A study published in Nature Communications reports that female mouse embryos developed male reproductive organs following a single letter change in a specific non-coding DNA region.
The Role of Sox9 and Enhancer 13 in Sex Determination
Typically, female mouse embryos with two X chromosomes develop ovaries due to the suppression of the Sox9 gene. In male mouse embryos (XY chromosomes), the expression of Sox9 initiates testis development.
Sox9 regulation in male mice involves enhancer 13 (Enh13), a segment of non-coding DNA. Prior studies indicated that deleting Enh13 caused XY mice to develop female organs. The effects of Enh13 modification in female (XX) mice were not previously established.
Groundbreaking Findings in Female Embryos
Nitzan Gonen and her research team demonstrated a significant breakthrough:
Nitzan Gonen and her research team demonstrated that modifying both copies of Enh13 in female mice resulted in the development of male genitals and small testes.
Female mice with only one modified Enh13 copy maintained female organ development. The team proposes that Enh13 acts as both an enhancer and a silencer of Sox9, influencing sex determination.
Clarifying Developmental Mechanisms
Katie Ayers, a genetics researcher, praised the study's impact on understanding embryonic development.
Katie Ayers, a genetics researcher, described this study as the first to clarify the mechanism behind ovary or testis development in an embryo.
Implications for Human Disorders of Sex Development
Ayres noted that the DNA region modified in the study is also significant for human sex determination. Approximately 50% of individuals with disorders affecting sexual development currently lack a genetic diagnosis, partly because sequencing methods often concentrate on protein-encoding genome sections.
Ayers suggested that further investigation into non-coding genomic areas, specifically minor changes in the Enh13 region, could lead to the identification of additional genetic alterations linked to disorders of sex development.
Building on Prior Research
Gonen previously contributed to the discovery of Enh13's role in sex development. In 2018, researchers found that deleting Enh13 caused XY male mice to develop female organs. A subsequent 2024 modification, removing transcription factor binding parts of Enh13, produced a similar sex reversal in XY mice.