Murine neonatal melanocytes exhibit a heightened proliferative response to ultraviolet radiation and migrate to the epidermal basal layer.
Melanocytes respond to UVR not only by producing melanin, but also by proliferating. This is essentially a protective response. We have studied the melanocyte proliferative response after a single UVR exposure to neonatal mice. At 3 days post-UVR in wild-type neonates we observed a marked melanocyte activation not seen in adults. Melanocytes migrated to the epidermal basal layer, their numbers peaking at 3-5 days after UVR then diminishing. They appeared to emanate from the hair follicle, migrating to the epidermis via the outer root sheath. In melanoma-prone mice with melanocyte-specific overexpression of Hras(G12V), basal layer melanocytes were increased in size and dendricity compared to UVR-treated wild-type mice. Melanocytes in mice carrying a pRb pathway cell-cycle defect (oncogenic Cdk4(R24C)) did not show an enhanced response to UVR such as those carrying Hras(G12V). The exquisite sensitivity to UVR-induced proliferation and migration that characterizes neonatal mouse melanocytes may partly explain the utility of this form of exposure for inducing melanoma in mice that carry oncogenic mutations.
Walker
Graeme J
GJ
Oncogenomic Laboratory, Queensland Institute of Medical Research, Herston, Queensland, Australia. Graeme.Walker@qimr.edu.au
Kimlin
Michael G
MG
Hacker
Elke
E
Ravishankar
Sugandha
S
Muller
H Konrad
HK
Beermann
Friedrich
F
Hayward
Nicholas K
NK
D000818:Animals; D000831:Animals, Newborn; D002465:Cell Movement; D049109:Cell Proliferation; D004260:DNA Repair; D004195:Disease Models, Animal; D004817:Epidermis / Q000378:metabolism*; D005786:Gene Expression Regulation; D015972:Gene Expression Regulation, Neoplastic; D018859:Hair Follicle / Q000378:metabolism; D008544:Melanocytes / Q000378:metabolism* / Q000528:radiation effects*; D008545:Melanoma / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D014466:Ultraviolet Rays