Biology subjects

Nudelman, F.

Publications and source records attributed to Nudelman, F..

4 recordsLinked to original sources

bioRxiv2026

Deciphering Coccolith Formation: Advanced Microscopy Insights from the Biomineralisation of Gephyrocapsa huxleyi

Coccolithophores are unicellular marine phytoplankton that produce complex and intricately shaped mineralised scales called coccoliths. Coccoliths are produced in an intracellular vesicle where crystal nucleation occurs, from which several individual calcite units develop with anisotropic crystallographic facets, prompting studies into the cellular mechanisms which control crystal growth within the cell. Here, we characterise those morphological developments in 3D that occur during the formation of coccoliths by the species Gephyrocapsa huxleyi using cryo-ptychographic X-ray computed tomography. This technique is ideally suited to study coccolith mineral development, as intracellular structures can be imaged intact in their native state without needing to disrupt cells. Combined with additional imaging of developing coccoliths using cryo-transmission electron microscopy and scanning electron microscopy, we report the developmental stages involved in coccolith growth across the complete mineralisation period, while also showing that the constrained space created by individual crystal units growing in close confinement affects the final crystal morphology and overall mineral structure. These findings provide clarification on the mineralisation pathways that coccolithophores and other biomineralising organisms use to control the formation of highly functionalised crystalline structures, particularly relevant in the design of materials with tunable properties.

biophysics↗

bioRxiv2025

Proteomic characterisation of matrix vesicles from primary osteoblasts indicates a mixed population with both exosomal and ectosomal routes of biogenesis.

Matrix Vesicles are a crucial step in producing a mineralised, healthy skeleton. Released from chondrocytes and osteoblasts, they concentrate calcium and phosphate to establish the deposition of hydroxyapatite around and within the collagen fibrils of the extracellular matrix, becoming embedded in the matrix in the process. In the 55 years since H. Clarke Anderson first described them, blebbing from the surface of chondrocytes, a consensus on their role, contents and their biogenesis, has yet to be reached. This is in part due to the range of cell types from which they are released and the multitude techniques that can be employed to isolate them. In this study, we, for the first time, characterise the proteome of matrix vesicles isolated from primary osteoblasts. By focussing on those vesicles that have become embedded within the matrix, we are able to avoid bias for specific modes of biogenesis and focus only on osteoblast-released vesicles that are associated with the matrix. Moreover, by studying these vesicles over a time course of mineralising activity, we are able to identify changes in the properties of these vesicles, and develop a more accurate picture of which proteins are involved specifically in mineralisation. In particular we identify the presence of markers associated with the ectosomal and exosomal release of matrix vesicles, as well as identifying proteins required for the maintenance and mineralisation of the extracellular matrix. These data portray a heterogeneous population of matrix vesicles, with different roles to play in bone development.

cell biology↗

bioRxiv2025

Polyanionic Non-Collagenous Proteins and Their Analogues Promote Artificial Mineralization of Embryonic Mouse Bone

Non-collagenous proteins (NCPs) are specialized biomacromolecules within the extracellular matrix (ECM) that regulate the mineralization of calcified tissues, such as bone and dentin. Numerous in vitro studies have demonstrated that natural polyanionic NCPs and their analogues can mediate intrafibrillar mineralization, characterized by the infiltration of apatite minerals into collagen fibrils. However, these studies primarily utilize self-assembled collagen fibrils or demineralized mature tissues, leaving it unclear whether pristine embryonic bone ECM at a developmental stage permissive to mineral deposition can regulate intrafibrillar mineralization independently or requires polyanionic NCP substitutes to promote the process artificially. To address this, we employed an ex vivo model of endochondral ossification using metatarsals isolated from 15-day-old embryonic mice (E15). In addition to a supersaturated calcium (Ca) and inorganic phosphate (Pi) medium, we introduced fetuin-A, a native polyanionic NCP or poly-DL-aspartic acid (pAsp), commonly used as an NCP substitute. The incorporation of either additive was essential for the effective mineralization of embryonic metatarsals. Both fetuin-A and pAsp played a direct role in facilitating the infiltration of Ca-Pi precursors into the avascular cartilaginous matrix. Raman spectroscopy and electron microscopy confirmed the formation of hydroxyapatite (HAp) exhibiting diverse levels of crystallinity, with fetuin-A supplementation resulting in the greatest HAp accumulation within the rudiments. HAp was localized in the perichondrium, a region conducive to initial mineralization and enriched with a fibrillar network of collagen types I and II. Three-dimensional reconstructions implementing Dijkstras algorithm revealed the association between HAp and collagen fibrils either organized in an intrafibrillar, extrafibrillar, or combined arrangement.

biophysics↗

bioRxiv2024

Dynamic change of calcium-rich compartments during coccolithophore biomineralization

Coccolithophores are abundant marine phytoplankton that produce biomineralized calcite scales, called coccoliths, which sequester substantial amounts of carbon and play a significant role in biogeochemical cycles. However, mechanisms underlying the storage and transport of ions essential for calcification remain unresolved. We used ptychographic X-ray computed tomography under cryogenic conditions to visualize intracellular calcium-rich structures involved in the storage of calcium ions in the coccolithophore species Chrysotila carterae. During calcification, we observed a range of structures, from small electron-dense bodies within larger compartments, to denser and distributed globular compartments, before returning to small bodies once scale formation is complete. Nanobeam-scanning X-ray fluorescence measurements further revealed these electron-dense bodies are rich in P and Ca (molar ratio of [~]4:1). We infer from the dynamic nature of structures that these bodies are part of required cellular calcium ion transport pathways, a fundamental process critical for understanding the response of coccolithophores to climate change.

cell biology↗