In vivo dynamics of G-quadruplex DNA structures during liver regeneration in mice

Guanine-rich DNA sequences can form four-stranded structures known as G-quadruplexes (G4s), which play important roles in cellular processes. However, direct observation of G4 dynamics in tissues remains challenging. Here, we report the in vivo dynamics of G4s during mouse liver regeneration after partial hepatectomy (PHx) using a G4-specific antibody. G4-positive hepatocytes gradually increased after PHx, peaking at 36 h, and then decreased, with signals predominantly in nuclei of cells in the peripheral region between the periportal and midzonal regions. Notably, double immunofluorescence analysis of cell cycle markers revealed that G4-positive cells colocalize with EdU- and Cyclin A2-positive cells, suggesting that G4 structures are formed during the S to G2 phases of the cell cycle. In mice deficient in high-mobility group box 2 (HMGB2), a candidate G4-interacting protein, G4-positive cells were significantly reduced compared with wild-type controls, although the temporal peak was preserved. Spatial distribution of G4-positive hepatocytes was also altered in Hmgb2^-/- mice. This study provides the first evidence that G4-binding protein knockout mice can be used to assess the effects of these proteins on DNA G4 formation in vivo.