Figure 1

Schematic drawings of the different housing conditions in the paternal behavior test. On day 1, one male (blue) or female (pink) mouse and their biological pups were housed (S1 and S5) or isolated alone (S6-1 and S6-2) or together (S2, S6-3) in home (black) or new (red) cages. Then, retrieval was examined for five pups placed in a remote area from the nest (yellow) (S3). The pups in the nest represent a retrieval (S4-2), and those outside the nest represent no retrieval of pups to the nest (S4-1) by the sires, retrievers and non-retrievers, respectively. The number and percentage of sires represent the rate of retrieval or non-retrieval behaviors out of sires tested in S1. The retrieval-positive sires (retrievers) or retrieval-negative sires (non-retrievers) were then housed together with mates and pups as a family (S5). On the following day (Day 2), the two types of sires were separated in three different conditions (S6-1, -2 and -3). Each experiment had a 10-min duration in each step (S2, S3, S4). At the S6 step, the mice were maintained for 30 min before sacrifice.