proximal-toward-distal axis of increasing follicular differentiation correlates with the sequential expression of first Hoxc13 and then Hoxc12. This indicates a reversal of the typical temporal colinearity of Hox gene activation otherwise observed along the anterior-posterior morphogenetic axis of the embryo (review: Cell 78 (1994) 191).