Dnmt3a Knockin mouse models

De novo methylation in hematopoiesis is dominated by Dnmt3a, ortholog of human DNMT3A, whose ADD domain is released from autoinhibition upon reading unmethylated H3K4, whose PWWP domain docks on H3K36 dimethylation to direct intergenic and heterochromatic targeting, and whose catalytic domain forms active tetramers with DNMT3L or DNMT3B. The leukemia hotspot R882H sits at the substrate binding interface and acts dominantly by poisoning tetramer formation, reducing methylation output well below simple haploinsufficiency and driving clonal hematopoiesis, AML, and T cell lymphoma. Design should therefore distinguish a conditional null, which reports stem cell self-renewal and differentiation blockade, from an inducible R882H knockin, which reproduces the dominant-negative epigenetic state seen in patients. Constitutive nulls survive gestation but die within weeks after birth, so conditional deletion with Mx1-Cre or Vav-Cre plus transplantation is standard. Dnmt3b overlaps only partially, and compound deletion collapses methylation far more severely than either allele alone.

Dnmt3a knockin models place a defined sequence at the endogenous locus. Expression stays under native regulation, which matters for reporters, tags, and precise allele swaps.