Social and maternal behavior in mesoderm specific transcript (Mest)-deficient mice

Mesoderm specific transcript (Mest)/paternally expressed gene-1 (Peg1) is an imprinted gene expressed predominantly from the paternal allele. Aberrations in maternal behavior were previously reported in a Mest global knockout mouse (Mest(tm1Masu)). In this study, we performed in-depth social and maternal behavioral testing in a mouse model of Mest inactivation developed in our laboratory (Mest(tm1.2Rkz)). Mice with paternal allele inactivation (Mest(pKO)) did not show anxiety after testing in the elevated plus maze, open field trial, and marble burying; nor depression-like behaviors in the tail suspension test. Mest(pKO) showed normal social behaviors and memory/cognition in the three-chamber box test and the novel object recognition test, respectively. Primiparous Mest(pKO) and Mest(gKO) (biallelic Mest inactivation) female mice exhibited normal nest building and maternal behavior; and, virgin Mest(pKO) and Mest(gKO) female mice showed normal maternal instinct. Analyses of gene expression in adult hypothalamus, embryonic day 14.5 whole brain and adult whole brain demonstrated full abrogation of Mest mRNA in Mest(pKO) and Mest(gKO) mice with no effect on miR-335 expression. Our data indicates no discernible impairments in object recognition memory, social behavior or maternal behavior resulting from loss of Mest. The basis for the differences in maternal phenotypic behaviors between Mest(tm1Masu) and Mest(tm1.2Rkz) is not known.