Rep. Nancy Mace, R-S.C., promoted legislation last week that she calls the “TRANS MICE Act,” which she says is intended to end the use of taxpayer dollars for “radical transgender-related experiments on animals.” After she announced the bill on X, numerous users and fact-checkers pointed out that the term “trans mice” in biomedical research refers to transgenic mice — animals whose genetic material has been deliberately altered — not transgender mice, according to a community note added to her post.
Mace, who has described herself as “Trump in high heels,” is leaving Congress next year after finishing last in the state’s Republican primary for governor. In a follow-up post she denied that she had confused the terms and urged people to read more about her bill.
The episode echoes a similar controversy that circulated in 2025, when the group Americans for Medical Progress, which supports animal testing in biomedical research, issued a statement correcting misinformation about what it termed “transgender mice.” The group noted that certain research grants that had drawn attention from the Trump administration and right-wing influencers were not related to making mice transgender but to understanding the role of sex hormones in specific medical conditions.
The term “transgenic” describes an organism that carries a gene from another organism that has been deliberately inserted into its genome. Transgenic mice are a widely used laboratory tool in biomedical research, including cancer research, according to standard scientific usage.