Amyloid-like substance in mice and human oocytes and embryos

Amyloid Fibrils of the s36 Protein Modulate the Morphogenesis of Drosophila melanogaster Eggshell

Drosophila melanogaster is the oldest classic model object in developmental genetics. It may seem that various structures of the fruit fly at all developmental stages have been well studied and described. However, recently we have shown that some specialized structures of the D. melanogaster eggshell contain an amyloid fibril network. Here, we demonstrate that this amyloid network is formed by the chorionic protein s36. The s36 protein colocalizes with the amyloid-specific dyes Congo Red and Thioflavin S in the micropyle, dorsal appendages, and pillars. The fibrils of s36 obtained from the eggs demonstrate amyloid properties. In the context of the CG33223 gene deletion, the s36 protein is produced but is not detected in the eggshell. The absence of amyloid fibrils of s36 in the eggshell disrupts the endochorion morphology and blocks the development of the micropyle, dorsal appendages, and pillars, leading to sterility. Our data show for the first time that amyloid fibrils are essential for morphogenesis modulation. We suggest that attachment of follicle cells to the s36 extracellular fibrils triggers signaling to enable subsequent cellular divisions needed for building the specialized eggshell structures.

Amyloids and prions in the light of evolution

Functional amyloids have been identified in a wide variety of organisms including bacteria, fungi, plants, and vertebrates. Intracellular and extracellular amyloid fibrils of different proteins perform storage, protective, structural, and regulatory functions. The structural organization of amyloid fibrils determines their unique physical and biochemical properties. The formation of these fibrillar structures can provide adaptive advantages that are picked up by natural selection. Despite the great interest in functional and pathological amyloids, questions about the conservatism of the amyloid properties of proteins and the regularities in the appearance of these fibrillar structures in evolution remain almost unexplored. Using bioinformatics approaches and summarizing the data published previously, we have shown that amyloid fibrils performing similar functions in different organisms have been arising repeatedly and independently in the course of evolution. On the other hand, we show that the amyloid properties of a number of bacterial and eukaryotic proteins are evolutionarily conserved. We also discuss the role of protein-based inheritance in the evolution of microorganisms. Considering that missense mutations and the emergence of prions cause the same consequences, we propose the concept that the formation of prions, similarly to mutations, generally causes a negative effect, although it can also lead to adaptations in rare cases. In general, our analysis revealed certain patterns in the emergence and spread of amyloid fibrillar structures in the course of evolution.

Protein Aggregation and Disaggregation in Cells and Development

Protein aggregation is a feature of numerous neurodegenerative diseases. However, regulated, often reversible, formation of protein aggregates, also known as condensates, helps control a wide range of cellular activities including stress response, gene expression, memory, cell development and differentiation. This review presents examples of aggregates found in biological systems, how they are used, and cellular strategies that control aggregation and disaggregation. We include features of the aggregating proteins themselves, environmental factors, co-aggregates, post-translational modifications and well-known aggregation-directed activities that influence their formation, material state, stability and dissolution. We highlight the emerging roles of biomolecular condensates in early animal development, and disaggregation processing proteins that have recently been shown to play key roles in gametogenesis and embryogenesis.

Search for functional amyloid structures in chicken and fruit fly female reproductive cells

We conducted a cytological search for amyloid structures in female reproductive cells of Gallus gallus domesticus and Drosophila melanogaster. We have shown that the amyloid-specific dye, Thioflavin S, but not Congo red, stains some cytoplasmic and even nuclear structures in chicken ovaries. In fruit fly eggs both Thioflavin S and Congo red specifically stain eggshell structures such as micropyle, dorsal appendages and pillars. Moreover, these structures, when stained with Congo red, demonstrate birefringence in polarized light, which is a characteristic feature of all classical amyloids. Our data show that female reproductive cells during evolution began to use amyloid fibrils to form various functional structures necessary for development under certain environmental conditions.