The impact of Intra- and Inter-Strain Cross-Fostering on Mouse Maternal Care

Rixt van der Veen [Leiden, The Netherlands]
The importance of maternal care in shaping an individual’s phenotype in health and disease is becoming more and more apparent in both human and animal studies. However, in mouse studies using inbred strains or knockout mice to analyze the genetic influences on the development of normal and aberrant behavioral phenotypes, maternal behavior is very poorly characterized and often ignored.
We performed an extensive analysis of spontaneous maternal behavior of inbred mice in several conditions. We compared two commonly used strains, the C57BL/6J (C57) and DBA/2J (DBA), in their behavior towards biological offspring and fostered offspring of the same strain (intra-strain cross-fostering). Moreover, we cross-fostered these pups to different strains of mothers with either high or low maternal care and analyzed the impact of this inter-strain cross-fostering. The Observer was used to measure maternal behavior in these three conditions. We report that the maternal behavior of C57 and DBA dams toward their biological offspring is highly similar and that intra-strain cross-fostering has minimal impact on maternal behavior of these dams. We also report that inter-strain cross-fostering does not modify the strain differences in maternal care observed between the foster mothers, but pup strain does influence the amount of maternal behavior shown by both mothers in inter-strain cross-fostering. These latter findings demonstrate that both mother strain and pup strain are key determinants of maternal behavior. 

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