PKD2 Cation Channel Is Required for Directional Sperm Movement and Male Fertility

The role of polycystic kidney disease-like homologs in planarian nervous system regeneration and function

Planarians are an excellent model for investigating molecular mechanisms necessary for regenerating a functional nervous system. Numerous studies have led to the generation of extensive genomic resources, especially whole-animal single-cell RNA-seq resources. These have facilitated in silico predictions of neuronal subtypes, many of which have been anatomically mapped by in situ hybridization. However, our knowledge of the function of dozens of neuronal subtypes remains poorly understood. Previous investigations identified that polycystic kidney disease (pkd)-like genes in planarians are strongly expressed in sensory neurons and have roles in mechanosensation. Here, we examine the expression and function of all the pkd genes found in the Schmidtea mediterranea genome and map their expression in the asexual and hermaphroditic strains. Using custom behavioral assays, we test the function of pkd genes in response to mechanical stimulation and in food detection. Our work provides insight into the physiological function of sensory neuron populations and protocols for creating inexpensive automated setups for acquiring and analyzing mechanosensory stimulation in planarians.

Cross-Species Insights into Autosomal Dominant Polycystic Kidney Disease: Provide an Alternative View on Research Advancement

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a prevalent hereditary disorder that affects the kidneys, characterized by the development of an excessive number of fluid-filled cysts of varying sizes in both kidneys. Along with the progression of ADPKD, these enlarged cysts displace normal kidney tissue, often accompanied by interstitial fibrosis and inflammation, and significantly impair renal function, leading to end-stage renal disease. Currently, the precise mechanisms underlying ADPKD remain elusive, and a definitive cure has yet to be discovered. This review delineates the epidemiology, pathological features, and clinical diagnostics of ADPKD or ADPKD-like disease across human populations, as well as companion animals and other domesticated species. A light has been shed on pivotal genes and biological pathways essential for preventing and managing ADPKD, which underscores the importance of cross-species research in addressing this complex condition. Treatment options are currently limited to Tolvaptan, dialysis, or surgical excision of large cysts. However, comparative studies of ADPKD across different species hold promise for unveiling novel insights and therapeutic strategies to combat this disease.

A synthetic method to assay polycystin channel biophysics

Ion channels are biological transistors that control ionic flux across cell membranes to regulate electrical transmission and signal transduction. They are found in all biological membranes and their conductive states are frequently disrupted in human diseases. Organelle ion channels are among the most resistant to functional and pharmacological interrogation. Traditional channel protein reconstitution methods rely upon exogenous expression and/or purification from endogenous cellular sources which are frequently contaminated by resident ionophores. Here we describe a fully synthetic method to assay the functional properties of the polycystin subfamily of transient receptor potential (TRP) channels that natively traffic to primary cilia and endoplasmic reticulum organelles. Using this method, we characterize their membrane integration, orientation and conductance while comparing these results to their endogenous channel properties. Outcomes define a novel synthetic approach that can be applied broadly to investigate other channels resistant to biophysical analysis and pharmacological characterization.

Structure of putative epidermal sensory receptors in an acoel flatworm, Praesagittifera naikaiensis

Acoel flatworms possess epidermal sensory-receptor cells on their body surfaces and exhibit behavioral repertoires such as geotaxis and phototaxis. Acoel epidermal sensory receptors should be mechanical and/or chemical receptors; however, the mechanisms of their sensory reception have not been elucidated. We examined the three-dimensional relationship between epidermal sensory receptors and their innervation in an acoel flatworm, Praesagittifera naikaiensis. The distribution of the sensory receptors was different between the ventral and dorsal sides of worms. The nervous system was mainly composed of a peripheral nerve net, an anterior brain, and three pairs of longitudinal nerve cords. The nerve net was located closer to the body surface than the brain and the nerve cords. The sensory receptors have neural connections with the nerve net in the entire body of worms. We identified five homologs of polycystic kidney disease (PKD): PKD1-1, PKD1-2, PKD1-3, PKD1-4, and, PKD2, from the P. naikaiensis genome. All of these PKD genes were implied to be expressed in the epidermal sensory receptors of P. naikaiensis. PKD1-1 and PKD2 were dispersed across the entire body of worms. PKD1-2, PKD1-3, and PKD1-4 were expressed in the anterior region of worms. PKD1-4 was also expressed around the mouth opening. Our results indicated that P. naikaiensis possessed several types of epidermal sensory receptors to convert various environmental stimuli into electrical signals via the PKD channels and transmit the signals to afferent nerve and/or effector cells.

The Drosophila melanogaster Y-linked gene, WDY, is required for sperm to swim in the female reproductive tract

Unique patterns of inheritance and selection on Y chromosomes have led to the evolution of specialized gene functions. We report CRISPR mutants in Drosophila of the Y-linked gene, WDY, which is required for male fertility. We demonstrate that the sperm tails of WDY mutants beat approximately half as fast as those of wild-type and that mutant sperm do not propel themselves within the male ejaculatory duct or female reproductive tract. Therefore, although mature sperm are produced by WDY mutant males, and are transferred to females, those sperm fail to enter the female sperm storage organs. We report genotype-dependent and regional differences in sperm motility that appear to break the correlation between sperm tail beating and propulsion. Furthermore, we identify a significant change in hydrophobicity at a residue at a putative calcium-binding site in WDY orthologs at the split between the melanogaster and obscura species groups, when WDY first became Y-linked. This suggests that a major functional change in WDY coincided with its appearance on the Y chromosome. Finally, we show that mutants for another Y-linked gene, PRY, also show a sperm storage defect that may explain their subfertility. Overall, we provide direct evidence for the long-held presumption that protein-coding genes on the Drosophila Y regulate sperm motility.

Finishing the egg

Gamete development is a fundamental process that is highly conserved from early eukaryotes to mammals. As germ cells develop, they must coordinate a dynamic series of cellular processes that support growth, cell specification, patterning, the loading of maternal factors (RNAs, proteins, and nutrients), differentiation of structures to enable fertilization and ensure embryonic survival, and other processes that make a functional oocyte. To achieve these goals, germ cells integrate a complex milieu of environmental and developmental signals to produce fertilizable eggs. Over the past 50 years, Drosophila oogenesis has risen to the forefront as a system to interrogate the sophisticated mechanisms that drive oocyte development. Studies in Drosophila have defined mechanisms in germ cells that control meiosis, protect genome integrity, facilitate mRNA trafficking, and support the maternal loading of nutrients. Work in this system has provided key insights into the mechanisms that establish egg chamber polarity and patterning as well as the mechanisms that drive ovulation and egg activation. Using the power of Drosophila genetics, the field has begun to define the molecular mechanisms that coordinate environmental stresses and nutrient availability with oocyte development. Importantly, the majority of these reproductive mechanisms are highly conserved throughout evolution, and many play critical roles in the development of somatic tissues as well. In this chapter, we summarize the recent progress in several key areas that impact egg chamber development and ovulation. First, we discuss the mechanisms that drive nutrient storage and trafficking during oocyte maturation and vitellogenesis. Second, we examine the processes that regulate follicle cell patterning and how that patterning impacts the construction of the egg shell and the establishment of embryonic polarity. Finally, we examine regulatory factors that control ovulation, egg activation, and successful fertilization.

Seriously cilia: A tiny organelle illuminates evolution, disease, and intercellular communication

The borders between cell and developmental biology, which have always been permeable, have largely dissolved. One manifestation is the blossoming of cilia biology, with cell and developmental approaches (increasingly complemented by human genetics, structural insights, and computational analysis) fruitfully advancing understanding of this fascinating, multifunctional organelle. The last eukaryotic common ancestor probably possessed a motile cilium, providing evolution with ample opportunity to adapt cilia to many jobs. Over the last decades, we have learned how non-motile, primary cilia play important roles in intercellular communication. Reflecting their diverse motility and signaling functions, compromised cilia cause a diverse range of diseases collectively called "ciliopathies." In this review, we highlight how cilia signal, focusing on how second messengers generated in cilia convey distinct information; how cilia are a potential source of signals to other cells; how evolution may have shaped ciliary function; and how cilia research may address thorny outstanding questions.

CRISPR/Cas9-mediated genome editing of gustatory receptor NlugGr23a causes male sterility in the brown planthopper Nilaparvata lugens

Gustatory receptors (Grs) have an essential role in chemical recognition so as to evaluate food quality. Insect Grs also participate in non-gustatory functions, such as olfaction, temperature sensing, and mating. In this study, we knocked out NlugGr23a, a putative fecundity-related Gr, using the CRISPR/Cas9 system in the brown planthopper Nilaparvata lugens, a serious insect pest of rice. Surprisingly, homozygous NlugGr23a mutant (NlugGr23a^-/-) males were sterile but their sperm were motile and morphologically normal. DAPI staining of mutant sperm inseminated eggs showed that most of NlugGr23a^-/- sperm failed to fertilize eggs, even if they were capable of entering into the egg as a result of their arrested development prior to male pronucleus formation. Immunohistochemistry demonstrated the expression of NlugGr23a in testis. Moreover, prior mating by NlugGr23a^-/- males suppressed female fertility. To our knowledge, it is the first report that a chemoreceptor is implicated in male sterility and provides a potential molecular target for genetic pest control alternatives.

Proteomic analysis reveals the potential positive effects of Mito-TEMPO on ram sperm motility and fertility during cryopreservation

The aim of this study was to investigate the effects of mitochondria-targeted antioxidant Mito-TEMPO on the protein profile of ram sperm during cryopreservation and evaluate the cryoprotective roles of Mito-TEMPO on ram sperm quality and fertilization capacity. Semen collected from 8 Dorper rams was cryopreserved in TCG-egg yolk extender supplemented with various concentrations of Mito-TEMPO (0, 20, 40 and 60 μM). After thawing, sperm characteristics, antioxidant status and the abundance of hexose transporters (GLUT 3 and 8) were analyzed. The cervical artificial insemination (AI) was performed to evaluate the fertilization ability of cryopreserved ram sperm. The alterations of sperm proteomic profile between the control and MT₄₀ groups were determined using iTRAQ-coupled LC-MS. Supplementation with 40 μM of Mito-TEMPO resulted in the highest post-thaw sperm motility and kinematics. Sperm quality, antioxidant capacity and glucose transporter abundance of frozen-thawed ram sperm were elevated in the MT₄₀ group. The inclusion of 40 μM Mito-TEMPO in freezing extender also resulted in the higher pregnancy rate of ewes. A total of 457 proteins including 179 upregulated proteins and 278 downregulated proteins were defied as differentially expressed proteins (DEPs) using fold change (FC) > 1.2 with P < 0.05. Sixty-one DEPs with (FC > 1.5) were dramatically regulated by Mito-TEMPO. These DEPs are mainly involved in sperm motility, energy metabolism and capacitation. Our data suggest that the beneficial effects of Mito-TEMPO on sperm motility and fertility potential of cryopreserved ram semen are achieved by regulating sperm antioxidant capacity and sperm proteins related to energy metabolism and fertility.

The Drosophila melanogaster Y-linked gene, WDY, is required for sperm to swim in the female reproductive tract

Unique patterns of inheritance and selection on Y chromosomes lead to the evolution of specialized gene functions. Yet characterizing the function of genes on Y chromosomes is notoriously difficult. We report CRISPR mutants in Drosophila of the Y-linked gene, WDY, which is required for male fertility. WDY mutants produce mature sperm with beating tails that can be transferred to females but fail to enter the female sperm storage organs. We demonstrate that the sperm tails of WDY mutants beat approximately half as fast as wild-type sperm's and that the mutant sperm do not propel themselves within the male ejaculatory duct or female reproductive tract (RT). These specific motility defects likely cause the sperm storage defect and sterility of the mutants. Regional and genotype-dependent differences in sperm motility suggest that sperm tail beating and propulsion do not always correlate. Furthermore, we find significant differences in the hydrophobicity of key residues of a putative calcium-binding domain between orthologs of WDY that are Y-linked and those that are autosomal. Given that WDY appears to be evolving under positive selection, our results suggest that WDY's functional evolution coincides with its transition from autosomal to Y-linked in Drosophila melanogaster and its most closely related species. Finally, we show that mutants for another Y-linked gene, PRY, also show a sperm storage defect that may explain their subfertility. In contrast to WDY, PRY mutants do swim in the female RT, suggesting they are defective in yet another mode of motility, navigation, or a necessary interaction with the female RT. Overall, we provide direct evidence for the long-held presumption that protein-coding genes on the Drosophila Y regulate sperm motility.

Sperm morphological abnormalities in autosomal dominant polycystic kidney disease are associated with the Hippo signaling pathway via PC1

Background

Autosomal dominant polycystic kidney disease (ADPKD) is a hereditary kidney disorder mostly caused by mutations in PKD1 or PKD2 genes. Here, we report thirteen ADPKD males with infertility and investigated the sperm morphological defects associated with PC1 disruption.

Methods

Targeted next-generation sequencing was performed to detect PKD1 variants in patients. Sperm morphology was observed by immunostaining and transmission electron microscopy, and the sperm motility was assessed using the computer-assisted sperm analysis system. The Hippo signaling pathway was analyzed with by quantitative reverse transcription polymerase chain reaction (qPCR) and western blotting in vitro.

Results

The ADPKD patients were infertile and their sperm tails showed morphological abnormalities, including coiled flagella, absent central microtubules, and irregular peripheral doublets. In addition, the length of sperm flagella was shorter in patients than in controls of in in. In vitro, ciliogenesis was impaired in Pkd1-depleted mouse kidney tubule cells. The absence of PC1 resulted in a reduction of MST1 and LATS1, leading to nuclear accumulation of YAP/TAZ and consequently increased transcription of Aurka. which might promote HDAC6-mediated ciliary disassembly.

Conclusion

Our results suggest the dysregulated Hippo signaling significantly contributes to ciliary abnormalities in and may be associated with flagellar defects in spermatozoa from ADPKD patients.

miRNA Profiling of Major Testicular Germ Cells Identifies Stage-Specific Regulators of Spermatogenesis

Spermatogenesis is tightly controlled at transcriptional, post-transcriptional, and epigenetic levels by various regulators, including miRNAs. This study deals with the identification of miRNAs critical to the three important stages of germ cell development (spermatocytes, round spermatids, and mature sperm) during spermatogenesis. We used high-throughput transcriptome sequencing to identify the differentially expressed miRNAs in the pachytene spermatocytes, round spermatids, and mature sperm of rat. We identified 1843 miRNAs that were differentially expressed across the three stages of germ cell development. These miRNAs were further categorized into three classes according to their pattern of expression during spermatogenesis: class 1 - miRNAs found exclusively in one stage and absent in the other two stages; class 2 - miRNAs found in any two stages but absent in the third stage; class 3 - miRNAs expressed in all the three stages. Six hundred forty-six miRNAs were found to be specific to one developmental stage, 443 miRNAs were found to be common across any two stages, and 754 miRNAs were common to all the three stages. Target prediction for ten most abundant miRNAs specific to each category identified miRNA regulators of mitosis, meiosis, and cell differentiation. The expression of each miRNA is specific to a particular developmental stage, which is required to maintain a significant repertoire of target mRNAs in the respective stage. Thus, this study provided valuable data that can be used in the future to identify the miRNAs involved in spermatogenic arrest at a particular stage of the germ cell development.

Mining Lygus hesperus (western tarnished plant bug) transcriptomic data for transient receptor potential channels: Expression profiling and functional characterization of a Painless homolog

The transient receptor potential (TRP) family of cation channels are evolutionarily conserved proteins with critical roles in sensory physiology. Despite extensive studies in model species, knowledge of TRP channel functional diversity and physiological impact remains limited in many non-model insect species. To assess the TRP channel repertoire in a non-model agriculture pest species (Lygus hesperus), publicly available transcriptomic datasets were mined for potential homologs. Among the transcripts identified, 30 are predicted to encompass complete open reading frames that encode proteins representing each of the seven TRP channel subfamilies. Although no homologs were identified for the Pyrexia and Brivido channels, the TRP complement in L. hesperus exceeded the 13-16 channels reported in most insects. This diversity appears to be driven by a combination of alternative splicing, which impacted members of six subfamilies, and gene expansion of the TRPP subfamily. To validate the in silico data and provide more detailed analyses of L. hesperus TRP functionality, the putative Painless homolog was selected for more in depth analysis and its functional role in thermosensation examined in vitro. RT-PCR expression profiling revealed near ubiquitous expression of the Painless transcript throughout nymphal and adult development. Electrophysiological data generated using a Xenopus oocyte recombinant expression system indicated activation parameters for L. hesperus Painless homolog that are consistent with a role in noxious heat (40°-45 °C) thermosensation.

Membrane stretching activates calcium permeability of a putative channel Pkd2 during fission yeast cytokinesis

Pkd2 is the fission yeast homologue of polycystins. This putative ion channel localizes to the plasma membrane. It is required for the expansion of cell volume during interphase growth and cytokinesis, the last step of cell division. However, the channel activity of Pkd2 remains untested. Here, we examined the calcium permeability and mechanosensitivity of Pkd2 through in vitro reconstitution and calcium imaging of pkd2 mutant cells. Pkd2 was translated and inserted into the lipid bilayers of giant unilamellar vesicles using a cell-free expression system. The reconstituted Pkd2 permeated calcium when the membrane was stretched via hypoosmotic shock. In vivo, inactivation of Pkd2 through a temperature-sensitive mutation pkd2-B42 reduced the average intracellular calcium level by 34%. Compared with the wild type, the hypomorphic mutation pkd2-81KD reduced the amplitude of hypoosmotic shock-triggered calcium spikes by 59%. During cytokinesis, mutations of pkd2 reduced the calcium spikes, accompanying cell separation and the ensuing membrane stretching, by 60%. We concluded that fission yeast polycystin Pkd2 allows calcium influx when activated by membrane stretching, representing a likely mechanosensitive channel that contributes to the cytokinetic calcium spikes.

Polycystin-2 (TRPP2): Ion channel properties and regulation

Polycystin-2 (TRPP2, PKD2, PC2) is the product of the PKD2 gene, whose mutations cause Autosomal Dominant Polycystic Kidney Disease (ADPKD). PC2 belongs to the superfamily of TRP (Transient Receptor Potential) proteins that generally function as Ca²⁺-permeable nonselective cation channels implicated in Ca²⁺ signaling. PC2 localizes to various cell domains with distinct functions that likely depend on interactions with specific channel partners. Functions include receptor-operated, nonselective cation channel activity in the plasma membrane, intracellular Ca²⁺ release channel activity in the endoplasmic reticulum (ER), and mechanosensitive channel activity in the primary cilium of renal epithelial cells. Here we summarize our current understanding of the properties of PC2 and how other transmembrane and cytosolic proteins modulate this activity, providing functional diversity and selective regulatory mechanisms to its role in the control of cellular Ca²⁺ homeostasis.

Characteristics of miRNAs Present in Bovine Sperm and Associations With Differences in Fertility

Small non-coding RNAs have been linked to different phenotypes in bovine sperm, however attempts to identify sperm-borne molecular biomarkers of male fertility have thus far failed to identify a robust profile of expressed miRNAs related to fertility. We hypothesized that some differences in bull fertility may be reflected in the levels of different miRNAs in sperm. To explore such differences in fertility that are not due to differences in visible metrics of sperm quality, we employed Next Generation Sequencing to compare the miRNA populations in Bos taurus sperm from bulls with comparable motility and morphology but varying Sire Conception Rates. We identified the most abundant miRNAs in both populations (miRs -34b-3p; -100-5p; -191-5p; -30d-4p; -21-5p) and evaluated differences in the overall levels and specific patterns of isomiR expression. We also explored correlations between specific pairs of miRNAs in each population and identified 10 distinct pairs of miRNAs that were positively correlated in bulls with higher fertility and negatively correlated in comparatively less fertile individuals. Furthermore, 8 additional miRNA pairs demonstrated the opposite trend; negatively correlated in high fertility animals and positively correlated in less fertile bulls. Finally, we performed pathway analysis to identify potential roles of miRNAs present in bull sperm in the regulation of specific genes that impact spermatogenesis and embryo development. Together, these results present a comprehensive picture of the bovine sperm miRNAome that suggests multiple potential roles in fertility.

Sperm Ion Transporters and Channels in Human Asthenozoospermia: Genetic Etiology, Lessons from Animal Models, and Clinical Perspectives

In mammals, sperm fertilization potential relies on efficient progression within the female genital tract to reach and fertilize the oocyte. This fundamental property is supported by the flagellum, an evolutionarily conserved organelle that provides the mechanical force for sperm propulsion and motility. Importantly several functional maturation events that occur during the journey of the sperm cells through the genital tracts are necessary for the activation of flagellar beating and the acquisition of fertilization potential. Ion transporters and channels located at the surface of the sperm cells have been demonstrated to be involved in these processes, in particular, through the activation of downstream signaling pathways and the promotion of novel biochemical and electrophysiological properties in the sperm cells. We performed a systematic literature review to describe the currently known genetic alterations in humans that affect sperm ion transporters and channels and result in asthenozoospermia, a pathophysiological condition defined by reduced or absent sperm motility and observed in nearly 80% of infertile men. We also present the physiological relevance and functional mechanisms of additional ion channels identified in the mouse. Finally, considering the state-of-the art, we discuss future perspectives in terms of therapeutics of asthenozoospermia and male contraception.

Transient receptor potential polycystin-2 (TRPP2) regulates motility and intracellular calcium of porcine sperm

Polycystin-2, also known as transient receptor potential polycystin-2 (TRPP2), is a membrane protein that regulates calcium homeostasis in renal epithelial cells. Mutations in PKD2, the gene encoding human TRPP2, cause enlarged cystic kidneys and contribute to polycystic kidney disease (PKD). Male Drosophila melanogaster with mutations in amo, the homolog of PKD2, display a mild decrease in sperm motility but have a drastic reduction in fertility due to failed sperm migration and storage within the female tract. Although TRPP2 has critical roles for Drosophila sperm function, the protein has not been described in mammalian sperm. Herein, we report the localization of TRPP2 in porcine sperm and identify functions of TRPP2 in regulating intracellular Ca²⁺ and motility. Porcine sperm treated with an antibody to TRPP2 in capacitating medium had reduced average path velocity and curvilinear velocity (p < .05). Blocking TRPP2 also increased sperm tail beat-cross frequency (p < .05). After 90 min of capacitation, sperm incubated with TRPP2 antibody had decreased intracellular Ca²⁺ concentration compared to controls (p < .05), consistent with TRPP2 function as a plasma membrane cation channel. This is the first report that mammalian sperm contain TRPP2, which appears to regulate intracellular Ca²⁺ and motility patterns in porcine sperm.

Molecular characterizations and expression profiles of transient receptor potential channels in the brown planthopper, Nilaparvata lugens

Transient receptor potential (TRP) is a superfamily of important cation channels located on the cell membrane. It can regulate almost all sensory modality and control a series of behaviors, including hearing, locomotion, gentle touch, temperature sensation, dry air and food texture detection. The expression profiles of TRP channels have been well documented in the model insect Drosophila melanogaster. However, little is known about the TRP channels of agricultural pests. In this study, we cloned 9 TRP ion channel genes from brown planthopper. Their amino acid sequences are highly conserved with homologues of other insects and have typical TRP channel characteristics: six transmembrane domains (TM1 - TM6) and a pore region between TM5 and TM6. These TRP channels of N. lugens were expressed in all developmental stages and various body parts. The expression levels of almost all TRP channels were relatively higher in adults than nymph stages, and lowest in the eggs. Antenna and abdomen were the main body parts with high expression of these genes. Furthermore, the mRNA levels of these TRP genes were significantly decreased in the third-instar nymphs injected with double-stranded RNA (dsRNA). The survival rate of different TRP dsRNA injected nymphs all exceeded 81%, which was no significant difference compared with the control group. These results suggested that these 9 TRP channels are expressed throughout the body and all ages of the brown planthopper, and are involved in regulating multiple physiological and behavioral processes. The identification of TRP channel genes in this study not only provides a foundation for further exploring the potential roles of TRP channels, but also serves as targets to develop new insecticides for the control of agricultural pests.

Genes Regulating Spermatogenesis and Sperm Function Associated With Rare Disorders

Spermatogenesis is a cell differentiation process that ensures the production of fertilizing sperm, which ultimately fuse with an egg to form a zygote. Normal spermatogenesis relies on Sertoli cells, which preserve cell junctions while providing nutrients for mitosis and meiosis of male germ cells. Several genes regulate normal spermatogenesis, some of which are not exclusively expressed in the testis and control multiple physiological processes in an organism. Loss-of-function mutations in some of these genes result in spermatogenesis and sperm functionality defects, potentially leading to the insurgence of rare genetic disorders. To identify genetic intersections between spermatogenesis and rare diseases, we screened public archives of human genetic conditions available on the Genetic and Rare Diseases Information Center (GARD), the Online Mendelian Inheritance in Man (OMIM), and the Clinical Variant (ClinVar), and after an extensive literature search, we identified 22 distinct genes associated with 21 rare genetic conditions and defective spermatogenesis or sperm function. These protein-coding genes regulate Sertoli cell development and function during spermatogenesis, checkpoint signaling pathways at meiosis, cellular organization and shape definition during spermiogenesis, sperm motility, and capacitation at fertilization. A number of these genes regulate folliculogenesis and oogenesis as well. For each gene, we review the genotype–phenotype association together with associative or causative polymorphisms in humans, and provide a description of the shared molecular mechanisms that regulate gametogenesis and fertilization obtained in transgenic animal models.

Expression of Mst89B and CG31287 is Needed for Effective Sperm Storage and Egg Fertilization in Drosophila

In Drosophila, male reproductive fitness can be affected by any number of processes, ranging from development of gametes, transfer to and storage of mature sperm within the female sperm storage organs, and utilization of sperm for fertilization. We have previously identified the 89B cytogenetic map position of D. melanogaster as a hub for genes that effect male paternity success when disturbed. Here, we used RNA interference to test 11 genes that are highly expressed in the testes and located within the 89B region for their role in sperm competition and male fecundity when their expression is perturbed. Testes-specific knockdown (KD) of bor and CSN5 resulted in complete sterility, whereas KD of CG31287, Manf and Mst89B, showed a breakdown in sperm competitive success when second to mate (P2 < 0.5) and reduced fecundity in single matings. The low fecundity of Manf KD is explained by a significant reduction in the amount of mature sperm produced. KD of Mst89B and CG31287 does not affect sperm production, sperm transfer into the female bursa or storage within 30 min after mating. Instead, a significant reduction of sperm in female storage is observed 24 h after mating. Egg hatchability 24 h after mating is also drastically reduced for females mated to Mst89B or CG31287 KD males, and this reduction parallels the decrease in fecundity. We show that normal germ-line expression of Mst89B and CG31287 is needed for effective sperm usage and egg fertilization.

Schistosome TRP channels: An appraisal

Ion channels underlie electrical excitability in cells and are essential for a variety of functions, most notably neuromuscular and sensory activity. They are also validated targets for a preponderance of approved anthelmintic compounds. Transient receptor potential (TRP) channels constitute an ion channel superfamily whose members play important roles in sensory signaling, regulation of ion homeostasis, organellar trafficking, and other key cellular and organismal activities. Unlike most other ion channels, TRP channels are often polymodal, gated by a variety of mechanisms. Furthermore, TRP channels fall into several classes or subtypes based on sequence and structure. Until recently, there had been very little investigation of the properties and functions of TRP channels from parasitic helminths, including schistosomes, but that situation has changed in the past few years. Indeed, it is now clear that at least some schistosome TRP channels exhibit unusual pharmacological properties, and, intriguingly, both a mammalian and a schistosome TRP channel are activated by praziquantel, the current antischistosomal drug of choice. With the latest release of the Schistosoma mansoni genome database, several changes in predicted TRP channel sequences appeared, some of which were significant. This review updates and reassesses the TRP channel repertoire in S. mansoni, examines recent findings regarding these potential therapeutic targets, and provides guideposts for some of the physiological functions that may be mediated by these channels in schistosomes.

Pymetrozine inhibits reproductive behavior of brown planthopper Nilaparvata lugens and fruit fly Drosophila melanogaster

Pymetrozine is a promising chemical used to control brown planthopper, which developed resistance to imidacloprid and buprofezin in the past decade. Field efficacy indicates that pymetrozine can reduce the number of offsprings of brown planthopper, but the specific physiological mechanism is unknown. In this study, we systematically described the mating process of brown planthopper including 8 steps (abdominal vibration, following, positioning, wing extension, attempted copulation, copulation, terminated copulation and leaving) and explored the optimal mating time after adult eclosion (3-5 days) and observation time (30 mins). Also, behavioral data showed that pymetrozine can affect the mating behavior and female fecundity of brown planthopper and fruit fly. As one of the target genes for pymetrozine, Nanchung (Nan), the nan^36a mutant male courtship index, female receptivity and the number of offsprings were significantly decreased. Behavioral defects in nan^36a mutant flies can be rescued by expressed NlNan. Our results indicated that Nan plays essential roles in the mating behavior and female fecundity. These findings provide useful information for demonstrating that pymetrozine effectively reduce the reproduction of brown planthopper and contribute to our understanding of reproductive strategies controlled by pymetrozine in insects.

Post-ejaculatory modifications to sperm (PEMS)

Mammalian sperm must spend a minimum period of time within a female reproductive tract to achieve the capacity to fertilize oocytes. This phenomenon, termed sperm 'capacitation', was discovered nearly seven decades ago and opened a window into the complexities of sperm-female interaction. Capacitation is most commonly used to refer to a specific combination of processes that are believed to be widespread in mammals and includes modifications to the sperm plasma membrane, elevation of intracellular cyclic AMP levels, induction of protein tyrosine phosphorylation, increased intracellular Ca2+ levels, hyperactivation of motility, and, eventually, the acrosome reaction. Capacitation is only one example of post-ejaculatory modifications to sperm (PEMS) that are widespread throughout the animal kingdom. Although PEMS are less well studied in non-mammalian taxa, they likely represent the rule rather than the exception in species with internal fertilization. These PEMS are diverse in form and collectively represent the outcome of selection fashioning complex maturational trajectories of sperm that include multiple, sequential phenotypes that are specialized for stage-specific functionality within the female. In many cases, PEMS are critical for sperm to migrate successfully through the female reproductive tract, survive a protracted period of storage, reach the site of fertilization and/or achieve the capacity to fertilize eggs. We predict that PEMS will exhibit widespread phenotypic plasticity mediated by sperm-female interactions. The successful execution of PEMS thus has important implications for variation in fitness and the operation of post-copulatory sexual selection. Furthermore, it may provide a widespread mechanism of reproductive isolation and the maintenance of species boundaries. Despite their possible ubiquity and importance, the investigation of PEMS has been largely descriptive, lacking any phylogenetic consideration with regard to divergence, and there have been no theoretical or empirical investigations of their evolutionary significance. Here, we (i) clarify PEMS-related nomenclature; (ii) address the evolutionary origin, maintenance and divergence in PEMS in the context of the protracted life history of sperm and the complex, selective environment of the female reproductive tract; (iii) describe taxonomically widespread types of PEMS: sperm activation, chemotaxis and the dissociation of sperm conjugates; (iv) review the occurence of PEMS throughout the animal kingdom; (v) consider alternative hypotheses for the adaptive value of PEMS; (vi) speculate on the evolutionary implications of PEMS for genomic architecture, sexual selection, and reproductive isolation; and (vii) suggest fruitful directions for future functional and evolutionary analyses of PEMS.

Identification, Characterization and Expression Analysis of TRP Channel Genes in the Vegetable Pest, Pieris rapae

Transient receptor potential (TRP) channels are critical for insects to detect environmental stimuli and regulate homeostasis. Moreover, this superfamily has become potential molecular targets for insecticides or repellents. Pieris rapae is one of the most common and widely spread pests of Brassicaceae plants. Therefore, it is necessary to study TRP channels (TRPs) in P. rapae. In this study, we identified 14 TRPs in P. rapae, including two Water witch (Wtrw) genes. By contrast, only one Wtrw gene exists in Drosophila and functions in hygrosensation. We also found splice isoforms of Pyrexia (Pyx), TRPgamma (TRPγ) and TRP-Melastatin (TRPM). These three genes are related to temperature and gravity sensation, fine motor control, homeostasis regulation of Mg²⁺ and Zn²⁺ in Drosophila, respectively. Evolutionary analysis showed that the TRPs of P. rapae were well clustered into their own subfamilies. Real-time quantitative PCR (qPCR) showed that PrTRPs were widely distributed in the external sensory organs, including antennae, mouthparts, legs, wings and in the internal physiological organs, including brains, fat bodies, guts, Malpighian tubules, ovaries, as well as testis. Our study established a solid foundation for functional studies of TRP channels in P. rapae, and would be benefit to developing new approaches to control P. rapae targeting these important ion channels.

Identification of piRNAs in the testes of Sunite and Small-tailed Han sheep

P-element-induced wimpy testis-interacting RNAs (piRNAs) are small RNAs that are essential for mammalian spermatogenesis and testicular development. Comparative analyses of the molecular mechanisms of spermatogenesis among different organisms are therefore dependent on accurate piRNA characterizations. In this study, we identified piRNAs in the testes of two breeds of Mongolian sheep: the Sunite (SN), which has a low reproductive rate, and Small-tailed Han (STH), which has a high reproductive rate. A thorough understanding of the mechanisms underlying the differences in fecundity between the two breeds might provide insights for the improvement of fertility and reproductive success in these and other sheep breeds. We identified 835 piRNAs and 206 piRNA clusters across the two breeds. Of these, 29 putative piRNAs were expressed in the SN samples only, and 229 putative piRNAs were expressed in the STH samples only. In addition, 206 piRNA clusters were upregulated in STH sheep as compared to the SN sheep. Functional pathway analysis indicated that the genes neighboring the predicted piRNAs were likely associated with spermatogenesis. piRNAs might thus be linked to male fecundity in sheep. Our results increase knowledge of the association between piRNAs and male fertility.

Primary cilia: biosensors of the male reproductive tract

BACKGROUND

The primary cilium is a microtubule-based organelle that extends transiently from the apical cell surface to act as a sensory antenna. Initially viewed as a cellular appendage of obscure significance, the primary cilium is now acknowledged as a key coordinator of signaling pathways during development and in tissue homeostasis.

OBJECTIVES

The aim of this review was to present the structure and function of this overlooked organelle,with an emphasis on its epididymal context and contribution to male infertility issues.

MATERIALS AND METHODS

A systematic review has been performed in order to include main references relevant to the aforementioned topic.

RESULTS

Increasing evidence demonstrates that primary cilia dysfunctions are associated with impaired male reproductive system development and male infertility issues.

DISCUSSION

While a large amount of data exists regarding the role of primary cilia in most organs and tissues, few studies investigated the contribution of these organelles to male reproductive tract development and homeostasis.

CONCLUSION

Functional studies of primary cilia constitute an emergent and exciting new area in reproductive biology research.

Fission yeast TRP channel Pkd2p localizes to the cleavage furrow and regulates cell separation during cytokinesis

Force plays a central role in separating daughter cells during cytokinesis, the last stage of cell division. However, the mechanism of force sensing during cytokinesis remains unknown. Here we discovered that Pkd2p, a putative force-sensing transient receptor potential channel, localizes to the cleavage furrow during cytokinesis of the fission yeast, Schizosaccharomyces pombe. Pkd2p, whose human homologues are associated with autosomal polycystic kidney disease, is an essential protein whose localization depends on the contractile ring and the secretory pathway. We identified and characterized a novel pkd2 mutant pkd2-81KD. The pkd2 mutant cells show signs of osmotic stress, including temporary shrinking, paused turnover of the cytoskeletal structures, and hyperactivated mitogen-activated protein kinase signaling. During cytokinesis, although the contractile ring constricts more rapidly in the pkd2 mutant than the wild-type cells (50% higher), the cell separation in the mutant is slower and often incomplete. These cytokinesis defects are also consistent with misregulated turgor pressure. Finally, the pkd2 mutant exhibits strong genetic interactions with two mutants of the septation initiation network pathway, a signaling cascade essential for cytokinesis. We propose that Pkd2p modulates osmotic homeostasis and is potentially a novel regulator of cytokinesis.

Exploration of miRNA and mRNA Profiles in Fresh and Frozen-Thawed Boar Sperm by Transcriptome and Small RNA Sequencing

Due to lower farrowing rate and reduced litter size with frozen-thawed semen, over 90% of artificial insemination (AI) is conducted using liquid stored boar semen. Although substantial progress has been made towards optimizing the cryopreservation protocols for boar sperm, the influencing factors and underlying mechanisms related to cryoinjury and freeze tolerance of boar sperm remain largely unknown. In this study, we report the differential expression of mRNAs and miRNAs between fresh and frozen-thawed boar sperm using high-throughput RNA sequencing. Our results showed that 567 mRNAs and 135 miRNAs were differentially expressed (DE) in fresh and frozen-thawed boar sperm. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed that the majority of DE mRNAs were enriched in environmental information processing such as cytokine-cytokine receptor interactions, PI3K-Akt signaling, cell adhesion, MAPK, and calcium signaling pathways. Moreover, the targets of DE miRNAs were enriched in significant GO terms such as cell process, protein binding, and response to stimuli. In conclusion, we speculate that DE mRNAs and miRNAs are heavily involved in boar sperm response to environment stimuli, apoptosis, and metabolic activities. The differences in expression also reflect the various structural and functional changes in sperm during cryopreservation.

Drosophila Pif1A is essential for spermatogenesis and is the homolog of human CCDC157, a gene associated with idiopathic NOA

The dynamic process of spermatogenesis shows little variation between invertebrate models such as Drosophila, and vertebrate models such as mice and rats. In each case, germ stem cells undergo mitotic division to proliferate and then continue, via meiosis, through various stages of elongation and individualization from spermatogonia to spermatid to finally to form mature sperm. Mature sperm are then stored in the seminal vesicles for fertilization. Errors in any of these stages can lead to male infertility. Here, we identify that Drosophila Pif1A acts as a key regulator for sperm individualization. Loss of Pif1A leads to male sterility associated with irregular individualization complex and empty seminal vesicles without mature sperm. Pif1A is highly expressed in the testes of mated male adult flies and the Pif1A protein is expressed at a higher level in male than in female flies. Pif1A is homologous to mammalian coiled-coil domain-containing protein 157 (CCDC157), which is also enriched in the testes of humans and mice. Human CCDC157, with unknown function, was identified to be downregulated in men with idiopathic non-obstructive azoospermia (NOA). We map the function of Drosophila Pif1A during spermatogenesis, showing that Pif1A is essential for spermatide individualization and involved in the regulation of the lipid metabolism genes. Our findings might be applicable for studying the function of CCDC157 in spermatogenesis and other aspects of human male fertility.

Identification, characterization and expression analysis of transient receptor potential channel genes in the oriental fruit fly, Bactrocera dorsalis

BACKGROUND

Members of the transient receptor potential (TRP) superfamily are proteins that are critical for insects to detect changes in environmental stimuli and also play key roles in their sensory physiology. Moreover, this family provides potential targets for the design of insecticides. In contrast to a large number of studies conducted on Drosophila melanogaster, molecular studies to characterize TRP channels in agricultural pests are lacking.

RESULTS

In this study, we identified 15 TRP channel genes in the genome of a notorious agricultural pest, the oriental fruit fly (Bactrocera dorsalis). Comparative analysis of the TRP channels (TRPs) in B. dorsalis with those in D. melanogaster, Glossina morsitans, Musca domestica and the closely related Ceratitis capitata, and TRPs from mosquitoes, Hymenoptera, Lepidoptera, Coleoptera and Hemiptera reveals that members of TRPA and TRPP subfamily are most diverse among insects. The results also suggest that Tephritidae family have two TRP-Polycystin 2 members even though most insects either possess just one or none. The highest expression levels of these two genes are in the testes of B. dorsalis, implying a role in regulating sperm function. We analyzed the expression profiles of the TRP channels identified in this study at different life stages using quantitative real time PCR. The results of this study demonstrate that all TRP channels are mainly expressed in adults, especially at mature stages. The one exception to this trend is BdTRPM, which is more highly expressed in the eggs of B. dorsalis, implying an important role in early development. We also detected the spatial expression of TRP channels in mature adult fruit flies by investigating expression levels within various tissues including those involved in sensory function, such as antennae, compound eyes, mouthparts, legs, and wings, as well as tissues critical for homeostasis and physiology (i.e., Malpighian tubules, the brain and gut as well as fat bodies, ovaries, and testes).

CONCLUSION

The results of this study establish a solid foundation for future functional characterization of B. dorsalis TRP channels as well as those of other insects and will help future insecticide design targeting these channels.

A mosquito sperm's journey from male ejaculate to egg: Mechanisms, molecules, and methods for exploration

The fate of mosquito sperm in the female reproductive tract has been addressed sporadically and incompletely, resulting in significant gaps in our understanding of sperm-female interactions that ultimately lead to fertilization. As with other Diptera, mosquito sperm have a complex journey to their ultimate destination, the egg. After copulation, sperm spend a short time at the site of insemination where they are hyperactivated and quickly congregate near the entrance of the spermathecal ducts. Within minutes, they travel up the narrow ducts to the spermathecae, likely through the combined efforts of female transport and sperm locomotion. The female nourishes sperm and maintains them in these permanent storage organs for her entire life. When she is ready, the female coordinates the release of sperm with ovulation, and the descending egg is fertilized. Although this process has been well studied via microscopy, many questions remain regarding the molecular processes that coordinate sperm motility, movement through the reproductive tract, maintenance, and usage. In this review, we describe the current understanding of a mosquito sperm's journey to the egg, highlighting gaps in our knowledge of mosquito reproductive biology. Where insufficient information is available in mosquitoes, we describe analogous processes in other organisms, such as Drosophila melanogaster, as a basis for comparison, and we suggest future areas of research that will illuminate how sperm successfully traverse the female reproductive tract. Such studies may yield molecular targets that could be manipulated to control populations of vector species. Mol. Reprod. Dev. 83: 897-911, 2016 © 2016 Wiley Periodicals, Inc.

Severe Fertility Effects of sheepish Sperm Caused by Failure To Enter Female Sperm Storage Organs in Drosophila melanogaster

In Drosophila, mature sperm are transferred from males to females during copulation, stored in the sperm storage organs of females, and then utilized for fertilization. Here, we report a gene named sheepish (shps) of Drosophila melanogaster that is essential for sperm storage in females. shps mutant males, although producing morphologically normal and motile sperm that are effectively transferred to females, produce very few offspring. Direct counts of sperm indicated that the primary defect was correlated to failure of shps sperm to migrate into the female sperm storage organs. Increased sperm motion parameters were seen in the control after transfer to females, whereas sperm from shps males have characteristics of the motion parameters different from the control. The few sperm that occasionally entered the female sperm storage organs showed no obvious defects in fertilization and early embryo development. The female postmating responses after copulation with shps males appeared normal, at least with respect to conformational changes of uterus, mating plug formation, and female remating rates. The shps gene encodes a protein with homology to amine oxidases, including as observed in mammals, with a transmembrane region at the C-terminal end. The shps mutation was characterized by a nonsense replacement in the third exon of CG13611, and shps was rescued by transformants of the wild-type copy of CG13611 Thus, shps may define a new class of gene responsible for sperm storage.

Parallel Evolution of Sperm Hyper-Activation Ca2+ Channels

Sperm hyper-activation is a dramatic change in sperm behavior where mature sperm burst into a final sprint in the race to the egg. The mechanism of sperm hyper-activation in many metazoans, including humans, consists of a jolt of Ca²⁺ into the sperm flagellum via CatSper ion channels. Surprisingly, all nine CatSper genes have been independently lost in several animal lineages. In Drosophila, sperm hyper-activation is performed through the cooption of the polycystic kidney disease 2 (pkd2) Ca²⁺ channel. The parallels between CatSpers in primates and pkd2 in Drosophila provide a unique opportunity to examine the molecular evolution of the sperm hyper-activation machinery in two independent, nonhomologous calcium channels separated by > 500 million years of divergence. Here, we use a comprehensive phylogenomic approach to investigate the selective pressures on these sperm hyper-activation channels. First, we find that the entire CatSper complex evolves rapidly under recurrent positive selection in primates. Second, we find that pkd2 has parallel patterns of adaptive evolution in Drosophila. Third, we show that this adaptive evolution of pkd2 is driven by its role in sperm hyper-activation. These patterns of selection suggest that the evolution of the sperm hyper-activation machinery is driven by sexual conflict with antagonistic ligands that modulate channel activity. Together, our results add sperm hyper-activation channels to the class of fast evolving reproductive proteins and provide insights into the mechanisms used by the sexes to manipulate sperm behavior.

Insect TRP channels as targets for insecticides and repellents

This review provides a brief overview of ion channels, then focuses on TRP channels, describing the properties and functions of the seven TRP channel classes found in insects. Finally, recent work showing that a heteromeric channel composed of Nanchung and Inactive vanilloid TRP (TRPV) channel subunits is the target of the selective feeding blockers pymetrozine and pyrifluquinazon is described. The possible utility of other TRP channels as targets of insecticides and repellents is also considered.

Sperm Navigation Mechanisms in the Female Reproductive Tract

Fertilization, the union of an oocyte and a sperm, is a fundamental process that restores the diploid genome and initiates embryonic development. For the sperm, fertilization is the end of a long journey, one that starts in the male testis before transitioning to the female reproductive tract's convoluted tubule architecture. Historically, motile sperm were thought to complete this journey using luck and numbers. A different picture of sperm has emerged recently as cells that integrate complex sensory information for navigation. Chemical, physical, and thermal cues have been proposed to help guide sperm to the waiting oocyte. Molecular mechanisms are being delineated in animal models and humans, revealing common features, as well as important differences. Exposure to pheromones and nutritional signals can modulate guidance mechanisms, indirectly impacting sperm motility performance and fertility. These studies highlight the importance of sensory information and signal transduction in fertilization.

The spectrum of renal involvement in male patients with infertility related to excretory-system abnormalities: phenotypes, genotypes, and genetic counseling

BACKGROUND

While reproductive technologies are increasingly used worldwide, epidemiologic, clinical and genetic data regarding infertile men with combined genital tract and renal abnormalities remain scarce, preventing adequate genetic counseling.

METHODS

In a cohort-based study, we assessed the prevalence (1995-2014) and the clinical characteristics of renal disorders in infertile males with genital tract malformation. In a subset of 34 patients, we performed a detailed phenotype analysis of renal and genital tract disorders.

RESULTS

Among the 180 patients with congenital uni- or bilateral absence of vas deferens (CU/BAVD), 45 (25 %) had a renal malformation. We also identified 14 infertile men with combined seminal vesicle (SV) and renal malformation but no CU/BAVD. Among the 34 patients with detailed clinical description, renal disease was unknown before the assessment of the infertility in 27 (79.4 %), and 7 (20.6 %) had chronic renal failure. Four main renal phenotypes were observed: solitary kidney (47 %); autosomal-dominant polycystic kidney disease (ADPKD, 0.6 %); uni- or bilateral hypoplastic kidneys (20.6 %); and a complex renal phenotype associated with a mutation of the HNF1B gene (5.8 %). Absence of SV and azoospermia were significantly associated with the presence of a solitary kidney, while dilatation of SV and necroasthenozoospermia were suggestive of ADPKD.

CONCLUSION

A dominantly inherited renal disease (ADPKD or HNF1B-related nephropathy) is frequent in males with infertility and combined renal and genital tract abnormalities (26 %). A systematic renal screening should be proposed in infertile males with CU/BAVD or SV disorders.

Sperm mRNAs and microRNAs as candidate markers for the impact of toxicants on human spermatogenesis: an application to tobacco smoking

Spermatozoa contain a complex population of RNAs including messenger RNAs (mRNAs) and small RNAs such as microRNAs (miRNA). It has been reported that these RNAs can be used to understand the mechanisms by which toxicological exposure affects spermatogenesis. The aim of our study was to compare mRNA and miRNA profiles in spermatozoa from eight smokers and eight non-smokers, and search for potential relationships between mRNA and miRNA variation. All men were selected based on their answers to a standard toxic exposure questionnaire, and sperm parameters. Using mRNA and miRNA microarrays, we showed that mRNAs from 15 genes were differentially represented between smokers and non-smokers (p<0.01): five had higher levels and 10 lower levels in the smokers. For the microRNAs, 23 were differentially represented: 16 were higher and seven lower in the smokers (0.004≤p<0.01). Quantitative RT-PCR confirmed the lower levels in smokers compared to non-smokers for hsa-miR-296-5p, hsa-miR-3940, and hsa-miR-520d-3p. Moreover, we observed an inverse relationship between the levels of microRNAs and six potential target mRNAs (B3GAT3, HNRNPL, OASL, ODZ3, CNGB1, and PKD2). Our results indicate that alterations in the level of a small number of microRNAs in response to smoking may contribute to changes in mRNA expression in smokers. We conclude that large-scale analysis of spermatozoa RNAs can be used to help understand the mechanisms by which human spermatogenesis responds to toxic substances including those in tobacco smoke.

Intraciliary calcium oscillations initiate vertebrate left-right asymmetry

Background

Bilateral symmetry during vertebrate development is broken at the left-right organizer (LRO) by ciliary motility and the resultant directional flow of extracellular fluid. However, how ciliary motility is perceived and transduced into asymmetrical intracellular signaling at the LRO remains controversial. Previous work has indicated that sensory cilia and polycystin-2 (Pkd2), a cation channel, are required for sensing ciliary motility, yet their function and the molecular mechanism linking both to left-right signaling cascades is unknown.

Results

Here, we report novel intraciliary calcium oscillations (ICOs) at the LRO that connect ciliary sensation of ciliary motility to downstream left-right signaling. Utilizing cilia-targeted genetically-encoded calcium indicators in live zebrafish embryos, we show that ICOs depend on Pkd2 and are left-biased at the LRO in response to ciliary motility. Asymmetric ICOs occur with onset of LRO ciliary motility, thus representing the earliest known LR asymmetric molecular signal. Suppression of ICOs using a cilia-targeted calcium sink demonstrates that they are essential for LR development.

Conclusions

These findings demonstrate that intraciliary calcium initiates LR development and identify cilia as a functional ion signaling compartment connecting ciliary motility and flow to molecular LR signaling.

Regulation of salmonid fish sperm motility by osmotic shock-induced water influx across the plasma membrane

The motility of salmonid fish sperm is initiated by a decrease in the extracellular K(+) concentration. However, our previous studies revealed that salmonid fish sperm motility could be initiated in the presence of an inhibitory concentration of K(+) by drastic osmotic shock induced by suspension in a hypertonic glycerol solution and subsequent dilution in a hypotonic solution (glycerol-treatment). In the present study, we examined if an osmotic shock-induced water influx is involved in the regulation of salmonid fish sperm motility. HgCl2, a common inhibitor of aquaporins (AQPs), decreased the duration of salmonid fish sperm motility. Dilution of sperm cells in a hypotonic solution increased the cellular volume, whereas HgCl2 inhibited such an increase in cellular volume. Furthermore, the expression of AQP 1a and 10 in rainbow trout testes was confirmed. In contrast, HgCl2 did not affect glycerol-treated sperm motility, indicating that AQPs are not involved in glycerol-treated sperm motility. We also explored the possibility of aquaporin-independent water influx in glycerol-treated sperm by assessing the sperm membrane permeability using propidium iodide. The plasma membrane of glycerol-treated sperm was considerably permeabilized. The cellular volume was decreased in a hypertonic glycerol solution and increased upon subsequent hypoosmotic shock, indicating an AQP-independent water flux across the plasma membrane upon glycerol-treatment. Taken together, these results showed that water influx across the plasma membrane via AQP is crucial for the maintenance of salmonid fish sperm motility under normal conditions, whereas water influx by osmotic shock-induced membrane permeation is critical for the initiation of glycerol-treated sperm motility.

Expression of polycystins and fibrocystin on primary cilia of lung cells

Mutations in polycystin-1, polycystin-2, or fibrocystin account for autosomal dominant or recessive polycystic kidney disease. Renal cystogenesis is linked to abnormal localization and function of these cystoproteins in renal primary cilia. They are also expressed in extrarenal tissues in which their functions are unclear. Here we found that human type-II alveolar epithelial A549, airway submucosal Calu-3 cells, and rat bronchioles contain primary or multiple cilia in which we detected these cystoproteins. At sub-confluency, polycystin-1 was expressed on plasma membrane, while polycystin-2 was localized to the ER of resting cells. Both polycystins were detected on the spindle and mid-body of mitotic cells, while fibrocystin was on centrosome throughout cell cycle. Polycystins and fibrocystin may participate in regulating mucociliary sensing and transport within pulmonary airways.

The primary cilium as sensor of fluid flow: new building blocks to the model. A review in the theme: cell signaling: proteins, pathways and mechanisms

The primary cilium is an extraordinary organelle. For many years, it had the full attention of only a few dedicated scientists fascinated by its uniqueness. Unexpectedly, after decades of obscurity, it has moved very quickly into the limelight with the increasing evidence of its central role in the many genetic variations that lead to what are now known as ciliopathies. These studies implicated unique biological functions of the primary cilium, which are not completely straightforward. In parallel, and initially completely unrelated to the ciliopathies, the primary cilium was characterized functionally as an organelle that makes cells more susceptible to changes in fluid flow. Thus the primary cilium was suggested to function as a flow-sensing device. This characterization has been substantiated for many epithelial cell types over the years. Nevertheless, part of the central mechanism of signal transduction has not been explained, largely because of the substantial technical challenges of working with this delicate organelle. The current review considers the recent advances that allow us to fill some of the holes in the model of signal transduction in cilium-mediated responses to fluid flow and to pursue the physiological implications of this peculiar organelle.

Drosophila sperm proteome evolution: Insights from comparative genomic approaches

Despite their conserved functional role in sexually reproducing organisms, spermatozoa are a diverse and rapidly evolving cell type. This phenomenon is largely attributed to sexual selection in polygamous species where sperm from multiple males compete to fertilize a limited number of oocytes. Drosophila have proven to be a particularly informative model system for the study of spermatogenesis and in this review we discuss how the characterization of the Drosophila melanogaster sperm proteome has advanced our understanding of the evolutionary genomics of sperm form and function. We summarize the molecular evolutionary characteristics of sperm genes and highlight recent evidence demonstrating the importance of novel gene creation in the evolution of sperm function and competitive ability. Comparative proteomic evidence is also provided, supporting an overall functional conservation between the Drosophila and mouse sperm proteomes. This analysis reveals a diverse repertoire of proteins functioning in proteolytic pathways, as well as the presence of proteins of the complement and innate immunity systems. We propose that these pathways may have functional relevance to post-mating female immunological responses as well as coevolved interactions with pathways expressed in the female reproductive tract, including those involved in sperm-oocyte recognition and fertilization.

Novel roles of Pkd2 in male reproductive system development

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common inherited genetic diseases, caused by mutations in PKD1 and/ or PKD2. Infertility and reproductive tract abnormalities in male ADPKD patients are very common and have higher incidence than in the general population. In this work, we reveal novel roles of Pkd2 for male reproductive system development. Disruption of Pkd2 caused dilation of mesonephric tubules/efferent ducts, failure of epididymal coiling, and defective testicular development. Deletion of Pkd2 in the epithelia alone was sufficient to cause reproductive tract defects seen in Pkd2(-/-) mice, suggesting that epithelial Pkd2 plays a pivotal role for development and maintenance of the male reproductive tract. In the testis, Pkd2 also plays a role in interstitial tissue and testicular cord development. In-depth analysis of epithelial-specific knockout mice revealed that Pkd2 is critical to maintain cellular phenotype and developmental signaling in the male reproductive system. Taken together, our data for the first time reveal novel roles for Pkd2 in male reproductive system development and provide new insights in male reproductive system abnormality and infertility in ADPKD patients.

The TRPP subfamily and polycystin-1 proteins

It has been exciting times since the identification of polycystic kidney disease 1 (PKD1) and PKD2 as the genes mutated in autosomal dominant polycystic kidney disease (ADPKD). Biological roles of the encoded proteins polycystin-1 and TRPP2 have been deduced from phenotypes in ADPKD patients, but recent insights from vertebrate and invertebrate model organisms have significantly expanded our understanding of the physiological functions of these proteins. The identification of additional TRPP (TRPP3 and TRPP5) and polycystin-1-like proteins (PKD1L1, PKD1L2, PKD1L3, and PKDREJ) has added yet another layer of complexity to these fascinating cellular signalling units. TRPP proteins assemble with polycystin-1 family members to form receptor-channel complexes. These protein modules have important biological roles ranging from tubular morphogenesis to determination of left-right asymmetry. The founding members of the polycystin family, TRPP2 and polycystin-1, are a prime example of how studying human disease genes can provide insights into fundamental biological mechanisms using a so-called "reverse translational" approach (from bedside to bench). Here, we discuss the current literature on TRPP ion channels and polycystin-1 family proteins including expression, structure, physical interactions, physiology, and lessons from animal model systems and human disease.

Evolutionarily conserved, multitasking TRP channels: lessons from worms and flies

The Transient Receptor Potential (TRP) channel family is comprised of a large group of cation-permeable channels, which display an extraordinary diversity of roles in sensory signaling. TRPs allow animals to detect chemicals, mechanical force, light, and changes in temperature. Consequently, these channels control a plethora of animal behaviors. Moreover, their functions are not limited to the classical senses, as they are cellular sensors, which are critical for ionic homeostasis and metabolism. Two genetically tractable invertebrate model organisms, Caenorhabditis elegans and Drosophila melanogaster, have led the way in revealing a wide array of sensory roles and behaviors that depend on TRP channels. Two overriding themes have emerged from these studies. First, TRPs are multitasking proteins, and second, many functions and modes of activation of these channels are evolutionarily conserved, including some that were formerly thought to be unique to invertebrates, such as phototransduction. Thus, worms and flies offer the potential to decipher roles for mammalian TRPs, which would otherwise not be suspected.

Fluorescent imaging of Drosophila melanogaster sperm in the reproductive tract: a new model of flagellar motility

The sperm of Drosophila melanogaster stands out because of its enormous length and perplexing movements that break some norms of flagella. Most flagella with analyzed motility, ranging from flagella of Chlamydomonas to sperm of marine invertebrates and vertebrates, are from a few microns to at most 208 μm in length. Most flagella propagate waves in a constant direction, starting at the base of the flagellum and moving toward the tip (base-to-tip waves). In contrast, the fly sperm is 1.9-mm long and it propagates waves in base-to-tip or tip-to-base direction, generating head-leading or tail-leading movement. Of the two movement orientations, the sperm choose one or the other for a particular movement along the convoluted path leading to fertilization. For example, the sperm enter the seminal receptacle (SR) for storage with a tail-leading movement, but exit it for fertilization with a head-leading movement. Moreover, the sperm move with unusual waveforms. A modified sinusoidal or arc-line waveform generates semistationary movement-moving but staying at a general area-within temporary reservoirs (ejaculatory duct, uterus) and storage organs (SR, spermathecae). In contrast, a corkscrew-like helical waveform is ideal for rapid advancing movement and suspected for traveling through long tubules that interconnect these reservoirs. Here, we describe new methods for capturing these complex sperm movements that naturally occur in the reproductive tract. The imaging methods coupled with large mutant collections and genomic resources make the fly sperm a powerful new model for understanding flagellar motility and its dynamic regulation in vivo. The motility regulatory proteins we have identified in the fly are broadly conserved, thus illustrating a general utility of this model system.

Drosophila TRP channels and animal behavior

Multiple classes of cell surface receptors and ion channels participate in the detection of changes in environmental stimuli, and thereby influence animal behavior. Among the many classes of ion channels, Transient Receptor Potential (TRP) cation channels are notable in contributing to virtually every sensory modality, and in controlling a daunting array of behaviors. TRP channels appear to be conserved in all metazoan organisms including worms, insects and humans. Flies encode 13 TRPs, most of which are expressed and function in sensory neurons, and impact behaviors ranging from phototaxis to thermotaxis, gravitaxis, the avoidance of noxious tastants and smells and proprioception. Multiple diseases result from defects in TRPs, and flies provide an excellent animal model for dissecting the mechanisms underlying "TRPopathies." Drosophila TRPs also function in the sensation of botanically derived insect repellents, and related TRPs in insect pests are potential targets for the development of improved repellents to combat insect-borne diseases.

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.