Disentangling prenatal and postnatal maternal genetic effects reveals persistent prenatal effects on offspring growth in mice

Abstract

Mothers are often the most important determinant of traits expressed by their offspring. These "maternal effects" (MEs) are especially crucial in early development, but can also persist into adulthood. They have been shown to play a role in a diversity of evolutionary and ecological processes, especially when genetically based. Although the importance of MEs is becoming widely appreciated, we know little about their underlying genetic basis. We address the dearth of genetic data by providing a simple approach, using combined genotype information from parents and offspring, to identify "maternal genetic effects" (MGEs) contributing to natural variation in complex traits. Combined with experimental cross-fostering, our approach also allows for the separation of pre- and postnatal MGEs, providing rare insights into prenatal effects. Applying this approach to an experimental mouse population, we identified 13 ME loci affecting body weight, most of which (12/13) exhibited prenatal effects, and nearly half (6/13) exhibiting postnatal effects. MGEs contributed more to variation in body weight than the direct effects of the offsprings' own genotypes until mice reached adulthood, but continued to represent a major component of variation through adulthood. Prenatal effects always contributed more variation than postnatal effects, especially for those effects that persisted into adulthood. These results suggest that MGEs may be an important component of genetic architecture that is generally overlooked in studies focused on direct mapping from genotype to phenotype. Our approach can be used in both experimental and natural populations, providing a widely practicable means of expanding our understanding of MGEs.

Figure 1

Relative contribution of maternal and direct effects to variation in body weight from week 1 to week 10 of age. Values are given as a percentage of phenotypic variance. Direct effects data are from Table 2 in Hager et al. (2009).

Figure 2

Relative contribution of prenatal (dam) and postnatal (nurse) effects on body weight from week 1 to week 10 of age. Values are given as a percentage of phenotypic variance.

Figure 3

Relative contribution of additive and dominance maternal effects to variation in body weight from week 1 to week 10 of age. Values are given as a percentage of phenotypic variance. (A) Additive (a_M) and dominance (d_M) dam (prenatal) effects through time. (B) Additive (a_N) and dominance (d_N) nurse (postnatal) effects through time.