Biology subjects

Zinder, O. J.

Publications and source records attributed to Zinder, O. J..

3 recordsLinked to original sources

bioRxiv2026

Direct visualization of MCM helicase activation and replisome coupling in situ

Deciphering the spatial organization of molecular machines that copy the genome remains a fundamental challenge in biology. Essential for eukaryotic DNA replication, Mini-Chromosome Maintenance (MCM2-7) helicases are loaded during G1 as double hexamers (DHs) to license replication origins. Upon activation in S phase, each DH is thought to split into two single hexamers (SHs) that form the active CMG helicases and travel bidirectionally. However, the field has long been divided: biochemical and structural studies define CMG helicases as autonomous, independent motors, while genomic and cellular imaging assays suggest sister replisomes remain physically coupled within replication factories. Here, we use MINFLUX nanoscopy to localize individual MCM complexes down to nanometer precision in situ, directly resolving DHs in human cells and capturing their separation into SHs upon origin firing. We find that the resulting sister replisomes do not diffuse apart: they remain coupled at a characteristic distance of ~40 nm throughout S phase. Depletion experiments identify two distinct contributions to this coupling: local, protein-mediated tethering by the AND1 scaffold, and higher-order spatial confinement dependent on cohesin, which is dispensable for MCM loading in G1 but required to maintain coupling in S phase. By linking the nanometer-scale architecture of the replisome to the genome-wide topology of replication fountains, these findings provide direct spatial evidence that sister forks are coupled during DNA synthesis and define the molecular forces that organize replisomes within their native nuclear context.

cell biology↗

bioRxiv2021

An allelic series of spontaneous mutations in Rorb cause a gait phenotype, retinal abnormalities, and transcriptomic changes relevant to human neurodevelopmental conditions

Rorb encodes the Retinoic Acid Receptor-related orphan receptor beta. Mutations in either of the two transcripts of Rorb cause defects in multiple systems, including abnormal photoreceptor abundance and morphology in the retina and a characteristic "high-stepper" or "duck-like" gait arising from dysfunction of interneurons in the spinal cord. Rorb is also important for cortical development and cell fate specification in mice. Rorb variants segregate with epilepsy and comorbidities such as intellectual disability in numerous clinical cases. Here we describe five mouse strains with spontaneous mutations in Rorb identified by their gait phenotype. These mutations affect different domains and isoforms of Rorb, which correspond to the spectrum of anatomical and physiological phenotypes exhibited by these mice. Gene set analysis in Rorb mutants implicates pathways associated with development and nervous system function, and differential gene expression analysis indicates changes in numerous genes related to epilepsy, bipolar disorder, and autism spectrum disorder (ASD). Many of these genes and their protein products are known to interact during synapse formation and neuronal activity. These findings further illuminate the role of Rorb in nervous system development, provide further evidence for an association between Rorb and several neurological conditions, and describe an allelic series of Rorb mutant mice that will be useful for dissecting thalamocortical afferent (TCA) development, neural cell fate determination, and as animal models exhibiting transcriptomic shifts in neurological conditions such as epilepsy, bipolar disorder, and ASD. {blacksquare}Five mutant mice with a characteristic high-stepper gait phenotype have mutations in Rorb {blacksquare}These allelic series mutations manifest in a spectrum of anatomical and physiological abnormalities {blacksquare}Gene expression data suggest involvement of pathways related to neurodevelopmental disorders

genetics↗

bioRxiv2018

Regulation of KIF1A motility via polyglutamylation of tubulin C-terminal tails

Axonal transport is a highly regulated cellular process responsible for site-specific neuronal cargo delivery. This process is mediated in part by KIF1A, a member of the kinesin-3 family of molecular motors. It is imperative that KIF1As highly efficient, superprocessive motility along microtubules is tightly regulated as misregulation of KIF1A cargo delivery is observed in many neurodegenerative diseases. However, the regulatory mechanisms responsible for KIF1As motility, and subsequent proper spatiotemporal cargo delivery, are largely unknown. One potential regulatory mechanism of KIF1A motility is through the posttranslational modifications (PTMs) of axonal microtubules. These PTMs, often occurring on the C-terminal tails of the microtubule tracks, act as molecular \"traffic signals\" helping to direct kinesin motor cargo delivery. Occurring on neuronal microtubules, C-terminal tail polygutamylation is known to be important for KIF1A cargo transport. KIF1As initial interaction with microtubule C-terminal tails is facilitated by the K-loop, a positively charged surface loop of the KIF1A motor domain. However, the K-loops role in KIF1A motility and response to perturbations in C-terminal tail polyglutamylation is underexplored. Using single-molecule imaging, we present evidence of KIF1As previously unreported pausing behavior on multiple microtubule structures. Further analysis revealed that these pauses link multiple processive segments together, contributing to KIF1As characteristic superprocessive run length. We further demonstrate that KIF1A pausing is mediated by a K-loop/polyglutamylated C-terminal tail interaction and is a regulatory mechanism of KIF1A motility. In summary, we introduce a new mechanism of KIF1A motility regulation, providing further insight into KIF1As role in axonal transport.

biophysics↗