Investigating G-quadruplex structures in RPGR gene: Implications for understanding X-linked retinal degeneration

Aims: This pilot study investigates the potential pathogenic role of G-quadruplex (G4) structures
in RPGR-associated retinal degeneration, starting from a case of suspected X-linked form affected
family. We hypothesize that the stabilization of these structures might alter DNA replication and
transcription, inducing genetic instability and influencing gene expression.
Main methods: We conducted whole genome amplification experiments and next-generation
sequencing to detect the blockade of polymerase activity by G4 structures. Our specific focus
was the RPGR gene, which hosts a high concentration of predicted G4-forming motifs and is
implicated in most X-linked retinal degeneration cases. To understand the potential interference
of G4 structures, we applied computational and 3D molecular modeling to visualize interferences
in DNA replication and transcription regulation.
Key findings: Our data confirmed the obstruction of DNA polymerase enzymes by G4 structures,
particularly when stabilized by the compound pyridostatin. This obstruction was evident in the
reduced amplification of RPGR gene regions and a shift in the start/end sites of putative G4
motifs. Moreover, the modeling indicated a potential disruption of critical promoter elements and
RNA polymerase binding, which could drastically alter gene expression.
Significance: Our findings suggest that G4 formation in the RPGR gene could lead to genetic
instability and affect the expression of RPGR, contributing to retinal dystrophy. Moreover, this
study underscores the broader implications of G4 structures in other genetic disorders. Improved
understanding of G4 structures could reveal novel therapeutic targets to combat genetic disor ders, promoting the advancement of personalized medicine and precision healt