Figure 4.

NEK9 Mutation Impairs Follicular Differentiation

In NC103 lesional tissue, follicular differentiation was analyzed by immunofluorescence staining. Keratin 5 staining in all images marks the outer root sheath of the hair follicle. To characterize the stem cell pool in NC, staining for keratin 15 (K15) was performed. K15 localizes to the basal layer of keratinocytes within the bulge in normal hair follicles (A), but in NC was found to strongly localize to the basal layer throughout the follicle (B) and cyst (C). In normal tissue, keratin 6, AE15 and AE13 mark follicular differentiation in the companion layer, inner root sheath, and cuticle and cortex, respectively (D, G, and J). In NC, these were absent in the upper follicular regions (E, H, and K), as well as within cysts (F, I, and L), suggesting a shift in follicular fate to an IFE-like fate within NC tissue. To further assess differentiation of follicular cells, keratin 10 (K10) staining was examined. K10, a marker of suprabasal IFE, which is absent in sub-bulge regions of normal follicles (M), was found within the upper follicular and sub-bulge region of NC (N) and within the cysts of NC tissue (O), in both cases maintaining suprabasal localization. The dermal-epidermal junction is labeled with a dashed white line in each panel. Control tissue was obtained from discarded tips from surgical excision. Scale bar represents 20 μm in (A)–(C) and (M)–(O) and 50 μm in (D)–(L).