Tarnasky Heide, Cheng Min, Ou Young, Thundathil Jacob C, Oko Richard, van der Hoorn Frans A
Department of Biochemistry & Molecular Biology, University of Calgary, Calgary, Canada.
BMC Dev Biol. 2010 Jun 15;10:67. doi: 10.1186/1471-213X-10-67.
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.
XL169 ES cells have a beta-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.
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.
外致密纤维蛋白2（Odf2）是精子鞭毛中外致密纤维（ODF）的主要成分。ODF与构成轴丝的微管双联体相关。我们最近证明，Odf2的酪氨酸磷酸化对精子活力很重要。在使用Odf2基因敲除小鼠品系研究Odf2的过程中，我们观察到，使用XL169胚胎干细胞构建的高嵌合率雄性小鼠不育，而中低嵌合率的小鼠可育。
XL169胚胎干细胞在Odf2基因中插入了一个β-geo基因捕获盒。为了确定导致不育的潜在机制，我们分析了附睾精子，发现超过50%的精子尾巴弯曲。接下来，我们对高比例XL169嵌合小鼠的睾丸进行了超微结构分析。该分析表明，高比例XL169嵌合小鼠产生的延长型精子细胞在其线粒体中段和主段缺少一根或多根完整的外致密纤维。此外，我们还观察到延长型精子细胞的外致密纤维变细。延长型精子细胞中没有其他明显的异常或缺陷。高嵌合率的XL169小鼠附睾头部和尾部的精子显示出额外的尾巴缺陷，包括缺少一根或多根轴丝微管双联体和尾巴弯曲。尾巴弯曲的精子表现出异常的运动能力。
我们的结果证明了一个Odf2等位基因缺失对精子尾巴结构和功能的可能影响，从而导致一种新的精子尾巴表型。
