Contrasting Localization of c-Myc with Other Myc Superfamily Transcription Factors in the Human Hair Follicle and During the Hair Growth Cycle

Abstract

The mammalian hair follicle is a highly dynamic skin appendage that undergoes repeated cycles of growth and regression, involving closely co-ordinated regulation of cell proliferation, differentiation, and apoptosis. The Myc superfamily of transcription factors have been strongly implicated in the regulation of these processes in many tissues. Using immunohistochemistry, we have investigated the patterns of c-Myc, N-Myc, Max, and Mad1-4 expression at different stages of the human hair growth cycle. N-Myc, Max, Mad1, and Mad3 immunoreactivity was detected in the epidermis and the epithelium of both anagen and telogen hair follicles. Three distinct patterns of hair follicle c-Myc immunoreactivity were observed. In the infundibulum, c-Myc staining was predominantly in the basal layers, with little detectable immunoreactivity in the terminally differentiating suprabasal layers; this pattern was similar to that seen in the epidermis. In contrast, c-Myc expression in the follicle bulb was found both in the proliferating germinative epithelial cells and in the terminally differentiating matrix cells that give rise to the hair fiber. Finally, intense c-Myc immunoreactivity was detected in the bulge region of the outer root sheath. Using the C8/144B antibody as a bulge marker, we confirmed that c-Myc immunoreactivity in the outer root sheath correlates with the putative hair follicle stem cell compartment. c-Myc expression in the bulge was independent of the hair growth cycle stage. Our data suggest that Myc superfamily members serve different functions in separate epithelial compartments of the hair follicle and may play an important role in determining cell fate within the putative stem cell compartment.

Transcriptional control of epidermal specification and differentiation

“…Consistent with this, c-Myc epidermal expression is confined to the proliferating basal cells [11]. However, increasing expression of c-Myc in cultured keratinocytes promotes terminal differentiation and causes a progressive reduction in growth [12].…”

c-mycin the hematopoietic lineage is crucial for its angiogenic function in the mouse embryo

“…In the intestine, c-Myc is expressed in the proliferative zone of intestinal crypts, where putative intestinal stem cells reside, and is essential for the formation of these crypts (Bettess et al, 2005;Muncan et al, 2006). Similarly, in the skin epidermis, c-Myc is expressed in the proliferative basal layer and bulge region, where stem and progenitor cells are located (Bull et al, 2001). These new in vivo findings suggest that c-myc is uniquely required in the stem and progenitor cell compartments.…”

Role of HPV E6 proteins in preventing UVB-induced release of pro-apoptotic factors from the mitochondria

“…HPV typing of biopsies was performed using a degenerate PCR strategy that we have previously demonstrated to detect all known HPV types [24]. For immunohistochemistry, 4 µm thick paraffin embedded tissue sections were mounted and processed as previously described [47]. For antigen retrieval, sections were microwave treated under pressure for 4 min at 900 W in preheated citrate buffer pH 6.0.…”