Asebia-2J (Scd1(ab2J)): A new allele and a model for scarring alopecia

A spontaneous, autosomal, recessive mouse mutation exhibiting mild scaly sk in, progressive scarring alopecia, slightly runted growth, and photophobia arose at The Jackson Laboratory in 1993 in the inbred mouse strain DBA/1Lac J. Because this mutant mouse showed genetic, anatomical, and laboratory sim ilarities to the asebia mutation, crosses were done between the new mutant and mice carrying the asebia-J allele, Because the Fl offspring were affect ed, indicating the two mutants were allelic, the new mutation was named ase bia-2J, Careful histological analysis of skin development of mice homozygou s and heterozygous for either asebia-J or asebia-2J revealed that both type s of mutant mice are very similar regardless of their background. Notable h istopathological features of mice homozygous for either allele included ext reme sebaceous gland hypoplasia, abnormally long anagen follicles, retained inner root sheath, hair fiber perforation of the anagen follicle base, and progressive follicular replacement by scarring. In this article we present a new pathogenetic hypothesis based on the Importance of the sebaceous gla nd in hair fiber sheath dissociation: in the absence of a functional sebace ous gland the hair follicle is destroyed. The cutaneous pathology of this m utant mouse underscores the importance of the sebaceous gland to follicular biology and presents an animal model for studying the human scarring alope cias, which characteristically begin with sebaceous gland ablation.