Identification of three homozygous KCTD19 missense variants in three unrelated Chinese families. (A) Pedigrees of the three unrelated Han Chinese families. Solid symbols indicate the infertile males. Whole exome sequencing was performed for members indicated by the black arrows. Sanger sequencing chromatograms of KCTD19 variants are shown below the pedigrees and the red arrows indicate the variant positions. (B) Schematic representation of the protein domains of KCTD19. Variant positions were indicated. Sequence alignment shows the conservation of the mutated residues among different species. BTB, Broad-Complex, Tram track, and Bric-a-brac; POZ, poxvirus and zinc finger.