Zebrafish polg2 knock-out recapitulates human POLG-disorders; implications for drug treatment.
Raquel Brañas CasasAlessandro ZuppardoGiovanni RisatoAlberto DinarelloRudy CeleghinCamilla FontanaEleonora GrelloniAlexandru Ionut GileaCarlos Pardo-HernándezAndrea RasolaLuisa Dalla ValleTiziana LodiEnrico BaruffiniNicola FacchinelloFrancesco ArgentonNatascia TisoPublished in: Cell death & disease (2024)
The human mitochondrial DNA polymerase gamma is a holoenzyme, involved in mitochondrial DNA (mtDNA) replication and maintenance, composed of a catalytic subunit (POLG) and a dimeric accessory subunit (POLG2) conferring processivity. Mutations in POLG or POLG2 cause POLG-related diseases in humans, leading to a subset of Mendelian-inherited mitochondrial disorders characterized by mtDNA depletion (MDD) or accumulation of multiple deletions, presenting multi-organ defects and often leading to premature death at a young age. Considering the paucity of POLG2 models, we have generated a stable zebrafish polg2 mutant line (polg2 ia304 ) by CRISPR/Cas9 technology, carrying a 10-nucleotide deletion with frameshift mutation and premature stop codon. Zebrafish polg2 homozygous mutants present slower development and decreased viability compared to wild type siblings, dying before the juvenile stage. Mutants display a set of POLG-related phenotypes comparable to the symptoms of human patients affected by POLG-related diseases, including remarkable MDD, altered mitochondrial network and dynamics, and reduced mitochondrial respiration. Histological analyses detected morphological alterations in high-energy demanding tissues, along with a significant disorganization of skeletal muscle fibres. Consistent with the last finding, locomotor assays highlighted a decreased larval motility. Of note, treatment with the Clofilium tosylate drug, previously shown to be effective in POLG models, could partially rescue MDD in Polg2 mutant animals. Altogether, our results point at zebrafish as an effective model to study the etiopathology of human POLG-related disorders linked to POLG2, and a suitable platform to screen the efficacy of POLG-directed drugs in POLG2-associated forms.
Keyphrases
- mitochondrial dna
- endothelial cells
- copy number
- crispr cas
- wild type
- skeletal muscle
- major depressive disorder
- gene expression
- type diabetes
- cystic fibrosis
- ejection fraction
- end stage renal disease
- insulin resistance
- physical activity
- case report
- staphylococcus aureus
- chronic kidney disease
- adipose tissue
- pseudomonas aeruginosa
- peritoneal dialysis
- genome wide
- replacement therapy