New Perspectives on Melanoma_ The Role of PAX3

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Unformatted text preview: benign or malignant melanocytic lesions (Figure 3.2D), the distribution of cells that co‐ expressed PAX3 and MITF differed between the epidermis and hair follicles of normal skin. Around 90% of MITF‐positive melanocytes in the epidermis and the outer root sheath (ORS) of the hair follicle were PAX3‐positive, compared to only 65% of those in the bulbar area (Figure 3.3D). Interestingly there was a distinct location in the hair bulb, at the very base of the hair, populated exclusively by MITF‐positive melanocytes (Figure 3.2E). Given this difference between epidermal and follicular melanocytes, we thought it necessary to further characterise PAX3‐positive melanocytes in the normal skin. We therefore co‐stained PAX3 cells with Hairy and enhancer of split 1 (HES1) (Figure 3.3A and 3.4A‐C) or Melan‐A (MLANA, also known as MART‐1) (Figure 3.3B and 3.4D, E), markers of less or more differentiated cell phenotype respectively. Upon analysis of the distribution of double‐labelled cells we found that HES1 was expressed in a proportion of PAX3‐positive melanocytes, while cells that were only HES1‐positive were identified as keratinocytes [246,247] (Figure 3.3A). The number of PAX3‐positive melanocytes co‐expressing HES1 was lowest in the matrix of the hair bulb (10.5%), compared to the ORS (23.7%) and the epidermis (27.9%) (Figure 3.3D). By contrast, MLANA was expressed in more that 60% of both epidermal and ORS PAX3‐positive melanocytes, compared to 36% of those in the matrix of the hair bulb (Figure 3.3D). We have also observed a significant number of single MLANA‐labelled melanocytes (Figure 3.3B) (30.5% in the epidermis, 3.9% in ORS, and 40% in the hair bulb). 61 Chapter III – Medic and Ziman, 2010 Figure 3.3. Co­expression analysis of PAX3­expressing epidermal melanocytes of normal skin. Epidermal melanocytes of normal skin show variable differentiation status: less differentiated melanocytes co‐expressing PAX3 (mouse monoclonal antibody, DSHB) and HES1 (A); more differentiated co‐expressing PAX3 (rabbit polyclonal, Invitrogen) and MLANA (B); and mature melanocytes expressing only MLANA (B). Single HES1‐labbeled cells in the epidermis are keratinocytes...
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This document was uploaded on 03/06/2014 for the course CHEMISTRY 12 at National University of Singapore.

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