Germ line status of identified CSF3R variants. Protein schematics of CSF3R NM_000760.3 (A) and NM_156039.3 transcripts (B) showing the locations of known protein domains and 19 unique pathogenic variants, likely pathogenic variants, or variants of uncertain significance (VUSs) identified among 84 patients with CSF3R variants found on OncoPlus testing. Variants selected for further study of oncogenic potential are boxed in red. Transcript NM_156039.3 contains an additional 27 amino acid residues in the cytoplasmic domain that the primary transcript, NM_000760.3, lacks and includes the p.Arg698Cys variant. Sanger sequencing of genomic DNA extracted from cultured mesenchymal stromal cells confirmed the germ line origin of the CSF3R p.Trp547* variant in a patient with therapy-related MDS (C), the p.Ala119Thr variant in a patient with multiple myeloma (D), and the p.Pro784Thr variant in a patient with multiple myeloma (E). CRH, cytokine receptor homology; Ig, immunoglobulin; TM, transmembrane.