Étude génétique et biologique de la différenciation et de la maturation des cellules NK
Natural Killer (NK) cells, a subset of lymphocytes, are crucial in innate immunity due to their direct cytotoxicity towards tumors, viral infected cells and stressed cells. NK cells also contribute to the orchestration of the adaptive response by their ability to produce immunoregulatory cytokines. To develop those effector functions, NK cells require the integration of multiple signals. As of now, mature NK cells (mNK) can be separated into a four-stage model of functional maturation that concords with a polarization either toward proliferation and cytokine production or cytotoxic functional properties. In autoimmune diseases, like type 1 diabetes (T1D), a block in their maturation, and consequently an impaired functionality and diminished numbers, can be observed. Thus, in order to uncover the genetic regulation behind the proportion and functional maturation of NK cells, a linkage analysis was performed by our lab on F2 (B10.BR x NOD.H2k) and F2.Rag (B6.Rag1-/- x NOD.Rag1-/- intercross) mice, where the NOD genetic background is a model of T1D. This analysis revealed loci that were potentially involved in the regulation of mNK cells proportion, absolute numbers or functional maturation. Loci on chromosomes 8, 9 and 17 were linked to the proportion of mNK cells while loci on chromosomes 2, 4, 7, 10, 11 and 18 were linked to different subsets of functional mNK cells. Hence, we validated the influence of the chromosome 9 locus on the proportion of mNK cells by generating congenic sub-strains of mice with insertion of B10.BR genetic segments and NOD genetic background. The proportion and absolute numbers of mNK cells were assessed by flow cytometry and compared to those of wild-type mice. Regarding the functional maturation of mNK cells, we considered potential candidate genes, and their upstream regulators, that were linked to one or more mNK subsets, namely Tbx21, Zeb2, Myb, Trp53 and Pmaip1. From those, we also looked further their associated pathway with proteins such as Bim and Eomesodermin. We proceeded to the in vivo validation of their implication by qPCR, proliferation and apoptosis assays and the use of knock-out mice. Indeed, our results support a role for a locus on chromosome 9 in the regulation of mNK cells proportion and for Trp53, Bim and Pmaip1 in NK cell functional maturation. As such, our study has revealed new candidate genes in NK cell regulation. Further explorations of the mechanisms by which those genes act could lead to the development of cellular and genetic therapies for cancers and chronic infections.
Natural Killer cells Immunogenetics Linkage analysis Cellular proportion Functional maturation Differentiation pathway