GATA2-TGF-b1-TAL1 Axis Is Essential for Human NK Cell Development and Function

Introduction: Natural killer (NK) cells are the major innate cytotoxic lymphocytes that mediate rapid and robust effector responses against tumors and pathogens without prior sensitization. However, the transcriptional mechanisms involved in human NK cell development and functions are yet to be fully defined. The transcription factor (TF) GATA2 is essential for regulating the survival, proliferation, and differentiation of hematopoietic stem cells (HSCs) and NK cell development. GATA2 forms a chromatin-bound heptad complex with other TFs (TAL1, FLI1, RUNX1, LYL1, LMO2, and ERG) to regulate hundreds of target genes in HSCs, which are lineage and stage-specific. GATA2 promotes the transition of HSCs into common lymphoid progenitors (CLPs) and its mutation results in the reduction of CD56^Bright NK cells with or without reduced CD56^Dim NK cells. Variants, including T354M in the second DNA-binding zinc finger domain, impair human NK cell development and function. A member of the heptad complex is TAL1, a class II basic helix-loop-helix (bHLH) TF that plays an essential role in controlling hematopoiesis along with GATA2. TGF-b1 functions as a checkpoint to maintain NK cell immaturity at the CD56^Bright stage. However, it is unknown how TGF-b1 transcriptionally regulates human NK cell development and whether there are any links between GATA2, TGF-b1, and TAL1.

Results: We discovered that primary human NK cells express high levels of TAL1, and its target genes, including multiple GTPase of immunity-associated protein (GIMAP) family members, which were significantly upregulated in NK cells from patients with ten GATA2 pathogenic variants and GATA2 variant-expressing cells. GATA2 repressed TAL1 transcription, whereas GATA2^T354M failed to repress TAL1. In contrast, GATA2^T354M substantially reduced the expression of TGFB1 and known TGF-b1 target genes in human NK cells. Mechanistically, GATA2 regulated the TGFB1 promoter, and ATAC-seq and CUT&Tag assays using human primary NK cells revealed the TGFB1 promoter exists as accessible chromatin, GATA2 occupied the promoter. Occupancy was associated with elevated levels of H3K4me3, an active promoter mark. Thus, GATA2-mediated regulation of TGFB1 at an early commitment stage permits an orderly and successful transition of early NK cell developmental stages. Exogenous TGF-b1 augmented TAL1 degradation, suggesting that decreased TGF-b1 with a concomitant increase in TAL1 formed the mechanistic basis for defective NK cell development in patients with the GATA2^T354M variant. The interplay between GATA2, TGF-b1, and TAL1 provides an important missing link required for early human NK cell development.

Conclusion: We identified a GATA2-TAL1-TGF-b1 axis that is essential for human NK cell development and maturation. Dissecting the underlying mechanisms unveiled a new dimension in NK cell biology and pathology.

Thakar:Proteios Technology: Membership on an entity's Board of Directors or advisory committees; ImmunoVec: Membership on an entity's Board of Directors or advisory committees. Myers:Incyte: Research Funding; Elixirgen Therapeutics: Research Funding.