Hypothalamic Transcriptome Response To Simulated Diel Earthen Pond Hypoxia Cycles In Channel Catfish (Ictalurus punctatus)

Authors: Ott, Brian; Hulse-Kemp, Amanda; DUKE, MARY - Retired ARS Employee; GRIFFINS, MATT - Mississippi State University; Peterson, Brian; Scheffler, Brian; TORRANS, EUGENE - Retired ARS Employee; ALLEN, PETER - Mississippi State University

Submitted to: Physiological Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/27/2024
Publication Date: 5/29/2024
Citation: Ott, B.D., Torrans, E.L., Griffins, M.J., Allen, P.J., Duke, M.V., Peterson, B.C., Scheffler, B.E., Hulse-Kemp, A.M. 2024. Hypothalamic Transcriptome Response To Simulated Diel Earthen Pond Hypoxia Cycles In Channel Catfish (Ictalurus punctatus). Physiological Genomics. https://doi.org/10.1152/physiolgenomics.00007.2024.
DOI: https://doi.org/10.1152/physiolgenomics.00007.2024

Interpretive Summary: Channel catfish and other aquaculture species can experience daily periods of hypoxia that decrease appetite and ultimately. Scientists at the USDA-ARS Warmwater Aquaculture Research and Genomics and Bioinformatics Research Units collaborated with a scientist from Mississippi State University to map changes in genes expression in the channel catfish hypothalamus during hypoxia using RNA sequencing (RNAseq). Hypoxia induces dramatic changes in gene expression that subsides once environmental dissolved oxygen increases and charts and lists of those genes are provided in this manuscript. These results provide useful information for aquaculture and fisheries scientists investigating gene expression of catfish and other fishes during hypoxia.

Technical Abstract: Commercial culture of channel catfish (Ictalurus punctatus) occurs in earthen ponds, which are characterized by diel swings in dissolved oxygen concentration that can decrease to severe levels of hypoxia. Low dissolved oxygen concentration in catfish production ponds suppresses appetite and leads to suboptimal growth. To unravel the underlying molecular framework that may govern appetite in channel catfish during hypoxia, an investigation into the hypothalamus transcriptome was conducted. This investigation aimed to identify specific genes and gene expression patterns that respond to hypoxia, given the significance of the hypothalamus in regulating these processes in other fish species. Channel catfish were subjected to either constant normoxia or typical diel pond durations of hypoxia and normoxia, with 12 hours of hypoxia (20% oxygen saturation; 1.8 mg O2/L; 27 °C) followed by 12 hours of recovery in normoxic water (100.1% oxygen saturation; 8.0 mg O2/L). Fish were sampled at 0-, 6-, 12-, 18-, and 24-hour time points, with the 6- and 12-hour samplings occurring during hypoxia. Among the time points sampled, 190 genes were differentially expressed, with the greatest numbers found during hypoxia. When catfish returned to normoxia, the number of differentially expressed genes decreased sharply. Differentially expressed genes were grouped by function into Gene Ontology functional groupings and revealed that most were categorized as “responses to hypoxia” and “sprouting angiogenesis.” The observed gene expression patterns suggest an increase in vascularization coupled with a shift to anaerobic glycolysis may provide tissue-level protection from hypoxic damage. Notably, several gene candidates were identified in for future studies investigating the interaction of hypoxia and appetite in channel catfish, including adm, igfbp1a, igfbp7, and stc2b.