Research on diploidization of mouse haploid embryonic stem cells

The normal pattern of mouse somatic cells is typically diploid，with all chromosomes existing in pairs.In 2011 and 2012，research teams successfully established mouse haploid embryonic stem cells derived from parthenogenetic and androgenetic origins，respectively.These cells possess only one set of chromosomes，amounting to half the number found in mouse somatic cells.This characteristic offers unique advantages in fields such as sequencing，genetic screening，and gene and chromosome editing.Androgenetic haploid cells，in particular，can generate fertile offspring via injection into MII oocytes，significantly enhancing the efficiency of gene editing in mice，especially for large-fragment edits.However，the proportion of haploid cells in mouse haploid embryonic stem cell lines inevitably declines and eventually disappears with prolonged culture time and increased passages.This phenomenon，observed in the study of haploid animal cells，has considerably limited the application and promotion of haploid cells due to the inconveniences it causes.Over the years，reseachers have conducted multidimensional research and exploration into the causes and solutions of this phenomenon，achieving certain progress.This article provides a brief review and summarize previous research findings in two aspects：（1）the mechanisms underlying diploidization in mouse haploid embryonic stem cells and the associated scientific questions，and（2）the methods to address diploidization.It aims to facilitate understanding of this field for future researchers and provide inspiration.