Drosophila Dynein intermediate chain gene, Dic61B, is required for spermatogenesis

The Functions of Pt-DIC and Pt-Lamin B in Spermatogenesis of Portunus trituberculatus

Cytoplasmic Dynein is a multiple-subunit macromolecular motor protein involved in the transport process of cells. The Dynein intermediate chain (DIC) is one of the subunits of Dynein-1. In our previous studies, we showed that Pt-DIC may play an important role in the nuclear deformation of spermiogenesis in Portunus trituberculatus. Lamin B is essential for maintaining nuclear structure and functions. Surprisingly, Pt-Lamin B was expressed not only in the perinucleus but also in the pro-acrosome during spermiogenesis in P. trituberculatus. Studies have also shown that Dynein-1 can mediate the transport of Lamin B in mammals. Thus, to study the relationship of Pt-DIC and Pt-Lamin B in the spermatogenesis of P. trituberculatus, we knocked down the Pt-DIC gene in P. trituberculatus by RNAi. The results showed that the distribution of Pt-DIC and Pt-Lamin B in spermiogenesis was abnormal, and the colocalization was weakened. Moreover, we verified the interaction of Pt-DIC and Pt-Lamin B via coimmunoprecipitation. Therefore, our results suggested that both Pt-DIC and Pt-Lamin B were involved in the spermatogenesis of P. trituberculatus, and one of the functions of Dynein-1 is to mediate the transport of Lamin B in the spermiogenesis of P. trituberculatus.

Adenine nucleotide translocase 2 (Ant2) is required for individualization of spermatogenesis of Drosophila melanogaster

Successful completion of spermatogenesis is crucial for the perpetuation of the species. In Drosophila, spermatid individualization, a process involving changes in mitochondrial structure and function is critical to produce functional mature sperm. Ant2, encoding a mitochondrial adenine nucleotide translocase, is highly expressed in male testes and plays a role in energy metabolism in the mitochondria. However, its molecular function remains unclear. Here, we identified an important role of Ant2 in spermatid individualization. In Ant2 knockdown testes, spermatid individualization complexes composed of F-actin cones exhibited a diffuse distribution, and mature sperms were absent in the seminal vesicle, thus leading to male sterility. The most striking effects in Ant2-knockdown spermatids were decrease in tubulin polyglycylation and disruption of proper mitochondria derivatives function. Excessive apoptotic cells were also observed in Ant2-knockdown testes. To further investigate the phenotype of Ant2 knockdown in testes at the molecular level, complementary transcriptome and proteome analyses were performed. At the mRNA level, 868 differentially expressed genes were identified, of which 229 genes were upregulated and 639 were downregulated induced via Ant2 knockdown. iTRAQ-labeling proteome analysis revealed 350 differentially expressed proteins, of which 117 proteins were upregulated and 233 were downregulated. The expression of glutathione transferase (GstD5, GstE5, GstE8, and GstD3), proteins involved in reproduction were significantly regulated at both the mRNA and protein levels. These results indicate that Ant2 is crucial for spermatid maturation by affecting mitochondrial morphogenesis.

Structure and molecular basis of spermatid elongation in the Drosophila testis

Spermatid elongation is a crucial event in the late stage of spermatogenesis in the Drosophila testis, eventually leading to the formation of mature sperm after meiosis. During spermatogenesis, significant structural and morphological changes take place in a cluster of post-meiotic germ cells, which are enclosed in a microenvironment surrounded by somatic cyst cells. Microtubule-based axoneme assembly, formation of individualization complexes and mitochondria maintenance are key processes involved in the differentiation of elongated spermatids. They provide important structural foundations for accessing male fertility. How these structures are constructed and maintained are basic questions in the Drosophila testis. Although the roles of several genes in different structures during the development of elongated spermatids have been elucidated, the relationships between them have not been widely studied. In addition, the genetic basis of spermatid elongation and the regulatory mechanisms involved have not been thoroughly investigated. In the present review, we focus on current knowledge with regard to spermatid axoneme assembly, individualization complex and mitochondria maintenance. We also touch upon promising directions for future research to unravel the underlying mechanisms of spermatid elongation in the Drosophila testis.

Transcriptomes of Testes at Different Developmental Stages in the Opsariichthys bidens Predict Key Genes for Testis Development and Spermatogenesis

Testis development is a complex process involving multiple genes, and the molecular mechanisms underlying testis development in Opsariichthys bidens remain unclear. We performed transcriptome sequencing analysis on a total of 12 samples of testes from stages II, III, IV, and V of O. bidens and obtained a total of 79.52 Gb clean data, as well as 288,573 transcripts and 116,215 unigenes. Differential expression analysis showed that 22,857 differentially expressed genes (DEGs) were screened in six comparison groups (III vs. II, IV vs. II, V vs. II, IV vs. III, V vs. III, and V vs. IV). Kyoto Encyclopedia of Genes and Genomes enrichment analysis of DEGs showed that six comparison groups were significantly enriched for a total of 20 significantly up- or down-regulated pathways, including six pathways related to signal transduction, three pathways related to energy metabolism, five pathways related to disease, and two pathways related to ribosomes. Furthermore, our investigation revealed that DEGs were enriched in several important functional pathways, such as Huntington's disease signaling pathway, TGF-β signaling pathway, and ribosome signaling pathway. Protein-protein interaction network analysis of DEGs identified 63 up-regulated hub genes, including 9 kinesin genes and 2 cytoplasmic dynein genes, and 39 down-regulated hub genes, including 13 ribosomal protein genes. This result contributes to the knowledge of spermatogenesis and testis development in O. bidens.

Mutation in Drosophila concentrative nucleoside transporter 1 alters spermatid maturation and mating behavior

Concentrative nucleoside transporters (Cnts) are unidirectional carriers that mediate the energy-costly influx of nucleosides driven by the transmembrane sodium gradient. Cnts are transmembrane proteins that share a common structural organization and are found in all phyla. Although there have been studies on Cnts from a biochemical perspective, no deep research has examined their role at the organismal level. Here, we investigated the role of the Drosophila melanogaster cnt1 gene, which is specifically expressed in the testes. We used the CRISPR/Cas9 system to generate a mutation in the cnt1 gene. The cnt1 mutants exhibited defects in the duration of copulation and spermatid maturation, which significantly impaired male fertility. The most striking effect of the cnt1 mutation in spermatid maturation was an abnormal structure of the sperm tail, in which the formation of major and minor mitochondrial derivatives was disrupted. Our results demonstrate the importance of cnt1 in male fertility and suggest that the observed defects in mating behavior and spermatogenesis are due to alterations in nucleoside transport and associated metabolic pathways.

Molecular Cloning of Dynein Heavy Chain and the Effect of Dynein Inhibition on the Testicular Function of Portunus trituberculatus

Simple Summary

Portunus trituberculatus is a very important marine economic species. The study of its reproductive biology can provide a theoretical basis for its breeding. Dynein is a member of the motor protein family. It plays an important role in various life activities, such as cell division and intracellular material transport. In order to study the role of dynein in the testis of Portunus trituberculatus, we cloned the heavy chain of dynein and used the dynein inhibitor sodium orthovanadate to make the dynein lose its function. By detecting the localization of dynein, as well as the detection of various apoptosis indexes, antioxidant stress indexes and immune indexes, this study proved that dynein is essential in testis.

Abstract

Dynein is a motor protein with multiple transport functions. However, dynein’s role in crustacean testis is still unknown. We cloned the full-length cDNA of cytoplasmic dynein heavy chain (Pt-dhc) gene and its structure was analyzed. Its expression level was highest in testis. We injected the dynein inhibitor sodium orthovanadate (SOV) into the crab. The distribution of Portunus trituberculatus dynein heavy chain (Pt-DHC) in mature sperm was detected by immunofluorescence. The apoptosis of spermatids was detected using a TUNEL kit; gene expression in testis was detected by fluorescence quantitative PCR (qPCR). The expression of immune-related factors in the testis were detected by an enzyme activity kit. The results showed that the distribution of Pt-DHC was abnormal after SOV injection, indicating that the function of dynein was successfully inhibited. Apoptosis-related genes p53 and caspase-3, and antioxidant stress genes HSP70 and NOS were significantly decreased, and anti-apoptosis gene bcl-2 was significantly increased. The activities of superoxide dismutase (SOD) and alkaline phosphatase (AKP) were significantly decreased. The results showed that there was no apoptosis in testicular cells after dynein function was inhibited, but the cell function was disordered. This study laid a theoretical foundation for the further study of apoptosis in testis and the function of dynein in testis and breeding of P. trituberculatus.

The Drosophila orthologue of the primary ciliary dyskinesia-associated gene, DNAAF3, is required for axonemal dynein assembly

Ciliary motility is powered by a suite of highly conserved axoneme-specific dynein motor complexes. In humans, the impairment of these motors through mutation results in the disease primary ciliary dyskinesia (PCD). Studies in Drosophila have helped to validate several PCD genes whose products are required for cytoplasmic pre-assembly of axonemal dynein motors. Here we report the characterisation of the Drosophila orthologue of the less-known assembly factor DNAAF3. This gene, CG17669 (Dnaaf3), is expressed exclusively in developing mechanosensory chordotonal (Ch) neurons and the cells that generate spermatozoa, The only two Drosophila cell types bearing cilia/flagella containing dynein motors. Mutation of Dnaaf3 results in larvae that are deaf and adults that are uncoordinated, indicating defective Ch neuron function. The mutant Ch neuron cilia of the antenna specifically lack dynein arms, while Ca imaging in larvae reveals a complete loss of Ch neuron response to vibration stimulus, confirming that mechanotransduction relies on ciliary dynein motors. Mutant males are infertile with immotile sperm whose flagella lack dynein arms and show axoneme disruption. Analysis of proteomic changes suggest a reduction in heavy chains of all axonemal dynein forms, consistent with an impairment of dynein pre-assembly.

Expression and functional analysis of cytoplasmic dynein during spermatogenesis in Portunus trituberculatus

The mechanism of acrosome formation in the crab sperm is a hot topic in crustacean reproduction research. Dynein is a motor protein that performs microtubule-dependent retrograde transport and plays an essential role in spermatogenesis. However, whether cytoplasmic dynein participates in acrosome formation in the crab sperm remains poorly understood. In this study, we cloned the cytoplasmic dynein intermediate chain gene (Pt-DIC) from Portunus trituberculatus testis. Pt-DIC is composed of a p150glued-binding domain, a dynein light chain (DLC)-binding domain, and a dynein heavy chain (DHC)-binding domain. The Pt-DIC gene is widely expressed in different tissues, showing the highest expression in the testis, and it is expressed in different stages of spermatid development, indicating important functions in spermatogenesis. We further observed the colocalization of Pt-DIC and Pt-DHC, Pt-DHC and tubulin, and Pt-DHC and GM130, and the results indicated that cytoplasmic dynein may participate in nuclear shaping and acrosome formation via vesicle transport. In addition, we examined the colocalization of Pt-DHC and a mitochondrion (MT) tracker and that of Pt-DHC and prohibitin (PHB). The results indicated that cytoplasmic dynein participated in mitochondrial transport and mitochondrial degradation. Taken together, these results support the hypothesis that cytoplasmic dynein participates in acrosome formation, nuclear shaping, and mitochondrial transport during spermiogenesis in P. trituberculatus. This study will provide valuable guidance for the artificial fertilization and reproduction of P. trituberculatus.

Integrative bioinformatics approaches for identifying potential biomarkers and pathways involved in non-obstructive azoospermia

Background

Non-obstructive azoospermia (NOA) is a disease related to spermatogenic disorders. Currently, the specific etiological mechanism of NOA is unclear. This study aimed to use integrated bioinformatics to screen biomarkers and pathways involved in NOA and reveal their potential molecular mechanisms.

Methods

GSE145467 and GSE108886 gene expression profiles were obtained from the Gene Expression Omnibus (GEO) database. The differentially expressed genes (DEGs) between NOA tissues and matched obstructive azoospermia (OA) tissues were identified using the GEO2R tool. Common DEGs in the two datasets were screened out by the VennDiagram package. For the functional annotation of common DEGs, DAVID v.6.8 was used to perform Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. In accordance with data collected from the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database, a protein–protein interaction (PPI) network was constructed by Cytoscape. Cytohubba in Cytoscape was used to screen the hub genes. Furthermore, the hub genes were validated based on a separate dataset, GSE9210. Finally, potential micro RNAs (miRNAs) of hub genes were predicted by miRWalk 3.0.

Results

A total of 816 common DEGs, including 52 common upregulated and 764 common downregulated genes in two datasets, were screened out. Some of the more important of these pathways, including focal adhesion, PI3K-Akt signaling pathway, cell cycle, oocyte meiosis, AMP-activated protein kinase (AMPK) signaling pathway, FoxO signaling pathway, and Huntington disease, were involved in spermatogenesis. We further identified the top 20 hub genes from the PPI network, including CCNB2, DYNLL2, HMMR, NEK2, KIF15, DLGAP5, NUF2, TTK, PLK4, PTTG1, PBK, CEP55, CDKN3, CDC25C, MCM4, DNAI1, TYMS, PPP2R1B, DNAI2, and DYNLRB2, which were all downregulated genes. In addition, potential miRNAs of hub genes, including hsa-miR-3666, hsa-miR-130b-3p, hsa-miR-15b-5p, hsa-miR-6838-5p, and hsa-miR-195-5p, were screened out.

Conclusions

Taken together, the identification of the above hub genes, miRNAs and pathways will help us better understand the mechanisms associated with NOA, and provide potential biomarkers and therapeutic targets for NOA.

mRNA localization mediates maturation of cytoplasmic cilia in Drosophila spermatogenesis

Cytoplasmic cilia, a specialized type of cilia in which the axoneme resides within the cytoplasm rather than within the ciliary compartment, are proposed to allow for the efficient assembly of very long cilia. Despite being found diversely in male gametes (e.g., Plasmodium falciparum microgametocytes and human and Drosophila melanogaster sperm), very little is known about cytoplasmic cilia assembly. Here, we show that a novel RNP granule containing the mRNAs for axonemal dynein motor proteins becomes highly polarized to the distal end of the cilia during cytoplasmic ciliogenesis in Drosophila sperm. This allows for the incorporation of these axonemal dyneins into the axoneme directly from the cytoplasm, possibly by localizing translation. We found that this RNP granule contains the proteins Reptin and Pontin, loss of which perturbs granule formation and prevents incorporation of the axonemal dyneins, leading to sterility. We propose that cytoplasmic cilia assembly requires the precise localization of mRNAs encoding key axonemal constituents, allowing these proteins to incorporate efficiently into the axoneme.

Wampa is a dynein subunit required for axonemal assembly and male fertility in Drosophila

In cilia and flagella, dyneins form complexes which give rise to the inner and outer axonemal arms. Defects in the dynein arms are the leading cause of primary ciliary dyskinesia (PCD), which is characterized by chronic respiratory infections, situs inversus, and sterility. While the pathological features associated with PCD are increasingly well characterized, many of the causative genetic lesions remain elusive. Using Drosophila, here we analyze genetic requirements for wampa (wam), a previously uncharacterized component of the outer dynein arm. While homozygous mutant animals are viable and display no morphological defects, loss of wam results in complete male sterility. Ultrastructural analysis further reveals that wam mutant spermatids lack the axonemal outer dynein arms, which leads to a complete loss of flagellar motility. In addition to a role in outer dynein arm formation, we also uncover other novel microtubule-associated requirements for wam during spermatogenesis, including the regulation of mitochondrial localization and the shaping of the nuclear head. Due to the conserved nature of dyneins, this study advances our understanding of the pathology of PCD and the functional role of dyneins in axoneme formation and other aspects of spermatogenesis.

Drosophila ELYS regulates Dorsal dynamics during development

Embryonic large molecule derived from yolk sac (ELYS) is a constituent protein of nuclear pores. It initiates assembly of nuclear pore complexes into functional nuclear pores toward the end of mitosis. Using cellular, molecular, and genetic tools, including fluorescence and Electron microscopy, quantitative PCR, and RNAi-mediated depletion, we report here that the ELYS ortholog (dElys) plays critical roles during Drosophila development. dElys localized to the nuclear rim in interphase cells, but during mitosis it was absent from kinetochores and enveloped chromatin. We observed that RNAi-mediated dElys depletion leads to aberrant development and, at the cellular level, to defects in the nuclear pore and nuclear lamina assembly. Further genetic analyses indicated that dElys depletion re-activates the Dorsal (NF-κB) pathway during late larval stages. Re-activated Dorsal caused untimely expression of the Dorsal target genes in the post-embryonic stages. We also demonstrate that activated Dorsal triggers apoptosis during later developmental stages by up-regulating the pro-apoptotic genes reaper and hid The apoptosis induced by Reaper and Hid was probably the underlying cause for developmental abnormalities observed upon dElys depletion. Moreover, we noted that dElys has conserved structural features, but contains a noncanonical AT-hook-like motif through which it strongly binds to DNA. Together, our results uncover a novel epistatic interaction that regulates Dorsal dynamics by dElys during development.

Satellite DNA-containing gigantic introns in a unique gene expression program during Drosophila spermatogenesis

Intron gigantism, where genes contain megabase-sized introns, is observed across species, yet little is known about its purpose or regulation. Here we identify a unique gene expression program utilized for the proper expression of genes with intron gigantism. We find that two Drosophila genes with intron gigantism, kl-3 and kl-5, are transcribed in a spatiotemporal manner over the course of spermatocyte differentiation, which spans ~90 hours. The introns of these genes contain megabases of simple satellite DNA repeats that comprise over 99% of the gene loci, and these satellite-DNA containing introns are transcribed. We identify two RNA-binding proteins that specifically localize to kl-3 and kl-5 transcripts and are needed for the successful transcription or processing of these genes. We propose that genes with intron gigantism require a unique gene expression program, which may serve as a platform to regulate gene expression during cellular differentiation.

Introns are non-coding elements of eukaryotic genes, often containing important regulatory sequences. Curiously, some genes contain introns so large that more than 99% of the gene locus is non-coding. One of the best-studied large genes, Dystrophin, a causative gene for Duchenne Muscular Dystrophy, spans 2.2Mb, only 11kb of which is coding. This phenomenon, ‘intron gigantism’, is observed across species, yet little is known about its purpose or regulation. Here we identify a unique gene expression program utilized for the proper expression of genes with intron gigantism using Drosophila spermatogenic genes as a model system. We show that the gigantic introns of these genes are transcribed in line with the exons, likely as a single transcript. We identify two RNA-binding proteins that specifically localize to the site of transcription and are needed for the successful transcription or processing of these genes. We propose that genes with intron gigantism require a unique gene expression program, which may serve as a platform to regulate gene expression during cellular differentiation.

Survey of the Ciliary Motility Machinery of Drosophila Sperm and Ciliated Mechanosensory Neurons Reveals Unexpected Cell-Type Specific Variations: A Model for Motile Ciliopathies

The motile cilium/flagellum is an ancient eukaryotic organelle. The molecular machinery of ciliary motility comprises a variety of cilium-specific dynein motor complexes along with other complexes that regulate their activity. Assembling the motors requires the function of dedicated “assembly factors” and transport processes. In humans, mutation of any one of at least 40 different genes encoding components of the motility apparatus causes Primary Ciliary Dyskinesia (PCD), a disease of defective ciliary motility. Recently, Drosophila has emerged as a model for motile cilia biology and motile ciliopathies. This is somewhat surprising as most Drosophila cells lack cilia, and motile cilia are confined to just two specialized cell types: the sperm flagellum with a 9+2 axoneme and the ciliated dendrite of auditory/proprioceptive (chordotonal, Ch) neurons with a 9+0 axoneme. To determine the utility of Drosophila as a model for motile cilia, we survey the Drosophila genome for ciliary motility gene homologs, and assess their expression and function. We find that the molecules of cilium motility are well conserved in Drosophila. Most are readily characterized by their restricted cell-type specific expression patterns and phenotypes. There are also striking differences between the two motile ciliated cell types. Notably, sperm and Ch neuron cilia express and require entirely different outer dynein arm variants—the first time this has been clearly established in any organism. These differences might reflect the specialized functions for motility in the two cilium types. Moreover, the Ch neuron cilia lack the critical two-headed inner arm dynein (I1/f) but surprisingly retain key regulatory proteins previously associated with it. This may have implications for other motile 9+0 cilia, including vertebrate embryonic nodal cilia required for left-right axis asymmetry. We discuss the possibility that cell-type specificity in ciliary motility machinery might occur in humans, and therefore underlie some of the phenotypic variation observed in PCD caused by different gene mutations. Our work lays the foundation for the increasing use of Drosophila as an excellent model for new motile ciliary gene discovery and validation, for understanding motile cilium function and assembly, as well as understanding the nature of genetic defects underlying human motile ciliopathies.

Nanobody Detection of Standard Fluorescent Proteins Enables Multi-Target DNA-PAINT with High Resolution and Minimal Displacement Errors

DNA point accumulation for imaging in nanoscale topography (PAINT) is a rapidly developing fluorescence super-resolution technique, which allows for reaching spatial resolutions below 10 nm. It also enables the imaging of multiple targets in the same sample. However, using DNA-PAINT to observe cellular structures at such resolution remains challenging. Antibodies, which are commonly used for this purpose, lead to a displacement between the target protein and the reporting fluorophore of 20⁻25 nm, thus limiting the resolving power. Here, we used nanobodies to minimize this linkage error to ~4 nm. We demonstrate multiplexed imaging by using three nanobodies, each able to bind to a different family of fluorescent proteins. We couple the nanobodies with single DNA strands via a straight forward and stoichiometric chemical conjugation. Additionally, we built a versatile computer-controlled microfluidic setup to enable multiplexed DNA-PAINT in an efficient manner. As a proof of principle, we labeled and imaged proteins on mitochondria, the Golgi apparatus, and chromatin. We obtained super-resolved images of the three targets with 20 nm resolution, and within only 35 minutes acquisition time.

Protein profile of Dabry's sturgeon (Acipenser dabryanus) spermatozoa and relationship to sperm quality

Knowledge of conditions affecting sperm quality is essential for efficient culture of fish for commercial purposes and conservation of species. Two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization time of flight mass spectrometry were used to characterize the proteomic profile of Acipenser dabryanus spermatozoa relative to motility and fertilization capacity. There were differential amounts of protein in 313 spots in spermatozoa of males classified to have relatively greater or lesser spermatozoa quality. The functions of 43 of 50 selected proteins were identified. The proteins in 14 spots were involved in metabolism, and of these, proteins in 11 spots were highly abundant in spermatozoa of males categorized to have spermatozoa of greater quality, including pyruvate kinase, enolase B, phosphoglycerate kinase, lactate dehydrogenase, cytosolic malate dehydrogenase, brain creatine kinase b, Ckmb protein, and nucleoside diphosphate kinase. The proteins involved in mechanics of flagellum movement were identified, including the dynein intermediate chain, radial spoke head 1 homolog; ropporin-1-like, Bardet-Biedl syndrome 5, ADP-ribosylation factor-like protein 3, tektin-4, gamma-actin, and tubulin cytoskeleton proteins to be differentially abundant in spermatozoa that were classified relatively greater or lesser quality. Heat shock proteins, copper/zinc superoxide dismutase and peroxiredoxins, which are involved in stress response were of differential abundance in spermatozoa from males with spermatozoa in the two different classification groups. Proteins were also detected that are involved in protein folding and binding, or hydrolase activity. The results are valuable for the prediction of sperm quality and for reproduction management in A. dabryanus and other threatened species.

Ciliary dynein motor preassembly is regulated by Wdr92 in association with HSP90 co-chaperone, R2TP

Wdr92 is associated with the multifunctional cochaperone, R2TP, but its function is unknown. In this study, the authors show that Drosophila Wdr92 is exclusively required for preassembly of ciliary dynein motor complexes, which are confined to sensory neuron ciliary dendrites and sperm flagella. Wdr92 is proposed to direct R2TP/HSP90 to dynein chain clients to chaperone cytoplasmic preassembly.

The massive dynein motor complexes that drive ciliary and flagellar motility require cytoplasmic preassembly, a process requiring dedicated dynein assembly factors (DNAAFs). How DNAAFs interact with molecular chaperones to control dynein assembly is not clear. By analogy with the well-known multifunctional HSP90-associated cochaperone, R2TP, several DNAAFs have been suggested to perform novel R2TP-like functions. However, the involvement of R2TP itself (canonical R2TP) in dynein assembly remains unclear. Here we show that in Drosophila melanogaster, the R2TP-associated factor, Wdr92, is required exclusively for axonemal dynein assembly, likely in association with canonical R2TP. Proteomic analyses suggest that in addition to being a regulator of R2TP chaperoning activity, Wdr92 works with the DNAAF Spag1 at a distinct stage in dynein preassembly. Wdr92/R2TP function is likely distinct from that of the DNAAFs proposed to form dynein-specific R2TP-like complexes. Our findings thus establish a connection between dynein assembly and a core multifunctional cochaperone.

Evidence of Adaptive Evolution and Relaxed Constraints in Sex-Biased Genes of South American and West Indies Fruit Flies (Diptera: Tephritidae)

Several studies have demonstrated that genes differentially expressed between sexes (sex-biased genes) tend to evolve faster than unbiased genes, particularly in males. The reason for this accelerated evolution is not clear, but several explanations have involved adaptive and nonadaptive mechanisms. Furthermore, the differences of sex-biased expression patterns of closely related species are also little explored out of Drosophila. To address the evolutionary processes involved with sex-biased expression in species with incipient differentiation, we analyzed male and female transcriptomes of Anastrepha fraterculus and Anastrepha obliqua, a pair of species that have diverged recently, likely in the presence of gene flow. Using these data, we inferred differentiation indexes and evolutionary rates and tested for signals of selection in thousands of genes expressed in head and reproductive transcriptomes from both species. Our results indicate that sex-biased and reproductive-biased genes evolve faster than unbiased genes in both species, which is due to both adaptive pressure and relaxed constraints. Furthermore, among male-biased genes evolving under positive selection, we identified some related to sexual functions such as courtship behavior and fertility. These findings suggest that sex-biased genes may have played important roles in the establishment of reproductive isolation between these species, due to a combination of selection and drift, and unveil a plethora of genetic markers useful for more studies in these species and their differentiation.

Genomics of parallel adaptation at two timescales in Drosophila

Two interesting unanswered questions are the extent to which both the broad patterns and genetic details of adaptive divergence are repeatable across species, and the timescales over which parallel adaptation may be observed. Drosophila melanogaster is a key model system for population and evolutionary genomics. Findings from genetics and genomics suggest that recent adaptation to latitudinal environmental variation (on the timescale of hundreds or thousands of years) associated with Out-of-Africa colonization plays an important role in maintaining biological variation in the species. Additionally, studies of interspecific differences between D. melanogaster and its sister species D. simulans have revealed that a substantial proportion of proteins and amino acid residues exhibit adaptive divergence on a roughly few million years long timescale. Here we use population genomic approaches to attack the problem of parallelism between D. melanogaster and a highly diverged conger, D. hydei, on two timescales. D. hydei, a member of the repleta group of Drosophila, is similar to D. melanogaster, in that it too appears to be a recently cosmopolitan species and recent colonizer of high latitude environments. We observed parallelism both for genes exhibiting latitudinal allele frequency differentiation within species and for genes exhibiting recurrent adaptive protein divergence between species. Greater parallelism was observed for long-term adaptive protein evolution and this parallelism includes not only the specific genes/proteins that exhibit adaptive evolution, but extends even to the magnitudes of the selective effects on interspecific protein differences. Thus, despite the roughly 50 million years of time separating D. melanogaster and D. hydei, and despite their considerably divergent biology, they exhibit substantial parallelism, suggesting the existence of a fundamental predictability of adaptive evolution in the genus.

Both local adaptation on short timescales and the long-term accumulation of adaptive differences between species have recently been investigated using comparative genomic and population genomic approaches in several species. However, the repeatability of adaptive evolution at the genetic level is poorly understood. Here we attack this problem by comparing patterns of long and short-term adaptation in Drosophila melanogaster to patterns of adaptation on two timescales in a highly diverged congener, Drosophila hydei. We found, despite the fact that these species diverged from a common ancestor roughly 50 million years ago, the population genomics of latitudinal allele frequency differentiation shows that there is a substantial shared set of genes likely playing a role in the short term adaptive divergence of populations in both species. Analyses of longer-term adaptive protein divergence for the D. hydei-D. mojavensis and D. melanogaster-D. simulans clades reveal a striking level of parallel adaptation. This parallelism includes not only the specific genes/proteins that exhibit adaptive evolution, but extends even to the magnitudes of the selective effects on interspecific protein differences.

Identification of genetic networks that act in the somatic cells of the testis to mediate the developmental program of spermatogenesis

Spermatogenesis is a dynamic developmental process requiring precisely timed transitions between discrete stages. Specifically, the germline undergoes three transitions: from mitotic spermatogonia to spermatocytes, from meiotic spermatocytes to spermatids, and from morphogenetic spermatids to spermatozoa. The somatic cells of the testis provide essential support to the germline throughout spermatogenesis, but their precise role during these developmental transitions has not been comprehensively explored. Here, we describe the identification and characterization of genes that are required in the somatic cells of the Drosophila melanogaster testis for progress through spermatogenesis. Phenotypic analysis of candidate genes pinpointed the stage of germline development disrupted. Bioinformatic analysis revealed that particular gene classes were associated with specific developmental transitions. Requirement for genes associated with endocytosis, cell polarity, and microtubule-based transport corresponded with the development of spermatogonia, spermatocytes, and spermatids, respectively. Overall, we identify mechanisms that act specifically in the somatic cells of the testis to regulate spermatogenesis.

Sexual reproduction in animals requires the production of male and female gametes, spermatozoa and ova, respectively. Gametes are derived from specialized cells known as the germline through a process called gametogenesis. Gametogenesis typically takes place in a gonad and requires the germ cells to be surrounded by specialized somatic cells that support germline development. While many prior studies have identified germline specific genes required for gametogenesis few have systematically identified genes required in the somatic cells for gametogenesis. To this end we performed an RNAi screen where we disrupted the function of genes specifically in the somatic cyst cells of the Drosophila melanogaster testis. Using fertility assays we identified 281 genes that are required in somatic cyst cells for fertility. To better understand the role of these genes in regulating spermatogenesis we classified the resulting phenotypes by the stage of germline development disrupted. This revealed distinct sets of genes required to support specific stages of spermatogenesis. Our study characterizes the somatic specific defects resulting from disruption of candidate genes and provides insight into their function in the testes. Overall, our findings reveal the mechanisms controlling Drosophila melanogaster spermatogenesis and provide a resource for studying soma-germline interactions more broadly.

Decreased Expression of KIFC1 in Human Testes with Globozoospermic Defects

Globozoospermia is a rare (prevalence of <0.1%) but severe male infertility condition. In our previous study, we found that robust KIFC1 immunostaining was detected in the human elongating/elongated spermatids during human acrosomogenesis. However, the relationship between the decreased expression of KIFC1 and human globozoospermia remains largely unknown. Testicular biopsies of 30 globozoospermia and 30 obstructive azoospermia patients who underwent infertility evaluation and treatment were utilized in this study. Reverse transcriptase polymerase chain reaction (RT-PCR), Western blots, immunohistochemistry, an in vivo model, and intratesticular injection of small inhibitory RNA (siRNA) against the Kifc1 gene were employed, and sperm abnormalities were evaluated by hematoxylin and eosin (H&E) staining and immunocytochemistry. We revealed that the testicular level of KIFC1 mRNA in globozoospermia was significantly reduced compared with that in obstructive azoospermia, and the KIFC1 protein was barely detectable in testicular specimens in 30% (9 of 30) of patients with globozoospermia. Furthermore, knockdown of the Kifc1 gene in mice increased the percentage of sperm with globozoospermic defects (26.5%). Decreased KIFC1 expression was mainly observed in the testes of patients with globozoospermia at the spermatid stage, which may be useful for counseling and management of such patients.

Correlation between leucine rich domain and the stability of LRWD1 protein in human NT2/D1 cells

PURPOSE

LRWD1 is a protein that contains LRR and WDs domains and is important in regulating spermatogenesis. However, the roles of LRR or WDs domains in the expression of LRWD1 remain unclear.

MATERIALS AND METHODS

The NT2/D1 cells separately transfected with full length of LRWD1 gene (LRWD(WT)) or genes with deleted sequences in the LRR domain (LRWD1(ΔLRR)), WD1 domain (LRWD1(ΔWD1)), WD2 domain (LRWD1(ΔWD2)), WD3 domain (LRWD1(ΔWD3)) and entire three WD domains (LRWD1(Δ3×WD)) were applied to investigate the expression levels of LRWD1 protein by either Western blot or flow cytometry. The associated proteins in these mutated LRWD1 proteins were identified by mass spectrometry.

RESULTS

Deletion of the LRR domain significantly decreased the expression of LRWD1 protein. With the treatment of MG132, the LRR domain may functions in preventing LRWD1 protein from proteasome-mediated degradation. In the co-immunoprecipitation analysis, protein receptor of tumor necrosis factor 2 (TNFR2) was specifically observed to be associated with LRR-deficient LRWD1 protein.

CONCLUSIONS

The LRR domain is significantly correlated to the stability of LRWD1 protein. Determining if the stability is modulated by TNFR2 is worthy of further study.

Mutations in ZMYND10, a gene essential for proper axonemal assembly of inner and outer dynein arms in humans and flies, cause primary ciliary dyskinesia

Primary ciliary dyskinesia (PCD) is a ciliopathy characterized by airway disease, infertility, and laterality defects, often caused by dual loss of the inner dynein arms (IDAs) and outer dynein arms (ODAs), which power cilia and flagella beating. Using whole-exome and candidate-gene Sanger resequencing in PCD-affected families afflicted with combined IDA and ODA defects, we found that 6/38 (16%) carried biallelic mutations in the conserved zinc-finger gene BLU (ZMYND10). ZMYND10 mutations conferred dynein-arm loss seen at the ultrastructural and immunofluorescence level and complete cilia immotility, except in hypomorphic p.Val16Gly (c.47T>G) homozygote individuals, whose cilia retained a stiff and slowed beat. In mice, Zmynd10 mRNA is restricted to regions containing motile cilia. In a Drosophila model of PCD, Zmynd10 is exclusively expressed in cells with motile cilia: chordotonal sensory neurons and sperm. In these cells, P-element-mediated gene silencing caused IDA and ODA defects, proprioception deficits, and sterility due to immotile sperm. Drosophila Zmynd10 with an equivalent c.47T>G (p.Val16Gly) missense change rescued mutant male sterility less than the wild-type did. Tagged Drosophila ZMYND10 is localized primarily to the cytoplasm, and human ZMYND10 interacts with LRRC6, another cytoplasmically localized protein altered in PCD. Using a fly model of PCD, we conclude that ZMYND10 is a cytoplasmic protein required for IDA and ODA assembly and that its variants cause ciliary dysmotility and PCD with laterality defects.

Whole-organ isolation approach as a basis for tissue-specific analyses in Schistosoma mansoni

Background

Schistosomiasis is one of the most important parasitic diseases worldwide, second only to malaria. Schistosomes exhibit an exceptional reproductive biology since the sexual maturation of the female, which includes the differentiation of the reproductive organs, is controlled by pairing. Pathogenicity originates from eggs, which cause severe inflammation in their hosts. Elucidation of processes contributing to female maturation is not only of interest to basic science but also considering novel concepts combating schistosomiasis.

Methodology/Principal Findings

To get direct access to the reproductive organs, we established a novel protocol using a combined detergent/protease-treatment removing the tegument and the musculature of adult Schistosoma mansoni. All steps were monitored by scanning electron microscopy (SEM) and bright-field microscopy (BF). We focused on the gonads of adult schistosomes and demonstrated that isolated and purified testes and ovaries can be used for morphological and structural studies as well as sources for RNA and protein of sufficient amounts for subsequent analyses such as RT-PCR and immunoblotting. To this end, first exemplary evidence was obtained for tissue-specific transcription within the gonads (axonemal dynein intermediate chain gene SmAxDynIC; aquaporin gene SmAQP) as well as for post-transcriptional regulation (SmAQP).

Conclusions/Significance

The presented method provides a new way of getting access to tissue-specific material of S. mansoni. With regard to many still unanswered questions of schistosome biology, such as elucidating the molecular processes involved in schistosome reproduction, this protocol provides opportunities for, e.g., sub-transcriptomics and sub-proteomics at the organ level. This will promote the characterisation of gene-expression profiles, or more specifically to complete knowledge of signalling pathways contributing to differentiation processes, so discovering involved molecules that may represent potential targets for novel intervention strategies. Furthermore, gonads and other tissues are a basis for cell isolation, opening new perspectives for establishing cell lines, one of the tools desperately needed in the post-genomic era.

As a neglected disease, schistosomiasis is still an enormous problem in the tropics and subtropics. Since the 1980s, Praziquantel (PZQ) has been the drug of choice but can be anticipated to lose efficacy in the future due to emerging resistance. Alternative drugs or efficient vaccines are still lacking, strengthening the need for the discovery of novel strategies and targets for combating schistosomiasis. One avenue is to understand the unique reproductive biology of this trematode in more detail. Sexual maturation of the adult female depends on a constant pairing with the male. This is a crucial prerequisite for the differentiation of the female reproductive organs such as the vitellarium and ovary, and consequently for the production of mature eggs. These are needed for life-cycle maintenance, but they also cause pathogenesis. With respect to adult males, the production of mature sperm is essential for fertilisation and life-cycle progression. In our study we present a convenient and inexpensive method to isolate reproductive tissues from adult schistosomes in high amounts and purity, representing a source for gonad-specific RNA and protein, which will serve for future sub-transcriptome and -proteome studies helping to characterise genes, or to unravel differentiation programs in schistosome gonads. Beyond that, isolated organs may be useful for approaches to establish cell cultures, desperately needed in the post-genomic era.

Functional relevance of the newly evolved sperm dynein intermediate chain multigene family in Drosophila melanogaster males

In many animal species, traits associated with male fitness evolve rapidly. Intersexual conflict and male-male competition have been suggested to drive this rapid evolution. These fast evolutionary dynamics result in elevated rates of amino acid replacement and modification of gene expression attributes. Gene acquisition is another mechanism that might contribute to fitness differences among males. However, empirical evidence of fitness effects associated with newly evolved genes is scarce. The Sdic multigene family originated within the last 5.4 myr in the lineage that leads to D. melanogaster and encodes a sperm dynein intermediate chain presumably involved in sperm motility. The silencing of the Sdic multigene family, followed by the screening of relevant phenotypes, supports the role of the Sdic multigene family in sperm competition. The case of the Sdic multigene family illustrates the flexibility of genetic networks in incorporating lineage-specific gene novelties that can trigger an evolutionary arms race between males.

Drosophila spermiogenesis: Big things come from little packages

Drosophila melanogaster spermatids undergo dramatic morphological changes as they differentiate from small round cells approximately 12 μm in diameter into highly polarized, 1.8 mm long, motile sperm capable of participating in fertilization. During spermiogenesis, syncytial cysts of 64 haploid spermatids undergo synchronous differentiation. Numerous changes occur at a subcellular level, including remodeling of existing organelles (mitochondria, nuclei), formation of new organelles (flagellar axonemes, acrosomes), polarization of elongating cysts and plasma membrane addition. At the end of spermatid morphogenesis, organelles, mitochondrial DNA and cytoplasmic components not needed in mature sperm are stripped away in a caspase-dependent process called individualization that results in formation of individual sperm. Here, we review the stages of Drosophila spermiogenesis and examine our current understanding of the cellular and molecular mechanisms involved in shaping male germ cell-specific organelles and forming mature, fertile sperm.