Biology subjects

Ghorbani, S.

Publications and source records attributed to Ghorbani, S..

4 recordsLinked to original sources

bioRxiv2025

Cell-type-resolved NRXN1 isoforms across human brain tissues and hiPSC organoids

NRXN1 undergoes extensive alternative splicing that generates a highly diverse repertoire of isoforms, diversifying protein-protein interactions, shaping synaptic specialization, and contributing to neuropsychiatric disease when disrupted. However, the splicing landscape of NRXN1 across distinct human brain cell types remains poorly defined. Because NRXN1 expression level is relatively low in adult brains and human induced pluripotent stem cell (hiPSC) derived neurons, single-cell long-read cDNA sequencing often provides insufficient coverage to capture its full isoform diversity, particularly across heterogeneous cell populations. To address this gap, we developed an integrative sequencing strategy that combines single-cell transcriptomics, targeted enrichment of NRXN1 transcripts, and long-read sequencing. This approach reveals a comprehensive catalog of cell-type resolved NRXN1 isoforms across adult and fetal human postmortem brains as well as hiPSC-derived cortical organoids. From the adult prefrontal cortex (PFC) region, our analyses reveal distinct splicing programs across interneuron subtypes, pyramidal neurons, and glial lineages. Comparisons between prenatal and adult brains indicate that NRXN1 isoform profiles are established during early development and remain stable throughout neuronal maturation. In hiPSC organoid models, splicing profiles partially mirror both developmental and mature brain patterns, with a subset of splice sites exhibiting cell type - and stage-specific divergence. In the cerebellum of an autism case and in organoids derived from schizophrenia patients, carrying non-recurrent heterozygous NRXN1 deletions, we identify disrupted isoform expression and mutant NRXN1 isoforms and characterize their distribution across diverse cell types. Using this integrated long-read sequencing framework in patient-derived organoids, we further show that antisense oligonucleotide (ASO) targeting of mutant splice junctions reduces gain-of-function NRXN1 isoforms and reshapes splicing patterns in a cell type-specific manner, providing a platform for evaluating ASO efficiency. Together, these findings help understand the cell type-specific splicing landscape of NRXN1 and establish a framework for decoding cell type-specific isoform diversity and assessing transcript-targeted therapies for genes with low expression levels.

neuroscience↗

bioRxiv2025

Aging-enhanced accumulation of fibroblasts excludes oligodendrocytes in demyelinated lesions

Fibroblast dysregulation contributes to pathological fibrosis and aberrant repair. Emerging evidence suggest that fibroblasts accumulate in lesions following central nervous system injury, but whether and how they influence oligodendrocyte repair responses, including in aging, is uncertain. Here we report that fibroblasts accumulate in the parenchyma of spinal cord white matter lesions of 6 - 10 week old young mice after lysolecithin-induced demyelination. This was first observed through immunofluorescence microscopy that employed several markers attributed to fibroblasts, including platelet-derived growth factor-{beta}, collagen type 11, -smooth muscle actin, periostin and fibronectin; and by the use of platelet-derived growth factor-{beta} TdTomato reporter transgenic mice. Single-nucleus and spatial transcriptomics of lysolecithin lesions established the presence of fibroblasts in lysolecithin lesions and delineated them from closely related pericytes. CellChat ligand - receptor analyses highlight fibroblasts in the lysolecithin environment as a major source of input of signals for microglia/macrophages and oligodendrocyte precursor cells, with numerous reciprocal interactions. The infiltration of fibroblasts was promoted by microglia/macrophages, as anticipated by their temporal representation in lysolecithin lesions, and by tissue culture experiments where the migration of fibroblasts was enhanced by macrophages. Of particular relevance to spontaneous regenerative events in lysolecithin demyelination, areas of fibroblast accumulation were devoid of oligodendrocyte precursor cells. In tissue culture, oligodendrocyte precursor cells were excluded from fibroblast domains. Moreover, fibroblast accumulation after lysolecithin injury was enhanced with increasing age, a known detriment to the capacity to remyelinate after injury, and exclusion of oligodendrocyte precursor cells from fibroblast areas of 48 - 52 week mice exceeds that occurring in younger 6 - 10 weeks animals. Finally, by mining a publicly available single-nucleus RNA database of multiple sclerosis, we found fibroblasts in the edge of chronic active and chronic inactive lesions and in lesion core, and fewer in periplaque or normal white matter. We identified several communication networks between fibroblasts, microglia/macrophages and oligodendrocyte precursor cells in these MS lesions. Our collective results demonstrate a role of fibroblasts in demyelination-associated neuropathology, which is exacerbated by aging, and highlight the importance of regulating fibroblasts to promote effective CNS repair.

neuroscience↗

bioRxiv2023

Precise Therapeutic Targeting of Distinct NRXN1+/- Mutations

Given the large number of genes significantly associated with risk for neuropsychiatric disorders, a critical unanswered question is the extent to which diverse mutations --sometimes impacting the same gene--will require tailored therapeutic strategies. Here we consider this in the context of rare neuropsychiatric disorder-associated copy number variants (2p16.3) resulting in heterozygous deletions in NRXN1, a pre-synaptic cell adhesion protein that serves as a critical synaptic organizer in the brain. Complex patterns of NRXN1 alternative splicing are fundamental to establishing diverse neurocircuitry, vary between the cell types of the brain, and are differentially impacted by unique (non-recurrent) deletions. We contrast the cell-type-specific impact of patient-specific mutations in NRXN1 using human induced pluripotent stem cells, finding that perturbations in NRXN1 splicing result in divergent cell-type-specific synaptic outcomes. Via distinct loss-of-function (LOF) and gain-of-function (GOF) mechanisms, NRXN1+/- deletions cause decreased synaptic activity in glutamatergic neurons, yet increased synaptic activity in GABAergic neurons. Reciprocal isogenic manipulations causally demonstrate that aberrant splicing drives these changes in synaptic activity. For NRXN1 deletions, and perhaps more broadly, precision medicine will require stratifying patients based on whether their gene mutations act through LOF or GOF mechanisms, in order to achieve individualized restoration of NRXN1 isoform repertoires by increasing wildtype, or ablating mutant isoforms. Given the increasing number of mutations predicted to engender both LOF and GOF mechanisms in brain disorders, our findings add nuance to future considerations of precision medicine.

neuroscience↗

bioRxiv2023

Schizophrenia Risk Mapping and Functional Engineering of the 3D Genome in Three Neuronal Subtypes

Common variants associated with schizophrenia are concentrated in non-coding regulatory sequences, but their precise target genes are context-dependent and impacted by cell-type-specific three-dimensional spatial chromatin organization. Here, we map long-range chromosomal conformations in isogenic human dopaminergic, GABAergic, and glutamatergic neurons to track developmentally programmed shifts in the regulatory activity of schizophrenia risk loci. Massive repressive compartmentalization, concomitant with the emergence of hundreds of neuron-specific multi-valent chromatin architectural stripes, occurs during neuronal differentiation, with genes interconnected to genetic risk loci through these long-range chromatin structures differing in their biological roles from genes more proximal to sequences conferring heritable risk. Chemically induced CRISPR-guided chromosomal loop-engineering for the proximal risk gene SNAP91 and distal risk gene BHLHE22 profoundly alters synaptic development and functional activity. Our findings highlight the large-scale cell-type-specific reorganization of chromosomal conformations at schizophrenia risk loci during neurodevelopment and establish a causal link between risk-associated gene-regulatory loop structures and neuronal function.

genomics↗