Loss-of-function mutations in ten-eleven translocation-2 (TET2) are recurrent events in acute myeloid leukemia (AML) as well as in preleukemic hematopoietic stem cells (HSCs) of age-related clonal hematopoiesis. TET3 mutations are infrequent in AML, but the level of TET3 expression in HSCs has been found to decline with age. We examined the impact of gradual decrease of TET function in AML development by generating mice with Tet deficiency at various degrees. Tet2f/f and Tet3f/f mice were crossed with mice expressing Mx1-Cre to generate Tet2f/wtTet3f/fMx-Cre+ (T2ΔT3), Tet2f/fTet3f/wtMx-Cre+ (ΔT2T3), and Tet2f/fTet3f/fMx-Cre+ (ΔT2ΔT3) mice. All ΔT2ΔT3 mice died of aggressive AML at a median survival of 10.7 weeks. By comparison, T2ΔT3 and ΔT2T3 mice developed AML at longer latencies, with a median survival of ∼27 weeks. Remarkably, all 9 T2ΔT3 and 8 ΔT2T3 mice with AML showed inactivation of the remaining nontargeted Tet2 or Tet3 allele, respectively, owing to exonic loss in either gene or stop-gain mutations in Tet3. Recurrent mutations other than Tet3 were not noted in any mice by whole-exome sequencing. Spontaneous inactivation of residual Tet2 or Tet3 alleles is a recurrent genetic event during the development of AML with Tet insufficiency.

No abstract

Background: Loss-of-function mutations in ten-eleven-translocation-2 (TET2) have been identified in myeloid and lymphoid malignancies. They have also been found in pre-leukemic hematopoietic stem cells and even in elderly individuals without hematologic malignancies. Taken together, they suggest TET2 mutation may act as a strong initiator in the pathogenesis of leukemia. TET3 mutation, on the other hand, is rare and its level has been found to decline with age. We hypothesized that somatic mutations of TET2 and age-related downregulation of TET3 lead to impairment of TET enzymes giving rise to hematological malignancies. Methods: Tet2 fl and Tet3fl mice were crossed with mice expressing Mx1-Cre. Floxed alleles were then deleted by intraperitoneal injection with polyinosinic: polycytidilic acid to generate Tet2fl/flTet3fl/flMx-Cre+, Tet2fl/wtTet3fl/flMx-Cre+ and Tet2fl/flTet3fl/wtMx-Cre+. Moribund mice were analyzed by flow cytometry. Results: All Tet2fl/flTet3fl/flMx-Cre+ (homo/homo) mice developed acute myeloid leukemia (AML) and died within 16 weeks of age. Tet2fl/wtTet3fl/flMx-Cre+ (hetero/homo) and Tet2fl/flTet3fl/wtMx-Cre+ (homo/hetero) mice developed disease and died from 20 weeks onwards (median survival was 27 weeks in both groups). Among 13 hetero/homo mice, flow cytometry confirmed 11 cases of AML, 1 case of T-cell acute lymphoblastic leukemia (T-ALL), and 1 case of composite AML/T-ALL. Among 7 hetero/homo mice, there were 5 cases of AML, 1 T-ALL, and 1 composite AML/T-ALL. Leukemic cells from bone marrow of all genotypes were transplantable and could be established as cell lines. Multiplex PCR of 3 hetero/homo and 3 homo/hetero mice showed additional loss of wild type Tet2 allele in all three hetero/homo mice with AML. One of two homo/hetero mice with AML showed additional loss of wild-type Tet3 allele. Homo/hetero mouse with T-ALL showed presence of wild-type Tet3 allele. Exome sequencing revealed additional single nucleotide variants in these mice. Exome sequencing of chromosome 3 housing the Tet2 gene, showed uniparental disomy in two and deletion in one hetero homo mice respectively. Exome sequencing of chromosome 6 housing the Tet3 gene showed deletion in one mouse with AML; uniparental disomy was not observed. Conclusion: Four allele deletion of Tet2 and Tet3 led to aggressive development of AML in mice, suggesting that Tet2 and Tet3 interact to function as tumor suppressors. However, three allele deletion of Tet2/Tet3 resulted in both myeloid and T-cell malignancies after a longer latency. Additional loss of residual Tet2 or Tet3 in these mice showed an AML phenotype similar to that seen in Tet2/Tet3 double knockout mice. These results suggest that loss of both Tet2 and Tet3 are strongly associated with the pathogenesis of myeloid and lymphoid malignancies. Disclosures Chiba: Bristol Myers Squibb, Astellas Pharma, Kyowa Hakko Kirin: Research Funding.

No abstract

Since chemical pesticides have a variety of short- and long-term social, economic, and environmental repercussions, research was conducted in Baniyani, Jhapa, Nepal from January to July 2021 to manage the Yellow Stem Borer (YSB) of rice in an environmentally responsible manner.  The research followed the Randomized Complete Block Design (RCBD) with three replications and seven treatments using the spring rice variety Chaite-2. The seven treatments used were spinosad 45% SC, Bacillus Thuringensis var krustaki + saccharopolyspora spinosad 15% SC, Azadiractin 0.3%, Chinaberry (Bakaino) leaf extract, Mugwort (Titepati) leaf extract, Metarhizium anisopliae and untreated plot. In order to evaluate the efficacy of the treatments, the number of dead heart and white head symptoms were counted at various time intervals, namely 7, 15, and 21 days after spraying (DAS).  At the vegetative and reproductive stages of rice, the rice stem borer causes the symptoms known as "dead heart" and "white head," respectively. The eco-friendly insecticides significantly altered how the rice stem borer was affected.  Among the insecticides, Spinosad 45%SC caused the highest reduction in dead hearts and whiteheads. Spinosad 45% SC treated plot showed highest yield (7.5tha-1). Given its effectiveness and eco-friendliness, spinosad could be regarded as the most successful eco-friendly insecticide for controlling the rice pest known as the Rice Stem Borer.