Biology subjects

Wichterle, H.

Publications and source records attributed to Wichterle, H..

13 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↗

bioRxiv2024

Independent control of neurogenesis and dorsoventral patterning by NKX2-2

Human neurogenesis is disproportionately protracted, lasting >10 times longer than in mouse, allowing neural progenitors to undergo more rounds of self-renewing cell divisions and generate larger neuronal populations. In the human spinal cord, expansion of the motor neuron lineage is achieved through a newly evolved progenitor domain called vpMN (ventral motor neuron progenitor) that uniquely extends and expands motor neurogenesis. This behavior of vpMNs is controlled by transcription factor NKX2-2, which in vpMNs is co-expressed with classical motor neuron progenitor (pMN) marker OLIG2. In this study, we sought to determine the molecular basis of NKX2-2-mediated extension and expansion of motor neurogenesis. We found that NKX2-2 represses proneural gene NEUROG2 by two distinct, Notch-independent mechanisms that are respectively apparent in rodent and human spinal progenitors: in rodents (and chick), NKX2-2 represses Olig2 and the motor neuron lineage through its tinman domain, leading to loss of Neurog2 expression. In human vpMNs, however, NKX2-2 represses NEUROG2 but not OLIG2, thereby allowing motor neurogenesis to proceed, albeit in a delayed and protracted manner. Interestingly, we found that ectopic expression of tinman-mutant Nkx2-2 in mouse pMNs phenocopies human vpMNs, repressing Neurog2 but not Olig2, and leading to delayed and protracted motor neurogenesis. Our studies identify a Notch- and tinman-independent mode of Nkx2-2-mediated Neurog2 repression that is observed in human spinal progenitors, but is normally masked in rodents and chicks due to Nkx2-2s tinman-dependent repression of Olig2.

developmental biology↗

bioRxiv2024

Embryonic motor neuron programming factors reactivate immature gene expression and suppress ALS pathologies in postnatal motor neurons

Aging is a major risk factor in amyotrophic lateral sclerosis (ALS) and other adult-onset neurodegenerative disorders. Whereas young neurons are capable of buffering disease-causing stresses, mature neurons lose this ability and degenerate over time. We hypothesized that the resilience of young motor neurons could be restored by re-expression of the embryonic motor neuron selector transcription factors ISL1 and LHX3. We found that viral re-expression of ISL1 and LHX3 reactivates aspects of the youthful gene expression program in mature motor neurons and alleviates key disease-relevant phenotypes in the SOD1G93A mouse model of ALS. Our results suggest that redeployment of lineage-specific neuronal selector transcription factors can be an effective strategy to attenuate age-dependent phenotypes in neurodegenerative disease.

neuroscience↗

bioRxiv2023

A Potent and Selective CDKL5/GSK3 Chemical Probe is Neuroprotective

Despite mediating several essential processes in the brain, including during development, cyclin-dependent kinase-like 5 (CDKL5) remains a poorly characterized human protein kinase. Accordingly, its substrates, functions, and regulatory mechanisms have not been fully described. We realized that availability of a potent and selective small molecule probe targeting CDKL5 could enable illumination of its roles in normal development as well as in diseases where it has become aberrant due to mutation. We prepared analogs of AT-7519, a known inhibitor of several cyclin dependent and cyclin-dependent kinase-like kinases that has been advanced into Phase II clinical trials. We identified analog 2 as a highly potent and cell-active chemical probe for CDKL5/GSK3 (glycogen synthase kinase 3). Evaluation of its kinome-wide selectivity confirmed that analog 2 demonstrates excellent selectivity and only retains GSK3/{beta} affinity. As confirmation that our chemical probe is a high-quality tool to use in directed biological studies, we demonstrated inhibition of downstream CDKL5 and GSK3/{beta} signaling and solved a co-crystal structure of analog 2 bound to CDKL5. A structurally similar analog (4) proved to lack CDKL5 affinity and maintain potent and selective inhibition of GSK3/{beta}. Finally, we used our chemical probe pair (2 and 4) to demonstrate that inhibition of CDKL5 and/or GSK3/{beta} promotes the survival of human motor neurons exposed to endoplasmic reticulum (ER) stress. We have demonstrated a neuroprotective phenotype elicited by our chemical probe pair and exemplified the utility of our compounds to characterize the role of CDKL5/GSK3 in neurons and beyond.

cell biology↗

bioRxiv2022

Altered MAM function shifts mitochondrial metabolism in SOD1-mutant models of ALS

Mitochondrial defects are a common hallmark of familial and sporadic forms of amyotrophic lateral sclerosis (ALS). However, the origin of these defects, including reduced pyruvate metabolism and reduced oxygen consumption, is poorly understood. These metabolic functions are regulated in specialized endoplasmic reticulum (ER) domains in close contact with mitochondria, called mitochondrial-associated ER membranes (MAM). Recently it has been shown that MAM domains are disrupted in ALS, but the connection between MAM dysregulation and mitochondrial defects in ALS cells remains unclear. Using human embryonic stem cell (ESC)-derived motor neurons (hMNs) and mouse models with ALS-pathogenic mutations in superoxide dismutase 1 (SOD1), we found that the glycolytic deficiency in ALS is a direct consequence of the progressive disruption of MAM structure and function that hinders the use of glucose-derived pyruvate as a mitochondrial fuel and triggers a shift in mitochondrial substrates from pyruvate to fatty acids. This glycolytic deficiency, over time, induces significant alterations in mitochondrial electron flow and in the active/dormant (A/D) status of complex I in spinal cord, but not in brain. These data agree with a role for MAM in the maintenance and regulation of cellular glucose metabolism and suggest that MAM disruption in ALS could be the underlying cause of the bioenergetic deficits observed in the disease.

molecular biology↗

bioRxiv2022

Human-specific progenitor sub-domain contributes to extended neurogenesis and increased motor neuron production

Neurogenesis lasts ~10 times longer in developing humans compared to mice, resulting in >1000-fold more neurons in the human central nervous system. Expansion of human neocortex has been in part attributed to the population of outer radial glia and amplifying progenitors that increase the output of neurogenic lineages. However, outer radial glia appear to be absent in many regions of the developing human nervous system, prompting us to search for alternative populations of progenitors that contribute to the expansion of human neurogenesis in one such region - the developing spinal cord. To this end, we performed high-temporal resolution single-cell expression analysis of human and mouse motor neuron progenitors generated from pluripotent stem cells in vitro. Alignment of human and mouse data using canonical correlation analysis identified "human-specific" progenitor clusters characterized by early co-expression of NKX2-2 and OLIG2 that lacked an orthologous murine counterpart. A matching progenitor population has been previously described in the human embryonic spinal cord1, but its function remained unknown. Our lineage tracing analysis demonstrates that these cells function as ventral motor neuron progenitors (vpMNs), but in contrast to classical pMNs, vpMNs exhibit increased Notch activity and generate motor neurons in a delayed and protracted manner. Concomitantly, vpMNs undergo more rounds of cell division before undergoing neurogenesis, leading to ~2-fold increase in total motor neuron output, and contributing preferentially to later-born, limb-innervating motor neuron subtypes. Thus, instead of relying on transit-amplifying progenitors, human spinal cord evolved a novel progenitor subdomain that extends timescales and expands output of human motor neurogenesis.

developmental biology↗

bioRxiv2021

Ranking Reprogramming Factors for Directed Differentiation

Transcription factor over-expression is a proven method for reprogramming cells to a desired cell type for regenerative medicine and therapeutic discovery. However, a general method for the identification of reprogramming factors to create an arbitrary cell type is an open problem. We examine the success rate of methods and data for directed differentiation by testing the ability of nine computational methods (CellNet, GarNet, EBSeq, AME, DREME, HOMER, KMAC, diffTF, and DeepAccess) to correctly discover and rank candidate factors for eight target cell types with known reprogramming solutions. We compare methods that utilize gene expression, biological networks, and chromatin accessibility data to identify eight sets of known reprogramming factors and comprehensively test parameter and pre-processing of input data to optimize performance of these methods. We find the best factor identification methods can identify an average of 50-60% of reprogramming factors within the top 10 candidates, and methods that use chromatin accessibility perform the best. Among the chromatin accessibility methods, complex methods DeepAccess and diffTF are more likely to consistently correctly rank the significance of transcription factor candidates within reprogramming protocols for differentiation. We provide evidence that AME and DeepAccess are optimal methods for transcription factor recovery and ranking which will allow for systematic prioritization of transcription factor candidates to aid in the design of novel reprogramming protocols.

systems biology↗

bioRxiv2021

General and cell-type-specific aspects of the motor neuron maturation transcriptional program

Building a nervous system is a protracted process that starts with the specification of individual neuron types and ends with the formation of mature neural circuits. The molecular mechanisms that regulate the temporal progression of maturation in individual cell types remain poorly understood. In this work, we have mapped the gene expression and chromatin accessibility changes in mouse spinal motor neurons throughout their lifetimes. We found that both motor neuron gene expression and putative regulatory elements are dynamic during the first three weeks of postnatal life, when motor circuits are maturing. Genes that are up-regulated during this time contribute to adult motor neuron diversity and function. Almost all of the chromatin regions that gain accessibility during maturation are motor neuron specific, yet a majority of the transcription factor binding motifs enriched in these regions are shared with other mature neurons. Collectively, these findings suggest that a core transcriptional program operates in a context-dependent manner to access cell-type-specific cis-regulatory systems associated with maturation genes. Discovery of general principles governing neuronal maturation might inform methods for transcriptional reprogramming of neuronal age and for improved modelling of age-related neurodegenerative diseases.

developmental biology↗

bioRxiv2020

Dynamic extrinsic pacing of the HOX clock in human axial progenitors controls motor neuron subtype specification

SUMMARYRostro-caudal patterning of vertebrates depends on the temporally progressive activation of HOX genes within axial stem cells that fuel axial embryo elongation. Whether HOX genes sequential activation, the “HOX clock”, is paced by intrinsic chromatin-based timing mechanisms or by temporal changes in extrinsic cues remains unclear. Here, we studied HOX clock pacing in human pluripotent stem cells differentiating into spinal cord motor neuron subtypes which are progenies of axial progenitors. We show that the progressive activation of caudal HOX genes in axial progenitors is controlled by a dynamic increase in FGF signaling. Blocking FGF pathway stalled induction of HOX genes, while precocious increase in FGF alone, or with GDF11 ligand, accelerated the HOX clock. Cells differentiated under accelerated HOX induction generated appropriate posterior motor neuron subtypes found along the human embryonic spinal cord. The HOX clock is thus dynamically paced by exposure parameters to secreted cues. Its manipulation by extrinsic factors alleviates temporal requirements to provide unprecedented synchronized access to human cells of multiple, defined, rostro-caudal identities for basic and translational applications.View Full Text

developmental biology↗

bioRxiv2020

A bipartite element with allele-specific functions safeguards DNA methylation imprints at the Dlk1-Dio3 locus

Dysregulation of imprinted gene loci also referred to as loss of imprinting (LOI) can result in severe developmental defects and other diseases, but the molecular mechanisms that ensure imprint stability remain incompletely understood. Here, we dissect the functional components of the imprinting control region of the essential Dlk1-Dio3 locus (called IG-DMR) and the mechanism by which they ensure imprinting maintenance. Using pluripotent stem cells carrying an allele-specific reporter system, we demonstrate that the IG-DMR consists of two antagonistic regulatory elements: a paternally methylated CpG-island that prevents the activity of Tet dioxygenases and a maternally unmethylated regulatory element, which serves as a non-canonical enhancer and maintains expression of the maternal Gtl2 lncRNA by precluding de novo DNA methyltransferase function. Targeted genetic or epigenetic editing of these elements leads to LOI with either bi-paternal or bi-maternal expression patterns and respective allelic changes in DNA methylation and 3D chromatin topology of the entire Dlk1-Dio3 locus. Although the targeted repression of either IG-DMR or Gtl2 promoter is sufficient to cause LOI, the stability of LOI phenotype depends on the IG-DMR status, suggesting a functional hierarchy. These findings establish the IG-DMR as a novel type of bipartite control element and provide mechanistic insights into the control of Dlk1-Dio3 imprinting by allele-specific restriction of the DNA (de)methylation machinery. HIGHLIGHTSO_LIThe IG-DMR is a bipartite element with distinct allele-specific functions C_LIO_LIA non-canonical enhancer within the IG-DMR prevents DNA methyltransferase activity C_LIO_LITargeted epigenome editing allows induction of specific imprinting phenotypes C_LIO_LICRISPRi reveals a functional hierarchy between DMRs that dictates imprint stability C_LI

developmental biology↗

bioRxiv2019

Hox binding specificity is directed by DNA sequence preferences and differential abilities to engage inaccessible chromatin.

While Hox genes encode for conserved transcription factors (TFs), they are further divided into anterior, central, and posterior groups based on their DNA-binding domain similarity. The posterior Hox group expanded in the deuterostome clade and patterns caudal and distal structures. We aim to address how similar HOX TFs diverge to induce different positional identities. We studied HOX TF DNA-binding and regulatory activity during an in vitro motor neuron differentiation system that recapitulates embryonic development. We find diversity in the genomic binding profiles of different HOX TFs, even among the posterior group paralogs that share similar DNA binding domains. These differences in genomic binding are explained by differing abilities to bind to previously inaccessible sites. For example, the posterior group HOXC9 has a greater ability to bind occluded sites than the posterior HOXC10, producing different binding patterns and driving differential gene expression programs. From these results, we propose that the differential abilities of posterior HOX TFs to bind to previously inaccessible chromatin drive patterning diversification.

developmental biology↗

bioRxiv2019

Stem cell-derived cranial and spinal motor neurons reveal proteostatic differences between ALS resistant and sensitive motor neurons

In amyotrophic lateral sclerosis (ALS) spinal motor neurons (SpMN) progressively degenerate while a subset of cranial motor neurons (CrMN) are spared until late stages of the disease. Using a rapid and efficient protocol to differentiate mouse embryonic stem cells (ESC) to SpMNs and CrMNs, we now report that ESC-derived CrMNs accumulate less human (h)SOD1 and insoluble p62 than SpMNs over time. ESC-derived CrMNs have higher proteasome activity to degrade misfolded proteins and are intrinsically more resistant to chemically-induced proteostatic stress than SpMNs. Chemical and genetic activation of the proteasome rescues SpMN sensitivity to proteostatic stress. In agreement, the hSOD1 G93A mouse model reveals that ALS-resistant CrMNs accumulate less insoluble hSOD1 and p62-containing inclusions than SpMNs. Primary-derived ALS-resistant CrMNs are also more resistant than SpMNs to proteostatic stress. Thus, an ESC-based platform has identified a superior capacity to maintain a healthy proteome as a possible mechanism to resist ALS-induced neurodegeneration.

neuroscience↗

bioRxiv2018

High resolution discovery of chromatin interactions

Chromatin interaction analysis by paired-end tag sequencing (ChIA-PET) is a method for the genome-wide de novo discovery of chromatin interactions. Existing computational methods typically fail to detect weak or dynamic interactions because they use a peak-calling step that ignores paired-end linkage information. We have developed a novel computational method called Chromatin Interaction Discovery (CID) to overcome this limitation with an unbiased clustering approach for interaction discovery. CID outperforms existing chromatin interaction detection methods with improved sensitivity, replicate consistency, and concordance with other chromatin interaction datasets. In addition, CID also outperforms other methods in discovering chromatin interactions from HiChIP data. We expect that the CID method will be valuable in characterizing 3D chromatin interactions and in understanding the functional consequences of disease-associated distal genetic variations.

bioinformatics↗