%0 Journal Article
%T Epidermal stem cell dynamics
%A Maya Sieber-Blum
%J Stem Cell Research & Therapy
%D 2011
%I BioMed Central
%R 10.1186/scrt70
%X This commentary relates to the paper by Wong and Reiter [1], who report that basal cell carcinoma (BCC) can originate from the follicular bulge. Cytokeratins hetero-polymerise, with an acidic (type I) cytokeratin binding a neutral-basic (type II) cytokeratin. Cytokeratin 14 (K14) forms heterodimers with cytokeratin 5. In contrast, less is known about cytokeratin 15 (K15) and there is no known K15 binding partner (reviewed by [2]). During embryogenesis, postnatally, during wounding and in tumourigenesis, cytokeratins are differentially expressed in the basal layer of the mouse epidermis and in the hair follicle [2]. There is a relative lack of consensus among investigators, however, of marker specificity in terms of unequivocally identifying different subsets of stem cell.It has been well established that K14 is expressed in the basal layer of the epidermis in postnatal mouse skin and can therefore be considered a marker for stem cells/progenitors in the basal layer of the epidermis [3]. K14 is, however, significantly less useful for distinguishing between progenitor cells in the basal layer and follicular bulge stem cells, as K14-expressing cells have also been described in the bulge of hair follicles (see, for example, [4,5]).Conversely, while K15 has been used as a marker for follicular stem cells in the bulge, K15 has been reported to also be expressed in the basal layer of the epidermis and to thus mark the least differentiated cells in the neonatal epidermis and adult bulge [6]. Likewise, in a careful recent study in which peptide-specific antibodies to K15 were used, it has been found that K15-immunoreactive cells are not exclusively limited to the follicular bulge, but that K15 is also expressed in cells of the basal layer of the mouse epidermis during embryo-genesis and throughout adulthood [2]. Thus, during the time of SmoM2 activation in the study by Wong and Reiter [1], at 7.5 weeks of age, K15 is expressed not only in cells of the bulge but also by at le
%U http://stemcellres.com/content/2/3/29