Fig 1: A point mutation on H2-Aa results in pre-mRNA false splicing and protein frameshift in this specific mouse strain. (A, B) MHC II (A) and H2-Aa (B) expression of B cells treated with MG132 in wild-type and knockout mice. (C, D) MHC II (C) and H2-Aa (D) expression of B cells treated with Lys05 in wild-type and knockout mice. (E) Respective H2-Aa expression in the nucleus and cytoplasm in B cells of wild-type and knockout mice. (F) Analysis of ribosome profiles of B cells in wild-type mice and knockout mice and H2-Aa expression was detected at each stage of ribosome using quantitation real-time PCR. (G) Forward and reverse sequences of B cells and bone marrow-derived macrophage cDNA in wild-type and knockout mice were obtained and aligned. (H) 293T cells were transfected with full-length or eight-base deletion Flag-H2-Aa plasmid and the expressions of Flag and H2-Aa were detected by Western blot. (I) DNA of bone marrow-derived macrophages in wild-type and knockout mice was isolated and sequences were aligned. A point mutation was observed and it could induce wrong pre-mRNA splicing and deletion of eight bases in mRNA. (J) The molecular biology model of type II BLS phenotype in lc3b−/− mice. A mutation from A to G caused the splicing recognition to malfunction until the next AG position Therefore, in lc3b−/− mice, wrong pre-mRNA splicing, deletion of eight bases in mRNA, and frameshift of H2-Aa protein eventually resulted in the loss of H2-Aa protein and subsequent immunodeficiency. Data (A, C) are replicated in three independent experiments. Error bars, mean ± SEM.