A Genetic Screen Identifies Etl4-Deficiency Capable of Stabilizing the Haploidy in Embryonic Stem Cells

Mammalian haploid embryonic stem cells (haESCs) hold great promise for functional genetic studies and forward screening. However, all established haploid cells are prone to spontaneous diploidization during long-term culture, rendering application challenging. Here, we report a genome-wide loss-of-function screening that identified gene mutations that could significantly reduce the rate of self-diploidization in haESCs. We further demonstrated that CRISPR/Cas9-mediated Etl4 knockout (KO) stabilizes the haploid state in different haESC lines. More interestingly, Etl4 deficiency increases mitochondrial oxidative phosphorylation (OXPHOS) capacity and decreases glycolysis in haESCs. Mimicking this effect by regulating the energy metabolism with drugs decreased the rate of self-diploidization. Collectively, our study identified Etl4 as a novel haploidy-related factor linked to an energy metabolism transition occurring during self-diploidization of haESCs.