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Cell Jun 2023Sperm motility is crucial to reproductive success in sexually reproducing organisms. Impaired sperm movement causes male infertility, which is increasing globally. Sperm...
Sperm motility is crucial to reproductive success in sexually reproducing organisms. Impaired sperm movement causes male infertility, which is increasing globally. Sperm are powered by a microtubule-based molecular machine-the axoneme-but it is unclear how axonemal microtubules are ornamented to support motility in diverse fertilization environments. Here, we present high-resolution structures of native axonemal doublet microtubules (DMTs) from sea urchin and bovine sperm, representing external and internal fertilizers. We identify >60 proteins decorating sperm DMTs; at least 15 are sperm associated and 16 are linked to infertility. By comparing DMTs across species and cell types, we define core microtubule inner proteins (MIPs) and analyze evolution of the tektin bundle. We identify conserved axonemal microtubule-associated proteins (MAPs) with unique tubulin-binding modes. Additionally, we identify a testis-specific serine/threonine kinase that links DMTs to outer dense fibers in mammalian sperm. Our study provides structural foundations for understanding sperm evolution, motility, and dysfunction at a molecular level.
Topics: Male; Animals; Cattle; Sperm Tail; Sperm Motility; Semen; Microtubules; Axoneme; Spermatozoa; Mammals
PubMed: 37327785
DOI: 10.1016/j.cell.2023.05.026 -
Nature Jun 2023Motile cilia and flagella beat rhythmically on the surface of cells to power the flow of fluid and to enable spermatozoa and unicellular eukaryotes to swim. In humans,...
Motile cilia and flagella beat rhythmically on the surface of cells to power the flow of fluid and to enable spermatozoa and unicellular eukaryotes to swim. In humans, defective ciliary motility can lead to male infertility and a congenital disorder called primary ciliary dyskinesia (PCD), in which impaired clearance of mucus by the cilia causes chronic respiratory infections. Ciliary movement is generated by the axoneme, a molecular machine consisting of microtubules, ATP-powered dynein motors and regulatory complexes. The size and complexity of the axoneme has so far prevented the development of an atomic model, hindering efforts to understand how it functions. Here we capitalize on recent developments in artificial intelligence-enabled structure prediction and cryo-electron microscopy (cryo-EM) to determine the structure of the 96-nm modular repeats of axonemes from the flagella of the alga Chlamydomonas reinhardtii and human respiratory cilia. Our atomic models provide insights into the conservation and specialization of axonemes, the interconnectivity between dyneins and their regulators, and the mechanisms that maintain axonemal periodicity. Correlated conformational changes in mechanoregulatory complexes with their associated axonemal dynein motors provide a mechanism for the long-hypothesized mechanotransduction pathway to regulate ciliary motility. Structures of respiratory-cilia doublet microtubules from four individuals with PCD reveal how the loss of individual docking factors can selectively eradicate periodically repeating structures.
Topics: Humans; Male; Artificial Intelligence; Axonemal Dyneins; Axoneme; Cilia; Cryoelectron Microscopy; Flagella; Mechanotransduction, Cellular; Microtubules; Chlamydomonas reinhardtii; Ciliary Motility Disorders; Movement; Protein Conformation
PubMed: 37258679
DOI: 10.1038/s41586-023-06140-2 -
Cellular and Molecular Life Sciences :... Jun 2020The core axoneme structure of both the motile cilium and sperm tail has the same ultrastructural 9 + 2 microtubular arrangement. Thus, it can be expected that... (Review)
Review
The core axoneme structure of both the motile cilium and sperm tail has the same ultrastructural 9 + 2 microtubular arrangement. Thus, it can be expected that genetic defects in motile cilia also have an effect on sperm tail formation. However, recent studies in human patients, animal models and model organisms have indicated that there are differences in components of specific structures within the cilia and sperm tail axonemes. Primary ciliary dyskinesia (PCD) is a genetic disease with symptoms caused by malfunction of motile cilia such as chronic nasal discharge, ear, nose and chest infections and pulmonary disease (bronchiectasis). Half of the patients also have situs inversus and in many cases male infertility has been reported. PCD genes have a role in motile cilia biogenesis, structure and function. To date mutations in over 40 genes have been identified cause PCD, but the exact effect of these mutations on spermatogenesis is poorly understood. Furthermore, mutations in several additional axonemal genes have recently been identified to cause a sperm-specific phenotype, termed multiple morphological abnormalities of the sperm flagella (MMAF). In this review, we discuss the association of PCD genes and other axonemal genes with male infertility, drawing particular attention to possible differences between their functions in motile cilia and sperm tails.
Topics: Animals; Cilia; Ciliary Motility Disorders; Humans; Infertility, Male; Male; Mutation; Spermatozoa
PubMed: 31781811
DOI: 10.1007/s00018-019-03389-7 -
Seminars in Cell & Developmental Biology Jan 2023Ciliogenesis is a complex multistep process used to describe assembly of cilia and flagella. These organelles play essential roles in motility and signaling on the... (Review)
Review
Ciliogenesis is a complex multistep process used to describe assembly of cilia and flagella. These organelles play essential roles in motility and signaling on the surface of cells. Cilia are built at the distal ends of centrioles through the formation of an axoneme that is surrounded by the ciliary membrane. As is the case in the biogenesis of other cellular organelles, regulators of membrane trafficking play essential roles in ciliogenesis, albeit with a unique feature that membranes are organized around microtubule-based structures. Membrane association with the distal end of the centriole is a critical initiating step for ciliogenesis. Studies of this process in different cell types suggests that a singular mechanism may not be utilized to initiate cilium assembly. In this review, we focus on recent insights into cilium biogenesis and the roles membrane trafficking regulators play in described ciliogenesis mechanisms with relevance to human disease.
Topics: Humans; Centrioles; Axoneme; Cilia; Microtubules; Flagella
PubMed: 35351373
DOI: 10.1016/j.semcdb.2022.03.021 -
American Journal of Human Genetics Jan 2022Asthenoteratozoospermia, defined as reduced sperm motility and abnormal sperm morphology, is a disorder with considerable genetic heterogeneity. Although previous...
Asthenoteratozoospermia, defined as reduced sperm motility and abnormal sperm morphology, is a disorder with considerable genetic heterogeneity. Although previous studies have identified several asthenoteratozoospermia-associated genes, the etiology remains unknown for the majority of affected men. Here, we performed whole-exome sequencing on 497 unrelated men with asthenoteratozoospermia and identified DNHD1 bi-allelic variants from eight families (1.6%). All detected variants were predicted to be deleterious via multiple bioinformatics tools. Hematoxylin and eosin (H&E) staining revealed that individuals with bi-allelic DNHD1 variants presented striking abnormalities of the flagella; transmission electron microscopy (TEM) further showed flagellar axoneme defects, including central pair microtubule (CP) deficiency and mitochondrial sheath (MS) malformations. In sperm from fertile men, DNHD1 was localized to the entire flagella of the normal sperm; however, it was nearly absent in the flagella of men with bi-allelic DNHD1 variants. Moreover, abundance of the CP markers SPAG6 and SPEF2 was significantly reduced in spermatozoa from men harboring bi-allelic DNHD1 variants. In addition, Dnhd1 knockout male mice (Dnhd1) exhibited asthenoteratozoospermia and infertility, a finding consistent with the sperm phenotypes present in human subjects with DNHD1 variants. The female partners of four out of seven men who underwent intracytoplasmic sperm injection therapy subsequently became pregnant. In conclusion, our study showed that bi-allelic DNHD1 variants cause asthenoteratozoospermia, a finding that provides crucial insights into the biological underpinnings of this disorder and should assist with counseling of affected individuals.
Topics: Alleles; Animals; Asthenozoospermia; Axoneme; Computational Biology; DNA Mutational Analysis; Disease Models, Animal; Dyneins; Flagella; Gene Frequency; Genetic Association Studies; Genetic Predisposition to Disease; Humans; Infertility, Male; Male; Mice; Mice, Knockout; Mitochondria; Mutation; Pedigree; Phenotype; Semen Analysis; Sperm Tail; Exome Sequencing
PubMed: 34932939
DOI: 10.1016/j.ajhg.2021.11.022 -
Philosophical Transactions of the Royal... Feb 2020Cilia, or eukaryotic flagella, are microscopic active filaments expressed on the surface of many eukaryotic cells, from single-celled protozoa to mammalian epithelial...
Cilia, or eukaryotic flagella, are microscopic active filaments expressed on the surface of many eukaryotic cells, from single-celled protozoa to mammalian epithelial surfaces. Cilia are characterized by a highly conserved and intricate internal structure in which molecular motors exert forces on microtubule doublets causing cilia oscillations. The spatial and temporal regulations of this molecular machinery are not well understood. Several theories suggest that geometric feedback control from cilium deformations to molecular activity is needed. Here, we implement a recent sliding control model, where the unbinding of molecular motors is dictated by the sliding motion between microtubule doublets. We investigate the waveforms exhibited by the model cilium, as well as the associated molecular motor dynamics, for hinged and clamped boundary conditions. Hinged filaments exhibit base-to-tip oscillations while clamped filaments exhibit both base-to-tip and tip-to-base oscillations. We report the change in oscillation frequencies and amplitudes as a function of motor activity and sperm number, and we discuss the validity of these results in the context of experimental observations of cilia behaviour. This article is part of the Theo Murphy meeting issue 'Unity and diversity of cilia in locomotion and transport'.
Topics: Cell Movement; Cilia; Microtubules; Models, Biological
PubMed: 31884917
DOI: 10.1098/rstb.2019.0157 -
Cell Nov 2023To understand the molecular mechanisms of cellular pathways, contemporary workflows typically require multiple techniques to identify proteins, track their localization,...
To understand the molecular mechanisms of cellular pathways, contemporary workflows typically require multiple techniques to identify proteins, track their localization, and determine their structures in vitro. Here, we combined cellular cryoelectron tomography (cryo-ET) and AlphaFold2 modeling to address these questions and understand how mammalian sperm are built in situ. Our cellular cryo-ET and subtomogram averaging provided 6.0-Å reconstructions of axonemal microtubule structures. The well-resolved tertiary structures allowed us to unbiasedly match sperm-specific densities with 21,615 AlphaFold2-predicted protein models of the mouse proteome. We identified Tektin 5, CCDC105, and SPACA9 as novel microtubule-associated proteins. These proteins form an extensive interaction network crosslinking the lumen of axonemal doublet microtubules, suggesting their roles in modulating the mechanical properties of the filaments. Indeed, Tekt5 -/- sperm possess more deformed flagella with 180° bends. Together, our studies presented a cellular visual proteomics workflow and shed light on the in vivo functions of Tektin 5.
Topics: Animals; Male; Mice; Axoneme; Cryoelectron Microscopy; Flagella; Microtubules; Semen; Spermatozoa; Proteome
PubMed: 37865089
DOI: 10.1016/j.cell.2023.09.017 -
The World Journal of Men's Health Jan 2020Microtubules are the prime component of the cytoskeleton along with microfilaments. Being vital for organelle transport and cellular divisions during spermatogenesis and... (Review)
Review
Microtubules are the prime component of the cytoskeleton along with microfilaments. Being vital for organelle transport and cellular divisions during spermatogenesis and sperm motility process, microtubules ascertain functional capacity of sperm. Also, microtubule based structures such as axoneme and manchette are crucial for sperm head and tail formation. This review (a) presents a concise, yet detailed structural overview of the microtubules, (b) analyses the role of microtubule structures in various male reproductive functions, and (c) presents the association of microtubular dysfunctions with male infertility. Considering the immense importance of microtubule structures in the formation and maintenance of physiological functions of sperm cells, this review serves as a scientific trigger in stimulating further male infertility research in this direction.
PubMed: 30350487
DOI: 10.5534/wjmh.180066