Fig. 2

Ultrastructural defects in spermatozoa from two individuals carrying SPAG6 variants. A Scanning electron microscopy of the spermatozoa from a healthy control and F1 II-1. (i) normal morphology of spermatozoa from a healthy control man; (ii-v) scanning electron microscopy showed the multiple abnormalities of the sperm flagella from F1 II-1 individual, including short(ii), coiled (iii, iv), and absent(v). Scale bar: 5 μm. B transmission electron microscopy of the sperm flagella from a healthy control and two patients. (i-iii) cross-sections of the sperm flagella in a healthy control, including mid-piece, principal piece and end-piece, show the typical “9 + 2” axonemal structure and peri-axoneme structure. (iv-vi) and (vii-ix) axonemal cross-sections of the sperm flagella from F1 II-1 and F2 II-1, respectively. The overall axonemal ultrastructure was disrupted, and primarily presented an abnormal “9 + 0” configuration. Of these, the lack of the central microtubules was the main defect observed in sperm flagella from two probands, peripheral microtubule doublets and outer dense fibers were also translocated and disorganized. Scale bar: 200 nm. Abbreviations: CP, central pair of microtubules (blue triangles); MT, peripheral microtubule doublets (yellow triangles); ODF, outer dense fiber (red triangles);