CFAP91 and male infertility: Damaging mutations in genes encoding RS1 and RS2 components cause PCD [21, 23, 44, 68–71], while mutations in genes encoding RS3 proteins, CFAP61 [37, 38], CFAP91 [39], CFAP251 [36], and LRRC23 [16, 40] result in male infertility but not PCD.