| Description |
CXXC5 is a member of the CXXC-type zinc finger epigenetic regulators. We investigated the role of CXXC5 in development of B and myeloid cells after identifying a heterozygous de novo variant in CXXC5 (c.814C>T,p.Arg272Cys) in a patient with immunodeficiency, who progressed to bone marrow failure in over a 30-year period. Mouse bone marrow transplantation experiments using hematopoietic progenitor cells after Cxxc5 knockdown showed a decrease in B cell and monocyte production in the recipient mice. Ex vivo differentiation of mouse progenitor cells into B cells showed an increase in the cell number of developing B cells after Cxxc5 knockdown and a decrease in the cell number after overexpression of Cxxc5. In the ex vivo myeloid differentiation culture, Cxxc5 knockdown reduced monocytes and increased granulocyte development, while an increase in monocyte and decrease in granulocyte development were observed after Cxxc5 overexpression. Ex vivo proliferation experiments revealed that the expression of Cxxc5 affects the cell cycle in stem/progenitor cells. Downregulation of Cxxc5 lead to an increase in the percentage of cells in the S phase, while overexpression of wild-type Cxxc5 results in a decrease in the percentage of cells in the S phase. The Cxxc5 protein encoded by the Cxxc5 (c.814C>T) identified in the patient was not as efficient as the wild-type Cxxc5 in affecting the cell cycle. RNA sequencing of LSK cells and single-cell RNA sequencing of differentiating myeloid cells showed upregulation of genes involved in the regulation of the cell cycle after Cxxc5 knockdown and iv downregulation of genes involved in monocyte differentiation. Competition experiments using LSK cells infected with control shRNA or Cxxc5 shRNA showed that there was a proliferative advantage for LSK cells after Cxxc5 knockdown when compared to the control shRNA infected cells. These experiments provide novel insights into the physiological function of Cxxc5 during hematopoiesis. The experiments using the CXXC5R272C protein encoded by the patient Cxxc5 variant suggests that the encoded protein has a reduced ability to control cell cycle of the stem/progenitor cells, and this may lead to increased division and progressive loss of the stem cell pool, resulting in bone marrow failure. |
