A-kinase anchoring protein 4 is absent in sperm cells from patients with FSIP2 mutations. Sperm cells from a fertile control, the two patients FSIP2_3 and FSIP2_4, and three other patients mutated in dynein axonemal heavy chain 1 (DNAH1) gene, and in the cilia and flagella associated protein 43 (CFAP43) and 44 (CFAP44) genes, respectively, were stained with anti-A-kinase anchoring protein 4 (AKAP4: green) and anti-acetylated tubulin (red) antibodies. DNA was counterstained with DAPI showing sperm nuclear DNA (blue). The AKAP4 immunostaining is concentrated in the PP of the spermatozoa from the fertile control and the three patients mutated in DNAH1, CFAP43 and CFAP44. Conversely, AKAP4 staining is absent in sperm from the two patients FSIP2_3 and FSIP2_4. Scale bar 10 μm.