It is demonstrated that SYNGAP1 haploinsufficiency disrupts early human brain development and accelerates intrinsic neuronal maturation, with pathogenic mechanisms emerging before synaptogenesis and extending beyond SYNGAP1’s established synaptic role.
Montanna Waters, Lucas Teasdale, Sean Byars et al.· bioRxiv· 0 citations
Spinocerebellar ataxia type 3 (SCA3) is an inherited, fatal neurodegenerative disease caused by a pathological CAG repeat expansion in the ATXN3 gene, resulting in the selective degeneration of vulnerable neuronal populations. Recent work has identified impairments in oligodendrocyte maturation as a novel and robust feature of SCA3 pathogenesis. Oligodendrocytes synthesize myelin structural components through the endoplasmic reticulum (ER), rendering this organelle essential for white matter integrity. Despite this, the role of ER function in SCA3 remains unclear. In this study, we show that loss of FICD-mediated AMPylation, a post-translational modification regulating the ER-resident HSP70 chaperone, BiP, rescues motor impairments in a transgenic SCA3 mouse model. Ficd-/- SCA3 mice exhibit significantly reduced levels of nuclear ATXN3 in vulnerable brain regions, while Ficd+/+ littermates show an increased burden of AMPylated BiP in the spinal cord, identifying aberrant AMPylation as a novel contributor of SCA3 pathology. Using unbiased proteomics, we demonstrate that Ficd deletion mitigates the pathological decrease in myelin structural proteins and oligodendrocyte maturation factors, restoring levels of mature, myelinating oligodendrocytes. In parallel, we show that Ficd activates SREBP2-dependent cholesterol biosynthesis to support myelination. Taken as a whole, these findings posit ER homeostasis as a critical driver of oligodendrocyte pathology and identify FICD as a novel target for alleviating non-neuronal toxicity in SCA3.
Kate M. Van Pelt, Yamei Deng, Alexey I. Nesvizhskii et al.· bioRxiv· 0 citations
Background: Allan–Herndon–Dudley syndrome (AHDS) is an X-linked neurodevelopmental disorder caused by loss of the thyroid hormone (TH) transporter MCT8, resulting in central TH deprivation and disrupted cortical maturation, cognition, and motor control. MCT8/OATP1C1 double-knockout (dKO) mice faithfully model the human disease, recapitulating its postnatal hypomyelination, neuromotor impairment, and cortical defects. Yet, cell-type–specific pathologies underlying AHDS remain insufficiently defined. Methods: To uncover cellular perturbations by TH deprivation, we performed single-nucleus RNA sequencing on cortex and attached cerebral nuclei from P21 WT and dKO mice. Differential gene expression, trajectory, pseudotime and gene-set enrichment analyses, and NeuronChat-based cell–cell communication modeling were integrated with LC-MS/MS-based TH quantification, immunofluorescence, and RNAscope. Results: In 48 clusters identified across cortical and striatal regions, we found increased numbers of GABAergic striatal D1 and D2 neurons in dKO mice, whereas mature oligodendrocytes were reduced. Trajectory analysis uncovered a bifurcation within the oligodendrocyte lineage, separating WT and dKO maturation paths and producing a dKO branch with gene profiles reminiscent of a stress-responsive, demyelination-prone state, despite largely preserved expression of core myelination genes. Trajectory analyses revealed shifted pseudotime states and distinct gene expression profiles in glutamatergic intratelencephalic and corticothalamic lineages of dKO mice. Differential gene expression patterns showed limited correspondence to Slc16a2 or Slco1c1 transcript levels but aligned strongly with published TH deprivation datasets, validating our findings and indicating that cellular perturbations are largely established by P21. Cell–cell communication analysis revealed a network imbalance favoring GABAergic over glutamatergic signaling, accompanied by altered neurexin–neuroligin interactions. In parallel, we identified a coordinated dysregulation of cilia-related genes, together with changes in cilia length and number. Conclusions: Our findings provide the first single-cell–level cortical map of AHDS brain pathology, revealing cilia defects, excitation–inhibition imbalance, differing pseudotime trajectories in glutamatergic neuronal populations and altered oligodendrocyte maturation, with actionable candidate genes such as Lama2, Litaf, and Dcc, as promising targets for future mechanistic and therapeutic exploration in AHDS. Slc16a2 and Slco1c1 transcript abundance alone did not predict cellular vulnerability, highlighting TH availability rather than transporter expression as key determinant of cell-type sensitivity and core mechanism for cortical network homeostasis. Graphical abstract
Anna Molenaar, Ekta Pathak, Miriam Bernecker et al.· Thyroid· 0 citations
It is shown that neurogenesis is disrupted at multiple stages of lineage progression in both rodent and human neural stem cell models of Huntington's disease, and a panel of clinically relevant epigenetic compounds hold promise for stage-spanning therapeutic strategies capable of modifying disease trajectory.
Jessica Rosati, A. Casamassa, G. Ruotolo et al.· Cell Death and Differentiati...· 0 citations
Limb-girdle muscular dystrophy R2/2B (LGMDR2/2B) is an untreatable and progressive late-onset skeletal muscle disease caused by the loss of a membrane-repair protein dysferlin. Even before disease symptom onset, LGMDR2 muscles are infiltrated by pro-inflammatory macrophages (MP), implicating immune cells in disease pathogenesis. While MPs express dysferlin, defining the cell-autonomous roles of dysferlin in MP function has been challenging in vivo due to complex multicellular interactions and altered microenvironment in LGMDR2 muscle.
To address this, we generated human induced pluripotent stem cell (hiPSC)-derived macrophages (iMPs) from three healthy and three LGMDR2 donors to delineate cell-autonomous roles of dysferlin in macrophage: 1) polarization, 2) transcriptional profile, 3) secretome, and 4) phagocytotic and endocytic function.
Despite exhibiting comparable polarization under well-characterized pro- and anti-inflammatory cues, RNAseq analyses revealed downregulation of Gene Ontology terms related to cytokine secretion, phagocytosis, and receptor-mediated endocytosis in LGMDR2 iMPs. Proteomic analysis of iMP conditioned media revealed significant differences in 72 secreted proteins, including numerous chemokines, cytokines, and growth factors, suggesting an altered secretory phenotype. Functional assays found no significant differences in the phagocytosis of E. coli bioparticles or fluorescent myotube debris. However, receptor-mediated endocytosis of AcLDL was significantly lower in both M0 and M2 LGMDR2 vs. healthy iMPs. Pharmacological screens identified clathrin-dependent endocytosis as the primary pathway for AcLDL uptake in both genotypes, with altered clathrin trafficking and reduced scavenger receptor expression likely underlying LGMDR2 endocytic deficits.
Overall, dysferlin loss in iMPs results in cell-autonomously altered transcriptome, secretome, and endocytic function, which may contribute to LGMDR2 muscle pathology and disease progression.
Jain Foundation grant, NIH grant 1R01AR082979-01, National Science Foundation Graduate Research Fellowship
Immune Mechanisms of Human Disease (HUM)
Amber Detwiler, Rachel Luner, Alex Schneider et al.· Journal of Immunology· 0 citations
Cortical organoids are established as a robust human model of CDM-associated neurodevelopmental defects, uncover MBNL-dependent mechanisms underlying early corticogenesis impairment and demonstrate the utility of this platform for translational therapeutic discovery in DM1.
Azania Abatan, Jérôme Polentes, M. Bouquier et al.· bioRxiv· 0 citations
