Reverse genetics in humanized mice reveals CARD8-mediated pyroptosis causing pancytopenia in human DPP9 deficiency

Area of Science:

• Genetics
• Immunology
• Hematology

Background:

• Hatipoglu syndrome, caused by DPP9 mutations, leads to inflammasomopathy and pancytopenia.
• The precise mechanism of cell loss in human DPP9 deficiency remains unclear, as Dpp9 mutant mice exhibit normal hematopoiesis.

Purpose of the Study:

• To develop a humanized mouse model for DPP9 deficiency to investigate the underlying mechanisms of Hatipoglu syndrome.
• To elucidate the cellular and molecular basis of cytopenia in human DPP9 deficiency.

Main Methods:

• Utilized CRISPR editing to induce loss-of-function mutations in the human DPP9 gene within CD34+ hematopoietic stem and progenitor cells (HSPCs).
• Transplanted edited human HSPCs into MISTRG6 humanized mice to assess in vivo gene deletion and cellular consequences.
• Analyzed peripheral blood and bone marrow for cytopenia, gene expression changes, and inflammasome activation.

Main Results:

• CRISPR-mediated DPP9 deletion in human HSPCs resulted in efficient and persistent gene knockout in vivo.
• DPP9 deficiency recapitulated pancytopenia in peripheral blood and bone marrow, with cell loss being intrinsic to HSPCs.
• DPP9 deletion induced minimal transcriptional alterations, suggesting post-transcriptional regulation, and led to CARD8 inflammasome activation and pyroptosis in HSPCs.

Conclusions:

• DPP9 deficiency causes Hatipoglu syndrome through a unique human mechanism involving CARD8 inflammasome-mediated pyroptosis of hematopoietic stem and progenitor cells.
• This study reveals a novel disease mechanism distinct from observations in Dpp9 mutant mice.
• The findings offer potential therapeutic targets for Hatipoglu syndrome and related inflammasomopathies.