[Effect of Tumor Suppressor Gene Kmt2c Heterozygous Deletion on Hematopoietic System in Mice].

Objective: To explore the effect of heterozygous deletion of histone methyltransferase Kmt2c gene on the hematological system of mice.

Methods: CRISPR/Cas9 technology was used to construct mice model of Kmt2c heterozygous deletion (Kmt2c^+/-) and the changes of whole blood cell count in mice were continuously monitored by blood routine test. The clonal expansion ability of bone marrow cells was explored by colony formation assay in vitro and the proportion of primitive hematopoietic cells, including long-term hematopoietic stem cell (LT-HSC), short-term hematopoietic stem cell (ST-HSC), and multipotent progenitor cell in mutant mice was analyzed by flow cytometry.

Results: Kmt2c^+/- mice model was successfully constructed, and the mRNA expression level of Kmt2c was 28% of that of C57BL/6J mice. The colony formation ability of bone marrow cells of Kmt2c^+/- mice in vitro increased with the passage times, and the colony number in the fourth generation was significantly higher than that of control group (P <0.05). The proportions of LT-HSC and ST-HSC in the primitive hematopoietic cell population of Kmt2c^+/- mice was 19.6%±3.3% and 28.9%±4.9%, respectively, which showed an increasing trend compared with 16.9%±2.6% and 18.9%±2.5% in control group, but the difference was not statistically significant (P >0.05). The white blood cell count of Kmt2c^+/- mice gradually increased after 12 weeks of monitoring and reached (9.8±1.0)×10⁹/L at the 14^th week, which was significantly higher than (7.3±1.4)×10⁹/L of control group (P < 0.05).

Conclusion: The bone marrow cells of Kmt2c^+/- mice have potential of clonal expansion.