Effects of Pseudoloma neurophilia infection on the brain transcriptome in zebrafish (Danio rerio)

Abstract

Laboratory zebrafish are commonly infected with the intracellular, brain‐infecting microsporidian parasite Pseudoloma neurophilia. Chronic P. neurophilia infections induce inflammation in meninges, brain and spinal cord, and have been suggested to affect neural functions since parasite clusters reside inside neurons. However, underlying neural and immunological mechanisms associated with infection have not been explored. Utilizing RNA‐sequencing analysis, we found that P. neurophilia infection upregulated 175 and downregulated 45 genes in the zebrafish brain, compared to uninfected controls. Four biological pathways were enriched by the parasite, all of which were associated with immune function. In addition, 14 gene ontology (GO) terms were enriched, eight of which were associated with immune responses and five with circadian rhythm. Surprisingly, no differentially expressed genes or enriched pathways were specific for nervous system function. Upregulated immune‐related genes indicate that the host generally show a pro‐inflammatory immune response to infection. On the other hand, we found a general downregulation of immune response genes associated with anti‐pathogen functions, suggesting an immune evasion strategy by the parasite. The results reported here provide important information on host–parasite interaction and highlight possible pathways for complex effects of parasite infections on zebrafish phenotypes.

Behavioral and Reproductive Effects of Environmental Enrichment and Pseudoloma neurophilia infection on Adult Zebrafish (Danio rerio)

“…21 Our results support other recent studies outlining the adverse effects of P. neurophilia infection on zebr afish. 2,13,15,21,22,24,28,29 The many potential unintended effects in infected fish argue for efforts toward the eradication of P. neurophilia in laboratory zebrafish.…”

“…14 Naturally occurring clinical and subclinical infections in animals are well established to cause confounds and high variability that can lead to invalid or misinterpreted experiments and an accumulating body of experimental evidence has begun to characterize the adverse effects of P. neurophilia and other pathogens on zebrafish research. 2,13,15,21,22,24,28,29 However, subclinical PNI zebrafish often go undetected, and thus may be enrolled in, and potentially compromise, biomedical research projects. In addition, uninfected zebrafish may acquire the infection during the course of an experiment, potentially creating undesired effects on research outcomes.…”

Reviewing Pseudoloma neurophilia infections in the popular zebrafish model

“…Further, transcriptomic approaches to better understand the immune responses will allow developing suitable diagnosis methods. Recently, Midttun et al (2020b) described that in P. neurophilia infected zebrafish no differentially expressed genes or enriched pathways were specific for nervous system functions but classical upregulation of immune-related cascades such as pro-inflammatory Th1 response was observed.…”

Rederivation of a mutant line (prop 1) of zebrafish Danio rerio infected with Pseudoloma neurophilia using in vitro fertilization with eggs from pathogen‐free wild‐type (AB) females and sperm from prop 1 males

“…The parasite also causes reduced fecundity (Ramsay et al., 2009). Moreover, this is a serious concern as a cause of non‐protocol‐induced variation in research because apparently healthy fish have been shown to have alterations in behaviour (Midttun, Vindas, Nadler, et al., 2020; Midttun, Vindas, Whatmore, et al., 2020; Spagnoli, Xue, & Kent, 2015; Spagnoli, Xue, Murray, et al., 2015) and in transcriptome profiles (Midttun, Vindas, Nadler, et al., 2020; Midttun, Vindas, Whatmore, et al., 2020).…”

“…alterations in behaviour (Midttun, Vindas, Nadler, et al, 2020;Midttun, Vindas, Whatmore, et al, 2020;Spagnoli, Xue, Murray, et al, 2015) and in transcriptome profiles (Midttun, Vindas, Nadler, et al, 2020;Midttun, Vindas, Whatmore, et al, 2020).…”