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Description
The regulation of protein expression by cytoplasmic polyadenylation in neurons was demonstrated for a few
transcripts but was challenging to study due to the absence of reliable, quantitative methods. With the new
emerging technology of direct RNA sequencing on nanopores, it is now possible to sequence entire mRNA
molecules including the poly(A) tails. In the proposed project we will employ this method to characterize the
genome-wide mRNA poly(A) tail dynamics during neural activity-dependent synaptic plasticity. This initial
discovery stage will be followed by analyses of synaptic activity-dependent protein synthesis and plasticity.
After identifying the fraction of synaptic mRNAs that undergo cytoplasmic polyadenylation, we will search for
enzymes responsible for this process using in-house generated unique KO and knock-in mouse models.
Finally, we aim to elucidate mechanisms by which specific mRNAs are selected for cytoplasmic
polyadenylation.
In sum, this project, thanks to a combination of contemporary transcriptomic approaches with functional
studies on mouse KO models, will provide the first comprehensive picture of the role of cytoplasmic
polyadenylation in the regulation of local protein synthesis at synapses. The expertise of three partners from
Poland and Norway is indispensable for the success of this project.
Summary of project results
Neurons, the basic units of the brain, communicate through specialized structures known as synapses. These are not only the sites of electrical impulse transmission but also house the machinery necessary for protein synthesis within them—a process termed "local translation." Essential for synaptic function, this localized protein production depends on messenger RNAs (mRNAs) that travel from the neuron''s main body to these remote sites. Disturbances in this process can lead to significant neurodevelopmental disorders.
Recent advances in technology have shed light on these vital synaptic activities, yet the specific mechanisms regulating this protein synthesis remain largely unknown. One key aspect involves the modifications at the ends of mRNA molecules: a protective cap at the front and a polyadenine (poly(A)) tail at the end. The poly(A) tail, a chain of adenosine nucleotides, is usually added to the nucleus immediately after the mRNA is created and before it moves to the cytoplasm.
Emerging research suggests that this polyadenylation can also occur in the cytoplasm, specifically termed "cytoplasmic polyadenylation." In neurons, this modification of synaptic mRNAs was suggested to be essential for regulating protein synthesis. However, research on this has been limited to only a few mRNAs, leaving the broader impact and the enzymes involved largely unexplored. Our project aimed to deepen our understanding of cytoplasmic polyadenylation and its role in neuronal communication.
In this project, we used contemporary technologies to comprehensively analyze neuronal mRNAs and changes occurring during the induction of neuronal plasticity. These studies were performed for model systems in which we manipulated enzymes potentially responsible for the extension of poly(A) tails of mRNA in neurons. As a next step, we have performed functional studies aimed at gaining the understanding of the physiological roles of mRNA modifications by selected enzymes
This was a basic science project whose results will be of primary interest to scientists interested in post-transitional gene expression regulation in the nervous system.
Our project has made significant advancements in understanding how polyadenylation, a process essential for mRNA stability and function, influences brain activity and neuronal communication. Here are the primary findings:
Mapping Polyadenylation in the Hippocampus: We have detailed the polyadenylation landscape in the hippocampus following the induction of Long-Term Potentiation (LTP), a process critical for learning and memory. This study uncovered a group of neuronal mRNAs that feature semi-templated poly(A) tails, meaning that part of the tail is encoded directly within the genome, a novel discovery in neuronal biology.
Role of TENT2 in Memory Formation: Our research identified a critical function for the TENT2 (also known as GLD-2) poly(A) polymerase in modulating LTP. This appears to be executed through the monoadenylation of microRNAs, thereby impacting the post-transcriptional regulation of genes involved in neuronal signaling and memory processes.
TENT5A''s Influence on Hormonal Regulation: We discovered that the TENT5A poly(A) polymerase acts as a global regulator of neurohormone expression, significantly affecting the hormonal interactions between the hypothalamus and the pituitary gland. This finding highlights a new layer of complexity in how brain activity can influence bodily functions.
Summary of bilateral results
The bilateral collaboration between the Polish and Norwegian partners was successful, characterized by strong communication and effective teamwork. Both teams contributed significantly to the project''s progress, sharing expertise and resources that enhanced the overall quality of the research. Regular meetings, both virtual and in-person, facilitated a productive exchange of ideas and ensured that the project remained on track. The collaboration also extended to mentoring and training opportunities, with researchers from both countries benefiting from the shared knowledge and skills. However, it is noteworthy that in the published paper in Nature Communications, Norwegian partners were not listed among the co-authors. Their contributions are recognized in two subsequent manuscripts that are currently under review.