A remarkably diverse and well-organized virus community in a filter-feeding oyster.

BACKGROUND: Viruses play critical roles in the marine environment because of their interactions with an extremely broad range of potential hosts. Many studies of viruses in seawater have been published, but viruses that inhabit marine animals have been largely neglected. Oysters are keystone species in coastal ecosystems, yet as filter-feeding bivalves with very large roosting numbers and species co-habitation, it is not clear what role they play in marine virus transmission and coastal microbiome regulation. RESULTS: Here, we report a Dataset of Oyster Virome (DOV) that contains 728,784 nonredundant viral operational taxonomic unit contigs (≥ 800 bp) and 3473 high-quality viral genomes, enabling the first comprehensive overview of both DNA and RNA viral communities in the oyster Crassostrea hongkongensis. We discovered tremendous diversity among novel viruses that inhabit this oyster using multiple approaches, including reads recruitment, viral operational taxonomic units, and high-quality virus genomes. Our results show that these viruses are very different from viruses in the oceans or other habitats. In particular, the high diversity of novel circoviruses that we found in the oysters indicates that oysters may be potential hotspots for circoviruses. Notably, the viruses that were enriched in oysters are not random but are well-organized communities that can respond to changes in the health state of the host and the external environment at both compositional and functional levels. CONCLUSIONS: In this study, we generated a first "knowledge landscape" of the oyster virome, which has increased the number of known oyster-related viruses by tens of thousands. Our results suggest that oysters provide a unique habitat that is different from that of seawater, and highlight the importance of filter-feeding bivalves for marine virus exploration as well as their essential but still invisible roles in regulating marine ecosystems. Video Abstract.

Inhibition of YAP with siRNA prevents cartilage degradation and ameliorates osteoarthritis development.

The Hippo/YAP signaling pathway is important for mediating organ size and tissue homeostasis, but its role in osteoarthritis (OA) remains unclear. We aimed to investigate the role of Hippo/YAP signaling pathway in OA development. YAP expression in OA cartilage was assessed by immunohistochemistry, RT-qPCR, and Western blotting. The effects of YAP overexpression or knockdown on gene expression related to chondrocyte hypertrophy induced by IL-1ß were examined. The in vivo effects of YAP inhibition were studied. Subchondral bone was analyzed by micro-CT. YAP was increased in mice and human OA articular cartilage and chondrocytes. YAP mRNA expression level was also increased in IL-1ß-induced chondrocytes. YAP overexpression resulted in increased expression of catabolic genes in response to IL-1ß. Suppression of YAP by siRNA inhibited IL-1ß stimulated catabolic genes expression and chondrocytes apoptosis. Intra-articular injection of YAP siRNA ameliorated OA development in mice. Micro-CT results showed the aberrant subchondral bone formation was also reduced. We provided evidence that YAP was upregulated in OA cartilage. Inhibition of YAP using YAP siRNA is a promising way to prevent cartilage degradation in OA. KEY MESSAGES: YAP was upregulated in human and mice osteoarthritis cartilage and chondrocytes. YAP siRNA decreased IL-1ß-induced catabolic gene expression. Intra-articular injection of YAP siRNA ameliorated OA development. Intra-articular injection of YAP siRNA reduced aberrant subchondral bone formation.