SPbU Biologists: Birds Will Help Find the Key to Neuromuscular Degenerative Diseases
A group of St. Petersburg State University biologists has analysed the formation process of nuclear domains in avian oocytes (immature egg cells). The data obtained from the model object reveal parallels between pathological processes triggering neuromuscular degenerative diseases and the organisation of a normal cell nucleus. The findings are described in an article published in a prominent scientific journal Chromosoma. The first author of the article is Tatyana Kulikova, a St. Petersburg State University researcher.
A group of St. Petersburg State University biologists has analysed the formation process of nuclear domains in avian oocytes (immature egg cells). The data obtained from the model object reveal parallels between pathological processes triggering neuromuscular degenerative diseases and the organisation of a normal cell nucleus. The findings are described in an article published in a prominent scientific journal Chromosoma. The first author of the article is Tatyana Kulikova, a St. Petersburg State University researcher.
A eukaryotic cell (a cell with a defined nucleus) comprises a variety of organelles (mitochondria, lysosomes, etc.) with membranes separating them from the cytoplasm. The nucleus is an organelle as well; a double membrane separates it from the rest of the cell. However, the components of the nucleus itself – the genome, the RNA and regulatory apparatus (proteins and RNP) – have no membranes. The genome itself is normally built into the chromosome with specialised chromatin proteins, and the regulatory components of the genome expression mechanism are located in the nucleoplasm, where they may be clustered in special nuclear domains.
In the recent years, biologists have been able to identify the formation mechanisms of intranuclear structures. It turned out that the key role in their formation is played by RNA and RNA binding proteins. Most RNA binding proteins contain unstructured threads. The researchers hypothesise that the binding of such proteins and RNA may result in their aggregation (irreversible association) inside of the cell nucleus. At the same time, certain structural features of RNA binding proteins allow them to form dynamic drop-like formations: nuclear domains. In an article published in Chromosoma, the leading scientific journal in the field of chromosome studies, St. Petersburg State University researchers provide evidence of the work of the mechanism of nuclear domain formation.
The study analyses unusual nuclear domains – giant terminal RNP aggregates (GITERA). They are formed on certain avian chromosomes and contain a specific set of RNA binding proteins, including components of the RNA processing mechanism. Thus, GITERA formed at the termini of pigeon lampbrush chromosomes contain proteins with unstructured threads: p54nrb and hnRNP I / PTB.
RNA binding proteins containing unstructured threads or prion-like domains have the ability to aggregate and form amyloid-like fibres. It was previously proven that mutations in these regions of RNA binding proteins can lead to the formation of pathological aggregates in the cytoplasm and nuclei of human neurons and muscle cells in a number of neuromuscular degenerative diseases. It was assumed that the aggregate formation is an exclusively pathological feature. St. Petersburg State University researchers have reached the opposite conclusion: aggregate formation is possible in normal cells as well. The findings of SPbU scientists will make it possible to study this process in normal cells. This will help biologists to continue the study of the aggregation of proteins with unstructured threads; a process that can lead to neuro- and muscular degenerative diseases in humans.
More on the results of the study: Giant poly (A)-rich RNP aggregates form at terminal regions of avian lampbrush chromosomes. Chromosoma. 2015. 1–16 (doi:10.1007/s00412-015-0563-4)