Activity Of Cilia Research Articles

Manganese toxicity is targeting an early step in the dopamine signal transduction pathway that controls lateral cilia activity in the bivalve mollusc Crassostrea virginica

Manganese is a neurotoxin causing manganism, a Parkinson-like clinical disorder. Manganese has been shown to interfere with dopaminergic neurotransmission, but the neurotoxic mechanism involved is not fully resolved. In the bivalve mollusc Crassostrea virginica also known as the eastern oyster, beating rates of lateral cilia of the gill are controlled by dopaminergic-serotonergic innervation originating from their cerebral and visceral ganglia. Terminal release of dopamine activates D2-like receptors on these gill cells inhibiting adenylyl cyclase and slowing cilia beating rates. In C. virginica, manganese treatment disrupts this dopaminergic innervation of the gill, preventing the normal cilio-inhibitory response of lateral cells to dopamine. In this study an adenylyl cyclase activator (forskolin) and two different inhibitors (MDL-12,330A and SQ 22,536) were used to determine if manganese had any effects on the adenylyl cyclase step of the dopamine D2 receptor signal transduction pathway. The results showed that neither the adenylyl cyclase activator nor the inhibitors were affected by manganese in the control of lateral ciliary activity. This suggests that in C. virginica the mechanism of manganese toxicity on the dopaminergic control of lateral ciliary activity is targeting an early step in the D2R signal transduction pathway, which may involve interference with D2 receptor activation or alternatively some other downstream signaling activity that does not affect adenylyl cyclase.

Physiological Study of the Neurotoxic Actions of Manganese on Dopamine Cell Signaling in Crassostrea virginica, Downstream of D2‐Like Receptor Activation

Dopamine and serotonin are important neurotransmitters in invertebrates and have been well studied in bivalves with respect to gill and heart. Lateral gill cell cilia of Crassostrea virginica are controlled by a reciprocal dopaminergic‐serotonergic innervation from their ganglia. Dopamine slows down and stops beating of gill lateral cell cilia while serotonin accelerates cilia beating rates. Previously we found that dopamine postsynaptic receptors involved in controlling gill lateral cell cilia are D2‐like (D2DR). The D2DR signaling pathway involves steps that include inhibition of adenylyl cyclase and activation of phospholipase C (PLC). While the effects of dopamine on cAMP levels in oyster gill is well known, the activation of PLC by dopamine D2DR signaling has not been well studied. PLC activation increases cellular inositol trisphosphate (IP3) and diacylglycerol (DAG). IP3 and DAG are both second messengers. IP3 binds to IP3 receptors and increase cytoplasmic calcium levels. High cytoplasmic calcium levels have been shown to slow down gill lateral cell cilia beating. DAG activates protein kinase C. Manganese is a neurotoxin causing Manganism in people, a Parkinson's‐like syndrome. The dopamine induced cilio‐inhibition of gill lateral cell cilia activity in C. virginica is disrupted by manganese. Earlier work of our lab showed the site of action of manganese is the D2DR receptor. We hypothesize IP3 and DAG would be cilio‐inhibitory but not be effected by manganese treatments. We studied this by conducting acute experiments testing the effects of IP3, a DAG analog, a DAG kinase inhibitor, and manganese on gill lateral cell cilia beating. Ciliary activity of gill lateral cells was measured by stroboscopic microscopy and expressed as beats/min ± sem. The results showed that IP3, the DAG analog and the DAG kinase inhibitor each produced a dose dependent (10−6 – 10−4 M) decrease in gill lateral cell cilia beating. Acute treatments with 500 μM of manganese did not reduce the effectiveness of IP3 and the DAG analog to reduce cilia beating. This study provides new knowledge of the physiological actions of the PLC, IP3 and DAG components of the D2DR pathway on gill lateral cell cilia of C. virginica and demonstrates that manganese did not affect those aspects of the D2DR pathway. The study also provides a foundation to further study the physiological roles of PLC in bivalve gill as well as the neurotoxic actions of manganese on the physiology of the D2‐like receptors in the gill.Support or Funding InformationSupported in part by a Carnegie Foundation award.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

A new index for characterizing micro-bead motion in a flow induced by ciliary beating: Part I, experimental analysis.

Mucociliary clearance is one of the major lines of defense of the respiratory system. The mucus layer coating the pulmonary airways is moved along and out of the lung by the activity of motile cilia, thus expelling the particles trapped in it. Here we compare ex vivo measurements of a Newtonian flow induced by cilia beating (using micro-beads as tracers) and a mathematical model of this fluid flow, presented in greater detail in a second companion article. Samples of nasal epithelial cells placed in water are recorded by high-speed video-microscopy and ciliary beat pattern is inferred. Automatic tracking of micro-beads, used as markers of the flow generated by cilia motion, enables us also to assess the velocity profile as a function of the distance above the cilia. This profile is shown to be essentially parabolic. The obtained experimental data are used to feed a 2D mathematical and numerical model of the coupling between cilia, fluid, and micro-bead motion. From the model and the experimental measurements, the shear stress exerted by the cilia is deduced. Finally, this shear stress, which can easily be measured in the clinical setting, is proposed as a new index for characterizing the efficiency of ciliary beating.

A new index for characterizing micro-bead motion in a flow induced by ciliary beating: Part II, modeling.

Mucociliary clearance is one of the major lines of defense of the human respiratory system. The mucus layer coating the airways is constantly moved along and out of the lung by the activity of motile cilia, expelling at the same time particles trapped in it. The efficiency of the cilia motion can experimentally be assessed by measuring the velocity of micro-beads traveling through the fluid surrounding the cilia. Here we present a mathematical model of the fluid flow and of the micro-beads motion. The coordinated movement of the ciliated edge is represented as a continuous envelope imposing a periodic moving velocity boundary condition on the surrounding fluid. Vanishing velocity and vanishing shear stress boundary conditions are applied to the fluid at a finite distance above the ciliated edge. The flow field is expanded in powers of the amplitude of the individual cilium movement. It is found that the continuous component of the horizontal velocity at the ciliated edge generates a 2D fluid velocity field with a parabolic profile in the vertical direction, in agreement with the experimental measurements. Conversely, we show than this model can be used to extract microscopic properties of the cilia motion by extrapolating the micro-bead velocity measurement at the ciliated edge. Finally, we derive from these measurements a scalar index providing a direct assessment of the cilia beating efficiency. This index can easily be measured in patients without any modification of the current clinical procedures.

Neuroenzymatic activity and physiological energetics in Manila clam, Ruditapes philippinarum, during short-term sublethal exposure to harmful alga, Heterocapsa circularisquama

The harmful alga, Heterocapsa circularisquama, causes recurrent mortalities of bivalve molluscs in Japan, with demonstrated hemolysis and cytotoxicity in rabbit erythrocytes, HeLa cells, and bivalve tissues. Nonetheless, the effects of exposure to sublethal cell densities on the physiological energetics of bivalves have not been investigated, nor the potential involvement of neurotoxicity.In the present study, two sets of experiments were conducted with adult clams, Ruditapes philippinarum. In the first set, the clearance rate (CR), respiration rate (RR), absorption efficiency (AE), ingestion rate (IR), and absorption rate (AR) were examined in clams exposed to H. circularisquama to quantify the scope for growth (SFG) as an indicative of the bioenergetic status of clams (5, 50, 2.5×102, and 5×102cellsml−1; under 15°C and 20°C). In the second set, the activity of the biomarker of neurotoxic exposure, acetylcholinesterase (AChE), was monitored following 3, 6, 24, and 48h of exposure (5, 50, 5×102, and 103cellsml−1, at 20°C) in gills of R. philippinarum, and compared to that in Mediterranean mussels, Mytilus galloprovincialis; a species also affected by H. circualrisquama and in which AChE activity was more extensively studied.At 15°C, CR, IR, and AR were decreased for exposures to 50–5×102 cells ml−1 resulting in a significant decrease in the absorbed energy (A), and a significant decrease in SFG at 5×102cellsml−1. At 20°C, AE was null for exposures to 2.5×102 and 5×102cellsml−1. RR was decreased at 2.5×102 and 5×102cellsml−1, CR, IR, and AR were decreased at 5–5×102cellsml−1, and the AE was null for 2.5×102–5×102cellsml−1 resulting in a significant decrease in the respired energy (R), but mainly in (A) especially at 2.5×102 and 5×102cellsml−1 decreasing the SFG over the entire range of cell density with negative values for 2.5×102 and 5×102cellsml−1. The activity of AChE in both clams and mussels was significantly reduced following 3–48h of exposure to 5–5×102cellsml−1.Reduction in the energy available for clams to grow and reproduce was induced mainly via decreased energy acquisition, and delayed and/or reduced functions of the digestive organs. In addition, this is the first report of decreased neuroenzymatic activity in two bivalve molluscs induced by exposure to H. circularisquama potentially via either neurotoxic compounds affecting the activity of gill cilia and/or gill muscles, and/or potentially via either neurotoxic compounds affecting the activity of gill cilia and/or gill muscles, and/or non-cholinergic affects associated with other functions; both resulting in decreased SFG. The relationship between the decreased AChE and decreased SFG should be corroborated in future research.

In vivo micro-scale tomography of ciliary behavior in the mammalian oviduct.

Motile cilia in the mammalian oviduct play a key role in reproduction, such as transporting fertilized oocytes to the uterus for implantation. Due to their small size (~5–10 μm in length and ~300 nm in diameter), live visualization of cilia and their activity in the lumen of the oviduct through tissue layers represents a major challenge not yet overcome. Here, we report a functional low-coherence optical imaging technique that allows in vivo depth-resolved mapping of the cilia location and cilia beat frequency (CBF) in the intact mouse oviduct with micro-scale spatial resolution. We validate our approach with widely-used microscopic imaging methods, present the first in vivo mapping of the oviduct CBF in its native context, and demonstrate the ability of this approach to differentiate CBF in different locations of the oviduct at different post-conception stages. This technique opens a range of opportunities for live studies in reproductive medicine as well as other areas focused on cilia activity and related ciliopathies.

Chemotaxis as a mechanism of the locomotor activity of olfactory cilia

The article is devoted to a modern understanding of locomotor activity of olfactory cilia as a form of chemotaxis. It includes an analysis of published data and also the results of experimental research performed by the authors.

Histamine and Histamine Receptor Involvement in Sensory‐Motor Integration of Gill Lateral Cell Cilia Activity in the Bivalve Crassostrea viginica

Gill lateral ciliated cells of Crassostrea virginica are innervated by serotonin and dopamine nerves. Motor aspects have been well studied, but the sensory side hasn't. Histamine (HIS) a neurotransmitter in a variety of invertebrates rarely has been reported in bivalves. We quantified HIS in C. virginica and found gill lateral cell cilia beating changed in response to mantle sensory inputs including HIS. The mechanism involves mantle rim sensory tentacles and visceral ganglia. HIS does not alter beating when applied to gill. We hypothesize HIS receptors are present in mantle and can be confirmed by Western Blot (WB). For WB, mantle body and rim lysates were prepared in NP-40 detergent buffer containing protease inhibitor followed by centrifuging to obtain supernatant with solubilized mantle body and rim membrane proteins. H2 receptor immunoreactivity was revealed by 1̊ antibody followed by HRP-conjugated 2̊ antibody. Mantle body and rim H2 receptor protein was resolved by colormetric development using CN/DAB substrate kit. We also did a dose response of HIS H1, H2 and H3 receptor agonists and antagonist at the mantle rim and observed cilia beating in gill. WB showed a 70 kD band corresponding to HIS H2 receptors in mantle body and rim, and H2 agonists and antagonists had the strongest effects on cilia beating. The study shows mantle body and rim have HIS H2 receptors and demonstrates a physiological role of HIS in sensory-motor integration of gill lateral cell cilia activity.

Western Blot Identification of Dopamine and GABA Receptors in Gill of the Bivalve Crassostrea viginica

Gill lateral cells of the bivalve Crassostrea virginica are innervated by serotonin and dopamine (DA) nerves from their ganglia and regulate cilia beating rates. DA slows down cilia beating and serotonin speeds them up. GABA a neurotransmitter in vertebrates and many invertebrates rarely has been reported in bivalves. We showed GABA is present in C. virginica and GABA acts as a ganglionic neurotransmitter modulating gill lateral cell cilia activity. We used immunohistofluorescence to localize GABA receptors in ganglia and gill and identify DA receptors in gill lateral cells as D2‐like (D2DR). We hypothesize Western Blot (WB) would verify D2DR and GABA receptors in gill. For WB gill cell lysate was prepared by in NP‐40 detergent buffer containing protease inhibitor, followed by centrifuging to obtain supernatant with solubilized membrane proteins. Up to 30 µg of solubilized protein was subjected to SDS‐PAGE with 10% acrylamide gels and electroblotted onto nitrocellulose. D2DR and GABA receptor immunoreactivity was revealed by 1̊ antibodies followed by HRP‐conjugated 2̊ antibodies. WB showed 70 ‐ 75 kD bands corresponding to DA D2DR and GABA RA1‐6 receptors in gill. The present project allows us to confirm our previous studies showing the presence of DA and GABA and furthers the understanding of their physiological roles in C. virginica.

Assessment of the toxic effect exerted by fluorescent pseudomonads on embryos and larvae of the sea urchin Strongylocentrotus nudus

Strains of bacteria capable of growing on artificial culture media were isolated from the fouling of brass plates submerged in Nha Trang Bay, South China Sea, and from tissues of the seastar Distolasterias nipon, caught in Peter the Great Bay, Sea of Japan. According to the complex of data of genetic and physiological/biochemical analyzes, two strains of cultivated bacteria were identified by us as the species Pseudomonas aeruginosa, two strains as Pseudomonas fluorescens, and one strain as Ruegeria sp. It was shown that the cultivated strains of P. aeruginosa released exotoxins, particularly phenazine pigments, into the environment. Production of the toxins did not depend on presence of a target organism in the system and was aimed at regulation of interactions in the microbial community. The toxicity of the studied natural isolates of fluorescent pseudomonads was analyzed by using embryos and larvae of the sea urchin Strongylocentrotus nudus, which are the sensitive and dynamic toxicological sea-urchin embryo test (SET) system. As was established, exotoxins produced by the strains of P. aeruginosa inhibit activity of cilia in sea urchin larvae, as well as disturb processes of cell differentiation in embryos and larvae. Their toxic influence is accompanied by disturbances of protein synthesis and the disruptions of cytoskeleton in the course of zygote cleavage and larval development. Unlike P. aeruginosa, the strains of P. fluorescens and Ruegeria sp. did not exert the toxic effect on SET. The obtained data allow considering objects of the environment as the natural reservoir of opportunistic microorganisms posing a potential threat to human, whereas the use of SET for determination of toxicity of isolated bacteria provides an opportunity to study the mechanisms of their interactions with organisms in marine ecosystems.

The Action of Cilia in the Upper Reproductive Tract of Women Influences the Distribution of HIV

AIDS Research and Human RetrovirusesVol. 30, No. S1 Mucosal Immune Activation and InflammationThe Action of Cilia in the Upper Reproductive Tract of Women Influences the Distribution of HIVAnn M. Carias, Daniel Stieh, Danijela Maric, and Thomas J. HopeAnn M. CariasSearch for more papers by this author, Daniel StiehSearch for more papers by this author, Danijela MaricSearch for more papers by this author, and Thomas J. HopeSearch for more papers by this authorPublished Online:30 Oct 2014https://doi.org/10.1089/aid.2014.5503.abstractAboutSectionsView articleView Full TextPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail View article"The Action of Cilia in the Upper Reproductive Tract of Women Influences the Distribution of HIV." AIDS Research and Human Retroviruses, 30(S1), p. A229FiguresReferencesRelatedDetails Volume 30Issue S1Oct 2014 InformationCopyright 2014, Mary Ann Liebert, Inc.To cite this article:Ann M. Carias, Daniel Stieh, Danijela Maric, and Thomas J. Hope.The Action of Cilia in the Upper Reproductive Tract of Women Influences the Distribution of HIV.AIDS Research and Human Retroviruses.Oct 2014.A229-A229.http://doi.org/10.1089/aid.2014.5503.abstractPublished in Volume: 30 Issue S1: October 30, 2014PDF download

Amoeboid Swimming: A Generic Self-Propulsion of Cells in Fluids by Means of Membrane Deformations

Microorganisms, such as bacteria, algae, or spermatozoa, are able to propel themselves forward thanks to flagella or cilia activity. By contrast, other organisms employ pronounced changes of the membrane shape to achieve propulsion, a prototypical example being the Eutreptiella gymnastica. Cells of the immune system as well as dictyostelium amoebas, traditionally believed to crawl on a substratum, can also swim in a similar way. We develop a model for these organisms: the swimmer is mimicked by a closed incompressible membrane with force density distribution (with zero total force and torque). It is shown that fast propulsion can be achieved with adequate shape adaptations. This swimming is found to consist of an entangled pusher-puller state. The autopropulsion distance over one cycle is a universal linear function of a simple geometrical dimensionless quantity A/V(2/3) (V and A are the cell volume and its membrane area). This study captures the peculiar motion of Eutreptiella gymnastica with simple force distribution.

Respiratory and olfactory cilia molecular machines of locomotor apparatus

Physical activity of respiratory and olfactory cilia of animals and humans in the context of L.A. Blumenfeld concept, according to which protein molecules are "machines that perform chemical transformation" and create "a meaningful order", has been investigated and analyzed.

Respiratory Syncytial Virus Inhibits Ciliagenesis in Differentiated Normal Human Bronchial Epithelial Cells: Effectiveness of N-Acetylcysteine

Persistent respiratory syncytial virus (RSV) infections have been associated with the exacerbation of chronic inflammatory diseases, including chronic obstructive pulmonary disease (COPD). This virus infects the respiratory epithelium, leading to chronic inflammation, and induces the release of mucins and the loss of cilia activity, two factors that determine mucus clearance and the increase in sputum volume. These alterations involve reactive oxygen species-dependent mechanisms. The antioxidant N-acetylcysteine (NAC) has proven useful in the management of COPD, reducing symptoms, exacerbations, and accelerated lung function decline. NAC inhibits RSV infection and mucin release in human A549 cells. The main objective of this study was to analyze the effects of NAC in modulating ciliary activity, ciliagenesis, and metaplasia in primary normal human bronchial epithelial cell (NHBEC) cultures infected with RSV. Our results indicated that RSV induced ultrastructural abnormalities in axonemal basal bodies and decreased the expression of β-tubulin as well as two genes involved in ciliagenesis, FOXJ1 and DNAI2. These alterations led to a decrease in ciliary activity. Furthermore, RSV induced metaplastic changes to the epithelium and increased the number of goblet cells and the expression of MUC5AC and GOB5. NAC restored the normal functions of the epithelium, inhibiting ICAM1 expression, subsequent RSV infection through mechanisms involving nuclear receptor factor 2, and the expression of heme oxygenase 1, which correlated with the restoration of the antioxidant capacity, the intracellular H2O2 levels and glutathione content of NHBECs. The results presented in this study support the therapeutic use of NAC for the management of chronic respiratory diseases, including COPD.

A Study of GABA in Bivalve Molluscs

The nervous systems of most studied bivalves contain serotonin and dopamine in their ganglia that serve as neurotransmitters regulating various physiological functions such as heart rate, foot movement, reproduction and gill lateral cilia beating. GABA is a major inhibitory neurotransmitter found in the CNS of vertebrates and ganglia of many invertebrates. Its presence and functions have not been well studied in bivalves. Here we used a HPLC method with pre‐column derivatization and fluorescence detection to look for GABA in ganglia of Crassostrea virginica, Mercenaria mercenaria and Mytilus edulis. We also examined effects of GABA on beating of gill lateral cilia in C. virginica and M. edulis. GABA was detected in low ng amounts in each ganglia of each of the bivalves. In C. virginica and M. edulis GABA had no direct effect on lateral cilia activity when applied directly to the gill. However, when serotonin was applied to the cerebral ganglia, GABA, whether applied before or after serotonin, blocked the normal excitatory response of serotonin on the beating of the cilia. Furthermore, the GABA antagonist bicuculline methchloride blocked the effects of GABA in the cerebral ganglia of C. virginica. This study is showing that GABA is present and has a neurophysiological role in bivalve ganglia. This work was supported by grants 2R25GM0600309 of NIGMS, 0516041071 of NYSDOE and 0622197 of NSF.

Development and Validation of a Method of Cilia Motility Analysis for the Early Diagnosis of Primary Ciliary Dyskinesia

BackgroundPrimary ciliary dyskinesia (PCD) is a clinically uniform entity, but cilia motility and structure can vary between patients, making the diagnosis difficult. The aim of this study was to evaluate the sensitivity and specificity in diagnosing PCD of a system of high-resolution digital high-speed video analysis with proprietary software that we developed for analysis of ciliary motility (Desinsoft-Bio 200). The secondary aim was to correlate nasal ciliary activity with clinical and structural abnormalities in PCD. Material and methodsWe analysed nasal mucociliary transport, cilia ultrastructure, nasal ciliary beat frequency and beat pattern studied by high-resolution digital high-speed video in 25 cases of PCD (11 Kartagener syndrome), 27 secondary ciliary dyskinesia and 34 healthy volunteers. ResultsNasal mucociliary transport was defective in both primary and secondary ciliary dyskinesia. Ciliary immotility was observed only in 6 patients with Kartagener syndrome and correlated with the absence of dynein. We observed a correlation between partial dynein deficiencies and ciliary dyskinesia. Cilia activity and structure were normal in secondary ciliary dyskinesia. ConclusionNasal mucociliary transport showed high sensitivity for PCD diagnosis with a low specificity. High-resolution digital high-speed video has a high sensitivity and specificity for diagnosing PCD. This system of video analysis is more useful than ultrastructural study and mucociliary transport for PCD screening. Dynein absence is correlated with cilia immotility and is more common in patients with Kartagener syndrome.

Changes in the Activity of the Ciliary Apparatus of Ependymal Cells in the Midbrain Cerebral Aqueduct Induced by a Number of Cerebrospinal Fluid Neurotransmitters

Studies of the effects of neurotransmitter amino acids on the motor activity of the ciliary apparatus of ependymal cells of the midbrain cerebral aqueduct in neonatal white mice showed that addition of glutamate, GABA-aminobutyric acid, glycine, and taurine to the culture medium induced slowing and then complete cessation of the activity of the ciliary apparatus. Inhibition and cessation of the activity of cilia in response to neurotransmitters, especially glutamate at high concentrations, demonstrated the existence of the corresponding receptors on the membranes of ependymal cells in the cerebral aqueduct, and this was supported by experiments with prior addition of ion channel blockers to the growth medium, i.e., ketamine, strychnine, and bicuculline, which weakened the destructive influences of neurotransmitters and increased the duration of functioning of the ciliary apparatus.

Desarrollo y validación de un método de análisis de la movilidad ciliar para el diagnóstico precoz de la discinesia ciliar primaria

BackgroundPrimary ciliary dyskinesia (PCD) is a clinically uniform entity, but cilia motility and structure can vary between patients, making the diagnostic difficult. The aim of this study was to evaluate the sensitivity and specificity in diagnosing PCD of a system of high-resolution digital high-speed video analysis with proprietary software that we developed for analysis of ciliary motility (Desinsoft-Bio 200). The secondary aim was to correlate nasal ciliary activity with clinical and structural abnormalities in PCD. Material and methodsWe analysed nasal mucociliary transport, cilia ultrastructure, nasal ciliary beat frequency and beat pattern studied by high-resolution digital high-speed video in 25 cases of PCD (11 Kartagener syndrome), 27 secondary ciliary dyskinesia and 34 healthy volunteers. ResultsNasal mucociliary transport was defective in both primary and secondary ciliary dyskinesia. Ciliary immotility was observed only in 6 patients with Kartagener syndrome and correlated with the absence of dynein. We observed a correlation between partial dynein deficiencies and ciliary dyskinesia. Cilia activity and structure was normal in secondary ciliary dyskinesia. ConclusionNasal mucociliary transport showed high sensitivity for PCD diagnosis with a low specificity. High-resolution digital high-speed video has a high sensitivity and specificity for diagnosing PCD. This system of video analysis is more useful than ultrastructural study and mucociliary transport for PCD screening. Dynein absence is correlated with cilia immotility and is more common in patients with Kartagener syndrome.

Renal cystic disease proteins play critical roles in the organization of the olfactory epithelium.

It was reported that some proteins known to cause renal cystic disease (NPHP6; BBS1, and BBS4) also localize to the olfactory epithelium (OE), and that mutations in these proteins can cause anosmia in addition to renal cystic disease. We demonstrate here that a number of other proteins associated with renal cystic diseases – polycystin 1 and 2 (PC1, PC2), and Meckel-Gruber syndrome 1 and 3 (MKS1, MKS3) – localize to the murine OE. PC1, PC2, MKS1 and MKS3 are all detected in the OE by RT-PCR. We find that MKS3 localizes specifically to dendritic knobs of olfactory sensory neurons (OSNs), while PC1 localizes to both dendritic knobs and cilia of mature OSNs. In mice carrying mutations in MKS1, the expression of the olfactory adenylate cyclase (AC3) is substantially reduced. Moreover, in rats with renal cystic disease caused by a mutation in MKS3, the laminar organization of the OE is perturbed and there is a reduced expression of components of the odor transduction cascade (Golf, AC3) and α-acetylated tubulin. Furthermore, we show with electron microscopy that cilia in MKS3 mutant animals do not manifest the proper microtubule architecture. Both MKS1 and MKS3 mutant animals show no obvious alterations in odor receptor expression. These data show that multiple renal cystic proteins localize to the OE, where we speculate that they work together to regulate aspects of the development, maintenance or physiological activities of cilia.

Origin and early evolution of neural circuits for the control of ciliary locomotion

Behaviour evolved before nervous systems. Various single-celled eukaryotes (protists) and the ciliated larvae of sponges devoid of neurons can display sophisticated behaviours, including phototaxis, gravitaxis or chemotaxis. In single-celled eukaryotes, sensory inputs directly influence the motor behaviour of the cell. In swimming sponge larvae, sensory cells influence the activity of cilia on the same cell, thereby steering the multicellular larva. In these organisms, the efficiency of sensory-to-motor transformation (defined as the ratio of sensory cells to total cell number) is low. With the advent of neurons, signal amplification and fast, long-range communication between sensory and motor cells became possible. This may have first occurred in a ciliated swimming stage of the first eumetazoans. The first axons may have had en passant synaptic contacts to several ciliated cells to improve the efficiency of sensory-to-motor transformation, thereby allowing a reduction in the number of sensory cells tuned for the same input. This could have allowed the diversification of sensory modalities and of the behavioural repertoire. I propose that the first nervous systems consisted of combined sensory-motor neurons, directly translating sensory input into motor output on locomotor ciliated cells and steering muscle cells. Neuronal circuitry with low levels of integration has been retained in cnidarians and in the ciliated larvae of some marine invertebrates. This parallel processing stage could have been the starting point for the evolution of more integrated circuits performing the first complex computations such as persistence or coincidence detection. The sensory-motor nervous systems of cnidarians and ciliated larvae of diverse phyla show that brains, like all biological structures, are not irreducibly complex.