FSHB and Infertility: Comparative analyses of gene silencing along multiple points of the HPG axis in zebrafish have revealed that silencing of genes upstream in the axis (gnrh3-/- and kiss1-/-kiss2-/-) [44] seems to have no major phenotypes compared to silencing of downstream genes (fshb-/-, lhb-/-, fshr-/-, and lhr-/-) [25,56,57], which have sex-specific effects but mostly result in delayed gametogenesis and sometimes infertility.