Biology subjects

Ng, B. H.

Publications and source records attributed to Ng, B. H..

7 recordsLinked to original sources

bioRxiv2026

Dual curvature sensing governs cell orientation and curvotaxis

Cells lying in a curved environment can respond to the surface curvature by reorienting their shape. However, whether cells respond to the mean curvature and/or the Gaussian curvature remains largely unexplored. Here, inspired by experimental observations of how ovarian theca cells (TCs) orient themselves on substrates with different curvatures, we propose a theoretical framework for active nematic layers on curved surfaces. In this model, we assume that the nematic directors of the cells respond to both the mean curvature and the Gaussian curvature of the underlying substrate surface. Our theory predicts specific cell orientation patterns on hemicylindrical, hourglass- and dome-like substrates, consistent with experimental observations. In addition, by incorporating a curvotaxis traction, our model successfully recapitulates the experimental observation of TC accumulation at convex regions of hemicylindrical substrates as well as saddle-shaped regions of more complex geometries. Overall, our work reveals the unexpected role of cell curvature sensing in driving collective migration and pattern formation on various substrate curvatures. SIGNIFICANCESubstrate surface curvature is a critical environmental cue that can influence multicellular organization and functions. Yet how cells collectively align and migrate on complex curved surfaces remains unclear. Here, we proposed a hydrodynamic theory of active nematic layers over curved surfaces for contractile theca cells (TCs), where we assume that the nematic directors of cells can respond to both the mean curvature and the Gaussian curvature of the underlying substrates. Our theory predicts distinct cell orientation patterns on hemicylindrical, hourglass- and dome-like substrates, consistent with experimental observations. Furthermore, by introducing curvotaxis traction, our model recapitulates experimentally observed accumulation of TCs at the convex regions of hemicylindrical substrates as well as saddle-shaped regions of more complex geometries. Together, our study provides a simple theoretical framework to unify our understanding of curvature sensing across complex topology, providing insights into geometric control of tissue pattern formation.

biophysics↗

bioRxiv2026

Theca cell mechanosensing and regulation of follicular extracellular matrix during ovarian follicle development

Mammalian folliculogenesis is essential for female hormonal regulation and successful reproduction. While the steroidogenic functions of theca cells (TCs) have been implicated in ovarian diseases and infertility, the physico-structural properties of TCs and their associated extracellular matrix (ECM), or theca matrix, remain poorly understood. Using murine ovaries, we show that a stiff basement membrane (BM) and theca matrix constitute a mechanically instructive niche that modulates TC proliferation and Yes-associated protein (YAP) signalling in secondary follicles. We identify hyaluronic acid (HA) as a key matrix component that is actively secreted by contractile TCs. The HA scaffold, in turn, regulates TC proliferation, YAP signalling and motility, and is required for overall follicle growth. We showed that stiffer substrates enhance YAP nuclear transport in TCs, while mechanical stretch, cell packing, and curvature affect TC proliferation. In addition, TCs exhibit directed migration towards regions of positive curvature. Together, this study reveals a mechanochemical feedback mechanism that establishes TC mechanics and HA as key regulators of theca matrix formation that is essential for mammalian folliculogenesis. SIGNIFICANCEThe structural properties and mechanical functions of the basement membrane and theca cell-matrix encapsulating mammalian ovarian follicles are poorly understood. Our findings reveal that during early stage of follicle development, the basement membrane remains thin and stiff, while the theca cells actively secrete hyaluronic acid in a contractility-dependent manner. The hyaluronic acid scaffold, in turn, regulates theca cell YAP signalling, proliferation and motility that are required for functional growth of follicles. We further showed that the theca cells are mechanosensitive and fine-tune their proliferative capacity and Hippo pathways in response to substrate stiffness, stretch and curvature. Together, our study uncovers mechanoregulatory feedback between theca cells and associated extracellular matrix, offering new insights into environmental control of folliculogenesis in female reproduction.

developmental biology↗

bioRxiv2025

Critical phenomenon underlies de novo luminogenesis during mammalian follicle development

A key process during mammalian folliculogenesis is the formation of a fluid-filled antrum around the oocyte. While it is known that the antrum is critical for oocyte maturation and the eventual ovulation, the detailed process underlying de novo luminogenesis remains poorly understood. In this study, we investigated the spatiotemporal dynamics of lumen growth and the cellular mechanism driving this process, using advanced microscopy, molecular perturbations and computational modelling. We found that in secondary follicles, the interstitial gaps exist in a near-critical regime, characterised by a highly dynamic and interconnected fluid network with gap size obeying a power-law distribution. Above a critical size of 180 m, we observed an onset of cell death and the emergence of a stably growing dominant fluid cavity resembling phase separation. By modelling the granulosa cells and the interstitial fluid as a binary fluid, we reproduced the near-critical and phase-separated regimes and found that a spatial gradient of cell-fluid interfacial tension, as observed experimentally, is sufficient to robustly maintain the secondary follicles in a near-critical state. Reducing cell-fluid interfacial tension globally by weakening the cell-cell adhesion between granulosa cells leads to fragmentation of fluid and growth arrest of the dominant cavity, as predicted by the model. Importantly, perturbing the critical state in secondary follicles leads to impaired follicle growth. Altogether, our study reveals how collective spatiotemporal regulation of cell junction mechanics and cell death can contribute to the effective transition between distinct regimes of fluids, which are indispensable for functional maturation of follicles.

developmental biology↗

bioRxiv2025

Inclusion of JNK-independent drugs within multi-agent chemotherapy improves response in relapsed high-risk neuroblastoma

The acquisition of a chemoresistant state underlies poor prognosis in many cancers, including neuroblastoma. We previously demonstrated that heterogeneity in apoptosis induction through c-Jun N-Terminal Kinase (JNK) promotes a form of non-genetic chemoresistance in neuroblastoma observable at both patient and single-cell levels. As the maintenance of this JNK-impaired state in the relapse setting is a significant barrier to the efficacy of many standard-of-care chemotherapy drugs, we combined a mechanistic, mathematical model of JNK activation with a paediatric focused drug screen and identified approved oncology drugs capable of inducing apoptosis in a JNK-independent manner. Functional genomics further revealed that synergy between these JNK-independent drugs and standard-of-care chemotherapies emerged from differential utilisation of apoptotic network components, rather than from their direct mechanistic targets. Efficacy studies with PDX models also confirmed that including a JNK-independent drug within existing chemotherapy backbones significantly improved response in the relapse setting, where new approaches are urgently needed. One Sentence SummaryDrug combinations utilising differential sets of network components can overcome the apoptotic impaired state of relapsed high-risk neuroblastoma.

cancer biology↗

bioRxiv2024

PSKH1 kinase activity is differentially modulated via allosteric binding of Ca2+ sensor proteins

Protein Serine Kinase H1 (PSKH1) was recently identified as a crucial factor in kidney development and is overexpressed in prostate, lung and kidney cancers. However, little is known about PSKH1 regulatory mechanisms, leading to its classification as a "dark" kinase. Here, we used biochemistry and mass spectrometry to define PSKH1s consensus substrate motif, protein interactors, and how interactors, including Ca2+ sensor proteins, promote or suppress activity. Intriguingly, despite the absence of a canonical Calmodulin binding motif, Ca2+-Calmodulin activated PSKH1 while, in contrast, the ER-resident Ca2+ sensor of the CREC family, Reticulocalbin-3, suppressed PSKH1 catalytic activity. In addition to antagonistic regulation of the PSKH1 kinase domain by Ca2+ sensing proteins, we identified UNC119B as a protein interactor that activates PSKH1 via direct engagement of the kinase domain. Our findings identify complementary allosteric mechanisms by which regulatory proteins tune PSKH1s catalytic activity, and raise the possibility that different Ca2+ sensors may act more broadly to tune kinase activities by detecting and decoding extremes of intracellular Ca2+ concentrations.

biochemistry↗

bioRxiv2024

Theca cell mechanics and tissue pressure regulate mammalian ovarian folliculogenesis

The maturation of functional eggs within the ovaries is essential for successful reproduction and organismal functions in mammals. Yet, despite its biological and clinical importance, the underlying mechanisms regulating folliculogenesis remain enigmatic. Here, we report a novel role of the surface-anchoring theca cells (TCs) in regulating follicle growth through mechanical signalling. Direct mechanical measurements reveal that these TCs are highly contractile and exert compressive stress to the follicular interior, potentially through active assembly of fibronectin scaffold around the follicles. Abolishing TC contractility disrupts fibronectin assembly, increases follicle size, and decreases intrafollicular pressure and viscosity. We further reveal that the granulosa cells (GCs) within the follicles exhibit spatial patterns of YAP signalling and proliferation, which appear to be decoupled. Transient manipulation of tissue pressure through bulk follicle compression, laser ablation or pharmacological perturbation of TC contractility leads to changes in GC YAP signalling, proliferation, and oocyte-GC communications, while long term abrogation of TC contractility leads to impaired follicle growth. Altogether, our study unveils the unique role of TC-mediated tissue pressure in ensuring robust mammalian ovarian folliculogenesis.

developmental biology↗

bioRxiv2020

Direct RNA sequencing reveals structural differences between transcript isoforms

The ability to correctly assign structure information to an individual transcript in a continuous and phased manner is critical to understanding RNA function. RNA structure play important roles in every step of an RNAs lifecycle, however current short-read high throughput RNA structure mapping strategies are long, complex and cannot assign unique structures to individual gene-linked isoforms in shared sequences. To address these limitations, we present an approach that combines structure probing with SHAPE-like compound NAI-N3, nanopore direct RNA sequencing, and one-class support vector machines to detect secondary structures on near full-length RNAs (PORE-cupine). PORE-cupine provides rapid, direct, accurate and robust structure information along known RNAs and recapitulates global structural features in human embryonic stem cells. The majority of gene-linked isoforms showed structural differences in shared sequences both local and distal to the alternative splice site, highlighting the importance of long-read sequencing for phasing of structures. Structural differences between gene-linked isoforms are associated with differential translation efficiencies globally, highlighting the role of structure as a pervasive mechanism for regulating isoform-specific gene expression inside cells.

biochemistry↗