(A) RT-qPCR quantification of relative SMAD7 expression level in the epidermis of acutely irradiated (Ac-UV; +) ex vivo biopsies of human normal skin. SMAD7: no UV vs Ac-UV P = 0.032. N=4 biological replicates, one representative experiment is shown out of three independent experiments performed with the skin of three different donors. 