Deleterious variants identified in S1PR1 gene resulted in reduced expression of S1PR1. (A) The distribution of S1PR1 variants identified in the discovery and extended cohort of MCL patients. Altogether, 200 Swedish MCL samples from 179 patients were screened by WES and/or Sanger sequencing. Most of the variants identified in S1PR1 were frameshift insertion or deletions (indels). In P9, an identical mutation (p.S123Efs) was detected in all 3 samples. In P47, 2 mutations were detected. (B) S1PR1 protein expression in a fibroblast cell line (WB detection) transfected with wild-type (WT) or mutant S1PR1 constructs; β-actin was used as a loading control. In lane 2, a band between 15 and 20 kDa is detected, which is probably nonspecific because the mutations would lead to a truncated protein of ∼35 kDa. IHC staining of S1PR1 in control tonsil samples (C; note S1PR1 expression in the mantle zone of germinal centers) and in representative MCL cases (D) carrying WT (P7) or mutated S1PR1 (P56, P36, P45; note that in P45 different tumor areas vary in S1PR1 expression); magnification ×200. (E) The full summary on the S1PR1 expression by IHC in MCL cases.