A phylogenetic profiling approach identifies novel ciliogenesis genes in Drosophila and C. elegans

Comprehensive analysis of chromosomal breakpoints and candidate genes associated with male infertility: insights from cytogenetic studies and expression analyses

The study aimed to investigate prevalent chromosomal breakpoints identified in balanced structural chromosomal anomalies and to pinpoint potential candidate genes linked with male infertility. This was acchieved through a comprehensive approach combining RNA-seq and microarray data analysis, enabling precise identification of candidate genes. The Cytogenetics data from 2,500 infertile males referred to Royan Research Institute between 2009 and 2022 were analyzed, with 391 cases meeting the inclusion criteria of balanced chromosomal rearrangement. Of these, 193 cases exhibited normal variations and were excluded from the analysis. By examining the breakpoints, potential candidate genes were suggested. Among the remaining 198 cases, reciprocal translocations were the most frequent anomaly (129 cases), followed by Robertsonian translocations (43 cases), inversions (34 cases), and insertions (3 cases).Some patients had more than one chromosomal abnormality. Chromosomal anomalies were most frequently observed in chromosomes 13 (21.1%), 14 (20.1%), and 1 (16.3%) with 13q12, 14q12, and 1p36.3 being the most prevalent breakpoints, respectively. Chromosome 1 contributed the most to reciprocal translocations (20.2%) and inversions (17.6%), while chromosome 14 was the most involved in the Robertsonian translocations (82.2%). The findings suggested that breakpoints at 1p36.3 and 14q12 might be associated with pregestational infertility, whereas breakpoints at 13q12 could be linked to both gestational and pregestational infertility. Several candidate genes located on common breakpoints were proposed as potentially involved in male infertility. Bioinformatics analyses utilizing three databases were conducted to examine the expression patterns of 78 candidate genes implicated in various causes of infertility.‏ In azoospermic individuals, significant differential expression was observed in 19 genes: 15 were downregulated (TSSK2, SPINK2, TSSK4, CDY1, CFAP70, BPY2, BTG4, FKBP6, PPP2R1B, SPECC1L, CENPJ, ‏SKA3, FGF9, NODAL, CLOCK), while four genes were upregulated ‏(‏HSPB1, MIF, PRF1, ENTPD6). In the case of Asthenozoospermia, seven genes showed significant upregulation (PRF1, DDX21, KIT, SRD5A3, MTCH1, DDX50, NODAL). Though RNA-seq data for Teratozoospermia were unavailable, microarray data revealed differential expression insix genes: three downregulated (BUB1, KLK4, PIWIL2) and three upregulated (AURKC, NPM2, RANBP2). These findings enhance our understanding of the molecular basis of male infertility and could provide valuable insights for future diagnostic and therapeutic strategies.

A multistage Plasmodium CRL4WIG1 ubiquitin ligase is critical for the formation of functional microtubule organization centers in microgametocytes

Malaria is a mosquito-borne infectious disease caused by unicellular eukaryotic parasites of the Plasmodium genus. Protein ubiquitination by E3 ligases is a critical post-translational modification required for various cellular processes during the lifecycle of Plasmodium parasites. However, little is known about the repertoire and function of these enzymes in Plasmodium. Here, we show that Plasmodium expresses a conserved cullin RING E3 ligase (CRL) complex that is functionally related to CRL4 in other eukaryotes. In P. falciparum asexual blood stages, a cullin-4 scaffold interacts with the RING protein RBX1, the adaptor protein DDB1, and a set of putative receptor proteins that may determine substrate specificity for ubiquitination. These receptor proteins contain WD40-repeat domains and include WD-repeat protein important for gametogenesis 1 (WIG1). This CRL4-related complex is also expressed in P. berghei gametocytes, with WIG1 being the only putative receptor detected in both the schizont and gametocyte stages. WIG1 disruption leads to a complete block in microgamete formation. Proteomic analyses indicate that WIG1 disruption alters proteostasis of ciliary proteins and components of the DNA replication machinery during gametocytogenesis. Further analysis by ultrastructure expansion microscopy (U-ExM) indicates that WIG1-dependent depletion of ciliary proteins is associated with impaired the formation of the microtubule organization centers that coordinate mitosis with axoneme formation and altered DNA replication during microgametogenesis. This work identifies a CRL4-related ubiquitin ligase in Plasmodium that is critical for the formation of microgametes by regulating proteostasis of ciliary and DNA replication proteins.IMPORTANCEPlasmodium parasites undergo fascinating lifecycles with multiple developmental steps, converting into morphologically distinct forms in both their mammalian and mosquito hosts. Protein ubiquitination by ubiquitin ligases emerges as an important post-translational modification required to control multiple developmental stages in Plasmodium. Here, we identify a cullin RING E3 ubiquitin ligase (CRL) complex expressed in the replicating asexual blood stages and in the gametocyte stages that mediate transmission to the mosquito. WIG1, a putative substrate recognition protein of this ligase complex, is essential for the maturation of microgametocytes into microgametes upon ingestion by a mosquito. More specifically, WIG1 is required for proteostasis of ciliary proteins and components of the DNA replication machinery during gametocytogenesis. This requirement is linked to DNA replication and microtubule organization center formation, both critical to the development of flagellated microgametes.

NEKL-4 regulates microtubule stability and mitochondrial health in ciliated neurons

Ciliopathies are often caused by defects in the ciliary microtubule core. Glutamylation is abundant in cilia, and its dysregulation may contribute to ciliopathies and neurodegeneration. Mutation of the deglutamylase CCP1 causes infantile-onset neurodegeneration. In C. elegans, ccpp-1 loss causes age-related ciliary degradation that is suppressed by a mutation in the conserved NEK10 homolog nekl-4. NEKL-4 is absent from cilia, yet it negatively regulates ciliary stability via an unknown, glutamylation-independent mechanism. We show that NEKL-4 was mitochondria-associated. Additionally, nekl-4 mutants had longer mitochondria, a higher baseline mitochondrial oxidation state, and suppressed ccpp-1∆ mutant lifespan extension in response to oxidative stress. A kinase-dead nekl-4(KD) mutant ectopically localized to ccpp-1∆ cilia and rescued degenerating microtubule doublet B-tubules. A nondegradable nekl-4(PEST∆) mutant resembled the ccpp-1∆ mutant with dye-filling defects and B-tubule breaks. The nekl-4(PEST∆) Dyf phenotype was suppressed by mutation in the depolymerizing kinesin-8 KLP-13/KIF19A. We conclude that NEKL-4 influences ciliary stability by activating ciliary kinesins and promoting mitochondrial homeostasis.

Loss of cilia in chemosensory neurons inhibits pathogen avoidance in Caenorhabditis elegans

Pathogen avoidance is a crucial and evolutionarily conserved behavior that enhances survival by preventing infection in diverse species, including Caenorhabditis elegans (C. elegans). This behavior relies on multiple chemosensory neurons equipped with cilia that are exposed to the external environment. However, the specific role of neuronal cilia in pathogen avoidance has not been completely elucidated. Herein, we discovered that osm-3(p802) mutants, which lack chemosensory neuronal cilia, exhibit slower avoidance of the pathogen Pseudomonas aeruginosa PA14, but not Escherichia coli OP50. This observation was consistent when osm-3(p802) mutants were exposed to P. aeruginosa PAO1. Following an encounter with PA14, the pumping, thrashing, and defecation behaviors of osm-3 mutants were comparable to those of the wild-type. However, the osm-3 mutants demonstrated reduced intestinal colonization of PA14, suggesting that they have stronger intestinal clearance ability. We conducted RNA-seq to identify genes responding to external stimuli that were differentially expressed owing to the loss of osm-3 and PA14 infection. Using RNAi, we demonstrated that three of these genes were essential for normal pathogen avoidance. In conclusion, our findings demonstrate that the loss of chemosensory neuronal cilia reduces pathogen avoidance in C. elegans while delaying intestinal colonization.

The neuronal cilium - a highly diverse and dynamic organelle involved in sensory detection and neuromodulation

Cilia are fascinating organelles that act as cellular antennae, sensing the cellular environment. Cilia gained significant attention in the late 1990s after their dysfunction was linked to genetic diseases known as ciliopathies. Since then, several breakthrough discoveries have uncovered the mechanisms underlying cilia biogenesis and function. Like most cells in the animal kingdom, neurons also harbor cilia, which are enriched in neuromodulatory receptors. Yet, how neuronal cilia modulate neuronal physiology and animal behavior remains poorly understood. By comparing ciliary biology between the sensory and central nervous systems (CNS), we provide new perspectives on the functions of cilia in brain physiology.

NEKL-4 regulates microtubule stability and mitochondrial health in C. elegans ciliated neurons

Ciliopathies are often caused by defects in the ciliary microtubule core. Glutamylation is abundant in cilia, and its dysregulation may contribute to ciliopathies and neurodegeneration. Mutation of the deglutamylase CCP1 causes infantile-onset neurodegeneration. In C. elegans, ccpp-1 loss causes age-related ciliary degradation that is suppressed by mutation in the conserved NEK10 homolog nekl-4. NEKL-4 is absent from cilia, yet negatively regulates ciliary stability via an unknown, glutamylation-independent mechanism. We show that NEKL-4 was mitochondria-associated. nekl-4 mutants had longer mitochondria, a higher baseline mitochondrial oxidation state, and suppressed ccpp-1 mutant lifespan extension in response to oxidative stress. A kinase-dead nekl-4(KD) mutant ectopically localized to ccpp-1 cilia and rescued degenerating microtubule doublet B-tubules. A nondegradable nekl-4(PESTΔ) mutant resembled the ccpp-1 mutant with dye filling defects and B-tubule breaks. The nekl-4(PESTΔ) Dyf phenotype was suppressed by mutation in the depolymerizing kinesin-8 KLP-13/KIF19A. We conclude that NEKL-4 influences ciliary stability by activating ciliary kinesins and promoting mitochondrial homeostasis.

An internally controlled system to study microtubule network diversification links tubulin evolution to the use of distinct microtubule regulators

Diverse eukaryotic cells assemble microtubule networks that vary in structure and composition. While we understand how cells build microtubule networks with specialized functions, we do not know how microtubule networks diversify across deep evolutionary timescales. This problem has remained unresolved because most organisms use shared pools of tubulins for multiple networks, making it impossible to trace the evolution of any single network. In contrast, the amoeboflagellate Naegleria uses distinct tubulin genes to build distinct microtubule networks: while Naegleria builds flagella from conserved tubulins during differentiation, it uses divergent tubulins to build its mitotic spindle. This genetic separation makes for an internally controlled system to study independent microtubule networks in a single organismal and genomic context. To explore the evolution of these microtubule networks, we identified conserved microtubule binding proteins and used transcriptional profiling of mitosis and differentiation to determine which are upregulated during the assembly of each network. Surprisingly, most microtubule binding proteins are upregulated during only one process, suggesting that Naegleria uses distinct component pools to specialize its microtubule networks. Furthermore, the divergent residues of mitotic tubulins tend to fall within the binding sites of differentiation-specific microtubule regulators, suggesting that interactions between microtubules and their binding proteins constrain tubulin sequence diversification. We therefore propose a model for cytoskeletal evolution in which pools of microtubule network components constrain and guide the diversification of the entire network, so that the evolution of tubulin is inextricably linked to that of its binding partners.

Cep104 is a component of the centriole distal tip complex that regulates centriole growth and contributes to Drosophila spermiogenesis

Proper centrosome number and function relies on the accurate assembly of centrioles, barrel-shaped structures that form the core duplicating elements of the organelle. The growth of centrioles is regulated in a cell cycle-dependent manner; while new daughter centrioles elongate during the S/G2/M phase, mature mother centrioles maintain their length throughout the cell cycle. Centriole length is controlled by the synchronized growth of the microtubules that ensheathe the centriole barrel. Although proteins exist that target the growing distal tips of centrioles, such as CP110 and Cep97, these proteins are generally thought to suppress centriolar microtubule growth, suggesting that distal tips may also contain unidentified counteracting factors that facilitate microtubule polymerization. Currently, a mechanistic understanding of how distal tip proteins balance microtubule growth and shrinkage to either promote daughter centriole elongation or maintain centriole length is lacking. Using a proximity-labeling screen in Drosophila cells, we identified Cep104 as a novel component of a group of evolutionarily conserved proteins that we collectively refer to as the distal tip complex (DTC). We found that Cep104 regulates centriole growth and promotes centriole elongation through its microtubule-binding TOG domain. Furthermore, analysis of Cep104 null flies revealed that Cep104 and Cep97 cooperate during spermiogenesis to align spermatids and coordinate individualization. Lastly, we mapped the complete DTC interactome and showed that Cep97 is the central scaffolding unit required to recruit DTC components to the distal tip of centrioles.

Evolution: The ancient history of cilia assembly regulation

A new study identifies a conserved regulatory mechanism for cilia assembly in the closest unicellular relatives of animals, suggesting that this mechanism was already present in a common unicellular ancestor and was repurposed during the transition to multicellularity.