Nectin-2-Null Males Produce Severely Malformed Spermatozoa
No anatomical differences were detected in the reproductive system of nectin-2LacZ/LacZ males when compared to heterozygous and wt littermates. Testis size (data not shown) and sperm titers were comparable between the three genetic groups. Specifically, 27.4 ± 4.3 X 106, 29.1 ± 3.1 X 106, and 23.3 ± 4.9 X 106 spermatozoa (all values ± SD) were recovered from the cauda epididymis of nectin-2wt/wt, nectin-2wt/LacZ, and nectin-2LacZ/LacZ males, respectively; each value corresponds to the average of three age-matched males. However, the spermatozoa of nectin-2LacZ/LacZ males showed severe malformation of the head and the midpiece (Fig. 2). Ventolin oral inhaler
Although all spermatozoa were affected, the degree of malformation varied. No single common type of abnormality was observed; rather, a random disorganization of the sper-matozoan head and midpiece was seen. The more prevalent shapes that were observed included those depicted in Figure 2, I and J, with the head being curled back onto the midpiece, or those depicted in Figure 2, F and H, with a forward-oriented but irregularly shaped head. We also frequently noticed a rough appearance of the midpiece (Fig. 2L) or a midpiece that appeared to be much thinner than normal (Fig. 2D). This result suggests a disorganization of the mitochondrial sheath (Fig. 2L) or the total lack thereof (Fig. 2D), and it confirms the findings of Bouchard et al. with their nectin-2 knockout line derived by a different strategy. However, in all spermatozoa, the classic falciform shape of the normal spermatozoan head (Fig. 2B) was all but lost. In contrast to the phenotype described by Bouchard et al., we did not observe an undulation of, or any other changes affecting, the principal piece of the tail.
FIG. 2. Aberrant morphology of nectin-2LacZ/LacZ mouse spermatozoa. Scanning electron microscopy was performed as described in Materials and Methods. A and B) Nectin-2w/LacZ spermatozoa with wt morphology. C-L) Nectin-2LacZ/LacZ spermatozoa display a variety of severely malformed heads and midpieces. All homozygous spermatozoa show some degree of head malformation, ranging from the mildest observed phenotype (H) to the most severe phenotypes (D and L). Abnormalities include midpieces that are thinner than the principal piece, likely because of the absence of the mitochondrial sheath (D), disorganized mitochondrial sheath (L), curling back of the head (I and J), and a diverse range of misshapen heads (D, F, and H-L). Bar = 3 7 ^m (A, C, E, and G) and 3.7 ^m (B, D, F, and H-L)