Biology subjects

Kaltschmidt, J. A.

Publications and source records attributed to Kaltschmidt, J. A..

16 recordsLinked to original sources

bioRxiv2026

Transmembrane aminopeptidase Q (Taqpep) is a common mechanism in the establishment of periodic patterning in skin and intestine

Periodic patterns are a frequent motif in biology that occurs across diverse tissues and species. In mammals, pigmentation patterns such as zebra stripes or tiger stripes are well-known examples of periodic patterns; more recently, the myenteric plexus (MP) of the enteric nervous system (ENS), which controls gastrointestinal motility, has been found to exhibit a striped organization in humans and laboratory mice. In domestic cats and other felids, the Transmembrane aminopeptidase Q (Taqpep) gene plays a key role in color pattern establishment during skin development, but its patterning role has not been examined in other tissues. Here, we show that, in laboratory mice, Taqpep is required for normal patterning of developing hair follicles and the MP. Using both sequencing and histologic techniques, we found Taqpep is expressed in mesenchymal cells in embryonic skin and intestine directly adjacent to where periodic patterning occurs. We generated Taqpep mutant mice, which exhibit disrupted epidermal patterning akin to the changes in periodic coat patterning observed in Taqpep mutant cats. The intestine of Taqpep mutants has irregularly periodicity of enteric neuronal stripes, and enteric neurons in Taqpep mutants exhibit disrupted Wnt signaling. This work provides new insight into the mechanism of enteric neuronal patterning and identify Taqpep as a common and conserved mediator of periodic patterning across mammalian tissues and organisms. Author summaryPeriodic patterning is a frequent motif in biology. Examples include pigmentation patterning such as tiger stripes and, as recently identified in both mouse and human, the striped organization of enteric neurons in the myenteric plexus of the intestine. In domestic and wild cats, the Transmembrane aminopeptidase Q (Taqpep) gene is essential for the establishment of periodic patterning. Whether this gene plays a conserved role in periodic patterning across other tissues and species has yet to be explored. We found that Taqpep is expressed in mesenchymal cells in embryonic mouse skin and intestine at key locations and developmental stages to instruct periodic patterning. We next generated Taqpep mutant mice that exhibit disrupted periodic patterns in both developing skin follicles and in enteric neuron organization. Thus, Taqpep is essential in establishing periodic patterning in diverse mammals and tissues.

developmental biology↗

bioRxiv2026

Abnormal enteric nervous system organization and gastrointestinal motility in mice with valproic acid-induced neural tube defects

BackgroundNeurogenic bowel is a major cause of morbidity in patients affected by neural tube defects (NTDs) such as spina bifida, but the underlying reasons for bowel dysfunction are unknown. An absolute requirement for gastrointestinal (GI) motility is the enteric nervous system (ENS) located within the walls of the GI tract. Enteric neurons coalesce into circumferential stripes throughout embryonic and early postnatal development, and this gradual organization of the ENS into enteric neuronal stripes correlates with the emergence of neurogenic GI motility. We hypothesized that NTDs are associated with changes in ENS organization that correlate with specific GI motility defects. MethodsWe used prenatal valproic acid (VPA) exposure as a model for NTDs in embryonic mice. We used immunohistochemistry, high resolution confocal imaging, and ex vivo motility assays to assess enteric neuronal stripes and gastrointestinal motility in embryos with a VPA-induced neural tube defect. Key resultsGI tracts from embryos with a VPA-induced NTD contain blood. Structurally, the enteric neuronal stripes are thinner with a narrower interstripe distance, leading to an increased number of stripes. Functionally, GI motility is abnormal, with increased contraction frequency and increased length of contractile segments. Conclusions and inferencesENS organization and GI motility are disrupted in mouse embryos with a VPA-induced NTD. This has important implications for our understanding of neurogenic bowel in central nervous system diseases such as spina bifida. Key Points- VPA exposure is a reliable model of neural tube defects with variable intralitter susceptibility - Embryos with a VPA-induced neural tube defect have blood in the amniotic sac and within the lumen of the gastrointestinal tract - Enteric nervous system organization is abnormal in the duodenum and jejunum of embryos with a VPA-induced neural tube defect, with thinner enteric neuronal stripes and narrower interstripe distance - Ex vivo gastrointestinal motility is abnormal in the duodenum and jejunum of embryos with a VPA-induced neural tube defect, including increased contraction frequency and increased length of the contractile segment

neuroscience↗

bioRxiv2024

Gpr37 modulates the severity of inflammation-induced GI dysmotility by regulating enteric reactive gliosis.

The enteric nervous system (ENS) is contained within two layers of the gut wall and is made up of neurons, immune cells, and enteric glia cells (EGCs) that regulate gastrointestinal (GI) function. EGCs in both inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) change in response to inflammation, referred to as reactive gliosis. Whether EGCs restricted to a specific layer or region within the GI tract alone can influence intestinal immune response is unknown. Using bulk RNA-sequencing and in situ hybridization, we identify G-protein coupled receptor Gpr37, as a gene expressed only in EGCs of the myenteric plexus, one of the two layers of the ENS. We show that Gpr37 contributes to key components of LPS-induced reactive gliosis including activation of NF-kB and IFN-y signaling and response genes, lymphocyte recruitment, and inflammation-induced GI dysmotility. Targeting Gpr37 in EGCs presents a potential avenue for modifying inflammatory processes in the ENS.

neuroscience↗

bioRxiv2024

Enteric glutamatergic interneurons regulate intestinal motility

The enteric nervous system (ENS) controls digestion autonomously via a complex neural network within the gut wall. Enteric neurons expressing glutamate have been identified by transcriptomic studies as a distinct subpopulation, and glutamate can affect intestinal motility by modulating enteric neuron activity. However, the nature of glutamatergic neurons, their position within the ENS circuit, and their function in regulating gut motility are unknown. Here, we identify glutamatergic neurons as longitudinally projecting descending interneurons in the small intestine and colon, in addition to a novel class of circumferential neurons only in the colon. Both populations make synaptic contact with diverse neuronal subtypes, and signal with a variety of neurotransmitters and neuropeptides in addition to glutamate, including acetylcholine and enkephalin. Knocking out the glutamate transporter VGLUT2 from enkephalin neurons profoundly disrupts gastrointestinal transit, while ex vivo optogenetic stimulation of glutamatergic neurons initiates propulsive motility in the colon. This motility effect is reproduced when stimulating only the descending interneuron class, marked by Calb1 expression. Our results posit glutamatergic neurons as key interneurons that regulate intestinal motility.

neuroscience↗

bioRxiv2024

Hypoxia disrupts circadian rhythms in astrocytes and causes synapse engulfment defects

Astrocytes are emerging as key regulators of neuronal synaptic network maturation and function, through control of synaptic pruning. This is important, because individuals with ASD have excess glutamatergic synapses in the cortex, but the biological mechanisms underlying this phenotype remain unclear. Here, we used human cortical organoids (hCO) derived from induced pluripotent stem cells (hiPSCs), to examine the effect of hypoxia on synapse engulfment in human astrocytes at postnatal-equivalent stages of development. We identified that hypoxia significantly inhibits the synaptosome phagocytosis, and that this phenotype is mediated through disruptions in the astrocytic circadian rhythm molecular pathway and subsequent decreased expression of MEGF10. Lastly, we demonstrated that circadian clock disruptions are sufficient to induce these observed phenotypes even in the absence of hypoxia, both in hCOs and within the mouse hippocampus in vivo. Our study uncovers a novel mechanistic link between hypoxia, circadian rhythms disruptions, and synapse pruning by astrocytes, and provides insight into the pathophysiology of ASD, and other neuropsychiatric diseases. Separately, the demonstration of the presence of circadian rhythms in hCOs opens an unprecedented opportunity to dissect the role of circadian clocks in normal brain development and how it contributes to specific diseases of environmental or genetic origin.

neuroscience↗

bioRxiv2024

Gut Analysis Toolbox: Automating quantitative analysis of enteric neurons

The enteric nervous system (ENS) plays an important role in coordinating gut function. The ENS consists of an extensive network of neurons and glial cells within the wall of the gastrointestinal tract. Alterations in neuronal distribution, function, and type are strongly associated with enteric neuropathies and gastrointestinal (GI) dysfunction and can serve as biomarkers for disease. However, current methods for assessing neuronal counts and distribution suffer from undersampling. This is partly due to challenges associated with imaging and analyzing large tissue areas, and operator bias due to manual analysis. Here, we present the Gut Analysis Toolbox (GAT), an image analysis tool designed for characterization of enteric neurons and their neurochemical coding using 2D images of GI wholemount preparations. GAT is developed for the Fiji distribution of ImageJ. It has a user-friendly interface and offers rapid and accurate cell segmentation. Custom deep learning (DL) based cell segmentation models were developed using StarDist. GAT also includes a ganglion segmentation model which was developed using deepImageJ. In addition, GAT allows importing of segmentation generated by other software. DL models have been trained using ZeroCostDL4Mic on diverse datasets sourced from different laboratories. This captures the variability associated with differences in animal species, image acquisition parameters, and sample preparation across research groups. We demonstrate the robustness of the cell segmentation DL models by comparing them against the state-of-the-art cell segmentation software, Cellpose. To quantify neuronal distribution GAT applies proximal neighbor-based spatial analysis. We demonstrate how the proximal neighbor analysis can reveal differences in cellular distribution across gut regions using a published dataset. In summary, GAT provides an easy-to-use toolbox to streamline routine image analysis tasks in ENS research. GAT enhances throughput allowing unbiased analysis of larger tissue areas, multiple neuronal markers and numerous samples rapidly.

neuroscience↗

bioRxiv2023

Spiral NeuroString: High-Density Soft Bioelectronic Fibers for Multimodal Sensing and Stimulation

Bioelectronic fibers hold promise for both research and clinical applications due to their compactness, ease of implantation, and ability to incorporate various functionalities such as sensing and stimulation. However, existing devices suffer from bulkiness, rigidity, limited functionality, and low density of active components. These limitations stem from the difficulty to incorporate many components on one-dimensional (1D) fiber devices due to the incompatibility of conventional microfabrication methods (e.g., photolithography) with curved, thin and long fiber structures. Herein, we introduce a fabrication approach, "spiral transformation'', to convert two-dimensional (2D) films containing microfabricated devices into 1D soft fibers. This approach allows for the creation of high density multimodal soft bioelectronic fibers, termed Spiral NeuroString (S-NeuroString), while enabling precise control over the longitudinal, angular, and radial positioning and distribution of the functional components. We show the utility of S-NeuroString for motility mapping, serotonin sensing, and tissue stimulation within the dynamic and soft gastrointestinal (GI) system, as well as for single-unit recordings in the brain. The described bioelectronic fibers hold great promises for next-generation multifunctional implantable electronics.

bioengineering↗

bioRxiv2023

Spontaneous enteric nervous system activity precedes maturation of gastrointestinal motility

Spontaneous neuronal network activity is essential in development of central and peripheral circuits, yet whether this is a feature of enteric nervous system development has yet to be established. Using ex vivo gastrointestinal (GI) motility assays with unbiased computational analyses, we identify a previously unknown pattern of spontaneous neurogenic GI motility. We further show that this motility is driven by cholinergic signaling, which may inform GI pharmacology for preterm patients.

developmental biology↗

bioRxiv2023

Loss of ASD-Related Molecule Caspr2 Affects Colonic Motility in Mice

Gastrointestinal (GI) symptoms are highly prevalent among individuals with autism spectrum disorder (ASD), but the molecular link between ASD and GI dysfunction remains poorly understood. The enteric nervous system (ENS) is critical for normal GI motility and has been shown to be altered in mouse models of ASD and other neurological disorders. Contactin-associated protein-like 2 (Cntnap2) is an ASD-related synaptic cell-adhesion molecule important for sensory processing. In this study, we examine the role of Cntnap2 in GI motility by characterizing Cntnap2s expression in the ENS and assessing GI function in Cntnap2 mutant mice. We find Cntnap2 expression predominately in enteric sensory neurons. We further assess in-vivo and ex-vivo GI motility in Cntnap2 mutants and show altered transit time and colonic motility patterns. The overall organization of the ENS appears undisturbed. Our results suggest that Cntnap2 plays a role in GI function and may provide a molecular link between ASD and GI dysfunction.

neuroscience↗

bioRxiv2023

Comparison of wholemount dissection methods for neuronal subtype marker expression in the mouse myenteric plexus

BackgroundAccurately reporting the identity and representation of enteric nervous system (ENS) neuronal subtypes along the length of the gastrointestinal (GI) tract is critical to advancing our understanding of ENS control of GI tract function. Reports of varying proportions of subtype marker expression have employed different dissection techniques to achieve wholemount muscularis preparations of myenteric plexus. In this study we asked whether differences in GI dissection methods could introduce variability into the quantification of marker expression. MethodsWe compared three commonly used methods of ENS wholemount dissection: two flat-sheet preparations that differed in the order of microdissection and fixation as well as a rod-mounted peeling technique. We assessed marker expression using immunohistochemistry, genetic reporter lines, confocal microscopy, and automated image analysis. Key Results and ConclusionsWe found no significant differences between the two flat-sheet preparation methods in the expression of calretinin, neuronal nitric oxide synthase (nNOS), or somatostatin (SST) in ileum myenteric plexus. However, the rod-mounted peeling method resulted in decreased marker labeling for both calretinin and nNOS. This method also resulted in decreased transgenic reporter fluorescent protein (tdTomato) for substance P in ileum and choline acetyltransferase (ChAT) in both ileum and distal colon. These results suggest that labeling among some markers, both native protein and transgenic fluorescent reporters, is decreased by the rod-mounted mechanical method of peeling, demonstrating a critical variability in wholemount muscularis dissection methods.

neuroscience↗

bioRxiv2022

Anatomical and functional maturation of the mid-gestation human intestine

Gastrointestinal (GI) maturation is a key determinant of survival for extremely preterm infants. The enteric nervous system (ENS) controls GI motility, and immature GI motility limits enteral feeding and causes severe health complications.1 Due to the significant challenges in obtaining and studying human fetal tissue, little is known about when the human ENS becomes mature enough to carry out vital functions. Here we define the progressive anatomical maturation of the human fetal ENS and analyze GI motility in the second trimester of in utero development. We identify substantial structural changes in the ENS including the emergence of striped neuronal cytoarchitecture and a shift in the representation of excitatory and inhibitory neurons. We further analyze and pharmacologically manipulate GI motility in freshly collected human fetal intestines, which, to our knowledge, is a first functional analysis of intact human fetal organs ex vivo. We find that the ENS influences GI motility beginning at 21 postconceptional weeks (PCW), the earliest reported evidence of neurogenic GI motility. Our study provides unprecedented insight into human fetal ENS development, foundational knowledge which facilitates comparisons with common animal models to advance translational disease investigations and testing of pharmacological agents to enhance GI motility in prematurity.

developmental biology↗

bioRxiv2022

hPSC-Derived Enteric Ganglioids Model Human ENS Development and Function

The enteric nervous system (ENS) plays a central role in gut physiology and mediating the crosstalk between the gastrointestinal (GI) tract and other organs. The human ENS has remained elusive, highlighting the need for an in vitro modeling and mapping blueprint. Here we map out the developmental and functional features of the human ENS, by establishing robust and scalable 2D ENS cultures and 3D enteric ganglioids from human pluripotent stem cells (hPSCs). These models recapitulate the remarkable neuronal and glial diversity found in primary tissue and enable comprehensive molecular analyses that uncover functional and developmental relationships within these lineages. As a salient example of the power of this system, we performed in-depth characterization of enteric nitrergic neurons (NO neurons) which are implicated in a wide range of GI motility disorders. We conducted an unbiased screen and identified drug candidates that modulate the activity of NO neurons and demonstrated their potential in promoting motility in mouse colonic tissue ex vivo. We established a high-throughput strategy to define the developmental programs involved in NO neuron specification and discovered that PDGFR inhibition boosts the induction of NO neurons in enteric ganglioids. Transplantation of these ganglioids in the colon of NO neuron-deficient mice results in extensive tissue engraftment, providing a xenograft model for the study of human ENS in vivo and the development of cell-based therapies for neurodegenerative GI disorders. These studies provide a framework for deciphering fundamental features of the human ENS and designing effective strategies to treat enteric neuropathies.

developmental biology↗

bioRxiv2021

Landscape of human spinal cord cell type diversity at midgestation

Understanding spinal cord generation and assembly is essential to elucidate how motor behavior is controlled and how disorders arise. The cellular landscape of the human spinal cord remains, however, insufficiently explored. Here, we profiled the midgestation human spinal cord with single cell-resolution and discovered, even at this fetal stage, remarkable heterogeneity across and within cell types. Glia displayed diversity related to positional identity along the dorso-ventral and rostro-caudal axes, while astrocytes with specialized transcriptional programs mapped onto distinct histological domains. We discovered a surprisingly early diversification of alpha () and gamma ({gamma}) motor neurons that control and modulate contraction of muscle fibers, which was suggestive of accelerated developmental timing in human spinal cord compared to rodents. Together with mapping of disease-related genes, this transcriptional profile of the developing human spinal cord opens new avenues for interrogating the cellular basis of motor control and related disorders in humans.

neuroscience↗

bioRxiv2021

Transcription Factor Gene Pea3 Regulates Erectile Function in Mice

BackgroundMale mice with homozygous loss of function mutations of the ETS transcription factor gene Pea3 (Pea3 null) are infertile due to their inability to deposit semen plugs, however the specific deficits in male sexual behaviors that drive this phenotype are unknown. AimTo investigate the regulatory role of the Pea3 gene in organizing gross sexual behaviors and erectile functioning during active copulation. MethodsThe copulatory behavior of male mice (Pea3 null and control) with hormonally primed ovariectomized females was monitored via high-speed and high-resolution digital videography to assess for differences in female-directed social behaviors, gross sexual behaviors (mounting, thrusting), and erectile and ejaculatory function. OutcomesPea3 null male mice have dramatically reduced erectile function during sexual intercourse, however other aspects of male sexual behaviors are largely intact. ResultsPea3 null male mice exhibit greatly reduced erectile function, with 44% of males displaying no visible erections during mounting behaviors, and none achieving sustained erections. As such, Pea3 null males are incapable of intromission, and semen plug deposition, despite displaying largely normal female-directed social behaviors, mounting behaviors, and ejaculatory grasping behavior. Additionally, the coordination of the timing of thrusting trains is impaired in Pea3 null males. Clinical ImplicationsThe identification of the transcription factor Pea3 in regulating erectile function in mice may provide a useful target for understanding the genetics of male sexual dysfunction in human patients. Strengths and LimitationsHigh-speed and high-resolution videography allows for a detailed analysis of male sexual behaviors and erectile functioning in Pea3 null and control mice. How disruption of the Pea3 gene translates to erectile dysfunction is still unknown. ConclusionThe transcription factor gene Pea3 regulates the ability to achieve and maintain erections in male mice.

animal behavior and cognition↗

bioRxiv2021

Regional cytoarchitecture of the adult and developing mouse enteric nervous system

The enteric nervous system (ENS) populates the gastrointestinal (GI) tract and controls GI function. In contrast to the central nervous system, macrostructure of the ENS has been largely overlooked. Here, we visually and computationally demonstrate that the ENS is organized in circumferential stripes that regionally differ in development and neuronal composition. This characterization provides a blueprint for future understanding of region-specific GI function and identifying ENS structural correlates of GI disorders.

neuroscience↗

bioRxiv2020

COUNTEN an AI-driven tool for rapid, and objective structural analyses of the Enteric Nervous System

Healthy gastrointestinal functions require a healthy Enteric Nervous System (ENS). ENS health is often defined by the presence of normal ENS structure. However, we currently lack a comprehensive understanding of normal ENS structure as current methodologies of manual enumeration of neurons within tissue and ganglia can only parse limited tissue regions; and are prone to error, subjective bias, and peer-to-peer discordance. Thus, there is a need to craft objective methods and robust tools to capture and quantify enteric neurons over a large area of tissue and within multiple ganglia. Here, we report on the development of an AI-driven tool COUNTEN which parses HuC/D-immunolabeled adult murine myenteric ileal plexus tissues to enumerate and classify enteric neurons into ganglia in a rapid, robust, and objective manner. COUNTEN matches trained humans in identifying, enumerating and clustering myenteric neurons into ganglia but takes a fraction of the time, thus allowing for accurate and rapid analyses of a large tissue region. Using COUNTEN, we parsed thousands of myenteric neurons and clustered them in hundreds of myenteric ganglia to compute metrics that help define the normal structure of the adult murine ileal myenteric plexus. We have made COUNTEN freely and openly available to all researchers, to facilitate reproducible, robust, and objective measures of ENS structure across mouse models, experiments, and institutions.

neuroscience↗