Scd1 ab-Xyk : a new asebia allele characterized by a CCC trinucleotide insertion in exon 5 of the stearoyl-CoA desaturase 1 gene in mouse

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Abstract
We describe here a spontaneous, autosomal recessive mutant mouse suffering from skin and hair defects, which arose in the outbred Kunming strain. By haplotype analysis and direct sequencing of PCR products, we show that this mutation is a new allele of the asebia locus with a naturally occurring mutation in the Scd1 gene (a CCC insertion at nucleotide position 835 in exon 5), which codes for stearoyl-CoA desaturase 1. This mutation introduces an extra proline residue at position 279 in the Scd1 protein. The mutant mice, originally designated km/km but now assigned the name Scd1 ab-Xyk (hereafter abbreviated as ab Xyk / ab Xyk ), have a similar gross and histological phenotype to that reported for previously characterized allelic asebia mutations ( Scd1 ab , Scd1 abJ , Scd1 ab2J , and Scd1 tm1Ntam ). Histological analysis showed they were also characterized by hypoplasic sebaceous glands and abnormal hair follicles. In a cross between Kunming- ab Xyk / ab Xyk and ABJ/Le- ab J / ab J mice, all the progeny showed the same phenotype, indicating that the two mutations were non-complementing and therefore allelic. Comparisons with the other four allelic mutants indicate that the Scd1 ab-Xyk mutation causes the mildest change in Scd1 function. This new mouse mutant is a good model not only for the study of scarring alopecias in humans, which are characterized by hypoplasic sebaceous glands, but also for studying the structure and function of the Scd1 protein.