Distinct Branching Patterns Research Articles

Exposure to structurally unique β‐d‐glucans differentially affects inflammatory responses in male mouse lungs

AbstractPro‐inflammatory fungal β‐d‐glucan (BDG) polysaccharides cause respiratory pathology. However, specific immunological effects of unique BDG structures on pulmonary inflammation are understudied. We characterized the effect of four unique fungal BDGs with unique branching patterns, solubility, and molecular weights in murine airways. Scleroglucan (1 → 3)(1 → 6)‐highly branched BDG, laminarin (1 → 3)(1 → 6)‐branched BDG, curdlan (1 → 3)‐linear BDG, and pustulan (1 → 6)‐linear BDG were assessed by nuclear magnetic resonance spectroscopy. Each BDG was tested by inhalation model with C3HeB/FeJ mice and compared to saline‐exposed control mice and unexposed sentinels (n = 3–19). Studies were performed ±heat‐inactivation (1 h autoclave) to increase BDG solubility. Outcomes included bronchoalveolar lavage (BAL) differential cell counts (macrophages, neutrophils, lymphocytes, eosinophils), cytokines, serum IgE, and IgG2a (multiplex and ELISA). Ex vivo primary cells removed from lungs and plated at monolayer were stimulated (BDG, lipopolysaccharide (LPS), anti‐CD3), and cytokines compared to unstimulated cells. Right lung histology was performed. Inhalation of BDGs with distinct branching patterns exhibited varying inflammatory potency and immunogenicity. Lichen‐derived (1 → 6)‐linear pustulan was the most pro‐inflammatory BDG, increasing inflammatory infiltrate (BAL), serum IgE and IgG2a, and cytokine production. Primed lung cells responded to secondary LPS stimulation with a T‐cell‐specific response to pustulan. Glucan source and solubility should be considered in exposure and toxicological studies.

Membrane-Targeted palGFP Predominantly Localizes to the Plasma Membrane but not to Neurosecretory Vesicle Membranes in Rat Oxytocin Neurons.

Recent advances in viral vector technology, specifically using adeno-associated virus (AAV) vectors, have significantly expanded possibilities in neuronal tracing. We have utilized the Cre/loxP system in combination with AAV techniques in rats to explore the subcellular localization of palmitoylation signal-tagged GFP (palGFP) in oxytocin-producing neurosecretory neurons. A distinctive branching pattern of single axons was observed at the level of the terminals in the posterior pituitary. Despite challenges in detecting palGFP signals by fluorescent microscopy, immunoelectron microscopy demonstrated predominant localization on the plasma membrane, with a minor presence on the neurosecretory vesicle membrane. These findings suggest that membrane-anchored palGFP may undergo exocytosis, translocating from the plasma membrane to the neurosecretory vesicle membrane. In this study, we observed characteristic axon terminal structures in the posterior pituitary of oxytocin neurons. This study indicates the importance of understanding the plasma membrane-specific sorting system in neuronal membrane migration and encourages future studies on the underlying mechanisms.

3D anatomy of the supraorbital and greater occipital nerve trajectories.

This research aims to enhance understanding of the anatomy of the supraorbital nerve (SON) and greater occipital nerve (GON), focusing on their exit points, distal trajectories, and variability, utilizing a novel 3D representation. Ten cadaveric specimens underwent meticulous dissection, and 3D landmarks were registered. Models were generated from CT scans, and a custom 3D method was employed to visualize nerve trajectories. Measurements, including lengths and distances, were obtained for the SON and GON. The SON exhibited varied exit points, with the lateral branches being the longest. The GON showed distinct branching patterns, which are described relative to various anatomical reference points and planes. No systematic left-right differences were observed for either nerve. 3D analysis revealed significant interindividual variability in nerve trajectories. The closest approximation between the SON and GON occurred between lateral branches. The study introduces a novel 3D methodology for analyzing the SON and GON, highlighting considerable anatomical variation. Understanding this variability is crucial for clinical applications and tools targeting the skull innervation. The findings serve as a valuable reference for future research, emphasizing the necessity for personalized approaches in innervation-related interventions.

A mouse DRG genetic toolkit reveals morphological and physiological diversity of somatosensory neuron subtypes

Dorsal root ganglia (DRG) somatosensory neurons detect mechanical, thermal, and chemical stimuli acting on the body. Achieving a holistic view of how different DRG neuron subtypes relay neural signals from the periphery to the CNS has been challenging with existing tools. Here, we develop and curate a mouse genetic toolkit that allows for interrogating the properties and functions of distinct cutaneous targeting DRG neuron subtypes. These tools have enabled a broad morphological analysis, which revealed distinct cutaneous axon arborization areas and branching patterns of the transcriptionally distinct DRG neuron subtypes. Moreover, invivo physiological analysis revealed that each subtype has a distinct threshold and range of responses to mechanical and/or thermal stimuli. These findings support a model in which morphologically and physiologically distinct cutaneous DRG sensory neuron subtypes tile mechanical and thermal stimulus space to collectively encode a wide range of natural stimuli.

Branching Patterns and Variations of Facial Artery and Clinical Importance: A Cadaveric Study

Introduction: The facial artery (FA) was observed with distinctive variations and anomalous, which occur during the embryological developmental process due to the ablation of neural crest cells that impact embryonic aortic arch vessels, resulting in distinctive branching patterns. Therefore, this study aimed to investigate the types, clinical importance, localization, and differences of FA in fixed cadavers according to gender and body side. Methods: The current study was conducted on 19 formalin-fixed cadavers (68.4% males, n = 13; 31.6% females, n = 6). The types, variations, prevalence, and distance to nearby surgical landmarks of FA were recorded on both sides. Measurements were taken with a surgical microscope (Zeiss Meditec, Berlin, Germany) and a digital caliper (INCA, DCLA-0605, 0.6–150 mm). Results: Angular type % 73.1 (n = 14, right; n = 19, left), labial type % 5.3 (n = 1, right), alar type % 5.3 (n = 1, right), and nasal type % 5.3 (n = 1, right) were detected. The following parameters were significant according to gender; the distance between the ala of the nose and the origin of the FA on both sides (p = 0.007 right; p = 0.018 left), the diameter of FA at the cheilion (p = 0.019 left), diameters of the superior and inferior labial arteries at their origin (p = 0.031 right; p = 0.025 right) and PO lines. Conclusion: The significant differences in gender according to the distance of the FA and its branches from the origin should be considered to reduce complications during surgery. The differences in studies according to the types and variations of FA may be due to the scale of the study, gender, or study design.

Morphometric Analysis of Rat Prostate Development: Roles of MEK/ERK and Rho Signaling Pathways in Prostatic Morphogenesis.

The molecular mechanisms underlying prostate development can provide clues for prostate cancer research. It has been demonstrated that MEK/ERK signaling downstream of androgen-targeted FGF10 signaling directly induces prostatic branching during development, while Rho/Rho-kinase can regulate prostate cell proliferation. MEK/ERK and Rho/Rho kinase regulate myosin light chain kinase (MLCK), and MLCK regulates myosin light chain phosphorylation (MLC-P), which is critical for cell fate, including cell proliferation, differentiation, and apoptosis. However, the roles and crosstalk of the MEK/ERK and Rho/Rho kinase signaling pathways in prostatic morphogenesis have not been examined. In the present study, we used numerical and image analysis to characterize lobe-specific rat prostatic branching during postnatal organ culture and investigated the roles of FGF10-MEK/ERK and Rho/Rho kinase signaling pathways in prostatic morphogenesis. Prostates exhibited distinctive lobe-specific growth and branching patterns in the ventral (VP) and lateral (LP) lobes, while exogenous FGF10 treatment shifted LP branching towards a VP branching pattern. Treatment with inhibitors of MEK1/2, Rho, Rho kinase, or MLCK significantly inhibited VP growth and blocked branching morphogenesis, further supporting critical roles for MEK/ERK and Rho/Rho kinase signaling pathways in prostatic growth and branching during development. We propose that MLCK-regulated MLC-P may be a central downstream target of both signaling pathways in regulating prostate morphogenesis.

Mapping a Danger Zone of the Dorsal Nerve of the Clitoris: Implications in Female Cosmetic Genital Surgery.

The literature regarding the route of the dorsal nerve of the clitoris is sparse and lacks surgical focus. With an increasing number of procedures being performed on the labia, it is important to elucidate the route and note any variation from normal of the nerve. Fifty-one cadavers were dissected to yield 97 dorsal nerve of the clitoris samples. Measurements were taken from (1) the dorsal nerve of the clitoris penetration point of the perineal membrane to the urethra, (2) the nerve's penetration point of the perineal membrane to the pubic bone, (3) the angle of the clitoris to the branch point of the dorsal nerve of the clitoris, and (4) the branch point of the nerve to the distalmost point of the glans clitoris. Any anomalous branching patterns of the dorsal nerve of the clitoris were recorded and classified. The means and standard deviations of each measurement were used to create a surgical danger zone. The mean of each measurement was (1) 34.63 mm, (2) 5.74 mm, (3) -3.07 mm, and (4) 30.40 mm, respectively. In addition, six distinct branching patterns were observed, organized, and classified based on the location and number of branches observed. The dorsal nerve of the clitoris has multiple branching patterns and typically travels along the same course in most women. Further investigation of the course and three-dimensional position of the dorsal nerve of the clitoris is warranted to preserve sexual sensation as the frequency of procedures involving the female pudendum increases.

Anatomical feasibility of peripheral nerve transfer to reestablish external anal sphincter control - cadaveric study.

Motor deficits affecting anal sphincter control can severely impair quality of life. Peripheral nerve transfer has been proposed as an option to reestablish anal sphincter motor function. We assessed, in human cadavers, the anatomical feasibility of nerve transfer from a motor branch of the tibialis portion of the sciatic nerve to two distinct points on pudendal nerve (PN), through transgluteal access, as a potential approach to reestablish anal sphincter function. We dissected 24 formalinized specimens of the gluteal region and posterior proximal third of the thigh. We characterized the motor fascicle (donor nerve) from the sciatic nerve to the long head of the biceps femoris muscle and the PN (recipient nerve), and measured nerve lengths required for direct coaptation from the donor nerve to the recipient in both the gluteal region (proximal) and perineal cavity (distal). We identified three anatomical variations of the donor nerve as well as three distinct branching patterns of the recipient nerve from the piriformis muscle to the pudendal canal region. Donor nerve lengths (proximal and distal) were satisfactory for direct coaptation in all cases. Transfer of a motor fascicle of the sciatic nerve to the PN is anatomically feasible without nerve grafts. Donor nerve length was sufficient and donor nerve functionally compatible (motor). Anatomical variations in the PN could also be accommodated.

Glycomic analysis of antibody indicates distinctive glycosylation profile in patients with autoimmune cholangitis

Glycosylation of antibodies, particularly in the Fc domain, critically modulate the ability of antibodies to bind to FcRs, maintaining immune quiescence to achieve a finely orchestrated immune response. The removal of sialic acid and galactose residues dramatically alters the physiological function of IgGs, and alterations of Ig glycosylation have been associated with several autoimmune disorders. However, Ig glycosylation has not been extensively studied in autoimmune cholangitis. We applied triple quadruple mass spectroscopy with subsequent multiple reaction monitoring to elucidate the profile, composition and linkage of sugar residues of antibody glycans in patients with primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC) and healthy controls (HC). Agalactosylated, HexNAc terminated IgG1 glycoforms were enriched in both PBC and PSC. Levels of IgM glycans at site N439 and fucosylated glycans in J chain, were significantly decreased in PBC compared to PSC and HC. PSC patients had decreased bisecting glycoforms and increased biantennary glycoforms on IgA compared to PBC. Importantly, our data demonstrate the association of distinct branching and composition patterns of Ig glycoforms with disease severity and liver cirrhosis, which highlight the importance of glycan biology as a potential mechanism and/or a disease specific signal of inflammation.

ANALYSIS OF THE NORMAL PERIPHERAL RETINAL VASCULAR PATTERN AND ITS CORRELATION WITH MICROVASCULAR ABNORMALITIES USING ULTRA-WIDEFIELD FLUORESCEIN ANGIOGRAPHY.

To describe the retinal peripheral vascular morphology and to elucidate its relationship to microvascular abnormalities in normal fundus using ultra-widefield fluorescein angiography. A total of 242 eyes from 167 consecutive patients were categorized into 3 groups: bilateral normal (n = 64), normal with contralateral eye affected with vascular disease (n = 82), and early diabetic eyes (n = 96). Peripheral vascular morphology was described and classified according to the shape. Microvascular abnormalities such as capillary telangiectasia, microaneurysm, or vascular leakage were documented, and the relationship between those abnormalities in each groups were analyzed. There were two distinctive peripheral vascular morphologies-loop and branching patterns. Microvascular abnormalities were more frequently found as loop patterns; this difference was most prominent when both eyes were normal. In case of normal eyes with contralateral eye affected with vascular disease or diabetic eyes, branching pattern microvascular abnormalities were relatively increased, whereas loop pattern still showed a large degree of microvascular abnormalities. In normal retinal periphery, we observed microvascular abnormalities and their relationship with vascular morphology, which could be influenced by the condition of the contralateral eye or systemic disease such as diabetes mellitus.

Eugenia veraguensis (Myrtaceae), a new species from Golfo de Chiriquí in Veraguas Province, Panama, with notes on Eugenia rhombea

Eugenia veraguensis is described as a new species of Myrtaceae from Panama. It differs from E. rhombea, the most similar taxon, by a combination of its shrubby habit, a distinctive dichotomous branching pattern with 4 to 6 leaved branchlets, chartaceous or subcoriaceous leaves and its small number of stamens. It occurs in coastal forest and scrub on islands off Pacific Western Panama. Following the inclusion of a specimen of E. veraguensis as E. rhombea in Flora Mesoamericana, we discuss the occurrence of this latter species in Panama.

RPANDA: an R package for macroevolutionary analyses on phylogenetic trees

Summary A number of approaches for studying macroevolution using phylogenetic trees have been developed in the last few years. Here, we present RPANDA, an R package that implements model‐free and model‐based phylogenetic comparative methods for macroevolutionary analyses. The model‐free approaches implemented in RPANDA are recently developed approaches stemming from graph theory that allow summarizing the information contained in phylogenetic trees, computing distances between trees, and clustering them accordingly. They also allow identifying distinct branching patterns within single trees. RPANDA also implements likelihood‐based models for fitting various diversification models to phylogenetic trees. It includes birth–death models with i) constant, ii) time‐dependent and iii) environmental‐dependent speciation and extinction rates. It also includes models with equilibrium diversity derived from the coalescent process, as well as a likelihood‐based inference framework to fit the individual‐based model of Speciation by Genetic Differentiation, which is an extension of Hubbell's neutral theory of biodiversity. RPANDA can be used to (i) characterize trees by plotting their spectral density profiles (ii) compare trees and cluster them according to their similarities, (iii) identify and plot distinct branching patterns within trees, (iv) compare the fit of alternative diversification models to phylogenetic trees, (v) estimate rates of speciation and extinction, (vi) estimate and plot how these rates have varied with time and environmental variables and (vii) deduce and plot estimates of species richness through geological time. RPANDA provides investigators with a set of tools for exploring patterns in phylogenetic trees and fitting various models to these trees, thereby contributing to the ongoing development of phylogenetics in the life sciences.

The intersection of the extrinsic hedgehog and WNT/wingless signals with the intrinsic Hox code underpins branching pattern and tube shape diversity in the drosophila airways.

The tubular networks of the Drosophila respiratory system and our vasculature show distinct branching patterns and tube shapes in different body regions. These local variations are crucial for organ function and organismal fitness. Organotypic patterns and tube geometries in branched networks are typically controlled by variations of extrinsic signaling but the impact of intrinsic factors on branch patterns and shapes is not well explored. Here, we show that the intersection of extrinsic hedgehog(hh) and WNT/wingless (wg) signaling with the tube-intrinsic Hox code of distinct segments specifies the tube pattern and shape of the Drosophila airways. In the cephalic part of the airways, hh signaling induces expression of the transcription factor (TF) knirps (kni) in the anterior dorsal trunk (DTa1). kni represses the expression of another TF spalt major (salm), making DTa1 a narrow and long tube. In DTa branches of more posterior metameres, Bithorax Complex (BX-C) Hox genes autonomously divert hh signaling from inducing kni, thereby allowing DTa branches to develop as salm-dependent thick and short tubes. Moreover, the differential expression of BX-C genes is partly responsible for the anterior-to-posterior gradual increase of the DT tube diameter through regulating the expression level of Salm, a transcriptional target of WNT/wg signaling. Thus, our results highlight how tube intrinsic differential competence can diversify tube morphology without changing availabilities of extrinsic factors.

Rabbit hepatic arterial anatomy variations: implications on experimental design

The VX2 rabbit model of liver cancer is commonly used to evaluate the efficacy of locoregional anticancer therapy and knowledge of the hepatic arterial anatomy in the rabbit is important for catheter-directed experiments. To describe the normal anatomy and anatomic variations of the celiac axis and hepatic artery in the rabbit. Angiograms of 222 rabbits were retrospectively reviewed. The branching pattern of the celiac axis was classified and the diameters of the major branches were measured. Paired t-tests were used to compare the difference between the average sizes of arteries. Variant celiac axis or hepatic artery anatomy was noted in 25.9% of angiograms, with the gastric branches arising from the proper hepatic artery in 23.3% of cases. The celiac axis could be successfully classified into one of five distinct branching patterns in 193 (86.9%) cases. The mean diameters of the right and left hepatic arteries were 0.67 mm (95% CI [0.64, 0.7]) and 1.25 mm (95% CI [1.19, 1.31]), respectively. The mean diameters of the medial and lateral branches of the left hepatic artery were 0.63 mm (95% CI [0.6, 0.67]) and 0.91 mm (95% CI [0.86, 0.96]), respectively. The right hepatic artery was significantly smaller than the left hepatic artery and the lateral branch of the left hepatic artery (all P values <0.0001). Arterial variants in the rabbit are not uncommon. The proper hepatic artery often gives origin to gastric artery branches. To facilitate superselective intra-arterial intervention, the left lateral lobe of the liver should be targeted for tumor implantation because of the significant size difference between the right and left hepatic arteries.

Bifid median nerve variations: A cadaveric study

Bifid median nerve (BMN) is an anatomical variation that occurs when the main median nerve trunk splits into medial and lateral trunks prior to entering the hand within the carpal tunnel (CT). The classification of BMN can be further divided into subcategories, which are based on associated abnormalities and location of branching. In this study, the upper extremities of twenty‐nine cadaveric specimens were examined for the presence of BMN in the flexor forearm and hand regions (14 females, 15 males). Of the 58 upper extremities examined, 6 exhibited BMN patterns (10.3%; 4 female, 2 male), with both trunks traveling within the CT into the hand. Two distinct bifid branching patterns were also observed: (B1) mid‐forearm, proximal to carpal tunnel (n=2 females) and (B2) wrist level, within CT (n=2 females, 2 males). In both B1 cases, the smaller medial trunk pierced the flexor digitorum superficialis muscle, traveled within the CT with the larger lateral trunk, and gave off communicating branches to both the lateral trunk and superficial branch of the ulnar nerve after entering the left hand. Incidence of BMN was found to be higher in female cadavers (67%), and in left upper extremities (67%). Knowledge of variable median nerve branching patterns, especially as it is associated with the CT, is important for diagnostic and surgical interventions.Grant Funding Source: n/a

Complex Branching Patterns in a Newly Recognized Species of Compsocradus Berry et Stein (Iridopteridales) from the Middle Devonian of North Xinjiang, China

Specimens, including the largest known axes, of an iridopteridalean plant of late Middle Devonian age are described from northern Xinjiang, China. The plant consists of three orders branching and dichotomous appendages. The first-order axis probably represents the stem. Lateral organs (lower-order branches and appendages) are attached along the primary axis in up to 10 ranks. The insertion pattern can be broken down into cycles in which one lateral is inserted in each rank, and each cycle is divided into two loose whorls; in one loose whorl, laterals occur in about half of the ranks, some adjacent, and in the other loose whorl, laterals occur in the other ranks. These ranks are believed to map the position of xylem ribs of the vascular system, which has not been preserved. The appendages are isodichotomously divided up to five times. Pairs of recurved sporangia terminate the fertile appendages. A collection of small axes (second and third order) of this plant from the same locality, lacking the distinctive branching patterns displayed in our first order axes, was recently given the name Ramophyton givetianum by D. M. Wang. Our enlarged concept of the plant includes several morphological similarities to Compsocradus laevigatus Berry et Stein from Venezuela, particularly relating to the branching pattern. The Xinjiang plant is therefore reassigned to Compsocradus givetianus (Wang DM) Fu, Wang Y, Berry et Xu comb. nov. It further increases knowledge of branching patterns amongst Iridopteridales, important for evaluating relationships to other plant groups.

Variability of the lateral femoral cutaneous nerve: An anatomic basis for planning safe surgical approaches

Current surgical assumptions identify the lateral femoral cutaneous nerve (LFCN) running just under the inguinal ligament two fingerbreadths medial to the anterior superior iliac spine (ASIS). On the basis of the increasing incidence of Meralgia Paresthetica associated with various surgical procedures, it is clear that surgeons are relying on an inadequate description of the nerve's course. This study provides a better understanding of the variability of the LFCN with regards to its relationship to the ASIS and the depth at which it passes deep to the inguinal ligament. A total of 35 bodies were examined yielding 65 sets of data. Dissections were performed on 26 formalin fixed cadavers and 9 fresh morgue specimens. Measurements and calculations were made with regard to the distance from the LFCN to the ASIS along the inguinal ligament, the depth of the LFCN as it crossed the inguinal ligament, and the length of the inguinal ligament. The LFCN was observed to cross the inguinal ligament 1.4 +/- 0.4 cm medial to the ASIS with a standard deviation of 1.5 cm. The LFCN traversed the inguinal ligament 1.0 +/- 0.1 cm deep to the ligament with a standard deviation of 0.6 cm. The LFCN runs approximately one fingerbreadth medial to the ASIS. The nerve may be found far more medial or lateral than expected with several distinct branching patterns. In addition, the LFCN crosses deeper to the inguinal ligament than previously described in the literature, with a high variability of depth between specimens.

Pyloric Neuron Morphology in the Stomatogastric Ganglion of the Lobster, Panulirus interruptus

The pyloric network of decapod crustaceans has been intensively studied electrophysiologically in the infraorders Astacidea, Brachyura, and Palinura. The morphology of some or all pyloric neurons has been well described in Astacidea and Brachyura, but less so in Palinura. Given the large evolutionary distance between these three groups, and the large amount of electrophysiology that has been performed in palinuroid species, it is important to fill this gap. We describe here the gross morphology of all six pyloric neuron types in a palinuroid, P. interruptus. All pyloric neurons had complicated, extended dendritic trees that filled the majority of the neuropil, with most small diameter processes present in a shell near the surface of the ganglion. Certain neuron types showed modest preferences for somata location in the ganglion, but these differences were too weak to use as identifying characteristics. Quantitative measurements of secondary branch number, maximum branch order, total process length, and neuron somata diameter were also, in general, insufficient to distinguish among the neurons, although AB and LP neuron somata diameters differed from those of the other types. One neuron type (VD) had a distinctive neurite branching pattern consisting of a small initial branch followed shortly by a bifurcation of the main neurite. The processes arising from these two branches occupied largely non-overlapping neuropil. Electrophysiological recordings showed that each major branch had its own spike initiation zone and that, although the zones fired correlated spikes, they generated spikes independently. VD neurons in the other infraorders have similar morphologies, suggesting that having two arbors is important for the function of this neuron. These data are similar to those previously obtained in Brachyura and Astacidea. It thus appears that, despite their long evolutionary separation, neuron morphology in these three infraorders has not greatly diverged.

Spatial Regulation of nanos Is Required for Its Function in Dendrite Morphogenesis

Spatial control of mRNA translation can generate cellular asymmetries and functional specialization of polarized cells like neurons. A requirement for the translational repressor Nanos (Nos) in the Drosophila larval peripheral nervous system (PNS) implicates translational control in dendrite morphogenesis [1]. Nos was first identified by its requirement in the posterior of the early embryo for abdomen formation [2]. Nos synthesis is targeted to the posterior pole of the oocyte and early embryo through translational repression of unlocalized nos mRNA coupled with translational activation of nos mRNA localized at the posterior pole [3, 4]. Abolishment of nos localization prevents abdominal development, whereas translational derepression of unlocalized nos mRNA suppresses head/thorax development, emphasizing the importance of spatial regulation of nos mRNA [3, 5]. Loss and overexpression of Nos affect dendrite branching complexity in class IV dendritic arborization (da) neurons, suggesting that nos also might be regulated in these larval sensory neurons [1]. Here, we show that localization and translational control of nos mRNA are essential for da neuron morphogenesis. RNA-protein interactions that regulate nos translation in the oocyte and early embryo also regulate nos in the PNS. Live imaging of nos mRNA shows that the cis-acting signal responsible for posterior localization in the oocyte/embryo mediates localization to the processes of class IV da neurons but suggests a different transport mechanism. Targeting of nos mRNA to the processes of da neurons may reflect a local requirement for Nos protein in dendritic translational control.

Intrinsic Control of Precise Dendritic Targeting by an Ensemble of Transcription Factors

Proper information processing in neural circuits requires establishment of specific connections between pre- and postsynaptic neurons. Targeting specificity of neurons is instructed by cell-surface receptors on the growth cones of axons and dendrites, which confer responses to external guidance cues. Expression of cell-surface receptors is in turn regulated by neuron-intrinsic transcriptional programs. In the Drosophila olfactory system, each projection neuron (PN) achieves precise dendritic targeting to one of 50 glomeruli in the antennal lobe. PN dendritic targeting is specified by lineage and birth order , and their initial targeting occurs prior to contact with axons of their presynaptic partners, olfactory receptor neurons. We search for transcription factors (TFs) that control PN-intrinsic mechanisms of dendritic targeting. We previously identified two POU-domain TFs, acj6 and drifter, as essential players. After testing 13 additional candidates, we identified four TFs (LIM-homeodomain TFs islet and lim1, the homeodomain TF cut, and the zinc-finger TF squeeze) and the LIM cofactor Chip that are required for PN dendritic targeting. These results begin to provide insights into the global strategy of how an ensemble of TFs regulates wiring specificity of a large number of neurons constituting a neural circuit.