Plays a role in the regulation of the epidermis formation during early development. Required both as an inhibitor of basal cell proliferation and a promoter of differentiation of basal progenitor cell progeny. Localized at cell borders in single layered keratinocytes. Localized at cell borders in the basal and spinous layers but is more diffusely localized in the granular layer. Colocalized with actin near the cell membrane, especially in cellular protrusions. Expressed in basal and suprabasal layers of the epidermis as well as within the developing hair follicles and the lumen of the esophagus at 18 dpc. Shorthand (Shd), a recessive ethylnitrosurea-induced mutant with a frameshift that results in a longer protein with the C-terminal being out of frame. Shd displays shortened and fused limbs and craniofacial malformations, including shortened snout at 12.5 dpc. The affected mice display a thickened epidermis with increased basal keratinocyte proliferation and poorly-differentiated epidermal cells that fail to form a normal barrier at 18.5 dpc. Shd homozygotes died at birth, likely due to the epidermis covering the mouth and nose openings, preventing respiration (PubMed:24075906).