Gene trap mutation of murine Outer dense fiber protein-2 gene can result in sperm tail abnormalities in mice with high percentage chimaerism

<p>Abstract</p> <p>Background</p> <p>Outer dense fiber protein 2, Odf2, is a major component of the outer dense fibers, ODF, in the flagellum of spermatozoa. ODF are associated with microtubule doublets that form the axoneme. We recently demonstrated that tyrosine phosphorylation of Odf2 is important for sperm motility. In the course of a study of Odf2 using Odf2 mouse knockout lines we observed that males of a high percentage chimaerism, made using XL169 embryonic stem cells, were infertile, whereas mice of low-medium percentage chimaerism were fertile.</p> <p>Results</p> <p>XL169 ES cells have a β-geo gene trap cassette inserted in the Odf2 gene. To determine possible underlying mechanisms resulting in infertility we analyzed epididymal sperm and observed that >50% displayed bent tails. We next performed ultrastructural analyses on testis of high percentage XL169 chimaeric mice. This analysis showed that high percentage XL169 chimaeric mice produce elongating spermatids that miss one or more entire outer dense fibers in their midpiece and principal piece. In addition, we observed elongating spermatids that show thinning of outer dense fibers. No other obvious abnormalities or defects are present in elongating spermatids. Spermatozoa from the caput and cauda epididymis of XL169 mice of high percentage chimaerism show additional tail defects, including absence of one or more axonemal microtubule doublets and bent tails. Sperm with bent tails display abnormal motility.</p> <p>Conclusions</p> <p>Our results document the possible impact of loss of one Odf2 allele on sperm tail structure and function, resulting in a novel sperm tail phenotype.</p

Targeted Disruption of the Testicular SPAG5/Deepest Protein Does Not Affect Spermatogenesis or Fertility

In an effort to define the molecular basis for morphogenesis of major sperm tail structures, including outer dense fibers, we recently cloned the Spag5 gene by virtue of its strong and specific leucine-zipper-mediated interaction with Odf1, the 27-kDa major outer dense fiber protein. Spag5 is expressed during meiosis and in round spermatids and is similar, if not identical, to Deepest, a putative spindle pole protein. Here we report the disruption of the Spag5 gene by homologous recombination. Spag5-null mice lack Spag5 mRNA and protein. However, male mice are viable and fertile. Analysis of the process of spermatogenesis and sperm produced in Spag5-null mice did not reveal a major phenotype as a consequence of the knockout event. This result suggests that if Spag5 plays a role in spermatogenesis it is likely compensated for by unknown proteins