The possibility of men in same-sex relationships and people who do not have their own eggs having biological children has been advanced by new research into in vitro gametogenesis, in which functional haploid gametes are generated from diploid somatic cells.

In previous, proof-of-principle experiments showing that haploidy in somatic cell genomes can be induced experimentally by premature cell division, the authors reported successful generation of haploid chromosomes from somatic cells using mature oocytes using an adapted somatic cell nuclear transfer (SCNT) technique. “Conventional SCNT produces diploid eggs that cannot be fertilized with sperm,” says principal investigator Shoukhrat Mitalipov, continuing, “Thus, we developed and added to the SCNT approach an experimental reductive cell division, which enables ploidy reduction in diploid somatic cells and production of haploid SCNT oocytes.” In this adapted SCNT approach, a somatic cell nucleus is transferred into an enucleated, metaphase meiosis II (MII)-arrested oocyte. Metaphase activity in these oocytes induces premature cell division, resulting in ploidy reduction in transplanted G0–G1 diploid somatic cell genomes by bypassing the S phase. In this SCNT approach, the somatic chromosomes have pseudo-meiotic spindles derived from the diploid G0–G1 somatic nucleus that are composed of two single chromatids, and these chromatids can be segregated at fertilization. On fertilization, somatic chromosome segregation into pseudo polar body 2 and a female pronucleus occurs, and the sperm genome forms a male pronucleus. The resulting mouse zygotes containing somatic and sperm pronuclei were able to develop into diploid blastocysts, embryonic stem cells and live offspring, but with very low efficacy. However, the mechanisms and factors influencing spindle organization and chromosome segregation in SCNT were unclear from these initial experiments.