Puri, S. | bioRxiv Science

bioRxiv2022

Identification of circRNAs linked to Alzheimer's disease and related dementias

We conducted a circular-transcriptome-wide analysis and examined circRNA expression patterns associated with AD and clinical and neuropathological AD severity measures in human hippocampus and cortex brain regions. We validated prior studies of circRNA in AD cortex, and demonstrate novel patterns of expression in the AD hippocampus. We also examined circRNA expression across multiple types of dementia and show that circRNA expression differs by dementia subtype. We demonstrate robust circRNA expression in human neuronal precursor cells (NPCs). Then, using NPCs to study qPCR validated circRNA, we show that exposure to oligomeric tau elicits downregulation of circRNA similar to that observed in AD brain. These data identify circRNA that are changed with AD, and suggest that treating neuronal cells with oligomeric tau can recapitulate some of these changes.

molecular biology↗

bioRxiv2022

Corynebacterium matruchotii fitness enhancement of adjacent streptococci by multiple mechanisms

Polymicrobial biofilms are present in many environments particularly in the human oral cavity where they can prevent or facilitate the onset of disease. While recent advances have provided a clear picture of both the constituents and their biogeographical arrangement, it is still unclear what mechanisms of interaction occur between individual species in close proximity within these communities. In this study we investigated two mechanisms of interaction between the highly abundant supragingival plaque (SUPP) commensal Corynebacterium matruchotii and Streptococcus mitis which are directly adjacent in vivo. We discovered that C. matruchotii enhanced the fitness of streptococci dependent on its ability to detoxify streptococcal-produced hydrogen peroxide and its ability to oxidize lactate also produced by streptococci. We demonstrate that the fitness of adjacent streptococci was linked to that of C. matruchotii and that these mechanisms support the previously described "corncob" arrangement between these species but that this is favorable only in aerobic conditions. Further we utilized scanning electrochemical microscopy (SECM) to quantify lactate production and consumption between individual bacterial cells for the 1st time, revealing that lactate oxidation provides a fitness benefit to S. mitis and not pH mitigation. This study describes mechanistic interactions between two highly abundant human commensals that can explain their observed in vivo spatial arrangements and suggest a way by which they may help preserve a healthy oral bacterial community.

microbiology↗