The uterine environment enhances cognitive competence

Long-term and transgenerational effects of cryopreservation on rabbit embryos

The short-term effects of cryopreservation and embryo transfer are well documented (reduced embryo viability, changes in pattern expression), but little is known about their long-term effects. We examined the possibility that embryo vitrification and transfer in rabbit could have an impact on the long-term reproductive physiology of the offspring and whether these phenotypes could be transferred to the progeny. Vitrified rabbit embryos were warmed and transferred to recipient females (F0). The offspring of the F0 generation were the F1 generation (cryopreserved animals). Females from F1 generation offspring were bred to F1 males to generate an F2 generation. In addition, two counterpart groups of noncryopreserved animals were bred and housed simultaneously to F1 and F2 generations (CF1 and CF2, respectively). The reproductive traits studied in all studied groups were litter size (LS), number born alive at birth (BA), and postnatal survival at Day 28 (number of weaned/number born alive expressed as percentage). The reproductive traits were analyzed using Bayesian methodology. Features of the estimated marginal posterior distributions of the differences between F1 and their counterparts (F1 - CF1) and between F2 and their counterparts (F2 - CF2) in reproductive characters found that vitrification and transfer procedures cause a consistent increase in LS and BA between F1 and CF1 females (more than 1.4 kits in LS and more than 1.3 BA) and also between F2 and CF2 females (0.96 kits in LS and 0.94 BA). We concluded that embryo cryopreservation and transfer procedures have long-term effects on derived female reproduction (F1 females) and transgenerational effects on female F1 offspring (F2 females).

Maternal and genetic effects on the acoustic startle reflex and its sensitization in C3H/HeN, DBA/2JHd and NMRI mice following blastocyst transfer

In the present study, reciprocal embryo transfers were conducted to examine genetic and maternal effects on the baseline and fear-sensitized acoustic startle response (ASR) in the two inbred strains C3H/HeN and DBA/2JHd and the outbred strain NMRI. The largest differences in the ASR were found in untreated strains (effect size 0.6). The transfer procedure per se had a significant effect on the behavior of NMRI mice resulting in a reduction in the baseline, and an increase in the fear-sensitized ASR. In contrast, there were no significant effects of the transfer procedure in the two inbred strains. Autosomal genetic effects had a stronger impact on the amplitude of the ASR (effect sizes 0.5) than sex (effect sizes 0.06) as revealed by reciprocal embryo transfer. Nevertheless, the genetic effects on the fear-sensitized ASR were somewhat more variable and strain-dependent (effect sizes 0.1-0.2). Global maternal effects were detected after embryo transfer into NMRI mothers resulting in a larger reduction of the ASR in the offspring of DBA and NMRI donors than C3H donors (effect sizes 0.1-0.2). An additional fostering procedure was introduced to dissect uterine and postnatal maternal effects in NMRI offspring. Uterine factors changed the baseline ASR of the offspring in direction of the recipient mother strain. Surprisingly, postnatal maternal effects on the ASR were contrary to the behavior of the rearing mother. In conclusion, both genetic and prenatal/postnatal maternal factors persistently influenced the ASR of the offspring, whereas the fear-sensitized ASR was mainly influenced by genetic factors. Our study shows that uterine and postnatal maternal influences deserve more attention when determining the phenotype of genetically engineered mice at least in the first generation following embryo transfer.

Maternal and Genetic Effects on Anxiety-Related Behavior of C3H/HeN, DBA/2J and NMRI Mice in a Motility-Box Following Blastocyst Transfer

Reciprocal embryo transfers were conducted to examine genetic and maternal effects on the behavior of inbred C3H/HeN and DBA/2J mice, and outbred NMRI mice using a motility-box. The behavioral variables measured were (i) horizontal locomotor activity assessed as the path and time spent during traveling; (ii) vertical activity assessed as the time spent with and numbers of rearings/leanings; (iii) and the time spent in the more anxiogenic central field. The transfer procedure per se resulted in a minor increase in vertical activity of inbred C3H/HeN mice, but had no effect in inbred DBA/2J mice. In contrast, outbred NMRI mice displayed a lower central field activity following embryo transfer indicating a higher anxiety level. Moreover, genetic differences between the mouse strains studied remained stable following embryo transfer for locomotor and vertical activity, but not central field activity depending on the recipient mother strain. Maternal effects were found for (i) vertical activity in the two inbred mouse strains, (ii) all behavioral variables studied in outbred NMRI mice, and (iii) an interaction with gender for the time spent in the anxiogenic central field. An additional fostering procedure revealed that the vertical activity of NMRI mice was modified towards the behavior of the recipient C3H/HeN strain by uterine factors, whereas the postnatal maternal effect of C3H/HeN mothers was the opposite. In summary, the effects of the embryo transfer procedure per se, stability of genetic characteristics following embryo transfer and maternal effects were related to the mouse strains used as donators and recipients, and the behavioral variables studied.