Skin histopathology overview.

<p>(A) The dorsal skin of 44 wild type mice and 514 mutant mice were assessed by an expert dermatologist. 3 wild type mice and 30 targeted alleles (in 30 mutant strains) showed abnormalities in one or more of the phenotypic categories listed (35 abnormalities total). The phenotypes of abnormal hair shaft morphology and skin inflammation were observed in both wild type and mutants and taken to be a background phenotype, therefore were not considered significant in the overall phenotypic analysis. Wild type images for comparison are shown in (B) and (F). Phenotypes unique to mutant animals included abnormal hypodermis dermis morphology (C,D), abnormal pigmentation (E) and abnormally prominent arrector pilli muscle (G). More specifically, <i>Aldh18a1^tm1a/+</i> mice presented with mild, multifocal mixed inflammatory cell infiltration with mild fibrosis and distortion of adipocytes in the hypodermal fat layer potentially indicating abnormalities in white fat cells (C). <i>Prmt3^tm1a/tm1a</i> mutant mice exhibited granulomatous steatitis (red arrowheads) (D). <i>Arpc1b^tm1a/tm1a</i> mutant mice had mild to moderate multifocal areas of dermal fibrosis with pigment laden macrophages (yellow arrows) suggesting hair follicle rupture (E). <i>Rad18^tm1a/tm1a</i> mutant mice had normal skin but unusually prominent arrector pili muscles (black arrows) (G). Scale bars are 50 µm.