Portuguese researchers at the Gulbenkian Science Institute genetically engineered a mouse with two additional limbs by deactivating the Tgfbr1 gene.

The aim was to study the Tgfbr1 gene's influence on spinal cord development in mouse embryos.

Deactivating the gene during a specific stage of embryo development unexpectedly resulted in the growth of extra limbs rather than genitals.

This finding highlights the significant role of the Tgfbr1 gene in embryonic development, potentially advancing our understanding of similar processes in humans.