Biology subjects

Laube, B.

Publications and source records attributed to Laube, B..

4 recordsLinked to original sources

bioRxiv2025

Chromatin remodelling subunit SMARCB1 is implicated in dendrite development and complex brain functions

SMARCB1 encodes a core component of the BAF chromatin remodelling complex and pathogenic variants in this gene are associated with neurodevelopmental disorders such as Coffin-Siris syndrome. The relationship between altered SMARCB1 protein products and severe functional brain changes in Coffin-Siris syndrome remains largely unknown. We performed cellular, molecular, and behavioural analyses of a Coffin-Siris syndrome mouse model with a heterozygous nervous system-specific Smarcb1 mutation. In addition, we evaluated general cognitive abilities, as well as cognitive and behavioural functioning, in individuals with SMARCB1-related Coffin-Siris syndrome. Smarcb1 mutant mice exhibited deficits in fine motor coordination and balance, as well as impaired spatial learning and memory. Furthermore, these mice showed anxiety-like behaviours and agitation when exposed to novel environments. The detected behavioural abnormalities could indicate impaired decision-making, which results in impaired risk assessment. Comparable cognitive and behavioural deviations were identified in individuals with Coffin-Siris syndrome and SMARCB1 pathogenic variants. Our analysis of the Smarcb1 mouse model revealed structural alterations in the brain, including decreased dendritic length and complexity of dendritic trees. These alterations may explain the observed functional impairments. Notably, our finding of reduced Wasl transcripts in mutant Purkinje cell nuclei suggests that dysregulation of actin polymerization may be involved in the discovered dendritic defects. Taken together, we demonstrate a link between the chromatin remodelling complex component SMARCB1, complex brain functions, neuronal structure, and a key regulator of actin branching.

neuroscience↗

bioRxiv2025

Chromatin organization controls nuclear stiffness

Cellular differentiation is driven by epigenetic modifiers and readers, including the methyl CpG binding protein 2 (MeCP2), whose level and mutations cause the neurological disorder Rett syndrome. During differentiation, most of the genome gets densely packed into heterochromatin, whose function has been simplistically viewed as gene silencing. However, gene expression changes reported in mutations leading to Rett syndrome have failed to be a predictor of disease severity. Here, we show that MeCP2 increases nuclear stiffness in a concentration dependent manner and dependent on its ability to cluster heterochromatin during differentiation. MeCP2-dependent stiffness increase could not be explained by changes in the expression of mechanobiology-related genes, but we found it is disrupted by Rett syndrome mutations and correlated with disease severity. Our results highlight the impact of chromatin organization in the mechanical properties of the cell as an alternative or complementary mechanism to changes in cytoskeleton components. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=103 SRC="FIGDIR/small/643219v2_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@cb077dorg.highwire.dtl.DTLVardef@158c0c6org.highwire.dtl.DTLVardef@1d830e3org.highwire.dtl.DTLVardef@719456_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2021

Analysis of M4 transmembrane domains in NMDA receptor function: a negative allosteric modulation site at the GluN1 M4 is determining the efficiency of neurosteroid modulation

Ionotropic glutamate receptors (iGluRs) are tetrameric ligand-gated ion channels that play a crucial role in excitatory synaptic transmission in the central nervous system. Each subunit contributes with three transmembrane domains (M1, M3, and M4) and a pore loop (M2) forming the channel pore. Recent studies suggest that the architecture of all eukaryotic iGluRs derives from a common prokaryotic ancestral receptor that lacks M4 and consists only of the transmembrane domain segments M1-M3. Although a crucial contribution of M4 to the assembly and trafficking of iGluRs is suspected, the role of this additionally evolved domain in receptor function remains controversial. Here, we investigated how deletions and mutations of M4 in members of the NMDA receptor subfamily, the conventional heteromeric GluN1/GluN2 and glycine-gated GluN1/GluN3 NMDA receptors, affect expression and function in Xenopus oocytes. We show that deletion of M4 in the GluN1, GluN2, or GluN3 subunit, despite retained receptor assembly and cell surface expression, results in nonfunctional membrane receptors. Coexpression of the corresponding M4 domains as an isolated peptide in M4-deleted receptors rescued receptor function of GluN1/GluN2A NMDARs without altering the affinity of glutamate or glycine. Substitution of non-conserved residues and insertion of interhelical disulfide bridges confirmed the proximity of positions M813 and F817 in M4 of GluN1 to residues of the TMs of neighboring subunits. Electrophysiological analyses of agonist-induced receptor function and its modulation by the neurosteroid pregnenolone sulfate (PS) at mutations of the GluN1-M4/GluN2/3-TM interface indicate a crucial role of interdomain interactions in the functional coupling of M4 to the nuclear receptor and the modulatory effect of PS. Our results show that although the M4 domains in NMDA receptors are not important for receptor assembly and surface expression, residues at the subunit interface are substantially involved in M4 recognition to the core receptor and regulation of PS efficacy. Because mutations in the M4 of GluN1 specifically resulted in loss of PS-induced inhibition of NMDA receptor currents, our results point to distinct roles of M4s in NMDA receptor modulation and highlight the importance of evolutionarily newly evolved M4s for selective in vivo modulation of glutamate- and glycine-activated NMDA receptors by steroids. Highlights- The role of the M4 transmembrane domain in the assembly and function of ionotropic glutamate receptors remains controversial - Here we show that deletion of M4 in glutamate-gated GluN1/GluN2A and glycine-gated GluN1/GluN3A receptors results in nonfunctional NMDA receptors with retained surface expression - The functional loss in M4-deleted GluN1/GluN2A receptors is rescued without affecting agonist affinity by a M4 transmembrane domain of the respective subunit expressed as an isolated peptide - Specific interactions in the M4 interfaces with the M1 and M3 domain of the adjacent subunit are required for the recognition of the isolated M4 and the functional rescue - Finally, the M4 domain-interfaces of GluN1 determine the negative modulatory effect of pregnenolone sulfate in glutamate-gated GluN1/GluN2A and glycine-gated GluN1/GluN3A NMDA receptors

neuroscience↗

bioRxiv2021

Gating the channel pore of ionotropic glutamate receptors with bacterialsubstrate binding proteins

Tetrameric ionotropic glutamate receptors (iGluRs) mediate excitatory neurotransmission in the mammalian central nervous system and are involved in learning, memory formation, and pathological processes. Based on structural and sequence similarities of the ligand-binding and channel domains of iGluR subunits to bacterial binding proteins and potassium channels, iGluRs are thought to have originally arisen from their fusion. Here we report the functional coupling of the bacterial ectoine binding protein EhuB to the channel pore-forming transmembrane domains of the bacterial GluR0 receptor by stabilization of dimeric binding domains. Insertion of a disulfide bridge in the dimer interface abolished desensitization of the channel current analogous to mammalian iGluRs. These results demonstrate the functional compatibility of bacterial binding proteins to the gate of the channel pore of an iGluR. Moreover, our results highlight the modular structure and crucial role of binding domain dimerization in the functional evolution of iGluRs.

neuroscience↗