Want to Clone an Opposite-Sex Version of Yourself? Japanese Scientists Clone Female Mouse from Male for First Time

Summary

Researchers at the University of Yamanashi in Japan have achieved the world's first "male-to-female cloning," successfully converting male mouse embryos into females using CRISPR gene editing technology and producing fertile female cloned mice. The findings, published in a Nature subjournal, are hailed by the scientific community as a milestone in mammalian reproductive biology. Reproductive biologist Monica Ward of the University of Hawaii commented, "No one has ever done this before." The core of the technique lies in the precise removal of the Y chromosome. The team extracted nuclei from male mouse somatic cells and used the CRISPR system to target key sequences on the Y chromosome, causing it to be naturally lost during cell division. These X-only cells were then inserted into enucleated oocytes and developed into embryos via somatic cell nuclear transfer. Due to sex determination mechanisms, the absence of the Y chromosome triggers female differentiation, ultimately yielding individuals with an XX karyotype. This breakthrough not only stirs reproductive biology but also offers new possibilities for animal breeding, disease modeling, and regenerative medicine. Although the research is still at the mouse stage, its implications are profound: it proves that sex determination pathways can be reshaped via gene editing and cloning, making "cloning an opposite-sex self"…