mTOR-related neuropathology in mutant tsc2 zebrafish: Phenotypic, transcriptomic and pharmacological analysis

• Published in: Neurobiology of disease Vol. 108; pp. 225 - 237
• Main Authors: Scheldeman, Chloë, Mills, James D., Siekierska, Aleksandra, Serra, Ines, Copmans, Daniëlle, Iyer, Anand M., Whalley, Benjamin J., Maes, Jan, Jansen, Anna C., Lagae, Lieven, Aronica, Eleonora, de Witte, Peter A.M.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.12.2017; Elsevier
• Subjects: Animals; Animals, Genetically Modified; Brain - abnormalities; Disease Models, Animal; Epilepsy - genetics; Epilepsy - metabolism; Epilepsy - pathology; Gene Expression; Inflammation - metabolism; Inflammation - pathology; Intracellular Signaling Peptides and Proteins - genetics; Larva; Motor Activity - physiology; mTOR; Organ Size; Phenotype; Survival Analysis; TOR Serine-Threonine Kinases - metabolism; Transcriptome; Transcriptomics; Tuberous Sclerosis - genetics; Tuberous Sclerosis - metabolism; Tuberous Sclerosis - pathology; Tuberous sclerosis complex; Zebrafish; Zebrafish - genetics; Zebrafish Proteins - genetics; Zebrafish Proteins - metabolism; mTOR; Zebrafish; Transcriptomics; Tuberous sclerosis complex
• ISSN: 0969-9961; 1095-953X
• DOI: 10.1016/j.nbd.2017.09.004

Tuberous sclerosis complex (TSC) is a rare, genetic disease caused by loss-of-function mutations in either TSC1 or TSC2. Patients with TSC are neurologically characterized by the presence of abnormal brain structure, intractable epilepsy and TSC-associated neuropsychiatric disorders. Given the lack of effective long-term treatments for TSC, there is a need to gain greater insight into TSC-related pathophysiology and to identify and develop new treatments. In this work we show that homozygous tsc2−/− mutant zebrafish larvae, but not tsc2+/− and WT larvae, display enlarged brains, reduced locomotor behavior and epileptiform discharges at 7dpf. In addition, we pharmacologically validated the TSC model by demonstrating the dramatic rescue effect of pericardially injected rapamycin, a well-known mTOR inhibitor, on selected behavioral read-outs and at the molecular level. By means of trancriptome profiling we also acquired more insight into the neuropathology of TSC, and as a result were able to highlight possible new treatment targets. The gene expression profiles of WT and tsc2+/− larvae revealed 117 differentially expressed genes (DEGs), while between WT and tsc2−/− larvae and tsc2+/− and tsc2−/− larvae there were 1414 and 1079 DEGs, respectively. Pathway enrichment analysis from the WT and tsc2−/− DEGs, identified 14 enriched pathways from the up-regulated genes and 6 enriched pathways from the down-regulated genes. Moreover, genes related to inflammation and immune response were up-regulated in the heads of tsc2−/− larvae, in line with the findings in human brain tissue where inflammatory and immune responses appear to be major hallmarks of TSC. Taken together, our phenotypic, transcriptomic and pharmacological analysis identified the tsc2−/− zebrafish as a preclinical model that mirrors well aspects of the human condition and delineated relevant TSC-related biological pathways. The model may be of value for future TSC-related drug discovery and development programs. •tsc2−/− larvae show abnormal brain activity with reduced locomotor response.•Rapamycin, a well-known mTOR inhibitor rescues the phenotype.•Transcriptomics revealed 1414 differentially expressed genes between WT and tsc2−/−.•Genes related to inflammation and immune response were up-regulated in tsc2−/−.•The tsc2−/− zebrafish model is useful to identify new treatment targets for TSC.