Loss of the SAMD9L gain-of-function–mutated allele in myelodysplastic cells. (A) Microarray-based comparative genomic hybridization of bone marrow–derived DNA of F1:I-3 showing duplication of 1q (in red) and deletion of 7q (in green), consistent with the der(1;7)(q10;p10) finding by karyotype. (B) Fluorescence in situ hybridization analysis with chromosome 7 painting reveals monosomy 7 in bone marrow cells from F2:II-4. (C) Frequency of SAMD9L c.2956C>T mutation relative to wild type assessed by mutation-specific droplet-dPCR in fibroblasts and serial bone marrow samples of F1:I-3. (D) Frequency of SAMD9L c.2672T>C mutation relative to wild type assessed by mutation-specific dPCR in DNA derived from MDS, peripheral blood, and fibroblasts of F2:II-4. For each sample, the data displayed is the combination of at least 2 dPCR chips. Error bars show 95% confidence levels.