Fig 2: Bimodality of gene expression in sister blastomeres. (A,B) Expression levels and their histograms. (E1–E10) Embryos 1 to 10. The two (four) blastomeres of each embryo are randomly assigned to two (four) colors. (FPKM) Upper quartile normalized FPKM. (C) Anticorrelation of 2-cell bimodality genes Ap2s1 and Rsph3a. Juxtaposition (upper) and inter-blastomere difference (lower) of expression levels in the same embryos. (D) Correlated genes at the 4-cell stage. Cells from the same embryo have the same color. (r) Pearson correlation. (**) FDR < 0.01.

Fig 3: AP2S1 knockdown or overexpression oppositely regulates APP protein level and amyloidogenesis. A and B, Representative Western blots (left) and quantification (right) of APP, BACE1, CTFs and sAPPß in HEK-APP (A) and SH-SY5Y-APP (B) cells transfected with control (CTRL) or AP2S1 siRNA for 48 h. For better detection of CTFs, cells were treated with the ?-secretase inhibitor DAPT (250 nM) for 24 h. (C and D) Representative immunofluorescent images show APP (C) and Aß (D) protein intensity in SH-SY5Y-APP cells transfected with control or AP2S1 shRNA for 48 h (n = 3 biological replicates). Scale bar: 20 µm. (E and F) Aß42 and Aß40 levels were measured by ELISA in HEK-APP (E) and SH-SY5Y-APP (F) cells transfected with control or AP2S1 siRNA for 48 h. IC, intracellular; EC, extracellular. (G and H) Representative Western blots (left) and quantification (right) of APP, BACE1 and CTFs in HEK-APP (G) and SH-SY5Y-APP (H) cells transfected with control (CTRL) or AP2S1 plasmid for 48 h. (I) Representative immunofluorescent images show APP protein intensity in SH-SY5Y-APP cells transfected with control or AP2S1 plasmid for 48 h (n = 3 biological replicates). Scale bar: 20 µm. (J) Aß42 and Aß40 levels were measured by ELISA in SH-SY5Y-APP cells transfected with control or AP2S1 plasmid for 48 h. n.s., non-significant, *p < 0.05, **p < 0.01

Fig 4: AAV-mediated AP2S1 knockdown improves learning and memory in APP/PS1 mice. (A) In the hidden platform tests, escape latency (the time spent on reaching the platform) relative to the training day was recorded by ANY-maze tracking Software (n = 10 mice). WT-C/WT-S: wild-type mice injected with AAV control or AP2S1 shRNA; AD-C/AD-S: APP/PS1 mice injected with AAV control or AP2S1 shRNA. (B) Representative road maps showing the movement trajectory of mice in the probe trial on the sixth day. (C and D) In the probe trial on the last day, the time period of staying (C, staying time) and the number of times crossed the site (D, passing times) were recorded by ANY-maze software (n = 10 mice). (E and F) In the open field tests, the representative heatmaps (E) and bar plot summary (F) show that AD-S mice exhibit significantly reduced hyperactivity relative to AD-C (n = 10 mice). n.s., non-significant, *p < 0.05, **p < 0.01

Fig 5: Silencing of AP2S1 promotes the trans-localization of APP from LE to lysosome and LE-lyso fusion. A to C, Representative fluorescent images show colocalization of APP with Golgi marker GM130 (A), late endosome marker RAB9 (B) and lysosome marker LAMP1 (C) in SH-SY5Y-APP cells transfected with control or AP2S1 shRNA for 48 h, quantified by Pearson's co-localization coefficient (n = 3 biological replicates). The right two columns show single-channel images of the protein labeling from the left (same as below). Scale bar: 20 µm. (D) Representative fluorescent images show the colocalization of LAMP1 and M6PR in SH-SY5Y-APP cells transfected with control or AP2S1 shRNA for 48 h, quantified by Pearson's co-localization coefficient (n = 3 biological replicates). Scale bar: 20 µm. (E) Representative transmission electron micrographs of SH-SY5Y-APP cells transfected with control or AP2S1 shRNA for 48 h. LE, late endosome; LY, lysosome; N, nucleus. Scale bar: 1 µm. (F) Quantification per cell profile shows an increase in average number of endo-lysosomes fusion in AP2S1 shRNA cells (n = 3 biological replicates). n.s., non-significant, *p < 0.05, **p < 0.01