Utrophin Expression is Prevalent in Epidermis

Abstract

Utrophin protein was discovered to localize to the neuromuscular junctions and is thought to provide a critical linkage between integral proteins bound to the extracellular matrix outside the cell and the actin cytoskeleton inside the cell. Clinical implications of this protein include the upregulation of utrophin as a treatment for Duchenne Muscular Dystrophy, a disease in which utrophin's homologue (dystrophin) is functionally absent. In addition, utrophin gene expression is reduced in a variety of cancers. This study set out to identify whether utrophin is expressed within the epidermis—the top layer of skin. To date, four unique mRNA transcripts have been characterized for the human UTRN gene, supporting translation of two full-length utrophin proteins (utrophin A and utrophin B) and two short isoforms (Up 140 and Up71). All four of these human utrophin transcripts were detected within human epidermis using reverse-transcriptase PCR performed on RNA purified from human epidermis. In addition to the detection of utrophin mRNA within human epidermis, the full-length utrophin protein was also detected within human epidermis using immunofluorescence labeling—a technique used to detect specific proteins. Utrophin protein localizes to the area of the epidermis closest to the dermis termed the basement membrane zone. These data demonstrate that utrophin expression is prevalent in epidermis. Utrophin has been characterized as a member of the dystroglycan complex and dystroglycan has previously been identified within epidermis and too localizes to the basement membrane zone. Therefore, this study provides support for existence of a dystroglycan complex within epidermis as utrophin is the second member of this complex to be found within the epidermis.