Breeding the phenylketonuria mouse: novel dietary regimen enables breeding of female C57BL/6J mice homozygous for the Pahenu2 mutation without fostering.

The Pahenu2 mutation in C57BL/6J mice is a well characterized model for studying phenylketonuria (PKU), with Pahenu2 homozygotes displaying heightened blood phenylalanine and other characteristics of PKU. Pahenu2 homozygous females do not successfully rear young on any conventional diet due to their disease status. The most commonly used successful breeding strategy is crossing Pahenu2 heterozygous females with homozygous mutant males; producing litters of 50% homozygous and 50% heterozygous animals. In many treatment studies the heterozygous pups produced are not useable, but add to experimental costs and total animals used. To this end our lab created a dietary regimen with reduced phenylalanine and increased large neutral amino acid content, enabling homozygous mating. Phenylalanine levels in homozygous females and males on the new diet are significantly lower than that of homozygous females and males on traditional diets (p = 1.35x10-4 and p = 1.5x10-5 respectively). Litters born to Pahenu2 homozygous mothers on this diet demonstrate no significant difference in litter size compared to litters born to heterozygous mothers (p > 0.75). No observable defects were noted in litters born from homozygous crosses. This dietary regimen enables litter production of 100% Pahenu2 homozygous animals for investigators who wish to rapidly expand their Pahenu2 mouse colony size or do not require heterozygous littermate controls in their PKU studies.