VAMP4 KO mice exhibit hyperresponsiveness to glucose due to increased blood insulin levels. (A) Schematic diagram of strategies for the generation of VAMP4 knockout mice, in which the region of Vamp4 exon 3 to exon 7 was deleted, using the CRISPR/Cas9 technique. The solid bars represent ORFs, and the open bars represent UTRs. (B) Representative Western blot images showing the expression levels of VAMP4 in islets isolated from WT and KO mice (n = 3 biological independent samples). GAPDH was used as the loading control. 20 μg of protein was loaded in each lane. (C) Representative confocal images of VAMP4 staining (green) in primary β cells isolated from WT and KO mice (n = 3 biological independent samples). The nuclei of the cells were stained with DAPI (blue). Scale bars, 2 μm. (D) Body weight of male WT and KO mice (n = 6–9 mice per group). (E and F) GTT results (E) and blood insulin levels in the GTT (F) of male WT and KO mice at 14 wk of age for 2 g/kg body weight (n = 6–7 mice per group). (G) ITT results of male WT and KO mice at 16 wk of age for 0.5 U/kg body weight (n = 6–7 mice per group). (H) Ad libitum blood glucose in male WT and KO mice at the ages of 8 and 18 wk (n = 6–9 mice per group). The data are presented as the mean ± SEM. *, P < 0.05. The statistical analyses were performed with two-tailed unpaired Student’s t test (D–H). Source data are available for this figure: SourceData F1.