In Oerias, Portugal, scientists at the Gulbenkian Institute of Sciences have created a six-legged mouse embryo instead of external genitalia. The research was led by biologist Moises Mallo and his colleagues who were studying the receptor protein Tgfbr1, which plays a role in embryonic development.

The Tgfbr1 gene encodes a transforming growth factor receptor beta type 1, which is involved in cellular responses such as growth and cell division. Mutations in this gene can increase the risk of skin cancer. The researchers found that inactivating the Tgfbr1 gene in mouse embryos led to the development of hind legs instead of external genitalia.

The team discovered that Tgfbr1 dictates whether structures develop into genitalia or legs. This means that inactivating the protein can change the activity of other genes, resulting in mice with extra legs and no external genitalia. Further research will focus on understanding the broader implications of the Tgfbr1 gene in development and disease.

The study used embryos collected from 3-6 month old mice, which were dissected and analyzed without distinguishing between male and female embryos because their external genitalia are indistinguishable. The researchers plan to investigate how Tgfbr1 and related genes affect other systems, such as cancer metastasis, and whether similar processes occur in reptiles with double penises.

By Samantha Johnson

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