Abstract
Topoisomerase 1 (TOP1) relieves torsional stress in DNA during transcription and facilitates the expression of long (>100 kb) genes, many of which are important for neuronal functions. To evaluate how loss of Top1 affected neurons in vivo, we conditionally deleted (cKO) Top1 in postmitotic excitatory neurons in the mouse cerebral cortex and hippocampus. Top1 cKO neurons develop properly, but then show biased transcriptional downregulation of long genes, signs of DNA damage, neuroinflammation, increased poly(ADP-ribose) polymerase-1 (PARP1) activity, single-cell somatic mutations, and ultimately degeneration. Supplementation of nicotinamide adenine dinucleotide (NAD+) with nicotinamide riboside partially blocked neurodegeneration, and increased the lifespan of Top1 cKO mice by 30%. A reduction of p53 also partially rescued cortical neuron loss. While neurodegeneration was partially rescued, behavioral decline was not prevented. These data indicate that reducing neuronal loss is not sufficient to limit behavioral decline when TOP1 function is disrupted.
Highlights
Topoisomerase 1 (TOP1) relieves torsional stress in DNA during transcription and facilitates the expression of long (>100 kb) genes, many of which are important for neuronal functions
DNA damage-induced neurodegeneration is frequently associated with hyperactivation of the nicotinamide adenine dinucleotide (NAD+) consuming enzyme poly(ADP-ribose) polymerase-1 (PARP1) (poly(ADP-ribose) polymerase 1), which leads to energetic breakdown and cell death[17,18,19,20]
Given the extensive DNA damage observed in neurons from Top[1] cKO mice, we evaluated the extent to which PARP1 levels and activity were changed via western blot analysis for PARP1 and its post-translational modification poly-ADP ribose (PAR), in WT and Top[1] cKO P7 cortical lysates
Summary
Topoisomerase 1 (TOP1) relieves torsional stress in DNA during transcription and facilitates the expression of long (>100 kb) genes, many of which are important for neuronal functions. Using a single-cell RNA-sequencing (RNA-seq) approach, we found that excitatory neurons in lower cortical layers expressed long genes to a greater extent when compared to excitatory neurons in upper cortical layers in embryonic and early postnatal mice[27]. Based on these observations, we hypothesized that TOP1 might maintain genomic integrity and/or maintain transcriptional output in the central nervous system and that deletion of Top[1] would have the greatest impact on lower layer excitatory cortical neurons. We tested this hypothesis by conditionally deleting Top[1] in postmitotic excitatory neurons in the mouse cerebral cortex and hippocampus
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
