Loricrin

26 kDa protein found in keratinocytes. Loricrin is basic, insoluble and consists of many repeats of glycine/serine/cysteine "loops" interrupted by glutamine- and serine-rich segments. Loricrin is the major component of the so-called "cornified envelope" of keratinocytes and is first expressed in the stratum granulosum. The coding LORICRIN gene is located on chromosome 1q21 and probably consists of two exons. It exhibits several sequence variations, most of which result in insertions of four amino acids in the (glycine/serine/cysteine) loops in the protein loricrin. These variations do not appear to have disease value as they do not affect the function of the protein.

So far, the following clinical pictures with mutations of the loricin gene have been described:

• Keratosis palmoplantaris mutilans, type Camisa
• the"loricrin keratoderm" (a patchy palmoplantar keratosis associated with mild ichthyosis) first described by Takahashi and co-workers in 1999.

1. Drera B et al (2008) De novo occurrence of the 730insG recurrent mutation in an Italian family with the ichthyotic variant of Vohwinkel syndrome, loricrin keratoderma. Clin Genet 73:85-88
2. Kim BE et al (2008) Loricrin and involucrin expression is down-regulated by Th2 cytokines through STAT-6, Clin Immunol 126:332-337
3. Schmuth M et al (2007) Ichthyosis update: towards a function-driven model of pathogenesis of the disorders of cornification and the role of corneocyte proteins in these disorders. Adv Dermatol 23:231-256.