SF3B1 haploinsufficiency leads to formation of ring sideroblasts in myelodysplastic syndromes

• Published in: Blood Vol. 120; no. 16; pp. 3173 - 3186
• Main Authors: Visconte, Valeria, Rogers, Heesun J., Singh, Jarnail, Barnard, John, Bupathi, Manoj, Traina, Fabiola, McMahon, James, Makishima, Hideki, Szpurka, Hadrian, Jankowska, Anna, Jerez, Andres, Sekeres, Mikkael A., Saunthararajah, Yogen, Advani, Anjali S., Copelan, Edward, Koseki, Haruhiko, Isono, Kyoichi, Padgett, Richard A., Osman, Sami, Koide, Kazunori, O'Keefe, Christine, Maciejewski, Jaroslaw P., Tiu, Ramon V.
• Format: Journal Article
• Language: English
• Published: Washington, DC Elsevier Inc 18-10-2012; Americain Society of Hematology; American Society of Hematology
• Subjects: Adolescent; Adult; Aged; Anemia, Sideroblastic - etiology; Anemia, Sideroblastic - metabolism; Anemia, Sideroblastic - pathology; Animals; Biological and medical sciences; Biomarkers, Tumor - genetics; Biomarkers, Tumor - metabolism; Cells, Cultured; Female; Gene Expression Profiling; Haploinsufficiency; Hematologic and hematopoietic diseases; Humans; K562 Cells; Leukemias. Malignant lymphomas. Malignant reticulosis. Myelofibrosis; Male; Medical sciences; Mice; Mice, Inbred C57BL; Mice, Knockout; Middle Aged; Mutation - genetics; Myelodysplastic Syndromes - etiology; Myelodysplastic Syndromes - metabolism; Myelodysplastic Syndromes - pathology; Myeloid Neoplasia; Oligonucleotide Array Sequence Analysis; Phenotype; Phosphoproteins - genetics; Phosphoproteins - metabolism; Phosphoproteins - physiology; Plenary Paper; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; Ribonucleoprotein, U2 Small Nuclear - genetics; Ribonucleoprotein, U2 Small Nuclear - metabolism; Ribonucleoprotein, U2 Small Nuclear - physiology; RNA Splicing Factors; RNA, Messenger - genetics; Young Adult; Hematology; Ring; Loss of heterozygosity; Lead; Malignant hemopathy; Sideroblast; Myelodysplastic syndrome; Cancer; Heavy metal
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2012-05-430876

Whole exome/genome sequencing has been fundamental in the identification of somatic mutations in the spliceosome machinery in myelodysplastic syndromes (MDSs) and other hematologic disorders. SF3B1, splicing factor 3b subunit 1 is mutated in 60%-80% of refractory anemia with ring sideroblasts (RARS) and RARS associated with thrombocytosis (RARS-T), 2 distinct subtypes of MDS and MDS/myeloproliferative neoplasms (MDSs/MPNs). An idiosyncratic feature of RARS/RARS-T is the presence of abnormal sideroblasts characterized by iron overload in the mitochondria, called RS. Based on the high frequency of mutations of SF3B1 in RARS/RARS-T, we investigated the consequences of SF3B1 alterations. Ultrastructurally, SF3B1 mutants showed altered iron distribution characterized by coarse iron deposits compared with wild-type RARS patients by transmission electron microscopy. SF3B1 knockdown experiments in K562 cells resulted in down-regulation of U2-type intron-splicing by RT-PCR. RNA-sequencing analysis of SF3B1 mutants showed differentially used genes relevant in MDS pathogenesis, such as ASXL1, CBL, EZH, and RUNX families. A SF3B pharmacologic inhibitor, meayamycin, induced the formation of RS in healthy BM cells. Further, BM aspirates of Sf3b1 heterozygous knockout mice showed RS by Prussian blue. In conclusion, we report the first experimental evidence of the association between SF3B1 and RS phenotype. Our data suggest that SF3B1 haploinsufficiency leads to RS formation.