SMARCAL1 deficiency predisposes to non‐Hodgkin lymphoma and hypersensitivity to genotoxic agents in vivo

Schimke immuno-osseous dysplasia (SIOD) is a multisystemic disorder with prominent skeletal, renal, immunological, and ectodermal abnormalities. It is caused by mutations of SMARCAL1 (SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily a-like 1), which encodes a DNA stress response protein. To determine the relationship of this function to the SIOD phenotype, we profiled the cancer prevalence in SIOD and assessed if defects of nucleotide excision repair (NER) and of nonhomologous end joining (NHEJ), respectively, explained the ectodermal and immunological features of SIOD. Finally, we determined if Smarcal1del/del mice had hypersensitivity to irinotecan (CPT-11), etoposide and hydroxyurea (HU) and whether exposure to these agents induced features of SIOD. Among 71 SIOD patients, three had non-Hodgkin lymphoma (NHL) and one had osteosarcoma. We did not find evidence of defective NER or NHEJ; however, Smarcal1-deficient mice were hypersensitive to several genotoxic agents. Also, CPT-11, etoposide and HU caused decreased growth and loss of growth plate chondrocytes. These data, which identify an increased prevalence of NHL in SIOD and confirm hypersensitivity to DNA damaging agents in vivo, provide guidance for the management of SIOD patients.