SLURP1 and Palmoplantar hyperkeratosis: To the best of our knowledge, we believe that SLURP1 may act as a positive modulator, because mutations in SLURP1 cause Mal de Meleda (an inflammatory palmoplantar hyperkeratosis), and α7 nAChR plays a central role in the differentiation of stratified squamous epithelium (22, 56, 57).