Poster abstracts
Poster number 69 submitted by Kelsey Slattery
A potential role for G4R1/DHX36, a G4 helicase, in genomic maintenance in C9orf72 ALS/FTD
Kelsey G. Slattery (Department of Biology, Ball State University, Muncie, IN 47306, USA), Chance Creviston (Department of Biology, Ball State University, Muncie, IN 47306, USA), Philip J. Smaldino (Department of Biology, Ball State University, Muncie, IN 47306, USA)
Abstract:
Genomic instability and DNA damage are emerging as molecular hallmarks of neurodegenerative diseases, including C9orf72-linked amyotrophic lateral sclerosis and frontotemporal dementia (C9 ALS/FTD). C9 ALS/FTD is most commonly caused by an inherited hexanucleotide (G4C2)n-repeat expansion (HRE) mutation, which results in excessive formation of G-quadruplex (G4) DNA and RNA structures. G4 structures are stable secondary structures that modulate replication, transcription, translation, and are associated with genomic instability if left unresolved. In C9 ALS/FTD the GGGGCC-repeat codes for toxic repeat RNAs and dipeptide repeat (DPR) proteins that further exacerbate DNA damage. Previous in vitro and in vivo studies suggest that reduction of the G-quadruplex helicase, G4R1/DHX36, reduces toxic DPRs in C9 ALS/FTD, representing a potential therapeutic target. However, G4R1 plays a vital role in resolving G4 DNA structures during replication and transcription, suggesting that its loss may compromise genomic stability in central nervous tissues. To investigate this, I generated a CNS-specific G4R1/DHX36 knockout mouse model. To do this I crossed DHX36/G4R1 homozygous floxed mice with a transgenic mouse line in which Cre expression is driven by the rat Nestin gene promoter, restricting knockout to CNS tissues. Genotypical analysis revealed a stark absence of homozygous CNS deletion of DHX36/G4R1, demonstrating an essential role for G4R1/DHX36 during embryonic CNS development. Behavioral analysis of heterozygous G4R1/DHX36 knockout mice revealed significantly increased grip strength by two months of age, indicating an alteration of neuromuscular function following G4R1/DHX36 reduction. Ongoing molecular analysis of brain and spinal cord tissue, including qRT-PCR and ELISA aim to determine whether G4R1 loss increases markers of DNA damage. Collectively, this work establishes G4R1 as a critical regulator of embryonic CNS development and motor function and provides further exploration of targeting G4R1/DHX36 as a potential therapeutic target in C9 ALS/FTD.
Keywords: C9 ALS FTD, DHX36 G4R1