A Method to Quantify Mouse Coat-Color Proportions

Songthip Ounpraseuth,Tonya M Rafferty,Eric R Siegel,Erik A Nilsson,Craig A Cooney,Kristin L Wheeler,Rachel E Mcdonald-Phillips,Whitney M Gammill

doi:10.1371/journal.pone.0005414

Songthip Ounpraseuth, Tonya M Rafferty + Show 6 more

Open Access

https://doi.org/10.1371/journal.pone.0005414

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Abstract

Coat-color proportions and patterns in mice are used as assays for many processes such as transgene expression, chimerism, and epigenetics. In many studies, coat-color readouts are estimated from subjective scoring of individual mice. Here we show a method by which mouse coat color is quantified as the proportion of coat shown in one or more digital images. We use the yellow-agouti mouse model of epigenetic variegation to demonstrate this method. We apply this method to live mice using a conventional digital camera for data collection. We use a raster graphics editing program to convert agouti regions of the coat to a standard, uniform, brown color and the yellow regions of the coat to a standard, uniform, yellow color. We use a second program to quantify the proportions of these standard colors. This method provides quantification that relates directly to the visual appearance of the live animal. It also provides an objective analysis with a traceable record, and it should allow for precise comparisons of mouse coats and mouse cohorts within and between studies.

Highlights

Animals that exhibit coat-color variation and mosaicism have been used to evaluate a variety of effects in numerous studies [1,2,3,4,5,6,7,8,9]
We describe a method to quantify the coat color percentage in live yellow-agouti mottled mice using digital photographs saved as jpg files
Photographs of the same mouse taken on different days within a one-week period yielded very similar results from one photo session to the when we took reasonable steps to insure consistency of conditions among sessions

Summary

Introduction

Animals that exhibit coat-color variation and mosaicism have been used to evaluate a variety of effects in numerous studies [1,2,3,4,5,6,7,8,9]. In the yellow-agouti mouse model [10], the agouti protein antagonizes the melanocortin-1 receptor to promote the expression of the yellow pigment pheomelanin giving hairs a yellow color [11]. Over expression of agouti from this allele causes yellow hair. Determined coat color in this model is influenced by prenatal environmental exposure to compounds such as folate, vitamin B12 and methyl donors [2,15,16,18], isoflavone phytoestrogens [19], DNA methyltransferase gene dosage [5] and maternal epigenetics [2,10,14]. To measure the influence of treatment factors on coat color, each mouse is classified into a predefined category or ‘‘phenotype’’ that constitutes one of several ordinal categories spanning the range of coat colors from ‘‘pseudoagouti’’ (no yellow) to ‘‘clear yellow’’ (no agouti spots). The number of ordinal categories can be two [10], three [14], four [5], five [16,18,19], or six [2,15]

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