Biology subjects

Au, E.

Publications and source records attributed to Au, E..

8 recordsLinked to original sources

bioRxiv2025

A neuron type-specific microexon in Ank3/ankyrin-G modulates calcium activity and neuronal excitability

Recent studies have revealed many alternative exons differentially spliced across diverse neuron types in the mammalian brain, but their links to neuronal physiology remain unclear. Here we characterize a deeply conserved microexon E35a in Ank3 encoding ankyrin-G (AnkG), a multifaceted adaptor protein best known as a master organizer of the axon initial segment (AIS) and as a leading genetic risk factor for bipolar disorder. E35a is predominantly skipped in cortical glutamatergic neurons but included in cortical GABAergic neurons and cerebellar neurons, which is dictated by multiple neuronal splicing factors. In E35a-deletion mice we generated, interneurons show increased excitability and somatic Ca2+ activity, without disruption in AIS. Biochemical analyses suggest that E35a inclusion facilitates AnkG interaction with a protein complex involving inositol trisphosphate receptors (InsP3Rs) important for intracellular Ca2+ signaling. Alternative splicing therefore allows AnkG to modulate neuron type-specific excitability in addition to its ubiquitous pan-neuronal role in organizing the AIS.

neuroscience↗

bioRxiv2025

Hepatic Yap1 activates systemic catabolism and muscle loss during organ repair: evidence for a liver-derived common mechanism with cancer cachexia.

Recovery from critical injury concomitant with restoration of functional organ mass invokes a systemic catabolic response leading to muscle and fat loss, known as cachexia. We interrogated this process using mouse models of organ repair, including liver regeneration after hepatectomy, Yap1-mediated hepatomegaly, and pneumonectomy. Both hepatectomy and Yap1 induced systemic catabolism. Muscle and adipose wasting scaled with degree of liver growth, with 10-25% reduction of muscle mass and 50-80% of fat mass. In contrast, non-regenerative lung injury did not induce tissue wasting. Liver growth elevated resting energy expenditure. Tracer studies demonstrated redistribution of muscle-derived cholesterol and amino acids to regenerating liver. Gene expression changes in livers and muscles showed high concordance between the liver growth models and cancer cachexia models, including pancreatic adenocarcinoma cachexia. We propose that cachexia is a normal and essential reparative process in organ repair and regeneration and further, that cancer cachexia is a pathological exacerbation of an adaptive process mediated by activation of Yap1 in the liver.

physiology↗

bioRxiv2024

Reverse engineering neuron type-specific and type-orthogonal splicing-regulatory networks using single-cell transcriptomes

Cell type-specific alternative splicing (AS) enables differential gene isoform expression between diverse neuron types with distinct identities and functions. Current studies linking individual RNA-binding proteins (RBPs) to AS in a few neuron types underscore the need for holistic modeling. Here, we use network reverse engineering to derive a map of the neuron type-specific AS regulatory landscape from 133 mouse neocortical cell types defined by single-cell transcriptomes. This approach reliably inferred the regulons of 350 RBPs and their cell type-specific activities. Our analysis revealed driving factors delineating neuronal identities, among which we validated Elavl2 as a key RBP for MGE-specific splicing in GABAergic interneurons using an in vitro ESC differentiation system. We also identified a module of exons and candidate regulators specific for long- and short-projection neurons across multiple neuronal classes. This study provides a resource for elucidating splicing regulatory programs that drive neuronal molecular diversity, including those that do not align with gene expression-based classifications.

systems biology↗

bioRxiv2024

Multidimensional analysis of cortical interneuron synaptic features reveals underlying synaptic heterogeneity

Cortical interneurons represent a diverse set of neuronal subtypes characterized in part by their striking degree of synaptic specificity. However, little is known about the extent of synaptic diversity because of the lack of unbiased methods to extract synaptic features among interneuron subtypes. Here, we develop an approach to aggregate image features from fluorescent confocal images of interneuron synapses and their post-synaptic targets, in order to characterize the heterogeneity of synapses at fine scale. We started by training a model that recognizes pre- and post-synaptic compartments and then determines the target of each genetically-identified interneuron synapse in vitro and in vivo. Our model extracts hundreds of spatial and intensity features from each analyzed synapse, constructing a multidimensional data set, consisting of millions of synapses, which allowed us to perform an unsupervised analysis on this dataset, uncovering novel synaptic subgroups. The subgroups were spatially distributed in a highly structured manner that revealed the local underlying topology of the postsynaptic environment. Dendrite-targeting subgroups were clustered onto subdomains of the dendrite along the proximal to distal axis. Soma-targeting subgroups were enriched onto different postsynaptic cell types. We also find that the two main subclasses of interneurons, basket cells and somatostatin interneurons, utilize distinct strategies to enact inhibitory coverage. Thus, our analysis of multidimensional synaptic features establishes a conceptual framework for studying interneuron synaptic diversity.

neuroscience↗

bioRxiv2022

Patterns of gene expression and allele-specific expression vary among macular tissues and clinical stages of Age-related Macular Degeneration

Age-related macular degeneration (AMD) is a complex neurodegenerative disease and is the leading cause of blindness in the aging population. Early AMD is characterized by drusen in the macula and causes minimal changes in visual function. The later stages are responsible for the majority of visual impairment and blindness and can be either manifest as geographic atrophy (dry) or neovascular disease (wet). Available medicines are directed against the wet form and do not cure vision loss. Therefore, it is imperative to identify preventive and therapeutic targets. As the mechanism for AMD is unclear, we aim to interrogate the disease-affected tissue - the macular neural retina and macular retina pigment epithelium (RPE)/choroid. We investigated differentially expressed genes expression (DEG) across the clinical stages of AMD in meticulously dissected and phenotyped eyes using a standardized published protocol (Owen et al., 2019). Donor eyes (n=27) were obtained from Caucasian individuals with an age range of 60-94 and 63% were male, and tissue from the macula RPE/choroid and macula neural retina were taken from the same eye. Donor eyes were recovered within 6 hours post mortem interval time to ensure maximal preservation of RNA quality and accuracy of diagnosis. Eyes were then phenotyped by retina experts using multi modal imaging (fundus photos and SD-OCT). Utilizing DESeq2, followed PCA, Benjamini Hochberg adjustment to control for the false discovery rate, and Bonferonni correction for the number of paired comparisons: a total of 26,650 genes were expressed in the macula RPE/choroid and/or macula retina among which significant differential expression was found for 1,204 genes between neovascular AMD and normal eyes, 40 genes between intermediate AMD and normal eyes, and 1,194 genes between intermediate AMD and neovascular AMD. A comparison of intermediate AMD versus normal eyes included TCN2, PON1, IFI6, GPR123, and TIMD4 as being some of the most significant DEGs in the macula RPE/choroid. A comparison of neovascular AMD versus normal eyes included SLC1A2, SLC24A1, SCAMP5, PTPRN, and SEMA7A as being some of the most significant DEGs in the macula RPE/choroid. Top pathways of DEGs in the macular RPE/choroid identified through Ingenuity Pathway Analysis (IPA) for the comparison of intermediate AMD with normal eyes were interferon signaling and Th1 and Th2 activation, while those for the comparison of neovascular AMD with normal eyes were the phototransduction and SNARE signaling pathways. Allele-specific expression (ASE) in coding regions of previously reported AMD risk loci identified by GWAS (Fritsche et al, 2016) revealed significant ASEs for C3 rs2230199 and CFH rs1061170 in the macula RPE/choroid for normal eyes and intermediate AMD, and for CFH rs1061147 in the macula RPE/choroid for normal eyes and intermediate and neovascular AMD. An investigation of the 34 established AMD risk loci revealed that 75% of them were significantly differentially expressed between normal macular RPE/choroid and macular neural retina, with 75% of these loci showing higher expression in the RPE. Similarly, disease state differences for the GWAS loci were only found to be statistically differentially expressed in the macular RPE/choroid. Moreover, the known coding variants in the previously identified GWAS loci including, CFH, C3, CFB, demonstrated ASE across AMD clinical stages in the macular RPE/choroid and not in the neural retina. These data at the bulk level underscore the importance of the RPE/choroid to AMD pathophysiology. While many bulk RNASeq data sets are publicly available, to the best of our knowledge this is one of the first publicly available datasets with both maculae RPE/choroid and macula neural retina from the same well phenotyped donor eye(s) where the macula is separated from the periphery. Our findings also underscore the importance of studying both macular tissue types to gain a full understanding of mechanisms leading to AMD. Our results provide insights into underlying biological mechanisms that may differentiate the disease subtypes and into the tissues affected by the disease.

genomics↗

bioRxiv2021

St18 specifies globus pallidus projection neuron identity in MGE lineage

The medial ganglionic eminence (MGE) is a progenitor domain in the subpallium that produces both locally-projecting interneurons which undergo tangential migration in structures such as the cortex as well as long-range projection neurons that occupy subcortical nuclei. Very little is known about the transcriptional mechanisms specifying the migratory behavior and axonal projection patterns of these two broad classes of MGE-derived neurons. In this study, we identify St18 as a novel transcriptional determinant specifying projection neuron fate in the MGE lineage. St18 is transiently expressed in the MGE subventricular zone (SVZ) and mantle, and we assessed its function using an ES cell-based model of MGE development. Induction of St18 is sufficient to direct ES-derived MGE neurons to adopt a projection neuron-like identity as defined by migration and morphology. Using genetic loss-of-function in mice, we find that St18 is required for the production of globus pallidus pars externa (GPe) prototypic projection neurons. Single cell RNA sequencing revealed that St18 regulates MGE output of specific neuronal populations: in the absence of St18, we observe a large expansion of cortical interneurons at the expense of putative GPe neurons. Through gene expression analysis we identified a downstream effector of St18, Cbx7, which is a component of Polycomb repressor complex 1. We find that Cbx7 is essential for projection neuron-like migration and is not involved in St18-mediated projection neuron-like morphology. Our results characterize a novel transcriptional determinant that directs GPe prototypic projection neuron identity. Further, we identified a downstream target of St18, Cbx7, which regulates only the migratory behavior of long-range projection neurons, suggesting that specific features of MGE projection neuron identity may be governed in a compartmentalized fashion by distinct transcriptional modules downstream of St18.

developmental biology↗

bioRxiv2020

Loss of clustered protocadherin diversity alters the spatial distribution of cortical interneurons

Cortical interneurons (cINs) are locally-projecting inhibitory neurons that are distributed throughout the cortex. Due to their relatively limited range of influence, their arrangement in the cortex is critical to their function. cINs achieve this arrangement through a process of tangential and radial migration, and apoptosis during development. In this study, we investigated the role of clustered protocadherins (cPcdhs) in establishing the spatial patterning of cINs. cPcdhs are expressed in cINs, and are known to play key functions in cell spacing and cell survival, but their role in cINs is poorly understood. Using spatial statistical analysis, we found that the two main subclasses of cINs, parvalbumin-expressing (PV) and somatostatin-expressing (SST) cINs, are non-randomly spaced within subclass, but randomly with respect to each other. We also found that the relative laminar distribution of each subclass was distinctly altered in whole - or {beta}-cluster mutants. Examination of perinatal timepoints revealed that the mutant phenotypes emerged relatively late, suggesting that cPcdhs may be acting during cIN morphological elaboration and synaptogenesis. We then analyzed an isoform-specific knockout for pcdh-c2 and found that it recapitulated the -cluster knockout, but only in SST cells, suggesting that subtype-specific expression of cPcdh isoforms may help govern subtype-specific spatial distribution.

neuroscience↗

bioRxiv2020

Vascular-Derived SPARC and SerpinE1 Regulate Interneuron Tangential Migration and Accelerate Functional Maturation of Human Stem Cell-Derived Interneurons

Cortical interneurons establish inhibitory microcircuits throughout the neocortex and their dysfunction has been implicated in epilepsy and neuropsychiatric diseases. Developmentally, interneurons migrate from a distal progenitor domain in order to populate the neocortex - a process that occurs at a slower rate in humans than in mice. In this study, we sought to identify factors that regulate the rate of interneuron maturation across the two species. Using embryonic mouse development as a model system, we found that the process of initiating interneuron migration is regulated by blood vessels of the medial ganglionic eminence (MGE), an interneuron progenitor domain. We identified two endothelial cell-derived paracrine factors, SPARC and SerpinE1, that enhance interneuron migration in mouse MGE explants and organotypic cultures. Moreover, pre-treatment of human stem cell-derived interneurons (hSC-interneurons) with SPARC and SerpinE1 prior to transplantation into neonatal mouse cortex enhanced their migration and morphological elaboration in the host cortex. Further, SPARC and SerpinE1-treated hSC-interneurons also exhibited more mature electrophysiological characteristics compared to controls. Overall, our studies suggest a critical role for CNS vasculature in regulating interneuron developmental maturation in both mice and humans.

neuroscience↗