Inflammation fuels bone marrow exhaustion caused by Samd9l mutation

Area of Science:

• Hematology
• Genetics
• Immunology

Background:

• Sterile alpha motif domain-containing 9 (SAMD9) and SAMD9-like (SAMD9L) syndromes are inherited bone marrow failure syndromes.
• These syndromes are characterized by myelodysplastic syndrome and monosomy 7.
• Existing treatments for SAMD9/SAMD9L syndromes are limited.

Purpose of the Study:

• To develop and characterize a mouse model for SAMD9/SAMD9L syndromes.
• To investigate the cellular mechanisms underlying bone marrow failure in these syndromes.
• To explore potential therapeutic strategies for SAMD9/SAMD9L syndromes.

Main Methods:

• Generated a mouse model with a hematopoietic cell-specific heterozygous Samd9l mutation knockin.
• Assessed bone marrow failure phenotypes and allele loss in mutant mice.
• Analyzed hematopoietic stem progenitor cell fitness and investigated the role of TGF-β signaling.

Main Results:

• The mouse model recapitulated key features of human SAMD9/SAMD9L syndromes, including bone marrow failure and nonrandom loss of the mutant allele.
• Samd9l-mutant hematopoietic stem progenitor cells exhibited reduced fitness, exacerbated by inflammation.
• TGF-β hyperactivation was identified as a cause of reduced cell fitness, and TGF-β inhibition partially rescued this phenotype.

Conclusions:

• The developed mouse model is a valuable tool for studying SAMD9/SAMD9L syndromes.
• TGF-β signaling plays a critical role in the pathophysiology of these syndromes.
• TGF-β inhibitors represent a promising therapeutic avenue for treating SAMD9/SAMD9L syndromes.