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Clinical evolution, genetic landscape and trajectories of clonal hematopoiesis in SAMD9/SAMD9L syndromes

Sahoo SS, Pastor VB, Goodings C, Voss RK, Kozyra EJ, Szvetnik A, Noellke P, Dworzak M, Starý J, Locatelli F, Masetti R, Schmugge M, De Moerloose B, Catala A, Kállay K, Turkiewicz D, Hasle H, Buechner J, Jahnukainen K, Ussowicz M, Polychronopoulou S, Smith OP, Fabri O, Barzilai S, de Haas V, Baumann I, Schwarz-Furlan S, European Working Group of Myelodysplastic Syndrome (MDS) in Children (EWOG-Myelodysplastic Syndrome (MDS)), Niewisch MR, Sauer MG, Burkhardt B, Lang P, Bader P, Beier R, Müller I, Albert MH, Meisel R, Schulz A, Cario G, Panda PK, Wehrle J, Hirabayashi S, Derecka M, Durruthy-Durruthy R, Göhring G, Yoshimi-Noellke A, Ku M, Lebrecht D, Erlacher M, Flotho C, Strahm B, Niemeyer CM, Wlodarski MW.
Nature Medicine Oct 2021

Germline SAMD9 and SAMD9L mutations (SAMD9/9Lmut) predispose to myelodysplastic syndromes (MDS) with propensity for somatic rescue. In this study, we investigated a clinically annotated pediatric MDS cohort (n = 669) to define the prevalence, genetic landscape, phenotype, therapy outcome and clonal architecture of SAMD9/9L syndromes. In consecutively diagnosed MDS, germline SAMD9/9Lmut accounted for 8% and were mutually exclusive with GATA2 mutations present in 7% of the cohort. Among SAMD9/9Lmut cases, refractory cytopenia was the most prevalent MDS subtype (90%); acquired monosomy 7 was present in 38%; constitutional abnormalities were noted in 57%; and immune dysfunction was present in 28%. The clinical outcome was independent of germline mutations. In total, 67 patients had 58 distinct germline SAMD9/9Lmut clustering to protein middle regions. Despite inconclusive in silico prediction, 94% of SAMD9/9Lmut suppressed HEK293 cell growth, and mutations expressed in CD34+ cells induced overt cell death. Furthermore, we found that 61% of SAMD9/9Lmut patients underwent somatic genetic rescue (SGR) resulting in clonal hematopoiesis, of which 95% was maladaptive (monosomy 7 ± cancer mutations), and 51% had adaptive nature (revertant UPD7q, somatic SAMD9/9Lmut). Finally, bone marrow single-cell DNA sequencing revealed multiple competing SGR events in individual patients. Our findings demonstrate that SGR is common in SAMD9/9Lmut MDS and exemplify the exceptional plasticity of hematopoiesis in children.




Institution Type


Indication / Modality

Myelodysplastic Syndrome (MDS)

Goal of Study

Clonal Heterogeneity

Key Genes


PAD Project


Analytes Assessed

CNV, InDels, SNV

Sample Storage

Fresh Frozen

Sample Prep

Whole Cells

Sample Type

Patient Material

Tissue / Organ

Bone Marrow Aspirates



Panel Used


Proof Point Demonstrated

Clonality, Co-occurrence, Phylogeny