Fig 1: Effect of PNN stabilization during adolescence on PNN build-up, PV expression, and memory.(A) Experimental paradigm for HAPLN1 injection. (B) Injection of HAPLN1 prevented the time-dependent reduction of freezing (Veh: n = 12, HAPLN1: n = 11, two-way RM ANOVA: Age at test: F(1.933,41.86) = 14.70 p < 0.001, HAPLN1: F(1,21) = 0.2303 p = 0.636, Age at test × HAPLN1: F(1.993,41.86) = 3.761 p = 0.032, Šídák’s post-hoc test: Veh: p32 vs. p60: p = 0.002, p45 vs. p60: p = 0.007; p60: Veh vs. HAPLN1: p = 0.038). (C) Representative images (top) and quantifications demonstrated significantly increased WFA+ cell densities (bottom left, Veh: n = 12, Hapln1: n = 11, unpaired two-tailed t test: t21 = 4.577 p < 0.001) and PV+ cells (bottom right, Veh: n = 12, Hapln1: n = 11, unpaired two-tailed t test: t21 = 2.490 p = 0.0212) in the RSP of HAPLN1-injected mice. Experimental diagrams were created in BioRender. Zhang, H. (2026) https://BioRender.com/th31zfo. Data represent mean ± s.e.m., *** p < 0.001; ** p < 0.01; * p < 0.05. The data underlying this Figure can be found in S1 Data.