Microtubule plus-end regulation by centriolar cap proteins

Centrioles are microtubule-based organelles required for the formation of centrosomes and cilia. Centriolar microtubules, unlike their cytosolic counterparts, grow very slowly and are very stable. The complex of centriolar proteins CP110 and CEP97 forms a cap that stabilizes the distal centriole end and prevents its over-elongation. Here, we used in vitro reconstitution assays to show that whereas CEP97 does not interact with microtubules directly, CP110 specifically binds microtubule plus ends, potently blocks their growth and induces microtubule pausing. Cryo-electron tomography indicated that CP110 binds to the luminal side of microtubule plus ends and reduces protofilament peeling. Furthermore, CP110 directly interacts with another centriole biogenesis factor, CPAP/SAS-4, which tracks growing microtubule plus ends, slows down their growth and prevents catastrophes. CP110 and CPAP synergize in inhibiting plus-end growth, and this synergy depends on their direct binding. Together, our data reveal a molecular mechanism controlling centriolar microtubule plus-end dynamics and centriole biogenesis.

A ciliopathy complex builds distal appendages to initiate ciliogenesis

Cells inherit two centrioles, the older of which is uniquely capable of generating a cilium. Using proteomics and superresolved imaging, we identify a module that we term DISCO (distal centriole complex). The DISCO components CEP90, MNR, and OFD1 underlie human ciliopathies. This complex localizes to both distal centrioles and centriolar satellites, proteinaceous granules surrounding centrioles. Cells and mice lacking CEP90 or MNR do not generate cilia, fail to assemble distal appendages, and do not transduce Hedgehog signals. Disrupting the satellite pools does not affect distal appendage assembly, indicating that it is the centriolar populations of MNR and CEP90 that are critical for ciliogenesis. CEP90 recruits the most proximal known distal appendage component, CEP83, to root distal appendage formation, an early step in ciliogenesis. In addition, MNR, but not CEP90, restricts centriolar length by recruiting OFD1. We conclude that DISCO acts at the distal centriole to support ciliogenesis by restraining centriole length and assembling distal appendages, defects in which cause human ciliopathies.

A dynamic basal complex modulates mammalian sperm movement

Reproductive success depends on efficient sperm movement driven by axonemal dynein-mediated microtubule sliding. Models predict sliding at the base of the tail – the centriole – but such sliding has never been observed. Centrioles are ancient organelles with a conserved architecture; their rigidity is thought to restrict microtubule sliding. Here, we show that, in mammalian sperm, the atypical distal centriole (DC) and its surrounding atypical pericentriolar matrix form a dynamic basal complex (DBC) that facilitates a cascade of internal sliding deformations, coupling tail beating with asymmetric head kinking. During asymmetric tail beating, the DC’s right side and its surroundings slide ~300 nm rostrally relative to the left side. The deformation throughout the DBC is transmitted to the head-tail junction; thus, the head tilts to the left, generating a kinking motion. These findings suggest that the DBC evolved as a dynamic linker coupling sperm head and tail into a single self-coordinated system.

Fluorescence-Based Ratiometric Analysis of Sperm Centrioles (FRAC) Finds Patient Age and Sperm Morphology Are Associated With Centriole Quality

A large proportion of infertility and miscarriage causes are unknown. One potential cause is a defective sperm centriole, a subcellular structure essential for sperm motility and embryonic development. Yet, the extent to which centriolar maladies contribute to male infertility is unknown due to the lack of a convenient way to assess centriole quality. We developed a robust, location-based, ratiometric assay to overcome this roadblock, the Fluorescence-based Ratiometric Assessment of Centrioles (FRAC). We performed a case series study with semen samples from 33 patients, separated using differential gradient centrifugation into higher-grade (pellet) and lower-grade (interface) sperm fractions. Using a reference population of higher-grade sperm from infertile men with morphologically standard sperm, we found that 79% of higher-grade sperm of infertile men with substandard sperm morphology have suboptimal centrioles (P = 0.0005). Moreover, tubulin labeling of the sperm distal centriole correlates negatively with age (P = 0.004, R = −0.66). These findings suggest that FRAC is a sensitive method and that patient age and sperm morphology are associated with centriole quality.

A ciliopathy complex builds distal appendages to initiate ciliogenesis

ABSTRACTCells inherit two centrioles, the older of which is uniquely capable of generating a cilium. We identified that three evolutionarily conserved proteins that underlie human ciliopathies, CEP90, MNR and OFD1, form a complex. This complex localized to both distal centrioles and centriolar satellites, proteinaceous granules surrounding centrioles. Cells and mice lacking CEP90 or MNR did not generate cilia, failed to assemble distal appendages, and did not transduce Hedgehog signals. Disrupting the satellite pools did not affect distal appendage assembly, indicating that it is the centriolar populations of MNR and CEP90 that are critical for ciliogenesis. CEP90 recruited the most proximal known distal appendage component, CEP83, to root distal appendages formation, an early step in ciliogenesis. In addition to distal appendage formation, MNR, but not CEP90, restricted centriolar length by recruiting OFD1. We conclude that a complex of disease- associated proteins, MNR, OFD1 and CEP90, acts at the distal centriole to support ciliogenesis by restraining centriole length and assembling distal appendages.

Centriolar defects, centrin 1 alterations, and FISH studies in human spermatozoa of a male partner of a couple that produces aneuploid embryos in natural and artificial fertilization

Purpose To study the potential paternal contribution to aneuploidies in the man of a couple who obtained trisomic embryos with natural and assisted fertilization. Methods Semen analysis, immunofluorescence for localization of tubulin and centrin 1, transmission electron microscopy (TEM), and fluorescence in situ hybridization (FISH) analysis for chromosomes 18 and 9 were performed. Sperm of fertile men were used as controls. Results The percentages of sperm motility and normal forms were decreased. The percentages of sperm with tail reduced in dimension, headless tails, coiled tails, and altered head-tail junction were significantly higher (P < 0.01) in the patient than in controls, whereas the percentage of sperm with a normal centrin 1 localization (two spots in the centriolar area) was significantly reduced (P < 0.01) in the patient. Immunofluorescence with anti-tubulin antibody showed that in most of the patient’s sperm connecting pieces (83.00 ± 1.78%), two spots were present, indicating prominent proximal centriole/centriolar adjunct and evident distal centriole, whereas controls’ sperm displayed a single spot, indicating the proximal centriole. The percentage of sperm with two spots was significantly higher (P < 0.01) in the patient than in controls. TEM analysis showed that centriolar adjuncts of the patient’s sperm were significantly longer (721.80 ± 122.26 nm) than in controls’ sperm (310.00 ± 64.11 nm; P < 0.001). The aneuploidy frequencies of the patient’s sperm, detected by FISH analysis, were increased with respect to controls. Conclusion A paternal contribution to sperm aneuploidies cannot be excluded since the patient’s sperm showed altered morphology, immature centriolar adjunct, presence of evident distal centriole, scarce presence of centrin 1, and high aneuploidy frequency.

A dynamic basal complex modulates mammalian sperm movement

Reproductive success depends on efficient sperm movement driven by dynein-mediated microtubule sliding in the axoneme 1-3. Models predict sliding at the base of the tail – the centriole – but such sliding has never been observed 4,5. Centrioles are evolutionarily-ancient organelles with a conserved architecture 6-8, and their rigidity is thought to restrict microtubule sliding 1. Here, we show that, in mammalian sperm, the atypical distal centriole (DC) and its surrounding atypical pericentriolar matrix 9,10 form a dynamic basal complex (DBC) that facilitates a cascade of internal sliding deformations, coupling tail beating with asymmetric head kinking. During asymmetric tail beating, the DC’s right side and its surroundings slide ~300 nm rostrally relative to the left side. This deformation is transmitted through the DBC to the head-tail junction; as a result, the head tilts to the left, generating a kinking motion. These findings suggest that the DBC evolved to act as a mechanotransducer, coupling sperm head and tail into a single self-coordinated system. The DBC may act as a morphological computer 11, regulating tail beating from external feedback imparted to the head during sperm navigation. We anticipate our findings will enable studies of coordinated motion in sperm and cilia in many contexts.

A dynamic basal complex modulates mammalian sperm movement

Reproductive success depends on efficient sperm movement driven by dynein-mediated microtubule sliding in the axoneme 1-3. Models predict sliding at the base of the tail – the centriole – but such sliding has never been observed 4,5. Centrioles are evolutionarily-ancient organelles with a conserved architecture 6-8, and their rigidity is thought to restrict microtubule sliding 1. Here, we show that, in mammalian sperm, the atypical distal centriole (DC) and its surrounding atypical pericentriolar matrix 9,10 form a dynamic basal complex (DBC) that facilitates a cascade of internal sliding deformations, coupling tail beating with asymmetric head kinking. During asymmetric tail beating, the DC’s right side and its surroundings slide ~300 nm rostrally relative to the left side. This deformation is transmitted through the DBC to the head-tail junction; as a result, the head tilts to the left, generating a kinking motion. These findings suggest that the DBC evolved to act as a mechanotransducer, coupling sperm head and tail into a single self-coordinated system. The DBC may act as a morphological computer 11, regulating tail beating from external feedback imparted to the head during sperm navigation. We anticipate our findings will enable studies of coordinated motion in sperm and cilia in many contexts.

A dynamic basal complex modulates mammalian sperm movement

Reproductive success depends on efficient sperm movement driven by dynein-mediated microtubule sliding in the axoneme 1-3. Models predict sliding at the base of the tail – the centriole – but such sliding has never been observed 4,5. Centrioles are evolutionarily-ancient organelles with a conserved architecture 6-8, and their rigidity is thought to restrict microtubule sliding 1. Here, we show that, in mammalian sperm, the atypical distal centriole (DC) and its surrounding atypical pericentriolar matrix 9,10 form a dynamic basal complex (DBC) that facilitates a cascade of internal sliding deformations, coupling tail beating with asymmetric head kinking. During asymmetric tail beating, the DC’s right side and its surroundings slide ~300 nm rostrally relative to the left side. This deformation is transmitted through the DBC to the head-tail junction; as a result, the head tilts to the left, generating a kinking motion. These findings suggest that the DBC evolved to act as a mechanotransducer, coupling sperm head and tail into a single self-coordinated system. The DBC may act as a morphological computer 11, regulating tail beating from external feedback imparted to the head during sperm navigation. We anticipate our findings will enable studies of coordinated motion in sperm and cilia in many contexts.

Ultrastructure of Spermatozoa of Elaphe schrenckii (Reptilia, Squamata)

Elaphe schrenckii (Serpentes, Colubridae), a kind of large nonvenomous snakes and great significance to maintain the stability of ecosystem in China. We provide detailed descriptions of the sperm microstructure and ultrastructure of E. schrenckii, experimented by light microscope and transmission electron microscope. The spermatozoon of E. schrenckii is filiform and consists of head and tail regions. The cross-section of acrosomal vesicle is always rounded and divided into medulla inside and cortex outside. The ultrastructure of acrosome complex observed the unilateral ridge, the single perforatorium, the perforatorium base plate, the epinuclear lucent zone, the subacrosomal space and the nuclear fossa at the end of nucleus connect the neck region. The neck region is short with the stratified laminar structure and observed the distal centriole and the proximal centriole are perpendicular and both consisted of nine triplets. Midpiece is long and observed the extracellular microtubules, the multilaminar membranec, the mitochondria with the dense bodies discontinuity distribting, the fibrous sheath, and the axoneme. The principal piece is after the annulus with no mitochondrias and the end piece with no mitochondrias neither the fibrous sheath. Our study contrasted the spermatozoa ultrastructure of 8 species belong to 5 families and 6 genera and added the sperm measurement compare, summarized that three Colubridae snakes are more similar than others momentarily but some specific characteristics in E. schrenckii and proved that the ultrastructure of sperm related to phylogeny in some ways.