Biology of the Cell最新文献

Background Information

Conventional Transmission Electron Microscopy analysis of biological samples often provides limited insights due to its inherent two-dimensional (2D) nature. This limitation hampers a comprehensive understanding of the three-dimensional (3D) complexity of cellular structures, occasionally leading to misinterpretations. Serial block-face scanning electron microscopy emerges as a powerful method for acquiring high-resolution 3D images of cellular volumes. By iteratively removing ultrathin sample sections and capturing images of each newly exposed surface, Serial block-face scanning electron microscopy allows for the meticulous reconstruction of a comprehensive 3D volume.

Results

In this study, we investigate the 3D architecture of altered mitochondrial morphologies in Saccharomyces cerevisiae using Serial block-face scanning electron microscopy imaging. We have developed a novel cryomethod based on plunge freezing and a dedicated freeze-substitution protocol.

Conclusion

This protocol enhances ultrastructural preservation enabling a more accurate understanding of mitochondrial defects observed in 2D electron microscopy.

Significance

Our findings underscore the utility of Serial block-face scanning electron microscopy coupled with optimized sample preparation techniques in elucidating complex cellular structures in 3D.

Lipids are crucial for various cellular functions. Besides the storage of energy equivalents, these include forming membrane bilayers and serving as signaling molecules. While significant progress has been made in the comprehension of the molecular and cellular biology of lipids, their functions in the cell nucleus remain poorly understood. The main role of the eukaryotic cell nucleus is to provide an environment for the storage and regulation of chromatin which is a complex of DNA, histones, and associated proteins. Recent studies suggest that nuclear lipids play a role in chromatin regulation and epigenetics. Here, we discuss various experimental methods in lipid-chromatin research, including biophysical, structural, and cell biology approaches, pointing out their strengths and weaknesses. We take the view that nuclear lipids have a far more widespread impact on chromatin than is currently acknowledged. This gap in comprehension is mostly due to existing experimental challenges in the study of lipid-chromatin biology. Several new, interdisciplinary approaches are discussed that could aid in elucidating the roles of nuclear lipids in chromatin regulation and gene expression.

The crustacean molting cycle is triggered by the elevation of ecdysteroid levels in the hemolymph during late pre-molt. It is known that these animals absorb water through the intestine and gills to promote bodily swelling and rupture of the old exoskeleton. The participation of two membrane proteins responsible for the most uptake of water during the late pre-molt has been shown in the gill and gut cells of the freshwater shrimp Palaemon argentinus: Na⁺/K⁺-ATPase (NKA), which generates an osmoionic gradient, and Aquaporins (AQPs), water channels, which provide higher water permeability. Studies investigating the action of ecdysteroids on these proteins are scarce. Therefore, we investigated 20-hydroxyecdisone (20E) in relation to the regulation of NKA and AQPs in the gill and gut cells of P. argentinus. We exposed primary cultures of both gut and gill cells to 20E. Gill cells treated with hormone in the presence of NKA-blockers, exhibited a reduction in volume, and cells treated with 20E showed a greater expression of NKA than untreated cells. Additionally, gills cells treated with 20E showed an increase in volume (∼60%), which the aquaporin inhibitor (HgCl₂) prevented. The participation of AQPs in the influx of water was corroborated by a greater expression of AQP in cells treated with 20E compared to untreated cells. Gut cells of animals in intermolt exposed to hormone (20E) maintained their initial cell volume. With the addition of HgCl2, these cells showed a reduction in volume similar to cells of animals in pre-molt. Immunocytochemistry showed a high expression of AQP in gut cells treated with 20E. These findings suggest that 20E regulates the expression of AQP and NKA in the late pre-molt, to provide water uptake for molting. This work offers new perspectives concerning the molting hormone, placing it as a crucial part of water uptake for ecdysis.

The CRCI²NA inaugural symposium, a meeting on tumor and immune ecosystems, took place in the vibrant and picturesque city of Nantes. The meeting gathered world-renowned experts in cancer biology and immunology. It showcased the most advanced science on mechanisms driving cellular heterogeneity, plasticity, and signaling in normal and cancer cellular ecosystems, which contribute to cancer development, progression, and therapeutic resistance. Recent developments in cancer immunotherapy and anti-tumor strategies were also discussed to collectively assess new therapeutic vulnerabilities to defeat cancer.

Backgound Information

Toxoplasma gondii has a relict plastid, the apicoplast, to which nuclear-encoded proteins are targeted after synthesis in the cytosol. Proteins exclusively found in the apicoplast use a Golgi-independent route for trafficking, while dually targeted proteins found in both the apicoplast and the mitochondrion use a Golgi-dependent route. For apicoplast targeting, N-terminal signal sequences have been shown to direct the localization of different reporters. In this study, we use chimeric proteins to dissect out the roles of N-terminal sequences and coding sequences in apicoplast localization and the choice of the trafficking route.

Results

We show that when the N-termini of a dually targeted protein, TgTPx1/2, or of an apicoplast protein, TgACP, are fused with the reporter protein, enhanced green fluorescent protein (eGFP) or endogenous proteins, TgSOD2, TgSOD3, TgACP, or TgTPx1/2, the chimeric proteins exhibit flexibility in apicoplast targeting depending on the coding sequences. Further, the chimeras that are localized to the apicoplast use different trafficking pathways depending on the combination of the N-terminal signals and the coding sequences.

Conclusion and Significance

This report shows, for the first time, that in addition to the N-terminal signal sequences, targeting and trafficking signals also reside within the coding sequences of apicoplast proteins.

Background Information

Microvilli are finger-like, straight, and stable cellular protrusions that are filled with F-actin and present a stereotypical length. They are present in a broad range of cell types across the animal tree of life and mediate several fundamental functions, including nutrient absorption, photosensation, and mechanosensation. Therefore, understanding the origin and evolution of microvilli is key to reconstructing the evolution of animal cellular form and function. Here, we review the current state of knowledge on microvilli evolution and perform a bioinformatic survey of the conservation of genes encoding microvillar proteins in animals and their unicellular relatives.

Results

We first present a detailed description of mammalian microvilli based on two well-studied examples, the brush border microvilli of enterocytes and the stereocilia of hair cells. We also survey the broader diversity of microvilli and discuss similarities and differences between microvilli and filopodia. Based on our bioinformatic survey coupled with carefully reconstructed molecular phylogenies, we reconstitute the order of evolutionary appearance of microvillar proteins. We document the stepwise evolutionary assembly of the “molecular microvillar toolkit” with notable bursts of innovation at two key nodes: the last common filozoan ancestor (correlated with the evolution of microvilli distinct from filopodia) and the last common choanozoan ancestor (correlated with the emergence of inter-microvillar adhesions).

Conclusion and Significance

We conclude with a scenario for the evolution of microvilli from filopodia-like ancestral structures in unicellular precursors of animals.

Background information

Extracellular matrix (ECM)-derived hydrogels are frequently used in three-dimensional (3D) cell culture and organoid formation in several tissues. However, in the 3D cultivation of testicular cells, the hyaluronic acid (HA) hydrogel has not received as much attention. This study examined the effects of three distinct composites, including HA-alginate (HA-Alg), HA-alginate-collagen (HA-Alg-Col), and HA-alginate-decellularized ECM (HA-Alg-dECM), on mouse testicular cell culture and in vitro spermatogenesis.

Methods

For the creation of composites, the concentration of biomaterials used was 0.5% HA, 1% alginate, 2.5 mg/mL collagen, and 25 mg/mL dECM derived from the testicles of Rams. After 3D culture of 5 days post-partum (dpp) mouse testicular cells for 14 days, HA-Alg was selected as a superior composite due to the greater number and size of the produced organoids. Then, cell culture was rerun by HA-Alg for 14 days, which was later extended for an additional 28 days. In addition, the 3D culture of 10 dpp mouse testicular cells was used to compare with 5 dpp mice on day 14. The morphology and gene expression were analyzed using appropriate techniques.

Results

On day 14, the HA-Alg hydrogel showed significantly more organoids in terms of size and number than the other two groups (p < 0.05); nevertheless, none of the groups showed the expected signs of testis organoids. Remarkably, on day 14, the histology and immunostaining tests revealed features of hepatocyte-like cells (HLCs) and albumin production as a marker of HLC functionality. Furthermore, the analysis of gene expression verified the significant expression of angiogenesis markers (p < 0.01). After the extended culture to 28 days, 5 dpp testicular cells once more differentiated into erythrocytes and HLCs, while a small number of organoids showed the characteristic of renal cells. Cell culture of 10 dpp mice for 14 days showed a wide range of cell lineages, including renal, glandular, chondrocyte, and hepatocyte-like cells in comparison to the 5 dpp mice.

Conclusion and significance

While the HA-Alg composite did not support spermatogenesis in the 3D culture of mouse testicular cells, it demonstrated an unpredicted potential for promoting the differentiation of neonate mouse testicular cells into HLC, erythrocytes, and other cell lineages.