Spatially patterned mitochondrial remodeling and metabolic changes during Muller glia-dependent retinal regeneration in zebrafish

Abstract

Muller glia regenerate retinal neurons after injury in zebrafish, but how their mitochondrial organization changes during regenerative activation remains poorly defined. Here, we combined mitochondrial imaging, Muller glial transcriptomics, and whole eyecup metabolomics to investigate the response to selective photoreceptor loss. A Muller glia mitochondrial reporter revealed spatial and temporal mitochondrial remodeling: morphological changes were detectable in inner retinal compartments before sustained increases in mitochondrial volume emerged in processes adjacent to injured photoreceptors. This response coincided with reduced respiratory chain transcript expression and selective induction of mitochondrial assembly and maintenance genes, while the eyecup underwent temporally patterned metabolic changes. Dichloroacetate (DCA), an inhibitor of pyruvate dehydrogenase kinases (PDK), attenuated outer-retinal Muller glial mitochondrial remodeling. DCA also reshaped the Muller glial transcriptional response to injury, suppressing reprogramming- and cell cycle associated programs and altering metabolic and mitochondrial gene expression. DCA treatment also blocked the formation of tuba1a:GFP+ Muller glia and PCNA expression, indicating that reprogramming and progenitor proliferation requires PDK activity. Together, our findings identify compartment-specific mitochondrial remodeling as an early event in the Muller glial regenerative response and demonstrate that mitochondrial remodeling and regenerative activation are sensitive to perturbation of the PDK/PDH regulatory axis.

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