Biology subjects

Campbell, R. F.

Publications and source records attributed to Campbell, R. F..

3 recordsLinked to original sources

bioRxiv2021

In vitro infection of human lung tissue with SARS-CoV-2: Heterogeneity in host defense and therapeutic response

Cell lines are the mainstay in understanding the biology of COVID-19 infection, but do not recapitulate many of the complexities of human infection. The use of human lung tissue is one solution for the study of such novel respiratory pathogens. We hypothesized that a cryopreserved bank of human lung tissue allows for the in vitro study of the inter-individual heterogeneity of host response to SARS-CoV-2 infection, thus providing a bridge between studies with cell lines and studies in animal models. We generated a cryobank of tissues from 16 donors, most of whom had risk factors for severe illness from COVID-19. Cryopreserved tissues preserved 90% of cell viability and contained heterogeneous populations of metabolically active epithelial, endothelial, and immune cell subsets of the human lung. Samples were readily infectible with HCoV-OC43 and SARS-CoV-2 coronavirus strains, and demonstrated comparable susceptibility to infection. In contrast, we observed a marked donor-dependent heterogeneity in the expression of IL-6, CXCL8 and IFN{beta} in response to SARS-CoV-2 infection. Treatment of tissues with dexamethasone and the experimental drug, N-hydroxycytidine, suppressed viral growth in all samples, whereas chloroquine and remdesivir had no detectable effect. Metformin and sirolimus, molecules with predicted antiviral activity, suppressed viral replication in tissues from a subset of donors. In summary, we developed a novel system for the in vitro study of human SARS-CoV-2 infection using primary human lung tissue from a library of donor tissues. This model may be useful for drug screening and for understanding basic mechanisms of COVID-19 pathogenesis. ImportanceThe current biological systems for the study of COVID-19 are in vitro systems that differ from the human lung in many respects, and animal hosts to which the virus is not adapted. We developed another alternative for studying pathogenesis and drug susceptibility of SARS-CoV-2 in a cryopreserved bank of human lung tissues. We consider the importance of this work to relate to the practical use of this culture system as a repeatable and scalable approach that allows for the study of an important infection in relevant tissues. The tissue bank highlights the heterogeneous response to SARS-CoV-2 infection and treatment, which allows researchers to investigate why treatments work in some donors but not others.

microbiology↗

bioRxiv2018

Laboratory evolution from social to solitary behavior in the N2 reference strain is unnecessary for its fitness advantages

The standard reference Caenorhabditis elegans strain, N2, has evolved marked behavioral changes since its isolation from the wild 67 years ago. Laboratory-derived variation in two genes, npr-1 and glb-5, suppress aerotaxis behaviors on food, resulting in N2 animals evolving from social to solitary feeding strategies. We show here that the derived alleles of npr-1 and glb-5 can confer large fitness advantages in standard laboratory conditions, suggesting that the changes in feeding strategies were beneficial to the N2 strain. However, by using environmental manipulations that suppress social behaviors, we showed the fitness advantages of the derived alleles remained unchanged, suggesting selection on these alleles acted through biological traits unrelated to solitary behavior. Transcriptomics analysis, developmental timing assays, and feeding assays showed that N2 animals mature faster, produce more sperm, and eat more food than a strain containing ancestral alleles of these genes (CX12311) regardless of the behavioral strategies. The O2-sensing neurons URX, AQR, and PQR and the pheromone biosynthesis and lipid regulating enzyme encoded by daf-22 are necessary for the full fitness advantages. We suggest that changes to social/solitary behavior in N2 were a pleiotropic consequence of npr-1 and glb-5s ability to modify integrated O2 and pheromone neural circuits that regulate feeding rate and reproductive development. Together, our results demonstrate how laboratory evolution can lead to profound changes in a strain used as a model by for understanding a variety of fundamental biological processes.

evolutionary biology↗

bioRxiv2017

Modeling of a negative feedback mechanism explains age-dependent genetic architecture in reproduction in domesticated C. elegans strains

Most biological traits and common diseases have a strong but complex genetic basis, controlled by large numbers of genetic variants with small contributions to a trait or disease risk. The effect-size of most genetic variants is not absolute, but can depend on a number of factors including the age and genetic background of an organism. In order to understand the mechanisms that cause these changes, we are studying heritable trait differences between two domesticated strains of C. elegans. We previously identified a major effect locus, caused by a mutation in a component of the NURF chromatin remodeling complex, that regulated reproductive output in an age-dependent manner. The effect-size of this locus changes from positive to negative over the course of an animals reproductive lifespan. Using a previously published macroscale model of egg-laying rate in C. elegans, we show how time-dependent effect-size can be explained by an unequal use of sperm combined with negative feedback between sperm and ovulation rate. We validate a number of key predictions of this model using controlled mating experiments and quantification of oogenesis and sperm use. By incorporating this model into QTL mapping, we identify and partition new QTLs into specific aspects of the egg-laying process. Finally, we show how epistasis between two genetic variants is predicted by this modeling as a consequence of unequal use of sperm. This work demonstrates how modeling of multicellular communication systems can improve our ability to predict and understand the role of genetic variation on a complex phenotype. Negative autoregulatory feedback loops, common in transcriptional regulation, could play an important role in modifying genetic architecture in other traits.\n\nAUTHOR SUMMARYComplex traits are influenced not only by the individual effects of genetic variants, but also how these variants interact with the environment, age, and each other. While complex genetic architectures seem to be ubiquitous in natural traits, little is known about the mechanisms that cause them. Here we identify an example of age-dependent genetic architecture controlling the rate and timing of reproduction in the hermaphroditic nematode C. elegans. Using computational modeling, we demonstrate how this age-dependent genetic architecture can arise as a consequence of two factors: hormonal feedback on oocytes mediated by major sperm protein (MSP) released by sperm stored in the spermatheca and life history differences in sperm use caused by genetic variants. Our work also suggests how age-dependent epistasis can emerge from multicellular feedback systems.

genetics↗