Forkhead box protein L2 (FOXL2) is a protein involved in ovary development and maintenance, among other functions. Mutations in its gene are involved in ovarian failure and granulosa cell tumors, being the latter a rare cancer type caused in most cases by the C134W mutation (c.402C>G) in the FOXL2 gene. By using CRISPR/Cas9 technology, researchers from Spain have aimed to remove this mutation in the FOLX2 gene from granulosa tumor cells.