Bar‑Ilan Shows One DNA Letter Reverses Sex in Mice
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- Bar‑Ilan University researchers introduced a one‑base‑pair insertion into the Enh13 regulatory element of XX mice using CRISPR, causing the mice to develop male testes and genitalia.
- Enh13 normally acts as a molecular switch that activates Sox9 in males and represses it in females; the mutation disrupted female repression, leading to Sox9 activation in XX mice.
- Nature Communications published the study in 2026, reporting that both a one‑base‑pair insertion and a three‑base‑pair deletion in Enh13 produced complete sex reversal in XX mice.
- Dr. Nitzan Gonen said the finding shows a single DNA letter out of ~2.8 billion can dramatically affect development, highlighting the importance of non‑coding DNA.
- Elisheva Abberbock noted that many DSD cases lack a genetic diagnosis because sequencing often focuses on protein‑coding regions, suggesting non‑coding mutations like those in Enh13 may be responsible.
- Dr. Ariel Afek collaborated on the research, helping to identify and test the regulatory element’s role in sex determination alongside Dr. Francis Poulat.
Why it matters: The discovery gives clinicians a new genetic target for diagnosing differences of sex development, a condition affecting 1 in 4,000 births, and forces researchers to expand genetic testing beyond protein‑coding regions, potentially reducing the half of undiagnosed cases and may improve treatment planning.
