Spermiogenesis and spermiation in a marsupial, the tammar wallaby (Macropus eugenii)

Fourteen steps of spermatid development in the tammar wallaby (Macropus eugenii), from the newly formed spermatid to the release of the spermatozoon into the lumen of the seminiferous tubules, were recognised at the ultrastructural level using transmission and scanning electron microscopy. This study confirmed that although the main events are generally similar, the process of the differentiation of the spermatid in marsupials is notably different and relatively more complex than that in most studied eutherian mammals and birds. For example, the sperm head rotated twice in the late stage of spermiogenesis: the shape of the spermatid changed from a T-shape at step 10 into a streamlined shape in step 14, and then back to T-shape in the testicular spermatozoa. Some unique figures occurring during the spermiogenesis in other marsupial species, such as the presence of Sertoli cell spurs, the nuclear ring and the subacrosomal space, were also found in the tammar wallaby. However, an important new finding of this study was the development of the postacrosome complex (PAC), a special structure that was first evident as a line of electron dense material on the nuclear membrane of the step 7 spermatid. Subsequently it became a discontinuous line of electron particles, and migrated from the ventral side of the nucleus to the area just behind the posterior end of the acrosome, which was closely located to the sperm–egg fusion site proposed for Monodelphis domestica (Taggart et al. 1993). The PAC and its possible role in both American and Australian marsupials requires detailed examination. Distinct immature features were discovered in the wallaby testicular spermatozoa. A scoop shape of the acrosome was found on the testicular spermatozoa of the tammar wallaby, which was completely different to the compact button shape of acrosome in ejaculated spermatozoa. The fibre network found beneath the cytoplasm membrane of the midpiece of the ejaculated sperm also did not occur in the testicular spermatozoa, although the structure of the principal piece was fully formed and had no obvious morphological difference from that of the epididymal and ejaculated spermatozoa. The time frame of the formation of morphologically mature spermatozoa in the epididymis of the tammar wallaby needs to be determined by further studies.     

Spermiogenesis and DNA Repair: A Possible Etiology of Human Infertility and Genetic Disorders

This paper reviews the possible origin of sperm DNA fragmentation and focuses on the nuclear events associated with spermiogenesis as a potential source of genetic instability and reduced fertilizing potential of the mature male gamete. Recent findings suggest a programmed DNA fragmentation and DNA damage response during the chromatin remodeling steps in spermatids. We also discuss the spermatid DNA repair mechanisms and the possible involvement of condensing proteins, such as transition proteins and protamines, in the process, as this DNA fragmentation is normally not found in late spermatids. We propose that alterations in the chromatin remodeling steps or DNA repair in elongating spermatids may lead to persistent DNA breaks. This vulnerable step of spermiogenesis may provide a clue to the etiology of sperm DNA fragmentation associated with infertility in humans. This vulnerability is further emphasized given the haploid character of spermatids that must resolve programmed double-stranded breaks by an error-prone DNA repair mechanism. Therefore, spermiogenesis has probably been overlooked as an important source of genetic instability.     

无标记定量方法在小鼠精子发生相关蛋白质组学研究中的应用

目的: 利用无标记定量蛋白质组学技术筛选在3周龄及成年小鼠睾丸中差异表达的蛋白质?方法:分别抽提3周龄及成年小鼠睾丸蛋白,酶解后所得肽段经纳升液相色谱分离,并经LTQ Obitrap质谱鉴定,在获得蛋白鉴定信息的同时根据相应肽段离子质谱峰强度对蛋白进行相对定量?结果:在3周龄及成年小鼠睾丸中共鉴定到非冗余蛋白319种,其中30种蛋白在两者之间存在显著的表达差异,这些蛋白主要参与形态发生?收缩?胞吞?受精等细胞事件,与精子变形过程及精子功能相关?结论:无标记定量蛋白质组学技术,具有方法简便?通量大?成本低廉等优点,利用其寻找睾丸发育,精子发生/功能相关蛋白具有广阔的前景?     

带绦虫精子发生过程中精子变形的超微结构观察

目的：研究带绦虫在精子发生过程中的精子变形。方法：透射电镜。结果：32个玫瑰花样的次级精母细胞经第2次减数分裂后,产生64个精细原形体（64－spermatid－plasmodium）。精细胞的变形过程复杂,首先见精细胞胞质和核伸长,胞质增多由胞质桥“cytophore”相连;然后是核的进一步伸长,核染色质聚合成线束状,最后脱离胞质桥,形成成熟精子。成熟的精子呈细线状,长约16．2－18．6μm,宽0．35－0．45μm,可分为有核的头部及无核的尾部两部分。头部长约5－6μm,占体长的1／3,有一个较长的核缠绕着轴丝,无线粒体。尾部长约11．2－16．6μm。在尾部的前段及头部的后方,纵断面上见一些线粒体包绕着轴丝,全长约1．6－1．7μm。精子的尾部只含一条结构为“9＋1”的轴丝。精子横断面,质膜下见46条微管（周围微管）。结论：带绦虫精子子的变形是一个非常复杂的过程。     

Acrosomo-Nuclear Syndrome in Canine Sperm

An acrosomo-nuclear syndrome in sperm of an infertile semicryptorchid dog is described. Based on an EM study of developing and mature sperm the syndrome is defined by simultaneous occurrence of these symptoms: 1) intranuclear inclusions of acrosomal origin, 2) maldifferentiated apical segment of acrosome, 3) intraacrosomal inclusions of Sertoli cell origin, 4) characteristic change of nuclear shape and 5) retained cytoplasmic droplet. The cause of the syndrome and possibility of a transfer of somatic factors are discussed.     

Mutagenesis-generated mouse models of human infertility with abnormal sperm

BACKGROUND: The aetiology of human male fertility, with impairment of sperm number, motility and morphology (oligoasthenoteratozoospermia), has been difficult to understand, partly for lack of animal models. METHODS: An ethylnitrosourea (ENU) mutagenesis strategy has been successful in producing heritable gene mutations with phenotypes similar to human male infertility, and here, we describe three independent ENU-induced mutations that cause a phenotype of oligoasthenoteratozoospermia in mice. RESULTS: The loci identified by these three mutations are designated swm2, repro2 and repro3. All mutant males were characterized by low sperm concentration, poor sperm morphology and negligible motility, but the infertile males were apparently normal in other respects. Sperm from mutant males failed to fertilize oocytes in vitro. Ultrastructural analyses revealed varied abnormalities apparent in both testicular spermatids and epididymal sperm. Genetic mapping placed the swm2 gene on chromosome 7, the repro2 gene on chromosome 5 and the repro3 gene on chromosome 10. CONCLUSION: The single-gene mutations caused complex and non-specific sperm pathologies, a point with important implications for managing cases of human male infertility. The ultimate identification of the loci for the mutations causing these phenotypes will clarify aetiology of complex syndromes of infertility with sperm abnormalities consistent with oligoasthenoteratozoospermia.     

Arrest of flagellum morphogenesis with fibrous sheath immaturity of human spermatozoa

Morphogenesis of the mammalian sperm flagellum is characterized by the assembly of axonemal and peri-axonemal structures. The incorporation of mitochondria into the flagellum results from complex cellular events, including flagellum compartmentalization and membrane and organelle reorganization. These events are striking in the annulus, which progressively relocates from the neck to the principal piece of the flagellum. This study presents a human sperm phenotype with failure of the annulus relocation, absence of mitochondrial sheath and a fibrous sheath at intermediate step of assembly. The sperm nucleus was fully condensed but with deep invaginations engulfing the acrosome. The distal pole of some mitochondria exhibited an unusual dense substance. This rare human sperm phenotype was found in a consanguineous patient, suggesting a genetic origin. These anomalies raise the question of the mechanisms that lead to impairment of both the annulus relocation and the deposit of proteins on the fibrous sheath during spermiogenesis.     

Molecular cloning and characterization of the human orthologue of the oppo 1 gene encoding a sperm tail protein

We report here the molecular cloning and characterization of a human orthologue of oppo 1, a mouse gene encoding a male germ-cell-specific sperm tail protein, and the organization of its genomic structure. The mRNA of the human oppo 1 gene (h-oppo 1) was expressed exclusively in the testis, and the 30 kDa protein encoded by the mRNA was detected in human testis and sperm. Immunohistochemical analyses showed that human OPPO 1 protein was localized in the flagellae of ejaculated sperm. A human genomic DNA database search indicated that the h-oppo 1 gene mapped to chromosome 17. The genomic structure of h-oppo 1 showed differences in exon/intron usage, the sequence of the 5'-flanking region, and the first intron was rich in Alu repeats as compared with the mouse oppo 1 gene. Comparison of the two genomic sequences indicated that human oppo 1 has evolved independently, resulting in substantial differences in the genomic structure after the human-mouse split, whereas the sequence of the basic functional unit of the oppo 1 gene seems to have been relatively well conserved.