Muro, T. | bioRxiv Science

bioRxiv2024

Hippocampal reactive neural stem cells are able to phagocytose and have an immunological molecular signature

Hippocampal neural stem cells (NSCs) are the drivers of neurogenesis in the dentate gyrus (DG) of most mammals including humans. During neuronal hyperactivity NSCs become reactive NSCs (react-NSCs), characterized by their activation, morphological changes, and symmetric division, abandoning their neurogenic programme and transforming into reactive astrocytes. Here, using different pathological models that induce react-NSCs in the DG, we looked for novel features of react-NSCs both histologically and by total RNA sequencing. We report that in two pathological models were react-NSCs emerge (mesial temporal lobe epilepsy (MTLE) and traumatic brain injury (TBI)) react-NSCs are capable of phagocytosis of dead cells, a typical immunological function carried out mainly by microglia in the brain. Importantly, MTLE-induced react-NSCs show phagocytic function in tissue and a predominantly immunological molecular signature, with a broad upregulation of phagocytosis-related gene expression. Our results describe a new function of react-NSCs as phagocytic and immunologically active cells in the hippocampal neurogenic niche.

neuroscience↗

bioRxiv2022

Two complete genomes of male-killing Wolbachia infecting Ostrinia moth species illuminate their evolutionary dynamics and association with hosts

Wolbachia is an extremely widespread endocellular symbiont which causes reproductive manipulation on various arthropod hosts. Male progenies are killed in Wolbachia-infected lineages of the Japanese Ostrinia moth population. While the mechanism of male killing and the evolutionary interaction between host and symbiont are significant concerns for this system, the absence of Wolbachia genomic information has limited approaches to these issues. We determined the complete genome sequences of wFur and wSca, the male-killing Wolbachia of O. furnacalis and O. scapulalis. The two genomes shared an extremely high degree of homology, with over 95% of the predicted protein sequences being identical. A comparison of these two genomes revealed nearly minimal genome evolution, with a strong emphasis on the frequent genome rearrangements and the rapid evolution of ankyrin repeat-containing proteins. Additionally, we determined the mitochondrial genomes of both species infected lineages and performed phylogenetic analyses to deduce the evolutionary dynamics of Wolbachia infection in the Ostrinia clade. According to the inferred phylogenetic relationship, Wolbachia infection was established in the Ostrinia clade prior to the speciation of related species such as O. furnacalis and O. scapulalis. Simultaneously, the relatively high homology of mitochondrial genomes suggested recent Wolbachia introgression between infected Ostrinia species. The findings of this study collectively shed light on the host-symbiont interaction from an evolutionary standpoint. SignificanceDespite the growing number of publicly available Wolbachia genome sequences, only a few high-quality male-killer genomes exist, particularly those found in lepidopteran hosts. The complete genomes of two male-killing Wolbachia of Ostrinia moth hosts were determined in this study. The genomic data obtained here will be used to elucidate the mechanism of reproductive manipulation and the origins of this endosymbionts extraordinary diversity. Additionally, phylogenetic analysis of mitochondria and Wolbachia revealed the evolutionary history of Ostrinia hosts and Wolbachia. The inferred dynamic pattern of infection adds to our understanding of evolution and ecology of Wolbachia endosymbiont, a promising agent for biological pest control.

microbiology↗