Maternal effects on body weight in mice selected for large and small size

UTERINE EFFECTS, EPIGENETICS, AND POSTNATAL SKELETAL DEVELOPMENT IN THE MOUSE

Reciprocal embryo transfer experiments show that skeletal dimensions in adult mice are significantly influenced by the genotype of the female providing the uterine environment in which they were raised. Embryo transfers among C3HeB/FeJ, SWR/J, and the C3SWF, hybrid strain (C3H females x SWR males) permit separation of uterine maternal genotype effects from effects arising from the progeny's own genotype. Many different aspects of adult skeletal form are significantly influenced by uterine genotype and, in some instances, the pattern of these effects correlates with events during skeletal embryology. Analyses involving the highly heterozygous C3SWF₁ strain demonstrate the existence of significant dominance in maternal genes affecting skeletal development in the progeny. Further, there is a large skeletal effect due to progeny heterosis. Uterine Utter size can be manipulated as a nonheritable component of variability in embryo transfer experiments, and it has a large and systemic effect on skeletal growth and morphogenesis that persists in adult mice. Heritable uterine maternal effects are epigenetic interactions during development that can be incorporated into models of evolutionary change to provide a more complete picture of the causal agents producing morphological change.

The effect of divergent selection for uterine capacity on fetal and placental development at term in rabbits: Maternal and embryonic genetic effects1

The aim of this work was to study the effects of the genotype of the dam, the embryo, or their interactions on prenatal growth by performing double-reciprocal embryo transfers between two lines of rabbits divergently selected for uterine capacity. Females from high (n = 53) and low (n = 48) lines were slaughtered at 72 h of gestation, and recovered embryos were transferred to the oviducts of recipient does from the high (n = 23) and low (n = 19) lines. Each recipient doe received eight embryos from the high line into one oviduct and eight embryos from the low line into the other. Recipient does were slaughtered on d 28 of gestation. The percentages of live fetuses at 28 d of gestation were 89.2 and 74% for high and low recipient lines, respectively. Length and weight of the empty uterine horn and weight of the full uterine horn were not affected by either the recipient or by donor line. Fetal weight was affected by the recipient line but not by the donor line. Fetuses gestated in high recipient does were 7% heavier (P < 0.10) than those in the low recipient does. There was a donor and a donor x recipient interaction effect on fetal placental weight. Fetal placental weight was heavier (7%, P < 0.01) for embryos from the low line. Embryos from the high line gestated in low-line uteri showed a lower fetal placenta weight than did low-line embryos gestated in high-line uteri and low-line uteri (P < 0.05). Linear regression coefficients of fetal weight at term on fetal placental weights differed (P < 0.05) for the high and low donors (4.33 +/- 0.28 and 3.41 +/- 0.29 respectively). A significant effect of the donor genotype on individual placental length was observed (P < 0.05), which might have resulted from a smaller individual placental length of low-line embryos gestated high-line uteri (P < 0.10). Neither donor nor recipient lines affected maternal placental weight or available space for fetuses. Fetuses and their fetal placentae were heavier when receiving more than four blood vessels than when receiving less than three blood vessels (13 and 17% respectively, P < 0.05). Neither recipient nor donor genotype affected the number of blood vessels arriving at each live fetus. Thus, fetal weight depends on the maternal genotype, whereas fetal placental weight depends on the embryo genotype in these two lines of rabbits divergently selected for uterine capacity.

Uterine and postnatal maternal effects in mice selected for differential rate of early development

A series of mouse lines was produced by long-term restricted index selection for divergent rate of growth during early and late postnatal development. The selection program was based on the following treatments: E(+) and E(-) lines were selected to alter birth to 10-day weight gain while holding late gain for both lines constant and a control line was established via random selection. Using embryo transfer and crossfostering methodology, we partitioned postnatal growth for E(+), E(-), and C lines into progeny genetic, uterine maternal, and nurse maternal components. Selection for differential early growth resulted in correlated response in uterine and nurse maternal effects on body weights, with significant genetic-by-environment interactions. Significant uterine effects were also observed in tail length measurements. Direct uterine effects on body weight were relatively small and resulted in growth rate differences early in development. Nurse effects were large, resulting in modification of progeny growth trajectory especially during early postnatal development. Genetic-by-uterine interactions were large and demonstrate progeny-specific effects of the prenatal uterine environment.

The effect of dam's strain on the intrauterine craniofacial growth of mouse fetuses

PURPOSE

The maternal effect is one of the important factors in mammalian growth in conjunction with the genetic effect. The present study investigated the prenatal maternal effect of a dam on the intrauterine craniofacial growth of a mouse fetus using embryo transfer and cephalometry. DDD/Qdj strain mouse embryos were transferred to four strains of recipient female mice (DDD/Qdj, C3H/Qdj, C57BL/Qdj, and DBA/1J Sea). Just after parturition cephalometric observation of the newborn offspring, which developed in the uteri of the four strains of dams, was performed and then the craniofacial size of the newborn offspring was calculated on the lateral cephalogram. Statistical analyses were performed to examine the correlation between the dam's weight and the craniofacial size of the newborn offspring, to test the significance of the effect of the dam's strain on the craniofacial size of the newborn offspring, and to evaluate the interstrain difference of the intrauterine craniofacial growth of the mouse fetuses.

RESULTS

It was disclosed that there were a direct relation between the dam's weight and the craniofacial size of the newborn offspring, a significant effect of the dam's strain on the craniofacial size of the newborn offspring, and a significant interstrain difference in the craniofacial size of the newborn offspring after eliminating the effects of litter size and gestation period on the craniofacial size of the newborn offspring (DDD/Qdj > C3H/Qdj = C57BL/Qdj > DBA/1J Sea).

CONCLUSION

Thus, it could be concluded that the four strains of dams affected differently the intrauterine craniofacial growth of the DDD/Qdj strain fetuses through each uterine condition, indicating that the dam's weight played an important role as one of the prenatal maternal effects on the intrauterine craniofacial growth of mouse fetuses.

Wild mice in the cold: some findings on adaptation

The house mouse, Mus domesticus, can thrive in natural environments much below its optimum temperature. Thermogenesis is then above that at more usual temperatures. In addition, body weight, and the weights of brown adipose tissue and the kidneys, may be higher than usual. In free populations of house mice cold lowers fertility and may prevent breeding. Other possible limiting factors on breeding are food supply, shelter for nesting and social interactions. In captivity, wild-type house mice exposed to severe cold (around 0 degrees C) at first adapt ontogenetically by shivering and reduced activity. But raised thermogenesis is soon achieved without shivering; nest-building improves; and readiness to explore may be enhanced. Endocrine changes probably include, at least initially, a rise in adrenal cortical activity and in catecholamine secretion. Some females become barren, but many remain fertile. The maturity of fertile females is, however, delayed and intervals between births are lengthened; nestling mortality rises. A limiting factor during lactation may be the capacity of the gut. Similar adaptive changes are observed during winter in some species of small mammals that do not hibernate. But neither the house mouse nor other species present a single, universal pattern of cold-adaptation. Wild-type mice bred for about 10 generations in a warm laboratory environment (20-23 degrees C) change little over generations. In cold they become progressively heavier and fatter at all ages; they mature earlier, and nestling mortality declines. The milk of such 'Eskimo' females is more concentrated than that of controls. If 'Eskimo' mice are returned to a warm environment, they are more fertile, and rear heavier young, than controls that remained in the warm. Despite the heavier young, litter size is not reduced: it may be increased, probably as a result of a higher ovulation rate. Parental effects have been analyzed by cross-fostering and hybridizing. Survival, growth and fertility are all favourably influenced by the intra-uterine and nest environments provided by 'Eskimo' females. 'Eskimo' males are also better fathers. Hence after ten generations the phenotype of cold-adapted house mice shows the combined effects of (a) an ontogenetic response to cold, (b) a superior parental environment and (c) a change genotype. The secular changes in the cold that lead to this phenotype give the appearance of evolution in miniature; but it is equally possible that they represent a genetical versatility that allows rapid, reversible shifts in response to environmental demands.(ABSTRACT TRUNCATED AT 400 WORDS)

Hybrids show parental influence in the adaptation of wild house mice to cold

Wild house mice, Mus musculus, were bred (a) at 3 °C (‘Eskimo’) and (b) at 23 °C. Mice of the ninth generation bred at 23°C were transferred to the cold environment. Their young, and Eskimo of the same (tenth) generation, were mated to give the four possible types of pairs: controls; the two reciprocal hybrid pairings; and Eskimo. In the resulting (eleventh) generation there were therefore two hybrid classes, genetically identical but with different parentage. The growth and reproduction of the eleventh generation were studied. At all ages from birth, mice with Eskimo mothers were heavier than those with control mothers. They were also better breeders: (1) they matured earlier; (2) their litters were larger; (3) the mortality of their young in the nest was lower. In one feature there was heterosis: of the four classes, the hybrids with Eskimo mothers produced the largest litters. These and previous findings suggest rapid selection, in the cold, for changes in growth, reproductive physiology and other aspects of metabolism. The cold-adapted mice of a given generation differed from the controls partly as a result of favourable parental effects, which acted in conjunction with genetical differences. It is hypothesized that the ecological versatility of Mus musculus depends partly on the presence, in each population, of alternative genotypes which allow rapid adaptation to new conditions.

A biometrical-genetic analysis of granule cell number in the area dentata of house mice

Considerable variability in the number of granule cells in the area dentata has been found among inbred strains of mice. In this report a simplified triple-test cross breeding design was employed to identify and discriminate between heritable and non-heritable sources of this variability. Granule cell numbers were estimated in two previously identified extreme strains of mice and in their reciprocal F1 hybrids with 3 strains of mice known to be intermediate between the 2 extremes. Analytical techniques of biometrical genetics applied to the neuron number estimates indicated that genetic transmission of this trait involves genes located upon autosomes. Transmission does not involve cytoplasmic factors within the female egg, or maternally-mediated differences in nutrition. Of the total variability in dentate granule cell number, 86% is estimated to be determined by an additive genetic component. A dorsal-to-ventral increase in the size of granule cell nuclei was found for all genotypes; some possible bases for this increase are discussed.