Inbred Laboratory Strains Research Articles

Abstract 2745: Tumor microenvironment and host genetics impact glioma progression in a Collaborative Cross-based orthotopic allograft model

Abstract Gliomas are diffusely invasive brain tumors with fatal outcomes and few effective treatments. Precision medicine focuses on targeting the genetics of individual tumors, but not host genetics, despite studies that have linked germline polymorphisms with glioma risk. Accordingly, glioma survival studies in mice utilize genetically variable tumors on identical host genetic backgrounds, which fails to differentiate between cancer cell-autonomous (CCA) and tumor microenvironment (TME) effects on glioma progression and host survival. The Collaborative Cross (CC) is a panel of genetically diverse mouse strains derived from both wild- and traditional inbred laboratory strains that facilitates high-resolution genetic mapping in models of complex disease. Here, we implement a novel platform to discover genetic modifiers of both CCA and TME phenotypes using genetically defined orthotopic murine allograft gliomas and CC hosts. We stereotactically injected Nf1;Trp53-/-oligodendrocyte progenitor-derived mouse tumor cells into syngeneic C57BL/6 control mice and 14 different CC strains. Seven strains survived significantly longer than controls (P<0.05), suggesting slower tumor growth (Gs, growth slow). The remaining 7 strains survived similarly to controls, suggesting fast growth (Gf, growth fast). Variable tumor growth in CC mice suggests that genetic background influences molecular processes in the TME that inhibit or potentiate tumor growth, respectively. To identify candidate genes, we performed RNA sequencing on 36 tumors from 3 Gf strains, 4 Gs strains, and controls. 134 genes were differentially expressed among Gf, Gs, and control tumors (P<0.05). Hierarchical clustering on these genes revealed that Gs strains clustered separately from Gf and controls. Gene ontology analysis using GOrilla showed 30 enriched processes, (FDR q<0.001), all of which were involved in immune responses or extracellular matrix biology. These results suggest that Gs strains activate immune and TME processes that slow tumor growth. Quantitative trait locus (QTL) analyses of host genetics and tumor data are pending and will facilitate identification of genetic variants that influence TME effects on tumor progression. Citation Format: Kasey Skinner, Martin Ferris, Ryan Bash, Abigail Shelton, Erin Smithberger, Steve Angus, Brian Golitz, Noah Sciaky, Jeremy Simon, Jason Stein, Glenn Matsushima, Quinn Ostrom, Lindsay Stetson, Jill Barnholtz-Sloan, Harshil Dhruv, Michael Berens, Fernando Pardo Manuel de Villena, C. Ryan Miller. Tumor microenvironment and host genetics impact glioma progression in a Collaborative Cross-based orthotopic allograft model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2745.

Oxidative stress resistance as a factor in aging: evidence from an extended longevity phenotype of Drosophila melanogaster.

Longevity of a species is a multifactorial quantitative trait influenced by genetic background, sex, age and environment of the organism. Extended longevity phenotypes (ELP) from experimental evolution in the laboratory can be used as model systems to investigate the mechanisms underlying aging and senescence. ELPs of Drosophila are correlated with various life history attributes such as resistance to environmental stressors (starvation, desiccation, cold and paraquat), developmental time, biochemical defenses, etc. The association between oxidative stress resistance and longevity is not clear and ELPs offer an opportunity to examine the role of oxidative stress resistance in longevity. Here, we have investigated the hypothesis that enhanced oxidative stress resistance and elevated antioxidant defense system play a positive role in longevity using an ELP of Drosophila melanogaster. An ELP of D. melanogaster isolated and characterized in our laboratory through artificial selection (inbred laboratory strain of Oregon K) is employed in this study. Our ELP, named as long lifespan (LLS) flies, shows marked extension in lifespan when compared to the progenitor population (normal lifespan, NLS) and makes a suitable model to study the role of mitochondrial genome in longevity because of its least heterogeneity. In this study, sensitivity to ethanol with age was employed as a measure of resistance to oxidative stress in NLS and LLS flies. Effect of age and oxidative stress on longevity was examined by employing NLS and LLS flies of different age groups against ethanol-induced oxidative stress. Results show that the lower mortality against ethanol was associated with enhanced oxidative stress resistance, higher antioxidant defenses, lower reactive oxygen species (ROS) levels, enhanced alcohol dehydrogenase activity and better locomotor ability attributes of LLS flies. In addition, age-related changes like locomotor impairments, decreased antioxidant defenses, higher ROS levels and sensitivity to oxidative stress were delayed in LLS flies when compared to NLS. Our study supports the hypothesis that higher oxidative stress resistance and enhanced antioxidant defenses are significant factors in extending longevity.

Profiling of cellular immune responses to Mycoplasma pulmonis infection in C57BL/6 and DBA/2 mice

Mycoplasma infections cause respiratory tract damages and atypical pneumonia, resulting in serious problems in humans and animals worldwide. It is well known that laboratory inbred mouse strains show various susceptibility to Mycoplasma pulmonis (M. pulmonis) infection, which causes murine respiratory mycoplasmosis. In this study, we aimed to demonstrate the difference in cellular immune responses between resistant strain, C57BL/6NCrSlc (B6) and susceptible strain, DBA/2CrSlc (D2) after challenging M. pulmonis infection. D2 mice showed higher amount of bacterial proliferation in lung, higher pulmonary infiltration of immune cells such as neutrophils, macrophages, and lymphocytes, and higher levels of interleukin (IL)-1β, IL-6, IL-17A, and tumor necrosis factor-α in bronchoalveolar lavage fluid than did B6 mice. The results of this study suggest that D2 mice are more susceptible than B6 mice to M. pulmonis infection due to a hyper-immune inflammatory response.

Configural learning in freshly collected, smart, wild Lymnaea.

An inbred laboratory strain (W-strain) of Lymnaeastagnalis is capable of configural learning. Configural learning, a higher form of learning, is an association between two stimuli experienced together that is different from the simple sum of their components. In our configural learning procedure, a food odour (carrot odour, CO) is experienced together with crayfish effluent (CE) (i.e. CO+CE). Following configural learning, CO now elicits a fear state rather than increased feeding. We hypothesized that freshly collected wild strains of predator-experienced L. stagnalis also possess the ability to form configural learning, even though they experience crayfish daily in their environment. We therefore subjected freshly collected wild strain L. stagnalis to the configural learning procedure. Following the configural learning procedure, CO became a risk signal and evoked anti-predator behaviours. Thus, configural learning was demonstrated in wild, freshly collected snails. We believe that configural learning occurs in the snail's natural environment and is important for their survival.

Xkr8 Modulates Bipolar Cell Number in the Mouse Retina.

The present study interrogated a quantitative trait locus (QTL) on Chr 4 associated with the population sizes of two types of bipolar cell in the mouse retina. This locus was identified by quantifying the number of rod bipolar cells and Type 2 cone bipolar cells across a panel of recombinant inbred (RI) strains of mice derived from two inbred laboratory strains, C57BL/6J (B6/J) and A/J, and mapping a proportion of that variation in cell number, for each cell type, to this shared locus. There, we identified the candidate gene X Kell blood group precursor related family member 8 homolog (Xkr8). While Xkr8 has no documented role in the retina, we localize robust expression in the mature retina via in situ hybridization, confirm its developmental presence via immunolabeling, and show that it is differentially regulated during the postnatal period between the B6/J and A/J strains using qPCR. Microarray analysis, derived from whole eye mRNA from the entire RI strain set, demonstrates significant negative correlation of Xkr8 expression with the number of each of these two types of bipolar cells, and the variation in Xkr8 expression across the strains maps a cis-eQTL, implicating a regulatory variant discriminating the parental genomes. Xkr8 plasmid electroporation during development yielded a reduction in the number of bipolar cells in the retina, while sequence analysis of Xkr8 in the two parental strain genomes identified a structural variant in the 3′ UTR that may disrupt mRNA stability, and two SNPs in the promoter that create transcription factor binding sites. We propose that Xkr8, via its participation in mediating cell death, plays a role in the specification of bipolar cell number in the retina.

Clonal and atypical Toxoplasma strain differences in virulence vary with mouse sub-species

The severe virulence of Toxoplasma gondii in classical laboratory inbred mouse strains contradicts the hypothesis that house mice (Mus musculus) are the most important intermediate hosts for its transmission and evolution because death of the mouse before parasite transmission equals death of the parasite. However, the classical laboratory inbred mouse strains (Mus musculus domesticus), commonly used to test Toxoplasma strain differences in virulence, do not capture the genetic diversity within Mus musculus. Thus, it is possible that Toxoplasma strains that are severely virulent in laboratory inbred mice are avirulent in some other mouse sub-species. Here, we present insight into the responses of individual mouse strains, representing strains of the genetically divergent Mus musculus musculus, Mus musculus castaneus and Mus musculus domesticus, to infection with individual clonal and atypical Toxoplasma strains. We observed that, unlike M. m. domesticus, M. m. musculus and M. m. castaneus are resistant to the clonal Toxoplasma strains. For M. m. musculus, we show that this is due to a locus on chromosome 11 that includes the genes that encode the interferon gamma (IFNG)-inducible immunity-related GTPases (Irgs) that can kill the parasite by localising and subsequently vesiculating the parasitophorous vacuole membrane. However, despite the localization of known effector Irgs to the Toxoplasma parasitophorous vacuole membrane, we observed that some atypical Toxoplasma strains are virulent in all the mouse strains tested. The virulence of these atypical strains in M. m. musculus could not be attributed to individual rhoptry protein 5 (ROP5) alleles, a secreted parasite pseudokinase that antagonises the canonical effector Irgs and is indispensable for parasite virulence in laboratory inbred mice (M. m. domesticus). We conclude that murine resistance to Toxoplasma is modulated by complex interactions between host and parasite genotypes and may be independent of known effector Irgs on murine chromosome 11.

The Genetic Basis of Albinism in the Hermaphroditic Freshwater SnailPlanorbella trivolvis

In many species, the difference between pigmented and non-pigmented individuals is due to a single recessive Mendelian gene. We have demonstrated that this is also the case in the freshwater hermaphroditic snail, Planorbella trivolvis (Say, 1817), and established an albino population with comparable genetic background to a wild population so that pigmentation can be used as a visible genetic marker to better understand the reproductive biology of these mollusks. We carried out Mendelian crosses between albino (A) individuals from an inbred laboratory strain and pigmented (P) individuals one generation removed from a natural population and assessed pigmentation of progeny from eggs collected immediately after mating and 11 weeks later. Results of parental, F1, and F2 generations and backcrosses to pure-breeding albinos were consistent with a Mendelian single gene inheritance pattern. Because we never observed albino progeny from any albino snails mated to pigmented sperm donors, we also confirmed that selfing is rare in P. trivolvis. A simple non-invasive paternity marker in this unusual hermaphrodite snail that displays almost no self-fertilization will facilitate experiments to understand its reproductive biology and provide a more complete picture of hermaphrodite mating strategies.

Population Differences in Fecundity Components in the Hermaphroditic Freshwater SnailPlanorbella trivolvis

Fecundity in outcrossing species can be influenced by both maternal and paternal parents. To tease out these influences, we observed egg production in two populations of the hermaphroditic freshwater snail, Planorbella trivolvis (Say 1817). We carried out both intra- and inter-population matings between individuals from an inbred albino laboratory strain and individuals one generation removed from a natural population, and measured egg production for two 3-week periods - immediately after mating and 11 weeks later. In the female role, individuals from the albino laboratory population produced significantly more egg masses than the wild derived snails, regardless of whether they were mated to a partner of wild or laboratory origin, indicating that egg mass production is controlled by the maternal parent. Conversely, regardless of their own origin (laboratory or wild), snails mated to individuals from the wild derived population laid more eggs in each egg mass than those fertilized by sperm from the lab population. These results indicate that the number of egg masses a snail lays is determined at least in part by a maternal contribution, and that the number of eggs deposited in each mass may be influenced by the origin of the sperm donor. In addition, we confirmed a short-term trade-off between growth and reproduction as differences in egg production among mating types were mirrored by differences in body size. Further investigation into the nature of these differences will lead to better understanding of the reproductive biology of these hermaphrodite mollusks.

The Evolution of Polymorphic Hybrid Incompatibilities in House Mice.

Resolving the mechanistic and genetic bases of reproductive barriers between species is essential to understanding the evolutionary forces that shape speciation. Intrinsic hybrid incompatibilities are often treated as fixed between species, yet there can be considerable variation in the strength of reproductive isolation between populations. The extent and causes of this variation remain poorly understood in most systems. We investigated the genetic basis of variable hybrid male sterility (HMS) between two recently diverged subspecies of house mice, Mus musculus domesticus and Mus musculus musculus We found that polymorphic HMS has a surprisingly complex genetic basis, with contributions from at least five autosomal loci segregating between two closely related wild-derived strains of M. m. musculus One of the HMS-linked regions on chromosome 4 also showed extensive introgression among inbred laboratory strains and transmission ratio distortion (TRD) in hybrid crosses. Using additional crosses and whole genome sequencing of sperm pools, we showed that TRD was limited to hybrid crosses and was not due to differences in sperm motility between M. m. musculus strains. Based on these results, we argue that TRD likely reflects additional incompatibilities that reduce hybrid embryonic viability. In some common inbred strains of mice, selection against deleterious interactions appears to have unexpectedly driven introgression at loci involved in epistatic hybrid incompatibilities. The highly variable genetic basis to F1 hybrid incompatibilities between closely related mouse lineages argues that a thorough dissection of reproductive isolation will require much more extensive sampling of natural variation than has been commonly utilized in mice and other model systems.

A method for single pair mating in an obligate parasitic nematode

Parasitic nematode species have extremely high levels of genetic diversity, presenting a number of experimental challenges for genomic and genetic work. Consequently, there is a need to develop inbred laboratory strains with reduced levels of polymorphism. The most efficient approach to inbred line development is single pair mating, but this is challenging for obligate parasites where the adult sexual reproductive stages are inside the host, and thus difficult to experimentally manipulate. This paper describes a successful approach to single pair mating of a parasitic nematode, Haemonchus contortus. The method allows for polyandrous mating behaviour and involves the surgical transplantation of a single adult male worm with multiple immature adult females directly into the sheep abomasum. We used a panel of microsatellite markers to monitor and validate the single pair mating crosses and to ensure that the genotypes of progeny and subsequent filial generations were consistent with those expected from a mating between a single female parent of known genotype and a single male parent of unknown genotype. We have established two inbred lines that both show a significant overall reduction in genetic diversity based on microsatellite genotyping and genome-wide single nucleotide polymorphism. There was an approximately 50% reduction in heterozygous SNP sites across the genome in the MHco3.N1 line compared with the MoHco3(ISE) parental strain. The MHco3.N1 inbred line has subsequently been used to provide DNA template for whole genome sequencing of H. contortus. This work provides proof of concept and methodologies for forward genetic analysis of obligate parasitic nematodes.

Sex-specific regulation of CNS autoimmunity by the signal lymphocytic activation molecule (Slam) locus

Abstract Multiple sclerosis (MS) is a demyelinating inflammatory disease of the central nervous system (CNS). Epidemiological studies have documented a 3–6 fold increase in MS incidence and prevalence in females over the last half-century, while remaining relatively stable in males. This establishes that gene×environment×sex interactions contribute to MS susceptibility. Genome-wide association studies (GWAS) of MS patients identified multiple candidate genes, including a locus containing the signal lymphocytic activation molecule (SLAM) family of receptors, a region rich in immune-relevant genes that is highly conserved between humans and mice. There are two major Slam haplotypes segregating in laboratory mice. Slam haplotype-1 is present in C57BL/6 (B6) mice and haplotype-2 is expressed in most other common inbred laboratory strains, including 129 mice. The congenic B6.129c1 mouse possesses the 129-derived Slam haplotype-2 locus on the B6 background, which allows for assessing the potential contribution of SLAM family genes to MS susceptibility using the myelin oligodendrocyte (MOG) model of experimental autoimmune encephalomyelitis (EAE). We show that male B6.129c1 congenic mice demonstrate significant protection against MOG-EAE, but only in males. Furthermore, draining lymph nodes from immunized B6.129c1 males, but not females, had increased Foxp3+ regulatory T cells (Treg) and IL-10 levels compared with B6, suggesting that SLAM/Slam haplotypes regulate autoimmunity by modulating the generation of immunoregulatory cells in a sex-specific manner. Taken together, our results support a role for the SLAM locus is MS pathogenesis, and reveal a novel sexual dimorphism in the genetic control of this autoimmune disease

Comparison of Adult Hippocampal Neurogenesis and Susceptibility to Treadmill Exercise in Nine Mouse Strains.

The genetic background of mice has various influences on the efficacy of physical exercise, as well as adult neurogenesis in the hippocampus. In this study, we investigated the basal level of hippocampal neurogenesis, as well as the effects of treadmill exercise on adult hippocampal neurogenesis in 9 mouse strains: 8 very commonly used laboratory inbred mouse strains (C57BL/6, BALB/c, A/J, C3H/HeJ, DBA/1, DBA/2, 129/SvJ, and FVB) and 1 outbred mouse strain (ICR). All 9 strains showed diverse basal levels of cell proliferation, neuroblast differentiation, and integration into granule cells in the sedentary group. C57BL/6 mice showed the highest levels of cell proliferation, neuroblast differentiation, and integration into granule cells at basal levels, and the DBA/2 mice showed the lowest levels. The efficacy of integration into granule cells was maximal in ICR mice. Treadmill exercise increased adult hippocampal neurogenesis in all 9 mouse strains. These results suggest that the genetic background of mice affects hippocampal neurogenesis and C57BL/6 mice are the most useful strain to assess basal levels of cell proliferation and neuroblast differentiation, but not maturation into granule cells. In addition, the DBA/2 strain is not suitable for studying hippocampal neurogenesis.

Genetic Background Limits Generalizability of Genotype-Phenotype Relationships

Genome-wide association studies (GWASs) have identified numerous loci that influence risk for psychiatric diseases. Genetically engineered mice are often used to characterize genes implicated by GWASs. These studies are based on the assumption that observed genotype-phenotype relationships will generalize to humans, implying that the results would at least generalize to other inbred mouse strains. Given current concerns about reproducibility, we sought to directly test this assumption. We produced F1 crosses between male C57BL/6J mice heterozygous for null alleles of Cacna1c and Tcf7l2 and wild-type females from 30 inbred laboratory strains. We found extremely strong interactions with geneticbackground that sometimes supported diametrically opposing conclusions. These results do not negate the invaluable contributions of mouse genetics to biomedical science, but they do show thatgenotype-phenotype relationships cannot be reliably inferred by studying a single genetic background, and thus constitute a major challenge to the status quo. VIDEO ABSTRACT.

West Nile virus infection in the Collaborative Cross mouse model recapitulates unique human disease states

Abstract West Nile Virus (WNV) is a cytopathic neurotropic flavivirus that causes a wide range of infection states in humans, ranging from asymptomatic to severe neuroinvasive disease. This variation supports the idea that host genetics play an important role in immunity to WNV infection. The significant individual to individual variation in immune responses within the human population can not be fully captured in single laboratory inbred strains, so a systems genetic approach requires the use of the Collaborative Cross (CC) mouse system to identify polymorphic host genes and networks that control the regulation of adaptive immunity to WNV infection. The CC is a panel of lines with over 40 million single nucleotide polymorphisms evenly distributed throughout the genome, providing the statistical power to map multiple genetic factors with small to moderate effect. In the CC model we have identified lines with unique human phenotypes that have not previously been captured in laboratory inbred strains, such as severe neuroinvasive disease and chronic WNV infection. Our use of the CC model shows differing immune responses to WNV in terms of T cell frequency and activation, antigen-specific CD8 T cell frequency, memory precursor cells, and T cell cytokine production between CC strains after WNV infection. A distinct immune signature is present in the chronic line, characterized by a strong systemic regulatory T cell response and late virus-specific response in the CNS due to viral persistence. Microarray analysis on spleen and CNS tissue reveals expression changes correlated with extreme immune phenotype responses within and between organ compartments, allowing for identification of correlates of protection and susceptibility to WNV infection.

Mouse genome-wide association study identifies polymorphisms on chromosomes 4, 11, and 15 for age-related cardiac fibrosis.

Dystrophic cardiac calcinosis (DCC), also called epicardial and myocardial fibrosis and mineralization, has been detected in mice of a number of laboratory inbred strains, most commonly C3H/HeJ and DBA/2J. In previous mouse breeding studies between these DCC susceptible and the DCC-resistant strain C57BL/6J, 4 genetic loci harboring genes involved in DCC inheritance were identified and subsequently termed Dyscalc loci 1 through 4. Here, we report susceptibility to cardiac fibrosis, a sub-phenotype of DCC, at 12 and 20months of age and close to natural death in a survey of 28 inbred mouse strains. Eight strains showed cardiac fibrosis with highest frequency and severity in the moribund mice. Using genotype and phenotype information of the 28 investigated strains, we performed genome-wide association studies (GWAS) and identified the most significant associations on chromosome (Chr) 15 at 72 million base pairs (Mb) (P<10(-13)) and Chr 4 at 122Mb (P<10(-11)) and 134Mb (P<10(-7)). At the Chr 15 locus, Col22a1 and Kcnk9 were identified. Both have been reported to be morphologically and functionally important in the heart muscle. The strongest Chr 4 associations were located approximately 6Mb away from the Dyscalc 2 quantitative trait locus peak within the boundaries of the Extl1 gene and in close proximity to the Trim63 and Cap1 genes. In addition, a single-nucleotide polymorphism association was found on chromosome 11. This study provides evidence for more than the previously reported 4 genetic loci determining cardiac fibrosis and DCC. The study also highlights the power of GWAS in the mouse for dissecting complex genetic traits.

Exaggerated male pheromones in rats may increase predation cost.

Male animals with more conspicuous visual and acoustic signals increase their mating success, but also increase the risk of being attacked by eavesdropping predators. In rodents, males with richer sex pheromones often have higher attractiveness to females, but whether or not the males are also at higher predation risk is poorly known. Here, we used 2 laboratory inbred strains of the rat Rattus norvegicus, Brown Norway (BN) and Lewis (LEW), and wild-captured rats as odor donors to assess the relationship between the pheromone levels in male rats and attractiveness to domestic cats Felis catus. LEW rats had significantly higher levels of male pheromones (e.g., 4-heptanone, 2-heptanone, and 9-hydroxy-2-nonanone) than BN rats. Simultaneously, wild-captured male rats were selectively assigned to 2 groups (HIGH or LOW) based on pheromone content as determined by gas chromatography–mass spectrometry (GC-MS). Binary choice tests were carried out during the night in the test room. We found that cats spent more time investigating male bedding and urine of LEW rats than the counterpart of BN rats. Likewise, cats also preferred bedding and urine odor of the HIGH wild rats compared with the counterparts of LOW wild rats. Adding synthetic analogs of the 3 pheromone ketones into the urine of either BN rats or LOW wild rats significantly increased their attractiveness to cats. Our data suggest that the rats with exaggerated male pheromones more strongly attracted predators and thus as a consequence may suffer from elevated predation risk.

The Mouse Universal Genotyping Array: From Substrains to Subspecies

Genotyping microarrays are an important resource for genetic mapping, population genetics, and monitoring of the genetic integrity of laboratory stocks. We have developed the third generation of the Mouse Universal Genotyping Array (MUGA) series, GigaMUGA, a 143,259-probe Illumina Infinium II array for the house mouse (Mus musculus). The bulk of the content of GigaMUGA is optimized for genetic mapping in the Collaborative Cross and Diversity Outbred populations, and for substrain-level identification of laboratory mice. In addition to 141,090 single nucleotide polymorphism probes, GigaMUGA contains 2006 probes for copy number concentrated in structurally polymorphic regions of the mouse genome. The performance of the array is characterized in a set of 500 high-quality reference samples spanning laboratory inbred strains, recombinant inbred lines, outbred stocks, and wild-caught mice. GigaMUGA is highly informative across a wide range of genetically diverse samples, from laboratory substrains to other Mus species. In addition to describing the content and performance of the array, we provide detailed probe-level annotation and recommendations for quality control.

Heterosis Increases Fertility, Fecundity, and Survival of Laboratory-Produced F1 Hybrid Males of the Malaria Mosquito Anopheles coluzzii.

The success of vector control strategies aiming to decrease disease transmission via the release of sterile or genetically-modified male mosquitoes critically depends on mating between laboratory-reared males and wild females. Unfortunately, mosquito colonization, laboratory rearing, and genetic manipulations can all negatively affect male competitiveness. Heterosis is commonly used to produce domestic animals with enhanced vigor and homogenous genetic background and could therefore potentially improve the mating performance of mass-reared male mosquitoes. Here, we produced enhanced hybrid males of the malaria mosquito Anopheles coluzzii by crossing two strains colonized >35 and 8 years ago. We compared the amount of sperm and mating plug proteins they transferred to females, as well as their insemination rate, reproductive success and longevity under various experimental conditions. Across experiments, widespread adaptations to laboratory mating were detected in the older strain. In large-group mating experiments, no overall hybrid advantage in insemination rates and the amount of sperm and accessory gland proteins transferred to females was detected. Despite higher sperm activity, hybrid males did not appear more fecund. However, individual-male mating and laboratory-swarm experiments revealed that hybrid males, while inseminating fewer females than older inbred males, were significantly more fertile, producing larger mating plugs and drastically increasing female fecundity. Heterotic males also showed increased longevity. These results validate the use of heterosis for creating hybrid males with improved fitness from long-established inbred laboratory strains. Therefore, this simple approach could facilitate disease control strategies based on male mosquito releases with important ultimate benefits to human health.

Transcriptome profiling reveals distinctive traits of retinol metabolism and neonatal parallels in the MRL/MpJ mouse.

BackgroundThe MRL/MpJ mouse is a laboratory inbred strain known for regenerative abilities which are manifested by scarless closure of ear pinna punch holes. Enhanced healing responses have been reported in other organs. A remarkable feature of the strain is that the adult MRL/MpJ mouse retains several embryonic biochemical characteristics, including increased expression of stem cell markers.ResultsWe explored the transcriptome of the MRL/MpJ mouse in the heart, liver, spleen, bone marrow and ears. We used two reference strains, thus increasing the chances to discover the genes responsible for the exceptional properties of the regenerative strain. We revealed several distinctive characteristics of gene expression patterns in the MRL/MpJ mouse, including the repression of immune response genes, the up-regulation of those associated with retinol metabolism and PPAR signalling, as well as differences in expression of the genes engaged in wounding response. Another crucial finding is that the gene expression patterns in the adult MRL/MpJ mouse and murine neonates share a number of parallels, which are also related to immune and wounding response, PPAR pathway, and retinol metabolism.ConclusionsOur results indicate the significance of retinol signalling and neonatal transcriptomic relics as the distinguishing features of the MRL/MpJ mouse. The possibility that retinoids could act as key regulatory molecules in this regeneration model brings important implications for regenerative medicine.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-2075-2) contains supplementary material, which is available to authorized users.

ID: 96: Two mutations in the GTPase domain of interferon-induced Mx1 are responsible for high influenza susceptibility of wild-derived CAST/EiJ mice

Type I and III interferon-regulated Mx genes encode evolutionary conserved antiviral restriction factors which inhibit a broad range of RNA viruses in most vertebrate species. In mice, the Mx1 locus confers resistance to members of the Orthomyxoviridae, such as influenza A and Thogoto viruses. Mice of strain A2G carry a functional Mx1 gene, while most other laboratory inbred mouse strains carry truncated and therefore defective Mx1 alleles. A recent study (Ferris MT et al. PLOS pathogens 9(2) 2013) investigating how genetic factors might contribute to influenza susceptibility showed that CAST/EiJ mice, an inbred strain derived from wild Mus musculus castaneus, are susceptible to influenza virus challenge although they carry a full-length Mx1 gene. Here we characterized CAST-derived Mx1 in order to better understand the molecular basis of its altered antiviral properties. We were able to show that CAST-derived Mx1 retains a low degree of anti-influenza activity but, surprisingly, is still able to confer full protection against Thogoto virus challenge. Sequencing revealed that CAST-derived Mx1 differs by two amino acids from A2G-derived Mx1 which are both localized in the GTPase (G) domain of the protein. These mutations lead to a reduction in GTPase activity. They further diminish Mx1 protein levels in organs of animals after interferon stimulation in vivo. Interestingly, these mutations have no effect on mRNA levels, suggesting that the reduced Mx1 protein levels might be attributed to differences in protein stability. In summary, our findings are able to explain the unexpected virus susceptibility of CAST/EiJ mice.