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Comparing Skin Pigmentation and Melanin Production to the Mutagenic Effects of Ultraviolet Rays Using Sordaria fimicola

By Ellen Cahill’13

ABSTRACT

UV light exposure activates melanocytes to produce the pigment melanin, which colors skin as it moves to the surface. Humans with darker skin have more melanin and it has been speculated that they may have a biological advantage in the form of resistance to UV damage and skin cancer. Therefore, the theory of photoprotection from melanin levels was investigated by using the fungus, Sordaria fimicola. The spores of two types of Sordaria fimicola were grown and exposed in varying concentrations and times to UV light, simulating skin pigments. Wild-type sordaria grew more often than did tan type after exposure. These results explain and help support the claim that those with darker skin do not get skin cancer as often as those with lighter skin, by demonstrating that darker skin pigmentation imparts a biological advantage against DNA damage from UV radiation.

INTRODUCTION

The connection between skin pigmentation, melanin production and UV light radiation is directly related to skin carcinogenesis (2). UV light exposure activates melanin production in the melanocytes, and skin cells hit by radiation become colored as they move to the surface. In other words, the more melanin you have in your skin, the darker your skin color should be. The epidermal pigment, melanin, which absorbs ultraviolet rays and limits the penetration into skin tissues, supposedly prevents the incidence of “ultraviolet-induced skin

Figure 1: Melanocytes stimulate the production of melanin in the epidermis layer of the skin.

cancer by shielding cell nuclei and reducing DNA damage formation” (1). Yet, many scientists have not been able to produce conclusive results. What is known is that dark skin offers more protection from UV-induced DNA damage than light skin because of the higher melanin levels, but what is not known is whether or not there is a photoprotective advantage from facultative pigmentation (2). Studies by FASEB Journal have shown that amount of pigmentation affects the probability of the presence of skin cancer, which most likely indicates the photoprotective benefit of melanin (3). For example, the rate that Caucasian people get skin cancer is 50 times higher than that of African Americans (3). What remains to be known is whether or not the apparent photoprotection is due to melanin alone as a “UV filter” or if there are other properties involved (3). Although much is known about melanin in relation to UV light, my experiment will try to determine whether or not skin pigmentation and the existence of melanin reduces the risk of skin cancer, therefore imparting a biological advantage (2). The goal of my research is to compare skin pigmentation and melanin production to the effects of ultraviolet rays using the fungus Sordaria Fimicola in two forms. My hypothesis is that the higher production rates of melanin in darker skin tones protect an organism from much of the UV damage, making tanning beneficial for those who produce more melanin. Yet, there is a point at which melanin