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Insects and other arthropods utilise external sensory structures for mechanosensory, olfactory, and gustatory reception. These sense organs have characteristic shapes related to their function, and in many cases are distributed in a fixed pattern so that they are identifiable individually. In Drosophila melanogaster, the identity of sense organs is regulated by specific combinations of transcription factors. In other arthropods, however, sense organ subtypes cannot be linked to the same code of gene expression. This raises the questions of how sense organ diversity has evolved and whether the principles underlying subtype identity in D. melanogaster are representative of other insects. Here, we provide evidence that such principles cannot be generalised, and suggest that sensory organ diversification followed the recruitment of sensory genes to distinct sensory organ specification mechanism. RESULTS: We analysed sense organ development in a nondipteran insect, the flour beetle Tribolium castaneum, by gene expression and RNA interference studies. We show that in contrast to D. melanogaster, T. castaneum sense organs cannot be categorised based on the expression or their requirement for individual or combinations of conserved sense organ transcription factors such as cut and pox neuro, or members of the Achaete-Scute (Tc ASH, Tc asense), Atonal (Tc atonal, Tc cato, Tc amos), and neurogenin families (Tc tap). Rather, our observations support an evolutionary scenario whereby these sensory genes are required for the specification of sense organ precursors and the development and differentiation of sensory cell types in diverse external sensilla which do not fall into specific morphological and functional classes. CONCLUSIONS: Based on our findings and past research, we present an evolutionary scenario suggesting that sense organ subtype identity has evolved by recruitment of a flexible sensory gene network to the different sense organ specification processes. A dominant role of these genes in subtype identity has evolved as a secondary effect of the function of these genes in individual or subsets of sense organs, probably modulated by positional cues.

Proper function of cell signaling pathways is dependent upon regulated membrane trafficking events that lead to the endocytosis, recycling, and degradation of cell surface receptors. The endosomal complexes required for transport (ESCRT) genes play a critical role in the sorting of ubiquitinated cell surface proteins. CHMP2B Intron5 , a truncated form of a human ESCRT-III protein, was discovered in a Danish family afflicted by a hereditary form of frontotemporal dementia (FTD). Although the mechanism by which the CHMP2B mutation in this family causes FTD is unknown, the resulting protein has been shown to disrupt normal endosomal-lysosomal pathway function and leads to aberrant regulation of signaling pathways. Here we have misexpressed CHMP2B Intron5 in the developing Drosophila external sensory (ES) organ lineage and demonstrate that it is capable of altering cell fates. Each of the cell fate transformations seen is compatible with an increase in Notch signaling. Furthermore, this interpretation is supported by evidence that expression of CHMP2B Intron5 in the notum environment is capable of raising the levels of Notch signaling. As such, these results add to a growing body of evidence that CHMP2B Intron5 can act rapidly to disrupt normal cellular function via the misregulation of critical cell surface receptor function., (© 2019 Wiley Periodicals, Inc.)

Spiders are equipped with a large number of innervated cuticular specializations, which respond to various sensory stimuli. The physiological function of mechanosensory organs has been analysed in great detail in some model spider species (e.g. Cupiennius salei); however, much less is known about the distribution and function of chemosensory organs. Furthermore, our knowledge on how the sense organ pattern develops on the spider appendages is limited. Here we analyse the development of the pattern and distribution of six different external mechano- and chemosensory organs in all postembryonic stages and in adult male and female spiders of the species Parasteatoda tepidariorum. We show that except for small mechanosensory setae, external sense organs appear in fixed positions on the pedipalps and first walking legs, arranged in longitudinal rows along the proximal-distal axis or in invariable positions relative to morphological landmarks (joints, distal tarsal tip). A comparison to other Entelegynae spiders shows that these features are conserved. We hope that this study lays the foundation for future molecular analysis to address the question how this conserved pattern is generated.

Species-specific traits are thought to have been acquired by natural selection. Transcription factors play central roles in the evolution of species-specific traits. Hox genes encode a set of conserved transcription factors essential for establishing the anterior-posterior body axis of animals. Changes in the expression or function of Hox genes can lead to the diversification of animal-body plans. The tunicate ascidian Ciona intestinalis Type A has an orange-colored structure at the sperm duct terminus. This orange-pigmented organ (OPO) is the characteristic that can distinguish this ascidian from other closely related species. The OPO is formed by the accumulation of orange-pigmented cells (OPCs) that are present throughout the adult body. We show that Hox13 is essential for formation of the OPO. Hox13 is expressed in the epithelium of the sperm duct and neurons surrounding the terminal openings for sperm ejection, while OPCs themselves do not express this gene. OPCs are mobile cells that can move through the body vasculature by pseudopodia, suggesting that the OPO is formed by the accumulation of OPCs guided by Hox13-positive cells. Another ascidian species, Ciona savignyi, does not have an OPO. Like Hox13 of C. intestinalis, Hox13 of C. savignyi is expressed at the terminus of its sperm duct; however, its expression domain is limited to the circular area around the openings. The genetic changes responsible for the acquisition or loss of OPO are likely to occur in the expression pattern of Hox13., Competing Interests: Declaration of competing interest The authors declare no competing interests., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Within the mammalian cochlea, sensory hair cells and supporting cells are aligned in curvilinear rows that extend along the length of the tonotopic axis. In addition, all of the cells within the epithelium are uniformly polarized across the orthogonal neural-abneural axis. Finally, each hair cell is intrinsically polarized as revealed by the presence of an asymmetrically shaped and apically localized stereociliary bundle. It has been known for some time that many of the developmental processes that regulate these patterning events are mediated, to some extent, by the core planar cell polarity (PCP) pathway. This article will review more recent work demonstrating how components of the PCP pathway interact with cytoskeletal motor proteins to regulate cochlear outgrowth. Finally, a signaling pathway originally identified for its role in asymmetric cell divisions has recently been shown to mediate several aspects of intrinsic hair cell polarity, including kinocilia migration, bundle shape, and elongation., (Copyright © 2020 Cold Spring Harbor Laboratory Press; all rights reserved.)

Barbels are important sensory organs in teleosts, reptiles, and amphibians. The majority of ∼4,000 catfish species, such as the channel catfish ( Ictalurus punctatus ), possess abundant whisker-like barbels. However, barbel-less catfish, such as the bottlenose catfish ( Ageneiosus marmoratus ), do exist. Barbeled catfish and barbel-less catfish are ideal natural models for determination of the genomic basis for barbel development. In this work, we generated and annotated the genome sequences of the bottlenose catfish, conducted comparative and subtractive analyses using genome and transcriptome datasets, and identified differentially expressed genes during barbel regeneration. Here, we report that chemokine C-C motif ligand 33 ( ccl33 ), as a key regulator of barbel development and regeneration. It is present in barbeled fish but absent in barbel-less fish. The ccl33 genes are differentially expressed during barbel regeneration in a timing concordant with the timing of barbel regeneration. Knockout of ccl33 genes in the zebrafish ( Danio rerio ) resulted in various phenotypes, including complete loss of barbels, reduced barbel sizes, and curly barbels, suggesting that ccl33 is a key regulator of barbel development. Expression analysis indicated that paralogs of the ccl33 gene have both shared and specific expression patterns, most notably expressed highly in various parts of the head, such as the eye, brain, and mouth areas, supporting its role for barbel development., Competing Interests: The authors declare no conflict of interest.

Hox genes are involved in the patterning of animal body parts at multiple levels of regulatory hierarchies. Early expression of Hox genes in different domains along the embryonic anterior-posterior (A/P) axis in insects, vertebrates, and other animals establishes segmental or regional identity. However, Hox gene function is also required later in development for the patterning and morphogenesis of limbs and other organs. In Drosophila, spatiotemporal modulation of Sex combs reduced (Scr) expression within the first thoracic (T1) leg underlies the generation of segment- and sex-specific sense organ patterns. High Scr expression in defined domains of the T1 leg is required for the development of T1-specific transverse bristle rows in both sexes and sex combs in males, implying that the patterning of segment-specific sense organs involves incorporation of Scr into the leg development and sex determination gene networks. We sought to gain insight into this process by identifying the cis-and trans-regulatory factors that direct Scr expression during leg development. We have identified two cis-regulatory elements that control spatially modulated Scr expression within T1 legs. One of these enhancers directs sexually dimorphic expression and is required for the formation of T1-specific bristle patterns. We show that the Distalless and Engrailed homeodomain transcription factors act through sequences in this enhancer to establish elevated Scr expression in spatially defined domains. This enhancer functions to integrate Scr into the intrasegmental gene regulatory network, such that Scr serves as a link between leg patterning, sex determination, and sensory organ development.

The lateral line system is a useful model for studying the embryonic and evolutionary diversification of different organs and cell types. In jawed vertebrates, this ancestrally comprises lines of mechanosensory neuromasts over the head and trunk, flanked on the head by fields of electrosensory ampullary organs, all innervated by lateral line neurons in cranial lateral line ganglia. Both types of sense organs, and their afferent neurons, develop from cranial lateral line placodes. Current research primarily focuses on the posterior lateral line primordium in zebrafish, which migrates as a cell collective along the trunk; epithelial rosettes form in the trailing zone and are deposited as a line of neuromasts, within which hair cells and supporting cells differentiate. However, in at least some other teleosts (e.g. catfishes) and all non-teleosts, lines of cranial neuromasts are formed by placodes that elongate to form a sensory ridge, which subsequently fragments, with neuromasts differentiating in a line along the crest of the ridge. Furthermore, in many non-teleost species, electrosensory ampullary organs develop from the flanks of the sensory ridge. It is unknown to what extent the molecular mechanisms underlying neuromast formation from the zebrafish migrating posterior lateral line primordium are conserved with the as-yet unexplored molecular mechanisms underlying neuromast and ampullary organ formation from elongating lateral line placodes. Here, we report experiments in an electroreceptive non-teleost ray-finned fish, the Mississippi paddlefish Polyodon spathula, that suggest a conserved role for Notch signaling in regulating lateral line organ receptor cell number, but potentially divergent roles for the fibroblast growth factor signaling pathway, both between neuromasts and ampullary organs, and between paddlefish and zebrafish., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

Hox transcription factors specify distinct cell types along the anterior-posterior axis of metazoans by regulating target genes that modulate signaling pathways. A well-established example is the induction of Epidermal Growth Factor (EGF) signaling by an Abdominal-A (Abd-A) Hox complex during the specification of Drosophila hepatocyte-like cells (oenocytes). Previous studies revealed that Abd-A is non-cell autonomously required to promote oenocyte fate by directly activating a gene (rhomboid) that triggers EGF secretion from sensory organ precursor (SOP) cells. Neighboring cells that receive the EGF signal initiate a largely unknown pathway to promote oenocyte fate. Here, we show that Abd-A also plays a cell autonomous role in inducing oenocyte fate by activating the expression of the Pointed-P1 (PntP1) ETS transcription factor downstream of EGF signaling. Genetic studies demonstrate that both PntP1 and PntP2 are required for oenocyte specification. Moreover, we found that PntP1 contains a conserved enhancer (PntP1OE) that is activated in oenocyte precursor cells by EGF signaling via direct regulation by the Pnt transcription factors as well as a transcription factor complex consisting of Abd-A, Extradenticle, and Homothorax. Our findings demonstrate that the same Abd-A Hox complex required for sending the EGF signal from SOP cells, enhances the competency of receiving cells to select oenocyte cell fate by up-regulating PntP1. Since PntP1 is a downstream effector of EGF signaling, these findings provide insight into how a Hox factor can both trigger and potentiate the EGF signal to promote an essential cell fate along the body plan.

AMPA-type glutamate receptors (GluAs) mediate fast excitatory transmission in the vertebrate central nervous system (CNS), and their function has been extensively studied in the mature mammalian brain. However, GluA expression begins very early in developing embryos, suggesting that they may also have unidentified developmental roles. Here, we identify developmental roles for GluAs in the ascidian Ciona intestinalis Mammals express Ca 2+ -permeable GluAs (Ca-P GluAs) and Ca 2+ -impermeable GluAs (Ca-I GluAs) by combining subunits derived from four genes. In contrast, ascidians have a single gluA gene. Taking advantage of the simple genomic GluA organization in ascidians, we knocked down (KD) GluAs in Ciona and observed severe impairments in formation of the ocellus, a photoreceptive organ used during the swimming stage, and in resorption of the tail and body axis rotation during metamorphosis to the adult stage. These defects could be rescued by injection of KD-resistant GluAs. GluA KD phenotypes could also be reproduced by expressing a GluA mutant that dominantly inhibits glutamate-evoked currents. These results suggest that, in addition to their role in synaptic communication in mature animals, GluAs also have critical developmental functions.

Nkx5 family members are homeobox transcription factors important for sensory organ development. Several members of the Nkx5 family are expressed in the eye, brain, developing ear, and lateral line. Members of this family have been previously identified in medaka, chick, and mouse. Here, we characterize two members of the Nkx5 family, Nkx5.3 and SOHo, in Xenopus laevis. We verify the identity of X. laevis Nkx5.3 and SOHo by phylogenetic comparison to chicken, medaka, and zebrafish orthologs. Both Nkx5.3 and SOHo are expressed in the developing eye, ear, lateral line system, and cranial neurons as determined by in situ hybridization.

In Bilateria, Pax6, Six, Eya and Dach families of transcription factors underlie the development and evolution of morphologically and phyletically distinct eyes, including the compound eyes in Drosophila and the camera-type eyes in vertebrates, indicating that bilaterian eyes evolved under the strong influence of ancestral developmental gene regulation. However the conservation in eye developmental genetics deeper in the Eumetazoa, and the origin of the conserved gene regulatory apparatus controlling eye development remain unclear due to limited comparative developmental data from Cnidaria. Here we show in the eye-bearing scyphozoan cnidarian Aurelia that the ectodermal photosensory domain of the developing medusa sensory structure known as the rhopalium expresses sine oculis (so)/six1/2 and eyes absent/eya, but not optix/six3/6 or pax (A&B). In addition, the so and eya co-expression domain encompasses the region of active cell proliferation, neurogenesis, and mechanoreceptor development in rhopalia. Consistent with the role of so and eya in rhopalial development, developmental transcriptome data across Aurelia life cycle stages show upregulation of so and eya, but not optix or pax (A&B), during medusa formation. Moreover, pax6 and dach are absent in the Aurelia genome, and thus are not required for eye development in Aurelia. Our data are consistent with so and eya, but not optix, pax or dach, having conserved functions in sensory structure specification across Eumetazoa. The lability of developmental components including Pax genes relative to so-eya is consistent with a model of sense organ development and evolution that involved the lineage specific modification of a combinatorial code that specifies animal sense organs.

Asymmetric cell division (ACD) is a simple and evolutionary conserved process whereby a mother divides to generate two daughter cells with distinct developmental potentials. This process can generate cell fate diversity during development. Fate asymmetry may result from the unequal segregation of molecules and/or organelles between the two daughter cells. Here, I will review how fate asymmetry is regulated in the sensory bristle lineage in Drosophila and focus on the molecular mechanisms underlying ACD of the sensory organ precursor cells (SOPs). For further resources related to this article, please visit the WIREs website., (© 2015 The Authors. WIREs Developmental Biology published by Wiley Periodicals, Inc.)

The bristle sensillum of the imago of Drosophila is made of four cells that arise from a sensory organ precursor cell (SOP). This SOP is selected within proneural clusters (PNC) through a mechanism that involves Notch signalling. PNCs are defined through the expression domains of the proneural genes, whose activities enables cells to become SOPs. They encode tissue specific bHLH proteins that form functional heterodimers with the bHLH protein Daughterless (Da). In the prevailing lateral inhibition model for SOP selection, a transcriptional feedback loop that involves the Notch pathway amplifies small differences of proneural activity between cells of the PNC. As a result only one or two cells accumulate sufficient proneural activity to adopt the SOP fate. Most of the experiments that sustained the prevailing lateral inhibition model were performed a decade ago. We here re-examined the selection process using recently available reagents. Our data suggest a different picture of SOP selection. They indicate that a band-like region of proneural activity exists. In this proneural band the activity of the Notch pathway is required in combination with Emc to define the PNCs. We found a sub-group in the PNCs from which a pre-selected SOP arises. Our data indicate that most imaginal disc cells are able to adopt a proneural state from which they can progress to become SOPs. They further show that bristle formation can occur in the absence of the proneural genes if the function of emc is abolished. These results suggest that the tissue specific proneural proteins of Drosophila have a similar function as in the vertebrates, which is to determine the time of emergence and position of the SOP and to stabilise the proneural state.

The recent advances on ascidian pigment sensory organ development and function represent a fascinating platform to get insight on the basic programs of chordate eye formation. This review aims to summarize current knowledge, at the structural and molecular levels, on the two main building blocks of ascidian light sensory organ, i.e. pigment cells and photoreceptor cells. The unique features of these structures (e.g., simplicity and well characterized cell lineage) are indeed making it possible to dissect the developmental programs at single cell resolution and will soon provide a panel of molecular tools to be exploited for a deep developmental and comparative-evolutionary analysis., (© 2014 Wiley Periodicals, Inc.)

Transcriptional cis-regulatory modules (CRMs), or enhancers, are responsible for directing gene expression in specific territories and cell types during development. In some instances, the same gene may be served by two or more enhancers with similar specificities. Here we show that the utilization of dual, or "shadow", enhancers is a common feature of genes that are active specifically in neural precursor (NP) cells in Drosophila. By genome-wide computational discovery of statistically significant clusters of binding motifs for both proneural activator (P) proteins and basic helix-loop-helix (bHLH) repressor (R) factors (a "P+R" regulatory code), we have identified NP-specific enhancer modules associated with multiple genes expressed in this cell type. These CRMs are distinct from those previously identified for the corresponding gene, establishing the existence of a dual-enhancer arrangement in which both modules reside close to the gene they serve. Using wild-type and mutant reporter gene constructs in vivo, we show that P sites in these modules mediate activation by proneural factors in "proneural cluster" territories, whereas R sites mediate repression by bHLH repressors, which serves to restrict expression specifically to NP cells. To our knowledge, our results identify the first direct targets of these bHLH repressors. Finally, using genomic rescue constructs for neuralized (neur), we demonstrate that each of the gene's two NP-specific enhancers is sufficient to rescue neur function in the lateral inhibition process by which adult sensory organ precursor (SOP) cells are specified, but that deletion of both enhancers results in failure of this event.

The aboral sensory organ (apical organ) of ctenophores contains a statocyst with a single large statolith. The statolith comprises living cells (lithocytes), each containing a large membrane-bound concretion. The statolith is supported on the distal ends of four compound motile mechanoresponsive cilia (balancers) which control the beat frequencies of the eight locomotory comb rows, and thereby the orientation of animals to gravity. In Mnemiopsis leidyi and Pleurobrachia pileus, lithocytes arise in the thickened epithelial floor of the apical organ on opposite sides along the tentacular plane. Lithocytes progressively differentiate and migrate toward the apical surface where they bud off next to the bases of the balancers. New lithocytes are transported up the balancers by ciliary surface motility to form the statolith (Noda, 2013). The statolith has a superellipsoidal shape due to the rectangular arrangement of the four balancers and the addition of new lithocytes to its ends via the balancers. The size of the statolith increases with animal size, starting at the highest rate of growth in younger stages and gradually decreasing in larger animals. The total number of developing lithocytes in the epithelial floor increases rapidly in smaller animals and reaches a plateau range in larger animals. Lithocytes are therefore produced continually throughout life for enlargement of the statolith and possibly for turnover and replacement of existing lithocytes. The dome cilia enclosing the statocyst were observed to propagate slow, low-ampitude waves distally. The dome cilia may act as an undulating screen to prevent foreign objects in the seawater from being transported non-specifically up the balancers to make a defective statolith., (© 2014 Marine Biological Laboratory.)

In mammals, formation of the auditory sensory organ (the organ of Corti) is restricted to a specialized area of the cochlea. However, the molecular mechanisms limiting sensory formation to this discrete region in the ventral cochlear duct are not well understood, nor is it known whether other regions of the cochlea have the competence to form the organ of Corti. Here we identify LMO4, a LIM-domain-only nuclear protein, as a negative regulator of sensory organ formation in the cochlea. Inactivation of Lmo4 in mice leads to an ectopic organ of Corti (eOC) located in the lateral cochlea. The eOC retains the features of the native organ, including inner and outer hair cells, supporting cells, and other nonsensory specialized cell types. However, the eOC shows an orientation opposite to the native organ, such that the eOC appears as a mirror-image duplication to the native organ of Corti. These data demonstrate a novel sensory competent region in the lateral cochlear duct that is regulated by LMO4 and may be amenable to therapeutic manipulation., (Copyright © 2014 the authors 0270-6474/14/3410072-06$15.00/0.)

microRNA are small non-coding RNA that modulate gene expression post-transcriptionally. Discovered 20 years ago, their individual functions start to be unraveled. Collectively, functional studies point to an important functional plasticity of microRNA, along the course of evolution, and across different cellular contexts. This is the case in particular for one of them, miR-9, a key factor of the regulation of the neural progenitor state in Vertebrates., (© 2013 médecine/sciences – Inserm.)

Eph receptors and their ephrin ligands are key conserved regulators of axon guidance and can function in a variety of signaling modes. Here we analyze the genetic and cellular requirements for Eph signaling in a Caenorhabditis elegans axon guidance choice point, the ventral guidance of axons in the amphid commissure. The C. elegans Eph receptor EFN-1 has both kinase-dependent and kinase-independent roles in amphid ventral guidance. Of the four C. elegans ephrins, we find that only EFN-1 has a major role in amphid axon ventral guidance, and signals in both a receptor kinase-dependent and kinase-independent manner. Analysis of EFN-1 and EFN-1 expression and tissue-specific requirements is consistent with a model in which VAB-1 acts in amphid neurons, interacting with EFN-1 expressed on surrounding cells. Unexpectedly, left-hand neurons are more strongly affected than right-hand neurons by loss of Eph signaling, indicating a previously undetected left-right asymmetry in the requirement for Eph signaling. By screening candidate genes involved in Eph signaling, we find that the Eph kinase-independent pathway involves the ABL-1 nonreceptor tyrosine kinase and possibly the phosphatidylinositol 3-kinase pathway. Overexpression of ABL-1 is sufficient to rescue EFN-1 ventral guidance defects cell autonomously. Our results reveal new aspects of Eph signaling in a single axon guidance decision in vivo.

Sensory cells contain ion channels involved in the organ-specific transduction mechanisms that convert different types of stimuli into electric energy. Here we focus on small-conductance calcium-activated potassium channel 1 (SK1) which plays an important role in all excitable cells acting as feedback regulators in after-hyperpolarization. This study was undertaken to analyze the pattern of expression of SK1 in the zebrafish peripheral nervous system and sensory organs using RT-PRC, Westernblot and immunohistochemistry. Expression of SK1 mRNA was observed at all developmental stages analyzed (from 10 to 100 days post fertilization, dpf), and the antibody used identified a protein with a molecular weight of 70kDa, at 100dpf (regarded to be adult). Cell expressing SK1 in adult animals were neurons of dorsal root and cranial nerve sensory ganglia, sympathetic neurons, sensory cells in neuromasts of the lateral line system and taste buds, crypt olfactory neurons and photoreceptors. Present results report for the first time the expression and the distribution of SK1 in the peripheral nervous system and sensory organs of adult zebrafish, and may contribute to set zebrafish as an interesting experimental model for calcium-activated potassium channels research. Moreover these findings are of potential interest because the potential role of SK as targets for the treatment of neurological diseases and sensory disorders., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Notch signalling is involved in numerous cellular processes during development and throughout adult life. Although ligands and receptors are largely expressed in the whole organism, activation of Notch receptors only takes place in a subset of cells and/or tissues and is accurately regulated in time and space. Previous studies have demonstrated that endocytosis and recycling of both ligands and/or receptors are essential for this regulation. However, the precise endocytic routes, compartments and regulators involved in the spatiotemporal regulation are largely unknown. In order to identify intracellular trafficking regulators of Notch signalling, we have undertaken a tissue-specific dsRNA genetic screen of candidates potentially involved in endocytosis and recycling within the endolysosomal pathway. dsRNA against 418 genes was induced in the Drosophila melanogaster sensory organ lineage in which Notch signalling regulates binary cell fate acquisition. Gain or loss of Notch signalling phenotypes were observed in adult sensory organs for 113 of them. Furthermore, 26 genes were found to regulate the steady state localisation of Notch, Sanpodo, a Notch co-factor, and/or Delta in the pupal lineage. In particular, we identified 20 genes with previously unknown function in D. melanogaster intracellular trafficking. Among them, we identified CG2747 and we show that it regulates the localisation of clathrin adaptor AP-1 complex, a negative regulator of Notch signalling. Together, our results further demonstrate the essential function of intracellular trafficking in regulating Notch-signalling-dependent binary cell fate acquisition and constitute an additional step toward the elucidation of the routes followed by Notch receptor and ligands during signalling.

The sensory pits of the nymphs of the planthopper Issus coleoptratus were investigated using light and electron microscopic techniques. Sensory pits consist of a bowl-shaped depression in the cuticle (25-70 μm in diameter) covered by a transparent cupola of presumably waxy material. Each pit is equipped with a long sensory hair that emerges from the inner wall of the pit and extends horizontally for about two thirds of the pit diameter. The cupola emerges from the rim of the pit opposite to the socket of this hair. Additional small sensory hairs extend into the base of the cupola. While the ultrastructure of these small hairs resembles that of other mechanoreceptive sensory hairs of insects, that of the long hairs shows several peculiarities. Sensory pits are dispersed over the frontal part of the head, the tergites of thoracic and abdominal segments. On the different parts of the exoskeleton, the orientation of long hairs within the pits varies in a systematic fashion with respect to the body axes. Size, location, and orientation of the pits show almost perfect bilateral symmetry. Their number increases with each moult. Comparative data show that the level of structural complexity of these sense organs varies considerably within this group of insects., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

In Drosophila melanogaster, cis-regulatory modules that are activated by the Notch cell-cell signaling pathway all contain two types of transcription factor binding sites: those for the pathway's transducing factor Suppressor of Hairless [Su(H)] and those for one or more tissue- or cell type-specific factors called "local activators." The use of different "Su(H) plus local activator" motif combinations, or codes, is critical to ensure that only the correct subset of the broadly utilized Notch pathway's target genes are activated in each developmental context. However, much less is known about the role of enhancer "architecture"--the number, order, spacing, and orientation of its component transcription factor binding motifs--in determining the module's specificity. Here we investigate the relationship between architecture and function for two Notch-regulated enhancers with spatially distinct activities, each of which includes five high-affinity Su(H) sites. We find that the first, which is active specifically in the socket cells of external sensory organs, is largely resistant to perturbations of its architecture. By contrast, the second enhancer, active in the "non-SOP" cells of the proneural clusters from which neural precursors arise, is sensitive to even simple rearrangements of its transcription factor binding sites, responding with both loss of normal specificity and striking ectopic activity. Thus, diverse cryptic specificities can be inherent in an enhancer's particular combination of transcription factor binding motifs. We propose that for certain types of enhancer, architecture plays an essential role in determining specificity, not only by permitting factor-factor synergies necessary to generate the desired activity, but also by preventing other activator synergies that would otherwise lead to unwanted specificities., Competing Interests: The authors have declared that no competing interests exist.

During development, proneural transcription factors of the basic helix-loop-helix (bHLH) family are required to commit cells to a neural fate. In Drosophila neurogenesis, a key mechanism promoting sense organ precursor (SOP) fate is the synergy between proneural factors and their coactivator Senseless in transcriptional activation of target genes. Here we present evidence that posttranslational modification by SUMO enhances this synergy via an effect on Senseless protein. We show that Senseless is a direct target for SUMO modification and that mutagenesis of a predicted SUMOylation motif in Senseless reduces Senseless/proneural synergy both in vivo and in cell culture. We propose that SUMOylation of Senseless via lysine 509 promotes its synergy with proneural proteins during transcriptional activation and hence regulates an important step in neurogenesis leading to the formation and maturation of the SOPs.

Somatic sexual dimorphisms outside of the nervous system in Drosophila melanogaster are largely controlled by the male- and female-specific Doublesex transcription factors (DSX(M) and DSX(F), respectively). The DSX proteins must act at the right times and places in development to regulate the diverse array of genes that sculpt male and female characteristics across a variety of tissues. To explore how cellular and developmental contexts integrate with doublesex (dsx) gene function, we focused on the sexually dimorphic number of gustatory sense organs (GSOs) in the foreleg. We show that DSX(M) and DSX(F) promote and repress GSO formation, respectively, and that their relative contribution to this dimorphism varies along the proximodistal axis of the foreleg. Our results suggest that the DSX proteins impact specification of the gustatory sensory organ precursors (SOPs). DSX(F) then acts later in the foreleg to regulate gustatory receptor neuron axon guidance. These results suggest that the foreleg provides a unique opportunity for examining the context-dependent functions of DSX.

TRPV4 is a nonselective cation channel that belongs to the vanilloid (V) subfamily of transient receptor potential (TRP) ion channels. While TRP channels have been found to be involved in sensing temperature, light, pressure, and chemical stimuli, TPRV4 is believed to be primarily a mechanosensor although it can also respond to warm temperatures, acidic pH, and several chemical compounds. In zebrafish, the expression of trpv4 has been studied during embryonic development, whereas its pattern of TPRV4 expression during the adult life has not been thoroughly analyzed. In this study, the occurrence of TRPV4 was addressed in the zebrafish sensory organs at the mRNA (RT-PCR) and protein (Westernblot) levels. Once the occurrence of TRPV4 was demonstrated, the TRPV4 positive cells were identified by using immunohistochemistry. TPRV4 was detected in mantle and sensory cells of neuromasts, in a subpopulation of hair sensory cells in the macula and in the cristae ampullaris of the inner ear, in sensory cells in the taste buds, in crypt neurons and ciliated sensory neurons of the olfactory epithelium, and in cells of the retina. These results demonstrate the presence of TRPV4 in all sensory organs of adult zebrafish and are consistent with the multiple physiological functions suspected for TRPV4 in mammals (mechanosensation, hearing, and temperature sensing), but furthermore suggest potential roles in olfaction and vision in zebrafish., (Copyright © 2011 Wiley Periodicals, Inc.)

The patterning of multicellular organisms is robust to environmental, genetic, or stochastic fluctuations. Mathematical modeling is instrumental in identifying mechanisms supporting this robustness. The principle of lateral inhibition, whereby a differentiating cell inhibits its neighbors from adopting the same fate, is frequently used for selecting a single cell out of a cluster of equipotent cells. For example, Sensory Organ Precursors (SOP) in the fruit-fly Drosophila implement lateral inhibition by activating the Notch-Delta pathway. We discuss parameters affecting the rate of errors in this process, and the mechanism (inhibitory cis interaction between Notch and Delta) predicted to reduce this error., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

All vertebrates can produce new neurons postnatally in discrete regions of their nervous system, but only some lower vertebrates (fish and amphibians) can significantly repair several neural structures, including brain, spinal cord, retina, olfactory and auditory-vestibular system, to compensate for neural tissue loss and recover significant functionality. Some regenerative ability, however, is found also in reptiles and birds, and even in mammals. The recognition that neurogenesis indeed occurs in the CNS of all adult vertebrates challenges the view that there is a simple relationship between maintenance of neurogenic regions in the adult CNS and regenerative capability. The aim of this review is to revisit this relationship in the light of recent literature focusing on selected examples of neurogenesis and regeneration, and discuss possible frameworks that may help to elucidate the relationship between adult neurogenesis and regeneration. This could provide useful paradigms for harnessing regeneration in the human CNS., (© 2011 The Author. European Journal of Neuroscience © 2011 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.)

The sensory systems develop in several sequences, with a process specific to each system and with a transnatal continuum. This development is based partly on interactions between the fetus and the newborn and their physical and human environments. These interactions are key drivers of the child development. The adaptation of the newborn's environment is crucial for his survival, his well-being and his development, especially if he is born prematurely. The physical environment of the hospital where immature infants are immersed differs greatly from the uterine environment from which they were extracted prematurely. There are discrepancies between their sensory expectations originating in the antenatal period and the atypical stimuli that newborns encounter in their postnatal nosocomial environment. These assertions are valid for all sensory modalities. Many studies have proven that very preterm infants are highly sensitive to this environment which can affect their physiological and behavioural well being. Moreover, it can alter their perception of important human sensory signals, particularly the ones coming from their mother. The long term impacts of this environment are more difficult to identify due to the multi-sensory nature of these stimuli and the multifactorial origin of the neurological disorders that these children may develop. However, the adaptation of their physical environment is one of the corner stones of specific developmental care programs, like the NIDCAP program that has been shown to be successful to improve their short and medium term outcomes. The architectural design, technical equipment and used health-care products, and the strategies and organizations of care are the main determinants of the physical environment of these children. Recommendations for the hospital environment, integrating a newborn's developmental perspective, have been made available. They should be applied more widely and should be completed. Technological equipment advances are also expected to allow better compliance to them. All these evolutions are completely in accordance with the concept of humane neonatal care., (Copyright © 2011 Elsevier Masson SAS. All rights reserved.)

Background: The conserved Notch signaling pathway regulates cell fate decisions and maintains stem cells in multicellular organisms. Up-regulation of Notch signaling is observed in several types of cancer and is causally involved in proliferation and survival of cancer cells. Thus, it is of great interest to look for anti-Notch reagents for therapeutic purposes. In model animal Drosophila, Notch signaling restricts selection of sensory organ precursors (SOPs) during external sensory (ES) organ development. To look for novel genes that can suppress Notch signaling, we performed a gain-of-function modifier screen to look for genes that enhance the phenotype of ectopic ES organs induced by overexpression of phyllopod, a gene required for SOP specification., Results: From the gain-of-function screen, we discovered that overexpression of polished rice/tarsal-less (pri/tal) increases the numbers of ES organs as well as SOPs. pri/tal is a polycistronic gene that contains four short open reading frames encoding three 11-amino acid and one 32-amino acid peptides. Ectopic expression of the 11 amino-acid peptides recapitulates the pri/tal misexpression phenotype in ectopic ES organ formation. In situ hybridization experiment reveals that pri/tal mRNA is expressed in the SOPs of the chemosensory organs and the stretch-sensing chordotonal organs.In Drosophila wing development, the Notch signaling pathway mediates the formation of the dorsal-ventral (DV) compartmental boundary and the restriction of the vein width from the primordial veins, the proveins. We also found that pri/tal mRNA is expressed in the DV boundary and the longitudinal proveins, and overexpression of Pri/Tal peptides disrupts the DV boundary formation and helps to expand the width of the wing vein. Genetic analyses further show that a Notch loss-of-function allele strongly enhances these two phenotypes. Cut and E(spl)mβ are target genes of the Notch pathway in DV boundary formation and vein specification, respectively. We also found that overexpression of Pri/Tal peptides abolishes Cut expression and co-expression of Pri/Tal peptides with phyl strongly reduces E(spl)mβ expression., Conclusions: We show for the first time that the overexpression of Pri/Tal 11-amino acid peptides disrupts multiple Notch-mediated processes and reduces Notch target gene expression in Drosophila, suggesting that these peptides have novel antagonistic activity to the Notch pathway. Thus, our discovery might provide insights into designing new therapeutic reagents for Notch-related diseases.

Since the discovery of Green Fluorescent Protein (GFP), there has been a revolutionary change in the use of live-cell imaging as a tool for understanding fundamental biological mechanisms. Striking progress has been particularly evident in Drosophila, whose extensive toolkit of mutants and transgenic lines provides a convenient model to study evolutionarily-conserved developmental and cell biological mechanisms. We are interested in understanding the mechanisms that control cell fate specification in the adult peripheral nervous system (PNS) in Drosophila. Bristles that cover the head, thorax, abdomen, legs and wings of the adult fly are individual mechanosensory organs, and have been studied as a model system for understanding mechanisms of Notch-dependent cell fate decisions. Sensory organ precursor (SOP) cells of the microchaetes (or small bristles), are distributed throughout the epithelium of the pupal thorax, and are specified during the first 12 hours after the onset of pupariation. After specification, the SOP cells begin to divide, segregating the cell fate determinant Numb to one daughter cell during mitosis. Numb functions as a cell-autonomous inhibitor of the Notch signaling pathway. Here, we show a method to follow protein dynamics in SOP cell and its progeny within the intact pupal thorax using a combination of tissue-specific Gal4 drivers and GFP-tagged fusion proteins. This technique has the advantage over fixed tissue or cultured explants because it allows us to follow the entire development of an organ from specification of the neural precursor to growth and terminal differentiation of the organ. We can therefore directly correlate changes in cell behavior to changes in terminal differentiation. Moreover, we can combine the live imaging technique with mosaic analysis with a repressible cell marker (MARCM) system to assess the dynamics of tagged proteins in mitotic SOPs under mutant or wildtype conditions. Using this technique, we and others have revealed novel insights into regulation of asymmetric cell division and the control of Notch signaling activation in SOP cells (examples include references 1-6, 7, 8).

Background: In both vertebrates and invertebrates, developing organs and tissues must be precisely patterned. One patterning mechanism is Notch/Delta-mediated lateral inhibition. Through the process of lateral inhibition, Drosophila sensory organ precursors (SOPs) are selected and sensory bristles form into a regular pattern. SOP cell fate is determined by high Delta expression and following expression of neurogenic genes like neuralized. SOP selection is spatially and temporally regulated; however, the dynamic process of precise pattern formation is not clearly understood., Results: In this study, using live-imaging analysis, we show that the appearance of neuralized-positive cells is random in both timing and position. Excess neuralized-positive cells are produced by developmental errors at several steps preceding and accompanying lateral inhibition. About 20% of the neuralized-positive cells show aberrant cell characteristics and high Notch activation, which not only suppress neural differentiation but also induce caspase-dependent cell death. These cells never develop into sensory organs, nor do they disturb bristle patterning., Conclusions: Our study reveals the incidence of developmental errors that produce excess neuralized-positive cells during sensory organ development. Notch activation in neuralized-positive cells determines aberrant cell fate and typically induces caspase-dependent cell death. Apoptosis is utilized as a mechanism to remove cells that start neural differentiation at aberrant positions and timing and to ensure robust spacing pattern formation., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

The adult of the ascidian Ciona intestinalis has cupular organs, i.e., putative hydrodynamic sensors, at the atrial epithelium. The cupular organ consists of support cells and sensory neurons, and it extends a gelatinous matrix, known as a cupula, toward the atrial cavity. These characteristics are shared with sensory hair cells in the vertebrate inner ear and lateral line neuromasts in fish and amphibians, which suggests an evolutionary link between the cupular organ and these vertebrate hydrodynamic sensors. In the present study, we have isolated and investigated two transposon-mediated enhancer detection lines that showed GFP expression in support cells of the cupular organs. Using the enhancer detection lines and neuron marker transgenic lines, we describe the position, morphology, and development of the cupular organs. Cupular organs were found at the atrial epithelium, but not in the branchial epithelium. We found that cupular organs are also present along the dorsal fold and the gonoducts. The cells lining the pre-atrial opening in juveniles are presumably precursor cells of the cupular organ. To our knowledge, the present study is the first precise description of the ascidian cupular organ, providing evidence that may help to resolve discrepancies among previous studies on the organ.

The nuchal organs of annelid Laonice bahusiensis (Spionidae) from northern Europe have been studied using scanning and transmission electron microscopy. L. bahusiensis is the first spionid species in which extensively developed, continuous nuchal organs are described. The nuchal organs of this genus are the longest known among polychaete annelids. They consist of paired double bands extending from the prostomium on a mid-dorsal caruncle for about 24-30 setigers. Their microanatomy corresponds to the general structural plan of nuchal organs: there are ciliated supporting cells and bipolar sensory cells with sensory cilia traversing an olfactory chamber. The organs are overlaid by a secondary paving-stone-like cover and innervated by one pair of longitudinally elongated nuchal nerves. These findings clearly favor the hypothesis that the paired, extensively developed ciliated structures found in some Spionidae are homologous with the prostomial nuchal organs characteristic of polychaete annelids.

Analysis of the retinal defects of a CK2 phosphomimetic variant of E(spl)M8 (M8S(159)D) and the truncated protein M8* encoded by the E(spl)D allele, suggest that the nonphosphorylated CtD "autoinhibits" repression. We have investigated this model by testing for inhibition (in "trans") by the CtD fragment in its nonphosphorylated (M8-CtD) and phosphomimetic (M8SD-CtD) states. In N(+) flies, ectopic M8-CtD compromises lateral inhibition, i.e., elicits supernumerary bristles as with loss of N signaling. This antimorphic activity of M8-CtD strongly rescues the reduced eye and/or bristle loss phenotypes that are elicited by ectopic M8SD or wild type M8. Additionally, the severely reduced eye of N(spl)/Y; E(spl)D/+ flies is also rescued by M8-CtD. Rescue is specific to the time and place, the morphogenetic furrow, where "founding" R8 photoreceptors are specified. In contrast, the phosphomimetic M8SD-CtD that is predicted to be deficient for autoinhibition, exhibits significantly attenuated or negligible activity. These studies provide evidence that autoinhibition by the CtD regulates M8 activity in a phosphorylation-dependent manner.

In many insect species, sex pheromone is processed by specific, enlarged glomeruli in the antennal lobes of males. In the male American cockroach, two closely located glomeruli (A and B) are responsible for processing the major pheromone components (periplanone-A and -B, respectively), and these collectively form the macroglomerular complex. Afferents originating from the dorsal and ventral surfaces of the antenna tend to project to the anterior and posterior regions of the macroglomerular complex via the dorsal and ventral antennal nerves, respectively. This topographic segregation of afferents is seen only in the macroglomerular complex, and not in other glomeruli that process normal environmental odors. Using differential, anterograde dye injection into the two antennal sensory nerves, we show that the macroglomerular complex is not formed by fusion of several glomeruli, as suggested in previous studies, but that the precursors of the A- and B-glomeruli already exist in the first larval instar. The volume of afferents in the macroglomerular complex precursor increases nearly exponentially with molting times, 430-fold from the first instar to the adult. The A- and B-glomeruli both undergo continuous growth during postembryonic development, but peak growth rates occur in different larval stages. The growth rate of the B-glomerulus peaked in the mid-developmental stage then declined, while growth of A-glomerulus was maintained at low level in early- to mid-developmental stages but increased greatly in later stages. These results suggest perception of sex pheromone occurs in early instars, and that PA and PB have distinct roles in different developmental stages.

The caspases comprise a family of cysteine proteases that function in various cellular processes, including apoptosis. However, how the balance is struck between the caspases' role in cell death and their nonapoptotic functions is unclear. To address this issue, we monitored the protein turnover of an endogenous caspase inhibitor, Drosophila IAP1 (DIAP1). DIAP1 is an E3 ubiquitin ligase that promotes the ubiquitination of caspases and thereby prevents caspase activation. For this study, we developed a fluorescent probe to monitor DIAP1 turnover in the external sensory organ precursor (SOP) lineage of living Drosophila. The SOP divides asymmetrically to make the shaft, socket, and sheath cells, and the neuron that comprise each sensory organ. We found that the quantity of DIAP1 changed dramatically depending on the cell type and maturity, and that the temporal regulation of DIAP1 turnover determines whether caspases function nonapoptotically in cellular morphogenesis or cause cell death.

Notch signaling is an evolutionarily conserved pathway essential for many cell fate specification events during metazoan development. We conducted a large-scale transposon-based screen in the developing Drosophila eye to identify genes involved in Notch signaling. We screened 10,447 transposon lines from the Exelixis collection for modifiers of cell fate alterations caused by overexpression of the Notch ligand Delta and identified 170 distinct modifier lines that may affect up to 274 genes. These include genes known to function in Notch signaling, as well as a large group of characterized and uncharacterized genes that have not been implicated in Notch pathway function. We further analyze a gene that we have named Amun and show that it encodes a protein that localizes to the nucleus and contains a putative DNA glycosylase domain. Genetic and molecular analyses of Amun show that altered levels of Amun function interfere with cell fate specification during eye and sensory organ development. Overexpression of Amun decreases expression of the proneural transcription factor Achaete, and sensory organ loss caused by Amun overexpression can be rescued by coexpression of Achaete. Taken together, our data suggest that Amun acts as a transcriptional regulator that can affect cell fate specification by controlling Achaete levels.

This review presents the analysis of the systematized data on human juxtaoral organ (JOO) development, structure and function based on the results of classical and recent morphological studies. JOO morphogenesis is traced, including the appearance of its anlage at the bottom of the primitive mouth, epithelial invagination into the mesenchyme, JOO detachment from the oral epithelium, its innervation, connective tissue capsule formation, and final maturation. The analysis of the results of macroscopical, histological, electron microscopical, histochemical and immunohistochemical studies is presented, suggesting high metabolic and synthetic activity of its epithelium, which expresses several neural markers, and emphasizing a rich innervation of both its epithelial and stromal components. The findings supporting the concepts of JOO secretory and mechanosensory functions, are examined. The data on the differential diagnosis between JOO and tumoral processes are discussed, as well as the pathological changes of JOO itself and their significance for the diagnosis of the diseases.

The peripheral nervous system is required for animals to detect and to relay environmental stimuli to central nervous system for the information processing. In Drosophila, the precise spatial and temporal expression of two proneural genes achaete (ac) and scute (sc), is necessary for development of the sensory organs. Here we present an evidence that the transcription co-repressor, dCtBP acts as a negative regulator of sensory organ prepattern. Loss of dCtBP function mutant exhibits ectopic sensory organs, while overexpression of dCtBP results in a dramatic loss of sensory organs. These phenotypes are correlated with mis-emerging of sensory organ precursors and perturbated expression of proneural transcription activator Ac. Mammalian CtBP-1 was identified via interaction with the consensus motif PXDLSX(K/R) of adenovirus E1A oncoprotein. We demonstrated that dCtBP binds directly to PLDLS motif of Drosophila Friend of GATA-1 protein, U-shaped and sharpens the adult sensory organ development. Moreover, we found that dCtBP mediates multivalent interaction with the GATA transcriptional activator Pannier and acts as a direct co-repressor of the Pannier-mediated activation of proneural genes. We demonstrated that Pannier genetically interacts with dCtBP-interacting protein HDAC1, suggesting that the dCtBP-dependent regulation of Pannier activity could utilize a repressive mechanism involving alteration of local chromatine structure.

One of the central regulators coupling tyrosine phosphorylation with cytoskeletal dynamics is the Abelson interactor (Abi). Its activity regulates WASP-/WAVE mediated F-actin formation and in addition modulates the activity of the Abelson tyrosine kinase (Abl). We have recently shown that the Drosophila Abi is capable of promoting bristle development in a wasp dependent fashion. Here, we report that Drosophila Abi induces sensory organ development by modulating EGFR signaling. Expression of a membrane-tethered activated Abi protein (Abi(Myr)) leads to an increase in MAPK activity. Additionally, suppression of EGFR activity inhibits the induction of extra-sensory organs by Abi(Myr), whereas co-expression of activated Abi(Myr) and EGFR dramatically enhances the neurogenic phenotype. In agreement with this observation Abi is able to associate with the EGFR in a common complex. Furthermore, Abi binds the Abl tyrosine kinase. A block of Abl kinase-activity reduces Abi protein stability and strongly abrogates ectopic sensory organ formation induced by Abi(Myr). Concomitantly, we noted changes in tyrosine phosphorylation supporting previous reports that Abi protein stability is linked to tyrosine phosphorylation mediated by Abl.

The sensilla are sensory organs formed by cuticular and cellular structures specialized in reception of chemical and physical stimuli from the environment and transmission to the insect's central nervous system. In function of the great concentration of sensilla, the antennae are the main organs for interaction between bees and with the environment. This work studied the presence of antennal sensilla in the different phases of pupal development of the stingless bee Melipona quadrifasciata anthidioides by means of scanning electron microscopy and light microscopy. The results showed that antennal sensilla begin their development in the transition of the prepupae to the white-eyed pupae and finish it in the pigmented-body pupae phase. The antennal sensilla were exposed to the environment in the black-eyed pupae when the old cuticle is completely digested, suggesting that only in the final pupal phases can these bees perceive the environmental stimuli., ((c) 2007 Wiley-Liss, Inc.)

The paired antennal lobes (ALs) of the sphinx moth Manduca sexta serve as a well-established model for studying development of the primary integration centers for odor information in the brain. To further reveal the role of neuropeptides during AL development, we have analyzed cellular distribution, developmental time course, and regulation of the neuropeptide M. sexta allatotropin (Mas-AT). On the basis of morphology and appearance during AL formation, seven major types of Mas-AT-immunoreactive (ir) cells could be distinguished. Mas-AT-ir cells are identified as local, projection, and centrifugal neurons, which are either persisting larval or newly added adult-specific neurons. Complementary immunostaining with antisera against two other neuropeptide families (A-type allatostatins, RFamides) revealed colocalization within three of the Mas-AT-ir cell types. On the basis of this neurochemistry, the most prominent type of Mas-AT-ir neurons, the local AT neurons (LATn), could be divided in three subpopulations. The appearance of the Mas-AT-ir cell types occurring during metamorphosis parallels the rising titer of the developmental hormone 20-hydroxyecdysone (20E). Artificially shifting the 20E titer to an earlier developmental time point resulted in the precocious occurrence of Mas-AT immunostaining. This result supports the hypothesis that the pupal rise of 20E is causative for Mas-AT expression during AL development. Comparing localization and developmental time course of Mas-AT and other neuropeptides with the time course of AL formation suggests various functions for these neuropeptides during development, including an involvement in the formation of the olfactory glomeruli.

mKirre is a novel member of the immunoglobulin superfamily, which is abundant in the developing and adult brain. In the present study, we showed mKirre gene expression in mouse sensory organs during development using in situ hybridization and immunohistochemistry. At embryonic day (E) 11.5, E15.5, and E17.5, we first detected signals for mKirre mRNA in the developing cochleae, retinae, and olfactory neuroepithelia, respectively. After birth, strong signals were observed in these sensory organs. In addition, at this stage, we found its expression in trigeminal ganglion neurons and neuronal populations forming sensory pathways in the olfactory bulb, midbrain, and pons. Furthermore, double-immunofluorescence staining revealed that nephrin-immunoreactivity was overlapping to mKirre-expressing cells in the developing sensory organs. These results suggest that mKirre may be involved in the establishment of the pathway from sensory organs to the brain not only in a homophilic manner but also with its heterophilic interaction to nephrin.

Ampullary organs of Acipenser naccarii sturgeons were examined by optical and electronic microscopy (transmission electron microscopy and scanning electron microscopy) from hatching until 1 month later when the juvenile phase is completely established. It was observed that, when A. naccarii begins to feed actively, the ultrastructural characteristics of ampullary organs already correspond to those of adult animals. These organs may, therefore, be functional and, together with taste buds, facilitate food search after exhaustion of yolk sac food reserves. Mature ampullary organs of A. naccarii are formed by an ampulla that communicates with the exterior by means of a short channel. These ampullae correspond to the sensory portion of these receptors and are formed by two cell types: receptor cells and support cells. Receptor cells present a kinocilium on their free surface and establish ribbon synapses with axon nerve endings that arise from the underlying conjunctive tissue. Support cells enclose receptor cells, bear stereocilia and occasional cilia, and are of a secretory nature. The mucus associated with ampullary organs mainly comprises neutral mucopolysaccharides, whereas mucopolysaccharides are usually acid in other fish groups., (Copyright 2007 Wiley-Liss, Inc.)

The Drosophila antenna is a sophisticated structure that functions in both olfaction and audition. Previous studies have identified Homothorax, Extradenticle, and Distal-less, three homeodomain transcription factors, as required for specification of antennal identity. Antennal expression of cut is activated by Homothorax and Extradenticle, and repressed by Distal-less. cut encodes the Drosophila homolog of human CAAT-displacement protein, a cell cycle-regulated homeodomain transcription factor. Cut is required for normal development of external mechanosensory structures and Malphigian tubules (kidney analogs). The role of cut in the Drosophila auditory organ, Johnston's organ, has not been characterized. We have employed the FLP/FRT system to generate cut null clones in developing Johnston's organ. In cut mutants, the scolopidial subunits that constitute Johnston's organ differentiate abnormally and subsequently degenerate. Electrophysiological experiments confirm that adult Drosophila with cut null antennae are deaf. We find that cut acts in parallel to atonal, spalt-major, and spalt-related, which encode other transcription factors required for Johnston's organ differentiation. We speculate that Cut functions in conjunction with these factors to regulate transcription of as yet unidentified targets.

Background: Insects detect a multitude of odors using a broad array of phenotypically distinct olfactory organs referred to as olfactory sensilla. Each sensillum contains one to several sensory neurons and at least three support cells; these cells arise from mitotic activities from one or a small group of defined precursor cells. Sensilla phenotypes are defined by distinct morphologies, and specificities to specific odors; these are the consequence of developmental programs expressed by associated neurons and support cells, and by selection and expression of subpopulations of olfactory genes encoding such proteins as odor receptors, odorant binding proteins, and odor degrading enzymes., Methodology/principal Findings: We are investigating development of the olfactory epithelium of adult M. sexta, identifying events which might establish sensilla phenotypes. In the present study, antennal tissue was examined during the first three days of an 18 day development, a period when sensory mitotic activity was previously reported to occur. Each antenna develops as a cylinder with an outward facing sensory epithelium divided into approximately 80 repeat units or annuli. Mitotic proliferation of sensory cells initiated about 20-24 hrs after pupation (a.p.), in pre-existing zones of high density cells lining the proximal and distal borders of each annulus. These high density zones were observed as early as two hr. a.p., and expanded with mitotic activity to fill the mid-annular regions by about 72 hrs a.p. Mitotic activity initiated at a low rate, increasing dramatically after 40-48 hrs a.p.; this activity was enhanced by ecdysteroids, but did not occur in animals entering pupal diapause (which is also ecdysteroid sensitive)., Conclusions/significance: Sensory proliferation initiates in narrow zones along the proximal and distal borders of each annulus; these zones rapidly expand to fill the mid-annular regions. These zones exist prior to any mitotic activity as regions of high density cells which form either at or prior to pupation. Mitotic sensitivity to ecdysteroids may be a regulatory mechanism coordinating olfactory development with the developmental choice of diapause entry.