Israeli Scientists Reverse Biological Sex in Mice Through Genetic Editing

Scientists at Bar-Ilan University have achieved a world-first breakthrough by reversing the biological sex of mice through a single-letter modification in a previously overlooked region of the genome known as "junk DNA." This research, led by Dr. Nitzan Gonen and doctoral student Elisheva Abberbock, utilized CRISPR technology to alter one DNA letter among approximately 2.8 billion, resulting in XX mice developing as males with fully formed testes and male genitalia. The findings were published in the peer-reviewed journal *Nature Communications*.

Times of Israel

The key to this transformation lies in a genetic switch called Enh13, which regulates the Sox9 gene essential for testis development. In typical embryonic development, the Sox9 gene must remain inactive for ovaries to form. By introducing specific mutations into Enh13, the researchers inadvertently activated Sox9 in XX mice, leading to male development. Dr. Gonen emphasized the significance of this discovery, stating that it highlights the potential of non-coding DNA to influence biological processes and diseases.

Times of Israel

This research could have profound implications for understanding and treating Differences of Sex Development (DSD), a condition affecting approximately one in 4,000 children, where reproductive anatomy does not conform to typical male or female definitions. Dr. Gonen noted that many individuals with DSD remain undiagnosed, receiving sub-optimal clinical care. The study aims to enhance diagnostic capabilities and clinical outcomes for these patients by exploring the genetic underpinnings of DSD.

Times of Israel

While the research opens new avenues for genetic understanding, it also raises ethical questions. Dr. Gonen expressed caution regarding the potential application of this discovery in fetal genetic modification, emphasizing the importance of understanding the implications of creating individuals who may be infertile. Associate Professor Katie Ayers from the Murdoch Children’s Research Institute highlighted that the findings could lead to better diagnoses and care for DSD patients, but also acknowledged the need for careful consideration of the ethical ramifications of genetic interventions.

Times of Israel

Dr. Gonen believes that the discovery of Enh13's function is merely the beginning, suggesting that numerous other enhancers scattered throughout the genome could similarly influence sex development and other genetic disorders. This ongoing research may eventually provide insights into various genetic diseases that remain unexplained.

Times of Israel

• “If you change just one letter in the DNA in a place that doesn’t create proteins, and does not encode for anything, you can prevent the ability to create an ovary, and instead you will get development of testes,” — Dr. Nitzan Gonen, Principal Investigator

Times of Israel

• “Understanding what is wrong gives people some peace of mind,” — Dr. Nitzan Gonen

Times of Israel

• “This work demonstrates that even very small changes in enhancers for testicular or ovarian development can cause disrupted gonad development,” — Associate Professor Katie Ayers

Times of Israel

This groundbreaking study not only advances the field of genetic research but also poses significant questions about the future of genetic editing and its ethical implications.

Times of Israel