Biology subjects

Mohamad, N.

Publications and source records attributed to Mohamad, N..

4 recordsLinked to original sources

bioRxiv2026

Organelle biogenesis on a synthetic bead

How cells build their many organelles remains poorly understood. Centrosomes are a striking example: structurally complex organelles built from more than one hundred different proteins. Here we show that a synthetic bead can generate centrosome-like particles (CLiPs) in early Drosophila embryos if it is programmed to recruit any one of five essential centrosome assembly proteins. CLiPs behave remarkably like centrosomes: organising centrosomal proteins, microtubules and actomyosin, forming spindle poles, and undergoing multiple rounds of duplication - all in synchrony with the embryonic cell cycle. The beads generate CLiPs because they recruit Plk4, the master regulator of centrosome biogenesis, in a specific manner that stimulates its assembly activity. Thus, recruiting a single protein to a synthetic surface is sufficient to seed the self-assembly of a complex, self-propagating entity. These findings suggest a general framework for organelle biogenesis in which simple localised molecular inputs can seed the self-assembly of highly complex cellular structures.

cell biology↗

bioRxiv2025

Structural insights into mitotic-centrosome assembly

Centrosomal material assembles rapidly in mitosis. In Drosophila, the coiled-coil protein Cnn forms a scaffold that recruits PCM clients; in C.elegans, SPD-5 plays an analogous role. Here we show that full-length Cnn and SPD-5 can both form spherical condensates in vitro, but that the interactions driving their assembly into scaffolds inside cells appear to diverge. We show that the Cnn PReM adopts a helical hairpin fold that autoinhibits CM2 binding but that phosphorylation appears to increase hairpin breathing to permit CM2 engagement and robust scaffold assembly. Phospho-blocking mutations prevent PReM-CM2 interactions and scaffold formation, whereas phospho-mimetic substitutions partially restore function. The human homologue CDK5RAP2 contains a CM2 domain that can partially substitute for fly CM2 in vivo and we identify a candidate CDK5RAP2 PReM region that forms macromolecular networks with human CM2 in vitro. By contrast, the putative PReM and CM2 regions of SPD-5 cannot substitute for their equivalent fly domains and they do not interact detectably, suggesting a distinct assembly mechanism in worms despite conserved PLK1-dependent control of PCM growth.

cell biology↗

bioRxiv2025

The Potential Neuroinflammatory Attenuation Effects of Thymoquinone against 3, 4-Methylenedioxymethamphetamine-Induced Microglial Activation in BV2 Mouse Cell Line

MDMA induced the activation of microglia in the brain which would lead to neurotoxicity. The activation of microglia is associated with morphological changes and the production of inflammatory phenotypes. While there is research suggesting that thymoquinone (TQ) may have anti-inflammatory effects and modulate microglial activation, studies specifically focusing on its impact on activated microglia induced by MDMA or Ecstasy appear to be limited or not yet available. In this study, the effects of MDMA and TQ in BV2 microglial cells were examined to see the differences in gene expression profile, and whether TQ could modulate the inflammatory genes in MDMA-induced BV2 microglial activation. Transcriptome analysis revealed that cytokines/chemokines and inflammation-related genes were significantly up-regulated in response to MDMA-induced microglial activation. TQ pre-treatment in the MDMA+TQ group appeared to have attenuated the morphological changes of microglia as compared to the MDMA group. RNA-Seq analysis revealed that TQ reduced inflammatory responses in MDMA-induced microglial activation by inhibiting the production of several pro-inflammatory genes such as Cxcl2, Ptgs2, C3ar1, Nfkbia, Il1a, Cxcl10, and Serpinf2 (P[≤]0.05). This study concluded that TQ possesses neuroprotective effects against MDMA-induced microglial activation by stabilizing the effects of microglia.

molecular biology↗

bioRxiv2024

Centrioles generate two scaffolds with distinct biophysical properties to build mitotic centrosomes

Mitotic centrosomes form when centrioles recruit large amounts of pericentriolar material (PCM) around themselves. The PCM comprises hundreds of proteins, yet it can assemble and disassemble within minutes, leading to much debate about its physical nature. Here we show that Drosophila Spd-2 fluxes out from centrioles, recruiting Polo and Aurora A to catalyse the assembly of a solid-like Cnn-scaffold and a more liquid-like TACC-scaffold, respectively. Both scaffolds can assemble and recruit PCM proteins independently, but both are required for proper centrosome assembly, with the Cnn-scaffold providing mechanical strength, and the TACC-scaffold locally concentrating centriole and centrosome proteins. Recruiting Spd-2, but not Cnn or TACC, to the surface of synthetic beads injected into early embryos reconstitutes several aspects of mitotic centrosome assembly on the bead surface, and this depends on the ability of Spd-2 to recruit Polo and AurA. Thus, Spd-2 molecules flux out from the centriole recruiting Polo and AurA to promote the assembly of two scaffolds with distinct properties to support mitotic centrosome assembly in flies.

cell biology↗