Durable pluripotency and haploidy in epiblast stem cells derived from haploid embryonic stem cells in vitro

harding michael;

Haploid pluripotent stem cells, such as haploid embryonic stem cells (haESCs), facilitate the genetic study of recessive traits. In vitro,
fish haESCs maintain haploidy in both undifferentiated and differentiated states, but whether mammalian haESCs can preserve pluripotency in the haploid state has not been tested. Here,wereport that mouse haESCs can differentiate in vitro into haploid epiblast stem
cells (haEpiSCs), which maintain an intact haploid genome, unlimited self-renewal potential, and durable pluripotency to differentiate
into various tissues in vitro and in vivo. Mechanistically, the maintenance of self-renewal potential depends on the Activin/bFGF
pathway. We further show that haEpiSCs can differentiate in vitro into haploid progenitor-like cells. When injected into the cytoplasm
of an oocyte, androgenetic haEpiSC (ahaEpiSCs) can support embryonic development until midgestation (E12.5). Together, these
results demonstrate durable pluripotency in mouse haESCs and haEpiSCs, aswell asthe valuable potential of using these haploid pluripotent stem cells in high-throughput genetic screening.