TGM1 and Hyperkeratosis: Kuramoto et al. (2002) previously reported that grafted mature transglutaminase 1 (TGase1)–deficient murine skin with remarkable epidermal hyperplasia and hyperkeratosis showed lower TEWL, similar to control TGase1-proficient mice. However, removal of the thick epidermal hyperkeratosis resulted in an increase in TEWL (Kuramoto et al. 2002).