The fine structure and development of the neck region of the mammalian spermatozoon

Fawcett, Don W.; Phillips, David M.

doi:10.1002/ar.1091650204

Cited by 221 publications

(160 citation statements)

References 19 publications

Supporting

Mentioning

151

Contrasting

Order By: Relevance

“…Spermatozoa in most species adopt a tadpole-like shape, and the sperm head and tail are bridged by the connecting piece, which not only serves as a physical linkage, but also participates in sperm motility by initiating and regulating the waveforms during swimming (38)(39)(40)(41). Given the high degree of similarity in sperm shape, it is not surprising that many spermiogenic genes are highly conserved across vertebrate species.…”

Section: Discussionmentioning

confidence: 99%

Spata6 is required for normal assembly of the sperm connecting piece and tight head–tail conjunction

Yuan

Stratton

Bao

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

127

View full text Add to dashboard Cite

"Pinhead sperm," or "acephalic sperm," a type of human teratozoospermia, refers to the condition in which ejaculate contains mostly sperm flagella without heads. Family clustering and homogeneity of this syndrome suggests a genetic basis, but the causative genes remain largely unknown. Here we report that Spata6, an evolutionarily conserved testis-specific gene, encodes a protein required for formation of the segmented columns and the capitulum, two major structures of the sperm connecting piece essential for linking the developing flagellum to the head during late spermiogenesis. Inactivation of Spata6 in mice leads to acephalic spermatozoa and male sterility. Our proteomic analyses reveal that SPATA6 is involved in myosin-based microfilament transport through interaction with myosin subunits (e.g., MYL6).M ale gametes-spermatozoa-are produced in the testis through a process termed spermatogenesis, which can be divided into three phases: mitotic, meiotic, and haploid (1). In the mitotic phase, spermatogonial stem cells proliferate and differentiate into spermatogonia, which subsequently enter the meiotic phase and become spermatocytes. Spermatocytes undergo crossover, followed by two consecutive meiotic cell divisions to produce haploid spermatids. Spermatids then undergo a multistep differentiation process, also called spermiogenesis, to form spermatozoa. Severe disruptions in either the mitotic or the meiotic phase tend to cause azoospermia, whereas spermiogenic defects often lead to reduced sperm counts, aberrant sperm motility, and deformed spermatozoa, a condition termed oligoasthenoteratozoospermia (OAT) in humans (2, 3).OAT accounts for a significant proportion of male idiopathic infertility cases (2, 4). Numerous cases of acephalic spermatozoa have been reported in teratozoospermic patients (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19). In these patients, the major anomaly lies in headless spermatozoa in the ejaculate, and the headless spermatozoa were initially called "pinhead sperm" because the investigators mistakenly regarded the retained cytoplasmic droplets, which are usually attached to the midprincipal piece junction of the flagella, as the heads of reduced size (8,13,14). Extensive ultrastructral studies on humans and animals with acephalic spermatozoa suggest that this condition results from defects in formation of the connecting piece of spermatozoa during late spermiogenesis, including failure for the proximal centrioles to attach normally to the caudal portion of the sperm nuclei, leading to abnormal head-midpiece alignment, or a nuclear defect that interferes with formation of the implantation fossa, the normal lodging site for the sperm proximal centriole (16). Aberrant formation of the connecting piece leads to independent development of the sperm heads and flagella, and eventually these structures become separated within the seminiferous tubules or during their transition through the seminal tract as a consequence of increased instability of the head-midpiece junction (16,18)....

show abstract

Section: Discussionmentioning

confidence: 99%

Spata6 is required for normal assembly of the sperm connecting piece and tight head–tail conjunction

Yuan

Stratton

Bao

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

127

View full text Add to dashboard Cite

show abstract

“…The structure at the base of the mammalian sperm flagellum, which anchors the ODFs, is called the connecting piece and has been extensively described (Fawcett and Phillips, 1969;Woolley et al, 2008;Ounjai et al, 2012). Woolley and Fawcett (1973) first discovered that during spermiogenesis in mammals the basal body that serves to nucleate the growth of the flagellum is lost.…”

Section: How the Sperm Tail Workmentioning

confidence: 99%

“…Since the geometric relationship between the structural elements was kept very close to that of a simple flagellum (such as a sea urchin sperm flagellum) we expect that this is a fairly good estimate of the relative bending resistance of a simple flagellum in the preferred bending plane and the off axis. This partitioning of the axoneme will also contribute to the differential bending resistance in mammalian sperm and help to define the beat plane.The structure at the base of the mammalian sperm flagellum, which anchors the ODFs, is called the connecting piece and has been extensively described (Fawcett and Phillips, 1969;Woolley et al, 2008;Ounjai et al, 2012). Woolley and Fawcett (1973) first discovered that during spermiogenesis in mammals the basal body that serves to nucleate the growth of the flagellum is lost.…”

mentioning

confidence: 99%

Functional anatomy of the mammalian sperm flagellum

2016

View full text Add to dashboard Cite

The eukaryotic flagellum is the organelle responsible for the propulsion of the male gamete in most animals. Without exception, sperm of all mammalian species use a flagellum for swimming. The mammalian sperm has a centrally located 9 1 2 arrangement of microtubule doublets and hundreds of accessory proteins that together constitute an axoneme. However, they also possess several characteristic peri-axonemal structures that make the mammalian sperm tail function differently. These modifications include nine outer dense fibers (ODFs) that are paired with the nine outer microtubule doublets of the axoneme, and are anchored in a structure called the connecting piece located at the base. The presence of the ODFs and connecting piece, and the absence of a basal body, dictate that physical forces generated by the dynein motors are transmitted to the base of the flagellum through the ODFs. Mammalian sperm flagella also possess a mitochondrial and a fibrous sheath that encircle most of the axoneme. These sheaths and the ODFs add mechanical rigidity to the flagellum creating the functional effect of increasing bend wavelength, which requires the entrainment of more dynein motors in the production of a single wave. The sheaths also act as a retinaculum and maintain the integrity of the central axoneme when large bending torques are generated by dynein. Large torque production is crucial to the process of hyperactivation and the unique motility transitions associated with effective fertilizing capacity. Consequently, these specialized anatomical features are essential for the effective interaction of sperm with the female reproductive tract and ovum. V C 2016 Wiley Periodicals, Inc.Key Words: axoneme; outer dense fibers; fibrous sheath; outer doublets; dynein; connecting piece; hyperactivation; sperm motility Introduction E ukaryotic cilia and flagella are highly conserved and ubiquitous organelles present in most animals, as well as many lower plants and eukaryotic protozoa. In the vertebrate lineage, the eukaryotic flagellum is universally employed to propel the male gamete. In the mammalian branch of the vertebrates, the sperm tail is always a modified flagellum with some characteristic accessory features that are added onto the basic 9 1 2 axoneme of microtubules found in most cilia and flagella. Figure 1 shows transmission electron micrographs (TEMs) of a mouse sperm flagellum in cross section at several positions along the length of the flagellum. The central axoneme is visible with its nine outer doublets surrounding a pair of single central microtubules (central pair or CP). Each of the outer microtubule doublets bears two rows of projections called the inner row and outer row of dynein arms. These arms are composed of the dynein motor proteins that power motility. The dynein arms are the source of the motive force that bends the flagellum. The dynein heavy chains (DHC) of the arms form bridges between the outer doublets and undergo a Mg-ATP driven power stroke that generates a sliding (or shearing) action between t...

show abstract

“…2b). The latter is considered to be homologous to the striated rootlets of cilia and connected to the nucleus through the structure called the implantation fossa [6,66]. The presence of a basal foot was described at least in spermatids, but its presence in mature spermatozoa is not clear.…”

Section: Structures Of the Flagellar Basementioning

confidence: 99%