Figure 1. A Haploid Genetic Screen Reveals SPPL3 as a Regulator of Antibody Accessibility to Membrane-Proximal HLA-I Regions.

(A) Schematic overview of a genome-wide haploid genetic screen using HLA-I-specific W6/32 antibody.

(B) Fish-tail plot showing per gene the mutation index (ratio of integrations mapped in the specified populations) against the amount of mapped integrations. A two-sided false discovery rate (FDR) (Benjamini-Hochberg) corrected Fisher’s exact test was applied. The symbol legend is indicated.

(C) (Left) Titration curves of four HLA-I-specific antibodies on mixed barcoded HAP1 cells (see Figure S1E). The individual antibody binding epitopes are shown on the HLA-I structure. (Right) Flow cytometry histograms of nonsaturating antibody stain as indicated by the arrow (close to EC₅₀ values). MFI, mean fluorescence intensity.

(D) Quantification of (C) using the ratio of WT and SPPL3^−/− EC₅₀ values. Mean ± SD is plotted (n = 5–8 independent experiments).

(E) SPPL3-susceptibility of different epitopes is plotted on the HLA-I/β₂m crystal structure (individual epitopes in Figures 1C and S2A).

See also Figures S1 and S2.