Dnmt1 is an enzyme that catalyzes the transfer of methyl groups in DNA methylation, and is responsible for maintaining DNA methylation, which ensures the fidelity of this epigenetic patterns across cell divisions. Aberrant methylation patterns are associated with certain human tumors and developmental abnormalities. Dnmt1 plays a critical role in hematopoietic stem cell (HSC) maintenance. HSCs with reduced DNMT1 fail to self-renew efficiently. Furthermore, It has been shown to be critical for other stem cell types such as intestinal stem cells (ISCs) and mammary stem cells (MaSCs).