Abstract
Haploidy is naturally observed in gametes; however, attempts of experimentally inducing haploidy in somatic cells have not been successful. Here, we demonstrate that the replacement of meiotic spindles in mature metaphases II (MII) arrested oocytes with nuclei of somatic cells in the G0/G1 stage of cell cycle results in the formation of de novo spindles consisting of somatic homologous chromosomes comprising of single chromatids. Fertilization of such oocytes with sperm triggers the extrusion of one set of homologous chromosomes into the pseudo-polar body (PPB), resulting in a zygote with haploid somatic and sperm pronuclei (PN). Upon culture, 18% of somatic-sperm zygotes reach the blastocyst stage, and 16% of them possess heterozygous diploid genomes consisting of somatic haploid and sperm homologs across all chromosomes. We also generate embryonic stem cells and live offspring from somatic-sperm embryos. Our finding may offer an alternative strategy for generating oocytes carrying somatic genomes.
Highlights
Haploidy is naturally observed in gametes; attempts of experimentally inducing haploidy in somatic cells have not been successful
We examined meiotic spindles in somatic cell nuclear transfer (SCNT) oocytes that were produced by transplanting a G0/G1 somatic cell depending on resting time after SCNT and confirmed the chromosome segregation after in vitro fertilization (NT-IVF)
Because we proposed that the premature chromosomes from the G0/G1 somatic cell could be similar to the prophase of meiosis I of the oocyte, we tested several incubation times in SCNT oocytes for 30 min, 1 h, and 2 h (Supplementary Fig. 1b and Supplementary Table 1)
Summary
Haploidy is naturally observed in gametes; attempts of experimentally inducing haploidy in somatic cells have not been successful. We demonstrate that the replacement of meiotic spindles in mature metaphases II (MII) arrested oocytes with nuclei of somatic cells in the G0/G1 stage of cell cycle results in the formation of de novo spindles consisting of somatic homologous chromosomes comprising of single chromatids. Fertilization of such oocytes with sperm triggers the extrusion of one set of homologous chromosomes into the pseudo-polar body (PPB), resulting in a zygote with haploid somatic and sperm pronuclei (PN). This study could provide a new strategy to generate oocytes carrying somatic genomes
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