Ehmt1, also known as euchromatic histone lysine methyltransferase 1 or GLP, is a pivotal epigenetic regulator. It is best-known for its role as an H3K9me1 and H3K9me2 methyltransferase, often dimerizing with Ehmt2 (G9A). These histone modifications are involved in transcriptional regulation, genome methylation, and DNA repair, and thus play a crucial role in diverse cellular processes and biological functions [1,2,3,4].

In oocyte-specific conditional knockout mouse models (Ehmt1 cKO), loss of Ehmt1 recapitulated meiotic defects and led to significant impairment in oocyte maturation and developmental competence, resulting in mid-gestation embryonic lethality. This indicates Ehmt1's critical role in oogenesis [4]. In Ehmt1+/- mouse models, there was a delay in the maturation of Parvalbumin-positive (PV+) interneurons in sensory cortical areas, and a shift in excitatory-inhibitory balance towards overexcitability, which may be related to the sensory processing deficits in Kleefstra syndrome caused by EHMT1 haploinsufficiency [6]. In alveolar rhabdomyosarcoma, suppression of EHMT1 in a mouse xenograft model impaired tumor cell motility, induced differentiation, and reduced tumor progression, suggesting its role in tumor progression [5].

In conclusion, Ehmt1 is a key epigenetic regulator with essential functions in oogenesis, neuronal development, and tumor progression. The use of Ehmt1 KO/CKO mouse models has significantly contributed to understanding its role in diseases such as Kleefstra syndrome and alveolar rhabdomyosarcoma, providing insights into disease mechanisms and potential therapeutic targets.