The eukaryotic flagellum makes the day: novel and unforeseen roles uncovered after post-genomics and proteomics data

Identification of Cell-Attachment Factors Derived from Green Algal Cells Disrupted by Sonication in Fabrication of Cell Plastics

Cell plastics which are composed of unicellular green algal cells have been proposed in previous studies. While unicellular green algae can be freely arranged using fabrication processes, a matrix is required to attach the cells together. To date, although the cell contents collected from Chlamydomonas reinhardtii show the possibility of attaching cells, but it is unclear which components can be considered attachment factors. Therefore, in this study, C. reinhardtii cells were disrupted with sonication, and the components were separated and purified with hexane. The cell plastics with only 0.5 wt% of intermediate showed similar mechanical properties to those with 17 wt% and 25 wt% of cell components that were untreated with hexane, meaning that the purified intermediates could function as matrices. The purified intermediate was composed of approximately 60 wt% of protein as the main component, and proteomic analysis was performed to survey the main proteins that remained after hexane treatment. The protein compositions of the cell content and purified intermediate were compared via proteomic analysis, revealing that the existing ratios of 532 proteins were increased in the purified intermediate rather than in the cell content. In particular, the outer structure of each of the 49 proteins-the intensity of which was increased by over 10 times-had characteristically random coil conformations, containing ratios of proline and alanine. The information could suggest a matrix of cell plastics, inspiring the possibility to endow the cell plastics with more properties and functions.

Molecular machineries of ciliogenesis, cell survival, and vasculogenesis are differentially expressed during regeneration in explants of the demosponge Halichondria panicea

Sponges are interesting animal models for regeneration studies, since even from dissociated cells, they are able to regenerate completely. In particular, explants are model systems that can be applied to many sponge species, since small fragments of sponges can regenerate all elements of the adult, including the oscula and the ability to pump water. The morphological aspects of regeneration in sponges are relatively well known, but the molecular machinery is only now starting to be elucidated for some sponge species. Here, we have used an explant system of the demosponge Halichondria panicea to understand the molecular machinery deployed during regeneration of the aquiferous system. We sequenced the transcriptomes of four replicates of the 5-day explant without an osculum (NOE), four replicates of the 17-18-day explant with a single osculum and pumping activity (PE) and also four replicates of field-collected individuals with regular pumping activity (PA), and performed differential gene expression analysis. We also described the morphology of NOE and PE samples using light and electron microscopy. Our results showed a highly disorganised mesohyl and disarranged aquiferous system in NOE that is coupled with upregulated pathways of ciliogenesis, organisation of the ECM, and cell proliferation and survival. Once the osculum is formed, genes involved in "response to stimulus in other organisms" were upregulated. Interestingly, the main molecular machinery of vasculogenesis described in vertebrates was activated during the regeneration of the aquiferous system. Notably, vasculogenesis markers were upregulated when the tissue was disorganised and about to start forming canals (NOE) and angiogenic stimulators and ECM remodelling machineries were differentially expressed once the aquiferous system was in place (PE and PA). Our results are fundamental to better understanding the molecular mechanisms involved in the formation of the aquiferous system in sponges, and its similarities with the early onset of blood-vessel formation in animal evolution.

Successful Results of Intracytoplasmic Sperm Injection of a Chinese Patient With Multiple Morphological Abnormalities of Sperm Flagella Caused by a Novel Splicing Mutation in CFAP251

Asthenospermia is one of the most important causes of male infertility. Among asthenospermia, multiple morphological abnormalities of sperm flagella (MMAF) are relatively rare idiopathic conditions characterized by multiple defects in sperm flagella. Although many studies focusing on the genetic factors of MMAF have been conducted, its pathogenesis and treatment effect remain largely unknown. Here, we report a male patient from a nonconsanguineous Chinese family who exhibited a typical MMAF phenotype revealed by morphological analysis. We identified splicing mutations in CFAP251 (c.1192-3C>G), and the mutation was proven to cause exon skipping. In addition, western blotting and immunofluorescence analysis of the spermatozoa from the proband and a control subject revealed a significantly lower expression of CFAP251 protein due to pathogenic mutation. Interestingly, the patient’s mother was a heterozygous carrier for the mutation, but his father was not, and finally, the inheritance pattern was proven to be maternal uniparental disomy. We applied an intracytoplasmic sperm injection and achieved a successful pregnancy. Above all, our findings expand the spectrum of CFAP251 pathogenic mutations and provide more indications for clinical genetic counseling and assisted reproductive treatment for such patients.

The distinctive flagellar proteome of Euglena gracilis illuminates the complexities of protistan flagella adaptation

The eukaryotic flagellum/cilium is a prominent organelle with conserved structure and diverse functions. Euglena gracilis, a photosynthetic and highly adaptable protist, employs its flagella for both locomotion and environmental sensing. Using proteomics of isolated E. gracilis flagella we identify nearly 1700 protein groups, which challenges previous estimates of the protein complexity of motile eukaryotic flagella. We not only identified several unexpected similarities shared with mammalian flagella, including an entire glycolytic pathway and proteasome, but also document a vast array of flagella-based signal transduction components that coordinate gravitaxis and phototactic motility. By contrast, the pellicle was found to consist of > 900 protein groups, containing additional structural and signalling components. Our data identify significant adaptations within the E. gracilis flagellum, many of which are clearly linked to the highly flexible lifestyle.

PLK1 regulates centrosome migration and spindle dynamics in male mouse meiosis

Cell division requires the regulation of karyokinesis and cytokinesis, which includes an essential role of the achromatic spindle. Although the functions of centrosomes are well characterised in somatic cells, their role during vertebrate spermatogenesis remains elusive. We have studied the dynamics of the meiotic centrosomes in male mouse during both meiotic divisions. Results show that meiotic centrosomes duplicate twice: first duplication occurs in the leptotene/zygotene transition, while the second occurs in interkinesis. The maturation of duplicated centrosomes during the early stages of prophase I and II are followed by their separation and migration to opposite poles to form bipolar spindles I and II. The study of the genetic mouse model Plk1(Δ/Δ) indicates a central role of Polo-like kinase 1 in pericentriolar matrix assembly, in centrosome maturation and migration, and in the formation of the bipolar spindles during spermatogenesis. In addition, in vitro inhibition of Polo-like kinase 1 and Aurora A in organotypic cultures of seminiferous tubules points out to a prominent role of both kinases in the regulation of the formation of meiotic bipolar spindles.

Identification of motility-associated progesterone-responsive differentially phosphorylated proteins

Progesterone is one of the regulators of sperm motility and hyperactivation. In human spermatozoa, the effects of progesterone are thought to be mediated by protein phosphorylation. In the present study, we identified 22 proteins that are differentially phosphorylated (12 phosphorylated and 10 dephosphorylated) by progesterone in human spermatozoa. Functionally, the differentially phosphorylated proteins are predicted to have cytoskeletal localisation and to be associated with sperm motility. 5µM of progesterone to capacitated increased the phosphorylation of tyrosine residues in the principal piece and protein tyrosine kinase activity increased by almost 3.5-fold. For the first time, we demonstrate that tyrosine phosphatases are also activated in response to progesterone and that inhibition of tyrosine phosphatases attenuates dephosphorylation of flagellar proteins. We propose that progesterone activates both kinase and phosphatase pathways, leading to changes in the phosphorylation of many proteins in sperm flagella to increase motility.

Targeted deletion of the AAA-ATPase Ruvbl1 in mice disrupts ciliary integrity and causes renal disease and hydrocephalus

Ciliopathies comprise a large number of hereditary human diseases and syndromes caused by mutations resulting in dysfunction of either primary or motile cilia. Both types of cilia share a similar architecture. While primary cilia are present on most cell types, expression of motile cilia is limited to specialized tissues utilizing ciliary motility. We characterized protein complexes of ciliopathy proteins and identified the conserved AAA-ATPase Ruvbl1 as a common novel component. Here, we demonstrate that Ruvbl1 is crucial for the development and maintenance of renal tubular epithelium in mice: both constitutive and inducible deletion in tubular epithelial cells result in renal failure with tubular dilatations and fewer ciliated cells. Moreover, inducible deletion of Ruvbl1 in cells carrying motile cilia results in hydrocephalus, suggesting functional relevance in both primary and motile cilia. Cilia of Ruvbl1-negative cells lack crucial proteins, consistent with the concept of Ruvbl1-dependent cytoplasmic pre-assembly of ciliary protein complexes.

A protein involved in building and maintaining thin protrusions from cell surfaces called cilia is implicated in “ciliopathies”, diseases in which ciliary function is disrupted. These include polycystic kidney disease and disorders collectively known as ciliary dyskinesias. “Primary cilia” perform sensory functions, detecting external chemical and physical signals and initiating responses within cells. In addition, “motile cilia” beat rhythmically to move fluids surrounding cells. Researchers in Germany and the Netherlands, led by Bernhard Schermer and Max C. Liebau at the University of Cologne, studied a protein called Ruvbl1, known to interact with DNA and other proteins. The researchers found it is crucial for the functioning of both types of cilia. Deleting the gene for Ruvbl1 in mice caused kidney failure and a build-up of fluid in the brain known as hydrocephalus. The research could help understand and ultimately treat ciliopathies.

p28 dynein light chains and ciliary motility in Tetrahymena thermophila

Dynein light chains are required for the assembly of axonemal dyneins into cilia and flagella. Most organisms express a single p28 dynein light chain and four to nine one-headed inner arm dynein heavy chains. In contrast, Tetrahymena encodes three p28 dynein light chain genes (p28A, p28B, and p28C) and 18 one-headed inner arm dynein heavy chains. In this article it is shown that mutations in p28A and p28B affected both beat frequency and waveform of cilia, while mutations in p28C affected only ciliary beat frequency. A similar set of dynein heavy chains were affected in both p28AKO and p28BKO, but a distinct set of heavy chains was affected in p28CKO. The results suggested that the p28s have non-redundant functions in Tetrahymena and that p28C was associated with a different set of dynein heavy chains than were p28A and p28B.

Permeability barriers for generating a unique ciliary protein and lipid composition

Cilia (and flagella) are microtubule-based protrusions that are found in single or multiple copies on the surface of most eukaryotic cells. Defects in cilia formation and/or function have now been correlated with an expanding spectrum of human genetic diseases termed ciliopathies. Recent work indicates that cilia are indeed a bona fide organelle with a unique protein and lipid content that enables specific cellular functions. Despite the physiological and clinical relevance of cilia, our understanding of how a unique protein and lipid composition is generated for this organelle remains poor. Here we review recent work on the mechanisms that determine the protein and lipid content, and thus the functional outputs, of this unique organelle.

Coiled-coil domain containing 42 (Ccdc42) is necessary for proper sperm development and male fertility in the mouse

Spermiogenesis is the differentiation of spermatids into motile sperm consisting of a head and a tail. The head harbors a condensed elongated nucleus partially covered by the acrosome-acroplaxome complex. Defects in the acrosome-acroplaxome complex are associated with abnormalities in sperm head shaping. The head-tail coupling apparatus (HTCA), a complex structure consisting of two cylindrical microtubule-based centrioles and associated components, connects the tail or flagellum to the sperm head. Defects in the development of the HTCA cause sperm decapitation and disrupt sperm motility, two major contributors to male infertility. Here, we provide data indicating that mutations in the gene Coiled-coil domain containing 42 (Ccdc42) is associated with malformation of the mouse sperm flagella. In contrast to many other flagella and motile cilia genes, Ccdc42 expression is only observed in the brain and developing sperm. Male mice homozygous for a loss-of-function Ccdc42 allele (Ccdc42(KO)) display defects in the number and location of the HTCA, lack flagellated sperm, and are sterile. The testes enriched expression of Ccdc42 and lack of other phenotypes in mutant mice make it an ideal candidate for screening cases of azoospermia in humans.

Merlin Isoforms 1 and 2 Both Act as Tumour Suppressors and Are Required for Optimal Sperm Maturation

The tumour suppressor Merlin, encoded by the gene NF2, is frequently mutated in the autosomal dominant disorder neurofibromatosis type II, characterised primarily by the development of schwannoma and other glial cell tumours. However, NF2 is expressed in virtually all analysed human and rodent organs, and its deletion in mice causes early embryonic lethality. Additionally, NF2 encodes for two major isoforms of Merlin of unknown functionality. Specifically, the tumour suppressor potential of isoform 2 remains controversial. In this study, we used Nf2 isoform-specific knockout mouse models to analyse the function of each isoform during development and organ homeostasis. We found that both isoforms carry full tumour suppressor functionality and can completely compensate the loss of the other isoform during development and in most adult organs. Surprisingly, we discovered that spermatogenesis is strictly dependent on the presence of both isoforms. While the testis primarily expresses isoform 1, we noticed an enrichment of isoform 2 in spermatogonial stem cells. Deletion of either isoform was found to cause decreased sperm quality as observed by maturation defects and head/midpiece abnormalities. These defects led to impaired sperm functionality as assessed by decreased sperm capacitation. Thus, we describe spermatogenesis as a new Nf2-dependent process. Additionally, we provide for the first time in vivo evidence for equal tumour suppressor potentials of Merlin isoform 1 and isoform 2.

Archaeal type IV pili and their involvement in biofilm formation

Type IV pili are ancient proteinaceous structures present on the cell surface of species in nearly all bacterial and archaeal phyla. These filaments, which are required for a diverse array of important cellular processes, are assembled employing a conserved set of core components. While type IV pilins, the structural subunits of pili, share little sequence homology, their signal peptides are structurally conserved allowing for in silico prediction. Recently, in vivo studies in model archaea representing the euryarchaeal and crenarchaeal kingdoms confirmed that several of these pilins are incorporated into type IV adhesion pili. In addition to facilitating surface adhesion, these in vivo studies also showed that several predicted pilins are required for additional functions that are critical to biofilm formation. Examples include the subunits of Sulfolobus acidocaldarius Ups pili, which are induced by exposure to UV light and promote cell aggregation and conjugation, and a subset of the Haloferax volcanii adhesion pilins, which play a critical role in microcolony formation while other pilins inhibit this process. The recent discovery of novel pilin functions such as the ability of haloarchaeal adhesion pilins to regulate swimming motility may point to novel regulatory pathways conserved across prokaryotic domains. In this review, we will discuss recent advances in our understanding of the functional roles played by archaeal type IV adhesion pili and their subunits, with particular emphasis on their involvement in biofilm formation.