Diet of sympatric Barn Owls Tyto alba and Short-eared Owls Asio flammeus in an agricultural landscape in south-east Spain

The diets of the Barn Owl Tyto alba and the Short-eared Owl Asio flammeus have been extensively studied worldwide over the past few years, especially on the Iberian Peninsula. Nevertheless, very few studies have examined the diets and the trophic niche overlap in areas where these two raptor species occur in sympatry. As such, in this study we compared the diets of the Barn Owl and the Short-eared Owl inhabiting agricultural landscapes of the Vega de Granada, south-east Spain, based on pellet analysis. The diets were very similar, as both owls preyed mainly on small mammals, the Algerian Mouse Mus spretus being the prey most commonly found in pellets from both species. Although the diet of the Barn Owl was more diverse than that of the Short-eared Owl, the food niche overlap was very high, thus indicating a low interspecific trophic segregation. Despite the similarities between both diets, the frequency of the Mediterranean Pine Vole Microtus duodecimcostatus was much higher in pellets from the Barn Owl, thus suggesting that the Barn Owl may exert pest control in years when the Mediterranean Pine Vole occurs in high numbers.

Neuron-specific chromosomal megadomain organization is adaptive to recent retrotransposon expansions

Regulatory mechanisms associated with repeat-rich sequences and chromosomal conformations in mature neurons remain unexplored. Here, we map cell-type specific chromatin domain organization in adult mouse cerebral cortex and report strong enrichment of Endogenous Retrovirus 2 (ERV2) repeat sequences in the neuron-specific heterochromatic B2NeuN+ megabase-scaling subcompartment. Single molecule long-read sequencing and comparative Hi-C chromosomal contact mapping in wild-derived SPRET/EiJ (Mus spretus) and laboratory inbred C57BL/6J (Mus musculus) reveal neuronal reconfigurations tracking recent ERV2 expansions in the murine germline, with significantly higher B2NeuN+ contact frequencies at sites with ongoing insertions in Mus musculus. Neuronal ablation of the retrotransposon silencer Kmt1e/Setdb1 triggers B2NeuN+ disintegration and rewiring with open chromatin domains enriched for cellular stress response genes, along with severe neuroinflammation and proviral assembly with infiltration of dendrites . We conclude that neuronal megabase-scale chromosomal architectures include an evolutionarily adaptive heterochromatic organization which, upon perturbation, results in transcriptional dysregulation and unleashes ERV2 proviruses with strong neuronal tropism.

Systematic Analysis of Monoallelic Gene Expression and Chromatin Accessibility Across Multiple Tissues in Hybrid Mice

In diploid eukaryotic organisms, both alleles of each autosomal gene are usually assumed to be simultaneously expressed at similar levels. However, some genes can be expressed preferentially or strictly from a single allele, a process known as monoallelic expression. Classic monoallelic expression of X-chromosome-linked genes, olfactory receptor genes and developmentally imprinted genes is the result of epigenetic modifications. Genetic-origin-dependent monoallelic expression, however, is caused by cis-regulatory differences between the alleles. There is a paucity of systematic study to investigate these phenomena across multiple tissues, and the mechanisms underlying such monoallelic expression are not yet fully understood. Here we provide a detailed portrait of monoallelic gene expression across multiple tissues/cell lines in a hybrid mouse cross between the Mus musculus strain C57BL/6J and the Mus spretus strain SPRET/EiJ. We observed pervasive tissue-dependent allele-specific gene expression: in total, 1,839 genes exhibited monoallelic expression in at least one tissue, and 410 genes in at least two tissues. Among these 88 are monoallelic genes with different active alleles between tissues, probably representing genetic-origin-dependent monoallelic expression. We also identified six autosomal monoallelic genes with the active allele being identical in all eight tissues, which are likely novel candidates of imprinted genes. To depict the underlying regulatory mechanisms at the chromatin layer, we performed ATAC-seq in two different cell lines derived from the F1 mouse. Consistent with the global expression pattern, cell-type dependent monoallelic peaks were found, and a higher proportion of C57BL/6J-active peaks were observed in both cell types, implying possible species-specific regulation. Finally, only a small part of monoallelic gene expression could be explained by allelic differences in chromatin organization in promoter regions, suggesting that other distal elements may play important roles in shaping the patterns of allelic gene expression across tissues.

Altering the Binding Properties of PRDM9 Partially Restores Fertility across the Species Boundary

Sterility or subfertility of male hybrid offspring is commonly observed. This phenomenon contributes to reproductive barriers between the parental populations, an early step in the process of speciation. One frequent cause of such infertility is a failure of proper chromosome pairing during male meiosis. In subspecies of the house mouse, the likelihood of successful chromosome synapsis is improved by the binding of the histone methyltransferase PRDM9 to both chromosome homologs at matching positions. Using genetic manipulation, we altered PRDM9 binding to occur more often at matched sites, and find that chromosome pairing defects can be rescued, not only in an intersubspecific cross, but also between distinct species. Using different engineered variants, we demonstrate a quantitative link between the degree of matched homolog binding, chromosome synapsis, and rescue of fertility in hybrids between Mus musculus and Mus spretus. The resulting partial restoration of fertility reveals additional mechanisms at play that act to lock-in the reproductive isolation between these two species.

NEURON-SPECIFIC CHROMOSOMAL MEGADOMAIN ORGANIZATION IS ADAPTIVE TO RECENT RETROTRANSPOSON EXPANSIONS

ABSTRACTHere, we mapped cell-type specific chromatin domain organization in adult mouse cerebral cortex and report strong enrichment of Endogenous Retrovirus 2 (ERV2) repeat sequences in the neuron-specific heterochromatic ‘B2NeuN+’ megabase-scaling subcompartment. Comparative chromosomal conformation mapping in Mus spretus and Mus musculus revealed neuron-specific reconfigurations tracking recent ERV2 retrotransposon expansions in the murine germline, with significantly higher B2 megadomain contact frequencies at sites with ongoing ERV2 insertions in Mus musculus. Ablation of the retrotransposon silencer Kmt1e/Setdb1 triggered B2 megadomain disintegration and rewiring with open chromatin domains enriched for cellular stress response genes, along with severe neuroinflammation and proviral assembly of ERV2/Intracisternal-A-Particles (IAPs) infiltrating dendrites and spines. We conclude that neuronal megadomain architectures include evolutionarily adaptive heterochromatic organization which, upon perturbation, unleashes ERV proviruses with strong tropism within mature neurons.

Evaluation of bioconcentration of trace elements in the Western Mediterranean mouse (Mus spretus Lataste, 1883) at two Moroccan wetland sites

Many micromammals were shown to be vulnerable to metallic trace elements and are therefore suitable for biomonitoring. The objective of our research is to assess the exposure of a small rodent, Mus spretus, as a bioindicator of pollution to trace elements. We have determined the concentrations of Cu, Pb, Cr, Zn and Fe in the liver, kidneys and heart of 71 individuals of Mus spretus in north-west Morocco in two areas: Merja Zerga and Dayet Erroumi. Tissue metal concentrations in this species varied widely with age, sex, sites and organs. The concentration of Cu in the liver was the highest among all the metals and was recorded in adult females of Merja Zerga with a maximum of 60 µg / g ; at Dayet Erroumi, it was around 14 µg / g. At the same time, we found a similar trend for Fe, Pb, Cr and Zn in the three organs in males and females at the two sites. Highly significant differences between females at the two sites were recorded for the variables weight (W) and head to body length (TL) (t = -3.992; p < 0.001 and t = -2.242, p < 0.05), however, males obtained equal values ​​in the two sites. Spatiotemporal monitoring in small mammals must be studied, but requires the application of a non-lethal estimator.

Divergent Seasonal Reproductive Patterns in Syntopic Populations of Two Murine Species in Southern Spain, Mus spretus and Apodemus sylvaticus

In most mammals with seasonal reproduction, males undergo testis regression during the non-breeding period. We performed a morphological, hormonal, functional, and molecular study of the testes of sexually inactive males of two species of murine rodents, the wood mouse, Apodemus sylvaticus, and the Algerian mouse, Mus spretus, in syntopic populations of southern Iberian peninsula. Both species reproduce during most of the year, but wood mice stop breeding in the summer whereas Algerian mice do it in winter. Sexually inactive males of A. sylvaticus show complete testis regression with reduced levels of serum testosterone and abnormal distribution of cell-adhesion molecules. Contrarily, inactive males of M. spretus maintain almost normal spermotogenesis despite a significant reduction of androgenic function. The lack of an evident explanation for the divergent seasonal breeding patterns found in southern populations of A. sylvaticus and M. spretus, compared with northern ones, implies that very subtle species/population-specific features and/or non-conspicuous environmental cues probably operate to determine their seasonal breeding pattern. These results also support the notion that multiple models of circannual testis variation are possible for different populations of the same species, showing that the mechanisms controlling seasonal reproduction are in fact very plastic and fast evolving.

NEW RECORD OF TWO RODENT SPECIES FROM KHENCHELA REGION (EAST OF ALGERIA)

Mus spretus is endemic to the Mediterranean region and Jaculus orientalis is only found in North Africa and Saudi Arabia. Their presence in Algeria was previously evidenced in other studies, the present paper focuses on the recent discovery of the Jaculus orientalis Erxleben, 1777 and Mus spretus Lataste, 1883 in a new locality of the East of Algeria, in Khenchela region (Aurès Mountain), based on weight and external measurements. The sampling period took four months between April and July 2019. This observation will enrich the knowledge of Algerian Rodents fauna in general and of Khenchela in particular.

Identification of a New QTL Region on Mouse Chromosome 1 Responsible for Male Hypofertility: Phenotype Characterization and Candidate Genes

Male fertility disorders often have their origin in disturbed spermatogenesis, which can be induced by genetic factors. In this study, we used interspecific recombinant congenic mouse strains (IRCS) to identify genes responsible for male infertility. Using ultrasonography, in vivo and in vitro fertilization (IVF) and electron microscopy, the phenotyping of several IRCS carrying mouse chromosome 1 segments of Mus spretus origin revealed a decrease in the ability of sperm to fertilize. This teratozoospermia included the abnormal anchoring of the acrosome to the nucleus and a persistence of residual bodies at the level of epididymal sperm midpiece. We identified a quantitative trait locus (QTL) responsible for these phenotypes and we have proposed a short list of candidate genes specifically expressed in spermatids. The future functional validation of candidate genes should allow the identification of new genes and mechanisms involved in male infertility.

Development of assisted reproductive technologies for Mus spretus†

The genus Mus consists of many species with high genetic diversity. However, only one species, Mus musculus (the laboratory mouse), is common in biomedical research. The unavailability of assisted reproductive technologies (ARTs) for other Mus species might be a major reason for their limited use in laboratories. Here, we devised ARTs for Mus spretus (the Algerian mouse), a commonly used wild-derived Mus species. We found that in vitro production of M. spretus embryos was difficult because of low efficacies of superovulation with equine chorionic gonadotropin or anti-inhibin serum (AIS) (5–8 oocytes per female) and a low fertilization rate following in vitro fertilization (IVF; 15.2%). The primary cause of this was the hardening of the zona pellucida but not the sperm’s fertilizing ability, as revealed by reciprocal IVF with laboratory mice. The largest number of embryos (16 per female) were obtained when females were injected with AIS followed by human chorionic gonadotropin and estradiol injections 24 h later, and then by natural mating. These in vivo-derived 2-cell embryos could be vitrified/warmed with a high survival rate (94%) using an ethylene glycol-based solution. Importantly, more than 60% of such embryos developed into healthy offspring following interspecific embryo transfer into (C57BL/6 × C3H) F1 female mice. Thus, we have devised practical ARTs for Mus spretus mice, enabling efficient production of embryos and animals, with safe laboratory preservation of their strains. In addition, we have demonstrated that interspecific embryo transfer is possible in murine rodents.