Offspring Genotypes Research Articles

Using Mendelian randomization to determine causal effects of maternal pregnancy (intrauterine) exposures on offspring outcomes: Sources of bias and methods for assessing them.

Mendelian randomization (MR), the use of genetic variants as instrumental variables (IVs) to test causal effects, is increasingly used in aetiological epidemiology. Few of the methodological developments in MR have considered the specific situation of using genetic IVs to test the causal effect of exposures in pregnant women on postnatal offspring outcomes. In this paper, we describe specific ways in which the IV assumptions might be violated when MR is used to test such intrauterine effects. We highlight the importance of considering the extent to which there is overlap between genetic variants in offspring that influence their outcome with genetic variants used as IVs in their mothers. Where there is overlap, and particularly if it generates a strong association of maternal genetic IVs with offspring outcome via the offspring genotype, the exclusion restriction assumption of IV analyses will be violated. We recommend a set of analyses that ought to be considered when MR is used to address research questions concerned with intrauterine effects on post-natal offspring outcomes, and provide details of how these can be undertaken and interpreted. These additional analyses include the use of genetic data from offspring and fathers, examining associations using maternal non-transmitted alleles, and using simulated data in sensitivity analyses (for which we provide code). We explore the extent to which new methods that have been developed for exploring violation of the exclusion restriction assumption in the two-sample setting (MR-Egger and median based methods) might be used when exploring intrauterine effects in one-sample MR. We provide a list of recommendations that researchers should use when applying MR to test the effects of intrauterine exposures on postnatal offspring outcomes and use an illustrative example with real data to demonstrate how our recommendations can be applied and subsequent results appropriately interpreted.

Using Genetic Variation to Explore the Causal Effect of Maternal Pregnancy Adiposity on Future Offspring Adiposity: A Mendelian Randomisation Study.

BackgroundIt has been suggested that greater maternal adiposity during pregnancy affects lifelong risk of offspring fatness via intrauterine mechanisms. Our aim was to use Mendelian randomisation (MR) to investigate the causal effect of intrauterine exposure to greater maternal body mass index (BMI) on offspring BMI and fat mass from childhood to early adulthood.Methods and FindingsWe used maternal genetic variants as instrumental variables (IVs) to test the causal effect of maternal BMI in pregnancy on offspring fatness (BMI and dual-energy X-ray absorptiometry [DXA] determined fat mass index [FMI]) in a MR approach. This was investigated, with repeat measurements, from ages 7 to 18 in the Avon Longitudinal Study of Parents and Children (ALSPAC; n = 2,521 to 3,720 for different ages). We then sought to replicate findings with results for BMI at age 6 in Generation R (n = 2,337 for replication sample; n = 6,057 for total pooled sample).In confounder-adjusted multivariable regression in ALSPAC, a 1 standard deviation (SD, equivalent of 3.7 kg/m2) increase in maternal BMI was associated with a 0.25 SD (95% CI 0.21–0.29) increase in offspring BMI at age 7, with similar results at later ages and when FMI was used as the outcome.A weighted genetic risk score was generated from 32 genetic variants robustly associated with BMI (minimum F-statistic = 45 in ALSPAC). The MR results using this genetic risk score as an IV in ALSPAC were close to the null at all ages (e.g., 0.04 SD (95% CI -0.21–0.30) at age 7 and 0.03 SD (95% CI -0.26–0.32) at age 18 per SD increase in maternal BMI), which was similar when a 97 variant generic risk score was used in ALSPAC.When findings from age 7 in ALSPAC were meta-analysed with those from age 6 in Generation R, the pooled confounder-adjusted multivariable regression association was 0.22 SD (95% CI 0.19–0.25) per SD increase in maternal BMI and the pooled MR effect (pooling the 97 variant score results from ALSPAC with the 32 variant score results from Generation R) was 0.05 SD (95%CI -0.11–0.21) per SD increase in maternal BMI (p-value for difference between the two results = 0.05). A number of sensitivity analyses exploring violation of the MR results supported our main findings. However, power was limited for some of the sensitivity tests and further studies with relevant data on maternal, offspring, and paternal genotype are required to obtain more precise (and unbiased) causal estimates.ConclusionsOur findings provide little evidence to support a strong causal intrauterine effect of incrementally greater maternal BMI resulting in greater offspring adiposity.

Evolution at 'Sutures' and 'Centers': Recombination Can Aid Adaptation of Spatially Structured Populations on Rugged Fitness Landscapes.

Epistatic interactions among genes can give rise to rugged fitness landscapes, in which multiple “peaks” of high-fitness allele combinations are separated by “valleys” of low-fitness genotypes. How populations traverse rugged fitness landscapes is a long-standing question in evolutionary biology. Sexual reproduction may affect how a population moves within a rugged fitness landscape. Sex may generate new high-fitness genotypes by recombination, but it may also destroy high-fitness genotypes by shuffling the genes of a fit parent with a genetically distinct mate, creating low-fitness offspring. Either of these opposing aspects of sex require genotypic diversity in the population. Spatially structured populations may harbor more diversity than well-mixed populations, potentially amplifying both positive and negative effects of sex. On the other hand, spatial structure leads to clumping in which mating is more likely to occur between like types, diminishing the effects of recombination. In this study, we use computer simulations to investigate the combined effects of recombination and spatial structure on adaptation in rugged fitness landscapes. We find that spatially restricted mating and offspring dispersal may allow multiple genotypes inhabiting suboptimal peaks to coexist, and recombination at the “sutures” between the clusters of these genotypes can create genetically novel offspring. Sometimes such an offspring genotype inhabits a new peak on the fitness landscape. In such a case, spatially restricted mating allows this fledgling subpopulation to avoid recombination with distinct genotypes, as mates are more likely to be the same genotype. Such population “centers” can allow nascent peaks to establish despite recombination. Spatial structure may therefore allow an evolving population to enjoy the creative side of sexual recombination while avoiding its destructive side.

Evidence of a genomic insertion in intron 2 of SOD1 causing allelic drop-out during routine diagnostic testing for canine degenerative myelopathy.

Degenerative myelopathy is a severe and progressive neurodegenerative disease and, in the majority of breeds, is associated with the c.118G>A substitution in exon 2 of the canine superoxide dismutase 1 (SOD1) gene. Our laboratories have been engaged in determining the cause of many discordant findings between the parental and the offspring genotypes found by different laboratories. In both cases, the discordant findings refer to actual heterozygous dogs that had been typed as homozygous for the variant allele. To that aim, the genomic context of the causative variant was investigated in two Hovawart dogs. An insertion of 54 nucleotides composed of a poly-T stretch and 15 nucleotides containing the duplication of the exon 2-intron 2 junction was found. The insertion was responsible for the partial mismatch of the reverse primer used for a direct sequencing assay. The mismatch hampered the amplification of the corresponding allele and caused an evident drop-out effect. The insertion is in complete linkage disequilibrium with the c.118G allele. The allele containing the insertion was highly prevalent in Hovawart dogs, accounting for the 26.6% of allele frequency. The insertion was also found in other unrelated breeds such as Rough Collies and Standard Poodles. In conclusion, the study illustrates the importance of correctly designing the primers to avoid inaccurate genotyping of the degenerative myelopathy causative variant in exon 2 of the SOD1 gene.

No evidence of prenatal diversifying selection at locus or supertype levels in the dog MHC class II loci.

BackgroundDespite decades of studying, the mechanisms maintaining high diversity in the genes of the Major Histocompatibility Complex (MHC) are still puzzling scientists. In addition to pathogen recognition and other functions, MHC molecules may act prenatally in mate choice and in maternal-foetal interactions. These interactions are potential selective mechanisms that increase genetic diversity in the MHC. During pregnancy, immune response has a dual role: the foetus represents foreign tissue compared to mother, but histo-incompatibility is required for successful pregnancy. We have studied the prenatal selection in MHC class II loci (DLA-DQA1, DLA-DQB1 and DLA-DRB1) in domestic dogs by comparing the observed and expected offspring genotype proportions in 110 dog families. Several potential selection targets were addressed, including the peptide-binding site, the MHC locus, three-locus haplotype and supertype levels. For the supertype analysis, the first canine supertype classification was created based on in silico analysis of peptide-binding amino-acid polymorphism.ResultsIn most loci and levels, no deviation from the expected genotype frequencies was observed. However, one peptide-binding site in DLA-DRB1 had an excess of heterozygotes among the offspring. In addition, if the father shared a DLA-DRB1 allele with the mother, that allele was inherited by the offspring more frequently than expected, suggesting the selective advantage of a histo-compatible foetus, in contrast to our expectations.ConclusionsWe conclude that there is some evidence of post-copulatory selection at nucleotide site level in the MHC loci of pet dogs. But due to no indication of selection at locus, three-locus, or supertype levels, we estimated that the prenatal selection coefficient is less than 0.3 in domestic dogs and very likely other factors are more important in maintaining the genetic diversity in MHC loci.Electronic supplementary materialThe online version of this article (doi:10.1186/s40575-016-0038-9) contains supplementary material, which is available to authorized users.

A New Metazoan Recombination Rate Record and Consistently High Recombination Rates in the Honey Bee Genus Apis Accompanied by Frequent Inversions but Not Translocations.

Western honey bees (Apis mellifera) far exceed the commonly observed 1–2 meiotic recombination events per chromosome and exhibit the highest Metazoan recombination rate (20 cM/Mb) described thus far. However, the reasons for this exceptional rate of recombination are not sufficiently understood. In a comparative study, we report on the newly constructed genomic linkage maps of Apis florea and Apis dorsata that represent the two honey bee lineages without recombination rate estimates so far. Each linkage map was generated de novo, based on SNP genotypes of haploid male offspring of a single female. The A. florea map spans 4,782 cM with 1,279 markers in 16 linkage groups. The A. dorsata map is 5,762 cM long and contains 1,189 markers in 16 linkage groups. Respectively, these map sizes result in average recombination rate estimates of 20.8 and 25.1 cM/Mb. Synteny analyses indicate that frequent intra-chromosomal rearrangements but no translocations among chromosomes accompany the high rates of recombination during the independent evolution of the three major honey bee lineages. Our results imply a common cause for the evolution of very high recombination rates in Apis. Our findings also suggest that frequent homologous recombination during meiosis might increase ectopic recombination and rearrangements within but not between chromosomes. It remains to be investigated whether the resulting inversions may have been important in the evolutionary differentiation between honey bee species.

MTHFR c.677C>T is a risk factor for non-syndromic cleft lip with or without cleft palate in Chile.

The functional variant within the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene c.677C>T, producing alterations in folate metabolism, has been associated with the risk of non-syndromic cleft lip with or without cleft palate (NSCL/P). We assessed this association in a Chilean population using a combined analysis of case-control and case-parent trio samples. Samples of 165 cases and 291 controls and 121 case-parent trios (sharing the cases) were genotyped. Odds ratio (OR) was estimated for case-control (allele and genotype frequency differences), and this result was confirmed by allele transmission distortion in trios. Due to that these samples are not independent, a combined OR was also computed. Maternal genotype effect was additionally evaluated based on a log-linear method. Borderline but not significant OR (1.28; CI 0.97-1.69) was observed for risk allele (T) in the case-control sample. However, triad sample showed a significant association (OR 1.56: CI 1.09-2.25) which was confirmed by the combined OR (1.37; CI 1.11-1.71). Maternal genotype has been also associated with the phenotype (P=0.002). In contrast to previous reports considering Chilean subjects, our results demonstrated that the offspring and maternal genotypes for MTHFR c.677C>T variant are strongly associated with NSCL/P in this Chilean population.

Log-linear model used in the hybrid design of case-parents triad/control-mother dyad

This study introduced the application of a log-linear model in the hybrid design of case-parents triad/control-mother dyad. Data related to the association between cleft lip with palate (CLP) and methylenetetrahydrofolate reductase (MTHFR) gene A1298C diversity was analyzed. Log-linear model based on likelihood ratio tests (LRTs) was used to analyze the relationships between mother, offspring genotypes and CLP. Data from our study noticed that children of mothers carrying the CC genotype presented a lower risk of CLP, comparing with the children of mothers carrying the AA genotype, with S2=0.45 (95%CI: 0.26-0.79). Offspring that carrying the AC genotype presented a lower risk of CLP, comparing with the offspring that carrying the AA genotype, with R1=0.69 (95% CI: 0.48-0.97). However, no other types of relationships were found. The power of hybrid design was greater than the case-parents study (0.86>0.78). MTHFR A1298C polymorphism seemed to have played an important role in the etiology on both cleft lip and palate. Data from the hybrid design and the log-linear model could help researchers to explore the effects of genotypes from both mothers and the offspring. This study design would present stronger power than the regular case-parents studies thus suitable for studies on the etiology of diseases in early lives, as birth defects.

Non-random paternity of offspring in a highly promiscuous marine snail suggests postcopulatory sexual selection

In the marine snail Littorina saxatilis females are highly polyandrous, resulting in simultaneous broods of offspring sired by ∼20 males. Such high polyandry, in combination with female sperm storage, is likely to promote postcopulatory sexual selection among males. In addition, females may gain direct reproductive benefits from multiple mating. Investigating sexual selection in males and female benefits in relation to the number of sires, we put single virgin females in aquaria with one, two, five or ten males for 80 days, during which each female mated a majority of available males. After removal of the males, females continued to produce offspring during >1 year. Offspring genotypes of 27 families showed multiple paternity with 76 % of males contributing to juveniles, but paternity deviated from random with one or a few males siring the majority of the offspring. Larger males tended to be overrepresented among the sires. Female reproductive output (newborn or juvenile stage) did, however, not increase with number of sires, and females seemed not limited by the number of available males. Because previous studies have shown that females are seemingly indiscriminative in their mate choice, and given that they mate many hundreds of times in their lifespan, this suggests there is comparatively limited scope for premating sexual selection in this species. Hence, we interpret these results mainly in the light of postcopulatory sexual selection. Sexual selection is a main component of evolution. In that context, mating behaviour is central, although it sometimes appears puzzling, even maladaptive. For example, matings are costly; still, in some species, females mate multiple times and with numerous males. Why this behaviour has evolved is intriguing. Extensive numbers of matings suggest less efficient precopulatory mate choice, opening for postcopulatory sexual selection through cryptic female choice and sperm competition. Using a highly promiscuous snail species with internal fertilisation and long-term sperm storage, we identified the fathers of 549 offspring. We found that while females mated most males available, the offspring were non-randomly distributed among mated males and large males were overrepresented among the sires. This suggests that sexual selection predominantly occurs after mating and that males benefit from size-related effects. Yet, we could not find any female benefits from mating multiple males.

Testing Allele Transmission of an SNP Set Using a Family-Based Generalized Genetic Random Field Method.

Family-based association studies are commonly used in genetic research because they can be robust to population stratification (PS). Recent advances in high-throughput genotyping technologies have produced a massive amount of genomic data in family-based studies. However, current family-based association tests are mainly focused on evaluating individual variants one at a time. In this article, we introduce a family-based generalized genetic random field (FB-GGRF) method to test the joint association between a set of autosomal SNPs (i.e., single-nucleotide polymorphisms) and disease phenotypes. The proposed method is a natural extension of a recently developed GGRF method for population-based case-control studies. It models offspring genotypes conditional on parental genotypes, and, thus, is robust to PS. Through simulations, we presented that under various disease scenarios the FB-GGRF has improved power over a commonly used family-based sequence kernel association test (FB-SKAT). Further, similar to GGRF, the proposed FB-GGRF method is asymptotically well-behaved, and does not require empirical adjustment of the type I error rates. We illustrate the proposed method using a study of congenital heart defects with family trios from the National Birth Defects Prevention Study (NBDPS).

Sex roles in nest keeping - how information asymmetry contributes to parent-offspring co-adaptation.

Parental food provisioning and offspring begging influence each other reciprocally. This makes both traits agents and targets of selection, which may ultimately lead to co‐adaptation. The latter may reflect co‐adapted parent and offspring genotypes or could be due to maternal effects. Maternal effects are in turn likely to facilitate in particular mother‐offspring co‐adaptation, further emphasized by the possibility that mothers are sometimes found to be more responsive to offspring need. However, parents may not only differ in their sensitivity, but often play different roles in postnatal care. This potentially impinges on the access to information about offspring need. We here manipulated the information on offspring need as perceived by parents by playing back begging calls at a constant frequency in the nest‐box of blue tits (Cyanistes caeruleus). We measured the parental response in provisioning to our treatment, paying particular attention to sex differences in parental roles and whether such differences alter the perception of the intensity of our manipulation. This enabled us to investigate whether an information asymmetry about offspring need exists between parents and how such an asymmetry relates to co‐adaptation between parental provisioning and offspring begging. Our results show that parents indeed differed in the frequency how often they perceived the playback due to the fact that females spent more time with their offspring in the nest box. Correcting for the effective exposure of an adult to the playback, the parental response in provisioning covaried more strongly (positive) with offspring begging intensity, independent of the parental sex, indicating coadaptation on the phenotypic level. Females were not more sensitive to experimentally increased offspring need than males, but they were exposed to more broadcasted begging calls. Therefore, sex differences in access to information about offspring need, due to different parental roles, have the potential to impinge on family conflicts and their resolution.

Genetic variation in offspring indirectly influences the quality of maternal behaviour in mice.

Conflict over parental investment between parent and offspring is predicted to lead to selection on genes expressed in offspring for traits influencing maternal investment, and on parentally expressed genes affecting offspring behaviour. However, the specific genetic variants that indirectly modify maternal or offspring behaviour remain largely unknown. Using a cross-fostered population of mice, we map maternal behaviour in genetically uniform mothers as a function of genetic variation in offspring and identify loci on offspring chromosomes 5 and 7 that modify maternal behaviour. Conversely, we found that genetic variation among mothers influences offspring development, independent of offspring genotype. Offspring solicitation and maternal behaviour show signs of coadaptation as they are negatively correlated between mothers and their biological offspring, which may be linked to costs of increased solicitation on growth found in our study. Overall, our results show levels of parental provisioning and offspring solicitation are unique to specific genotypes.

Heterozygous Dnmt3a Mutation Induces Expansion of Hematopoietic Stem Cell Pool in a Murine Model

Somatic mutations in DNMT3A, a member of the DNA methyltransferase family, have been identified in various kinds of hematologic malignancies including acute myeloid leukemia (AML), acute lymphoblastic leukemia, myeloproliferative neoplasms, and aplastic anemia. Especially, in cytogenetically normal AML, DNMT3A mutations are detected in 15-20% of cases and associated with poor prognosis. Approximately 40 to 60% of DNMT3A mutations reside at Arg882 (R882), forming hot spot mutation site, implying gain-of-functional property of the mutation in development of leukemia. So far, a functional role of DNMT3A mutation in leukemogenesis has been investigated by overexpressing DNMT3A R882 mutant or Dnmt3a knockout in murine hematopoietic cells. However, the consequenses of DNMT3A R882 mutant with endogenous expression have been largely unknown. To elucidate this, we generated a novel mouse model for Cre-mediated conditional expression of Dnmt3a R878C mutant (homologous to human R882C) from the endogenous locus of Dnmt3a. For hematopoietic cell-specific mutation in vivo, we crossed these mice with Vav-Cre mice. By analyzing genotypes of offspring derived from the pair of Dnmt3aR878C/wt; Vav-Crewt/wt mice and Dnmt3aR882C/wt; Vav-Cretg/wt mice, it is revealed that mice harboring homozygous mutation of Dnmt3a in hematopoietic cells (DNMT3AR882C/R882C; Vav-Cretg/wt) were not born for now. In contrast, Dnmt3aR882C/wt; Vav-Cretg/wt (hereafter Dnmt3a R878C) mice were normally born and they did not show any hematological or other disorders at least until 40 weeks after birth. Additionally, frequencies of peripheral blood mature cells in each lineage are not altered in Dnmt3a R878C mice compared to Dnmt3awt/wt Vav-Cretg/wt (hereafter control mice). To further investigate the effect of DNMT3A R882 mutation, we sacrificed Dnmt3a R878C and control mice at 8-12 weeks after birth and compared the distribution of hematopoietic cells by using flow cytometry. Although there was no obvious difference in the number of mononuclear cells in the whole bone marrow, we found a significant increase of the frequency of long-term hematopoietic stem cells (defined by CD150+ CD48- Lineage- c-Kit+ Sca-1+) in Dnmt3a R878C mice compared to control mice (0.040% and 0.019%, p = 0.022). The frequencies of other progenitors including short-term hematopoietic stem cells, multipotent progenitors, or Lineage- c-Kit+ Sca-1+ (LSK) cells were not changed between Dnmt3a R878C mice and control mice. Moreover, in order to determine whether DNMT3A mutation leads to a qualitative difference in HSCs, we performed colony forming assay. While control LSK cells could not form colonies at fifth round of replating, Dnmt3a R878C LSK cells could be serially replated up to five passages. Additionally, the numbers of colonies in each round were much higher in Dnmt3a R878C cells compared to control cells, suggesting HSCs with heterozygous Dnmt3a R878C mutation have aberrantly enhanced self-renewal capacity. Currently, we are performing competitive bone marrow transplantation assay to evaluate the functional role of DNMT3A mutation in vivo. We transplanted 500,000 bone marrow cells from Dnmt3a R878C or control mice, which are Ly5.2 background, together with the same number of Ly5.1-horboring competitor cells into Ly5.1-harboring lethally-irradiated recipient mice. Thus far, Peripheral blood chimerisms of donor cells have tended to be higher in recipients of Dnmt3a R878C mutant cells compared to control mice, suggesting that heterozygous Dnmt3a R878C mutation contribute to expansion of hematopoietic stem cell pool. Collectively, heterozygous Dnmt3a R878C mutant enhanced self-renewal capacity of HSCs and resulted in accumulation of HSCs in vivo, similar to mice models with overexpression of DNMT3A R882 mutants. Our results revealed that endogenous expression of DNMT3A mutant is sufficient for expansion of HSCs, revealing functional contribution of DNMT3A mutation in forming the backbone of premalignant status of HSCs. DisclosuresNo relevant conflicts of interest to declare.

The Quantitative-MFG Test: A Linear Mixed Effect Model to Detect Maternal-Offspring Gene Interactions.

Maternal-offspring gene interactions, aka maternal-fetal genotype (MFG) incompatibilities, are neglected in complex diseases and quantitative trait studies. They are implicated in birth to adult onset diseases but there are limited ways to investigate their influence on quantitative traits. We present the quantitative-MFG (QMFG) test, a linear mixed model where maternal and offspring genotypes are fixed effects and residual correlations between family members are random effects. The QMFG handles families of any size, common or general scenarios of MFG incompatibility, and additional covariates. We develop likelihood ratio tests (LRTs) and rapid score tests and show they provide correct inference. In addition, the LRT's alternative model provides unbiased parameter estimates. We show that testing the association of SNPs by fitting a standard model, which only considers the offspring genotypes, has very low power or can lead to incorrect conclusions. We also show that offspring genetic effects are missed if the MFG modeling assumptions are too restrictive. With genome-wide association study data from the San Antonio Family Heart Study, we demonstrate that the QMFG score test is an effective and rapid screening tool. The QMFG test therefore has important potential to identify pathways of complex diseases for which the genetic etiology remains to be discovered.

Resistance to Fusarium solani and characterization of hybrids from the cross between P. mucronata and P. edulis

The development of resistant cultivars is an alternative to control phytosanitary problems affecting passion fruit crops. This study was conducted to obtain progenies through interspecific crosses between Passiflora edulis × Passiflora mucronata, perform the genetic assessment of the progenies obtained, and evaluate and select genotypes resistant to Fusarium solani. When P. mucronata was used as female parent, 516 seeds were obtained, with 20 % germination and survival of nine hybrid genotypes. On the other hand, in the reciprocal cross, 9 seeds were obtained and only one genotype survived. Due to the small number of genotypes obtained, 10 hybrid genotypes and their parents P. edulis (susceptible) and P. mucronata (resistant) was propagated by cuttings. Nine plantlets of each genotype were taken to the field in a randomized block design, with three replications, aiming at morphological characterization. Twenty quantitative and 7 qualitative descriptors were assessed. Nine clones of each individual were kept in a greenhouse, inoculated with F. solani, and assessed 76 days after inoculation. Later, the fungus was re-isolated. The offspring genotypes of the cross in which P. edulis was the female parent did not flourish. For most quantitative and qualitative traits, hybrids were similar to P. mucronata. The genotypes studied formed six groups. Resistance to the fungus was detected in the genotypes of P. mucronata, from Bahia, and two hybrid genotypes. The resistant hybrid can be backcrossed with P. edulis and/or used as rootstock for sour passion fruit.

Pappa2 deletion in mice affects male but not female fertility.

BackgroundRecent studies have found associations between the gene encoding pregnancy associated plasma protein-A2 (PAPP-A2), a protease of insulin-like growth factor binding protein -5 (IGFBP-5), and measures of female reproductive performance in cattle. The purpose of the present study was to test the effects of Pappa2 deletion on reproduction in mice.FindingsWe measured the fertility and offspring growth of Pappa2 deletion females, and also performed reciprocal matings (i.e., deletion males mated to control females) to control for the effects of offspring genotype. Ovarian and testicular IGFBP-5 levels were measured by Western blotting. As expected, deletion of Pappa2 increased ovarian IGFBP-5 levels. However, Pappa2 deletion in females had no effect on the interval between pairing and the birth of the first litter, the interval between the births of the first and second litters, or litter size. Offspring weight was lower in the offspring of Pappa2 deletion females, but effects of similar magnitude were observed in the offspring of Pappa2 deletion males, suggesting that the effects were due to heterozygosity for the deletion in the offspring. Pappa2 deletion in males had no effect on litter size or the interval between pairing and the birth of the first litter. However, the interval between the births of the first and second litters was significantly longer in deletion males.ConclusionsPappa2 deletion had no effect on female reproductive performance. In contrast, Pappa2 deletion had subtle effects on male fertility, although the underlying mechanism remains to be elucidated.

Impaired Maternal Behavior in Usp46 Mutant Mice: A Model for Trans-Generational Transmission of Maternal Care.

Usp46 mutant mice (congenic strain on a B6 genetic background; MT mice) have a low weaning rate and display poor maternal behavior compared to C57BL/6J mice (B6 mice). Based on these observations, we examined how maternal behavior is shaped by cross-fostering and in-fostering MT and B6 mice. The experiments consisted of six groups: B6 mice fostered by their biological mother (B6-CO); MT mice fostered by their biological mother (MT-CO); B6 mice fostered by a different B6 mother (B6-IF); MT mice fostered by a different MT mother (MT-IF); B6 mice fostered by an MT mother (B6-CF); and MT mice fostered by a B6 mother (MT-CF). Maternal behavior was assessed using the pup-retrieval test in adult female offspring, and four parameters, time nursing pups in the nest, time sniffing or licking pups, rearing behavior, and latency to retrieve pups, were measured. Cross-fostering significantly reduced time spent nursing and sniffing/licking pup, and increased the number of instances of rearing in the B6-CF group, and improved three parameters of maternal behaviors (nursing, rearing and latency) in the MT-CF group. These results indicate that the level of maternal care is transmitted to their pups and proper maternal behaviors can be shaped if adequate postpartum maternal care is given, even in genetically vulnerable mice. However, the offspring’s genotype may also influence the development of maternal behaviors in adulthood. Thus, MT mice may prove useful as a model for trans-generational transmission of maternal care, and these findings may provide insight into the mechanisms of maltreating behaviors in human child abuse.

Evolutionary dynamics of a polymorphic self-replicator population with a finite population size and hyper mutation rate

Self-replicating biomolecules, subject to experimental evolution, exhibit hyper mutation rates where the genotypes of most offspring have at least a one point mutation. Thus, we formulated the evolutionary dynamics of an asexual self-replicator population with a finite population size and hyper mutation rate, based on the probability density of fitnesses (fitness distribution) for the evolving population. As a case study, we used a Kauffman׳s “NK fitness landscape”. We deduced recurrence relations for the first three cumulants of the fitness distribution and compared them with the results of computer simulations. We found that the evolutionary dynamics is classified in terms of two modes of selection: the “radical mode” and the “gentle mode”. In the radical mode, only a small number of genotypes with the highest or near highest fitness values can leave offspring. In the gentle mode, genotypes with moderate fitness values can leave offspring. We clarified how the evolutionary equilibrium and climbing rate depend on given parameters such as gradient and ruggedness of the landscape, mutation rate and population size, in terms of the two modes of selection. Roughly, the radical mode conducts the fast climbing but attains to the stationary states with low fitness, while the gentle mode conducts the slow climbing but attains to the stationary states with high fitness.

Comparative gene expression profiles in pancreatic islets associated with agouti yellow mutation and PACAP overexpression in mice

In diabetes mellitus, pituitary adenylate cyclase-activating polypeptide (PACAP) has insulinotropic and glucose-lowering properties. We previously demonstrated that transgenic mice overexpressing PACAP in pancreatic β-cells (PACAP-Tg) show attenuated pancreatic islet hyperplasia and hyperinsulinemia in type 2 diabetic models. To explore the underlying mechanisms, here we crossed PACAP-Tg mice with lethal yellow agouti (KKAy) diabetic mice, and performed gene chip analysis of laser capture microdissected pancreatic islets from four F1 offspring genotypes (wild-type, PACAP-Tg, KKAy, and PACAP-Tg:KKAy). We identified 1371 probes with >16-fold differences between at least one pair of genotypes, and classified the probes into five clusters with characteristic expression patterns. Gene ontology enrichment analysis showed that genes involved in the terms ribosome and intracellular organelles such as ribonucleoprotein complex, mitochondrion, and chromosome organization were significantly enriched in clusters characterized by up-regulated genes in PACAP-Tg:KKAy mice compared with KKAy mice. These results may provide insight into the mechanisms of diabetes that accompany islet hyperplasia and amelioration by PACAP.

Molecular assessment of mating strategies in a population of Atlantic spotted dolphins.

Similar to other small cetacean species, Atlantic spotted dolphins (Stenella frontalis) have been the object of concentrated behavioral study. Although mating and courtship behaviors occur often and the social structure of the population is well-studied, the genetic mating system of the species is unknown. To assess the genetic mating system, we genotyped females and their progeny at ten microsatellite loci. Genotype analysis provided estimates of the minimum number of male sires necessary to account for the allelic diversity observed among the progeny. Using the estimates of male sires, we determined whether females mated with the same or different males during independent estrus events. Using Gerud2.0, a minimum of two males was necessary to account for the genetic variation seen among progeny arrays of all tested females. ML-Relate assigned the most likely relationship between offspring pairs; half or full sibling. Relationship analysis supported the conservative male estimates of Gerud2.0 but in some cases, half or full sibling relationships between offspring could not be fully resolved. Integrating the results from Gerud2.0, ML-Relate with previous observational and paternity data, we constructed two-, three-, and four-male pedigree models for each genotyped female. Because increased genetic diversity of offspring may explain multi-male mating, we assessed the internal genetic relatedness of each offspring’s genotype to determine whether parent pairs of offspring were closely related. We found varying levels of internal relatedness ranging from unrelated to closely related (range -0.136–0.321). Because there are several hypothesized explanations for multi-male mating, we assessed our data to determine the most plausible explanation for multi-male mating in our study system. Our study indicated females may benefit from mating with multiple males by passing genes for long-term viability to their young.