They discussed all genes connected with Kallmann syndrome that had been previously described, including KAL1, FGFR1, PROKR2, PROK2, FGF8, CHD7, WDR11, heparan sulfate 6-O-sulfotransferase 1 HS6ST1, and semaphorin-3A SEMA3A (a protein SEMA3A that in humans is encoded by the SEMA3A gene). This evidence concerns the gene PROK2 and Kallmann syndrome.