Periodic Reporting for period 1 - SHAPE (SHAPE. Deciphering sarcoplasmic reticulum shaping in heart function)
Período documentado: 2023-11-01 hasta 2025-10-31
SHAPE aimed to uncover the role of sarcoplasmic reticulum (SR) morphology in cardiomyocyte and heart function.
Cardiac myocytes, the contractile cells of the heart, are highly differentiated and structurally specialised cells whose primary function is to sustain cardiac contractility and, ultimately, effective heart pump function. Central to this process is the SR, a specialised form of the endoplasmic reticulum (ER) that orchestrates calcium cycling—a fundamental mechanism for excitation–contraction coupling. Although the morphology and dynamics of the ER have been extensively studied, the specific proteins responsible for shaping and maintaining the unique architecture of the SR in cardiac cells remain largely unknown. This represents a significant gap in our understanding of cardiac physiology.
From a broader perspective, cardiovascular diseases remain the leading cause of mortality in Europe and globally, placing substantial pressure on healthcare systems and economies. The European Union and national research strategies emphasise the need to reduce the burden of heart disease through improved mechanistic understanding, early detection of dysfunction, and the identification of new therapeutic targets. In this political and strategic context, deciphering the molecular determinants of SR structure is not only scientifically relevant but also aligns with major public health priorities.
The overarching objective of SHAPE is therefore to identify the molecular players involved in SR establishment and morphology and to evaluate how alterations in these components affect cardiomyocyte and heart function. Using the powerful genetic model Drosophila melanogaster, I investigated the four best-characterised ER-shaping proteins, discovering that at least two of them are essential for proper cardiac performance. These findings highlight previously unrecognised molecular determinants of SR integrity and suggest new pathways that may be implicated in cardiac dysfunction.
By uncovering the proteins responsible for shaping the SR, this project provides foundational knowledge that may contribute to the development of future diagnostic markers or therapeutic approaches targeting subcellular structural defects. Understanding SR morphology is essential for interpreting early cellular changes that precede heart failure, making this research highly relevant for early-stage detection strategies and translational cardiology.
In summary, this project sets the scene for a deeper understanding of how intracellular structural organisation contributes to heart function, addressing a critical scientific gap while aligning with broader political and societal needs to combat cardiovascular disease.
Cardiac myocytes, the contractile cells of the heart, are highly differentiated and structurally specialised cells whose primary function is to sustain cardiac contractility and, ultimately, effective heart pump function. Central to this process is the SR, a specialised form of the endoplasmic reticulum (ER) that orchestrates calcium cycling—a fundamental mechanism for excitation–contraction coupling. Although the morphology and dynamics of the ER have been extensively studied, the specific proteins responsible for shaping and maintaining the unique architecture of the SR in cardiac cells remain largely unknown. This represents a significant gap in our understanding of cardiac physiology.
From a broader perspective, cardiovascular diseases remain the leading cause of mortality in Europe and globally, placing substantial pressure on healthcare systems and economies. The European Union and national research strategies emphasise the need to reduce the burden of heart disease through improved mechanistic understanding, early detection of dysfunction, and the identification of new therapeutic targets. In this political and strategic context, deciphering the molecular determinants of SR structure is not only scientifically relevant but also aligns with major public health priorities.
The overarching objective of SHAPE is therefore to identify the molecular players involved in SR establishment and morphology and to evaluate how alterations in these components affect cardiomyocyte and heart function. Using the powerful genetic model Drosophila melanogaster, I investigated the four best-characterised ER-shaping proteins, discovering that at least two of them are essential for proper cardiac performance. These findings highlight previously unrecognised molecular determinants of SR integrity and suggest new pathways that may be implicated in cardiac dysfunction.
By uncovering the proteins responsible for shaping the SR, this project provides foundational knowledge that may contribute to the development of future diagnostic markers or therapeutic approaches targeting subcellular structural defects. Understanding SR morphology is essential for interpreting early cellular changes that precede heart failure, making this research highly relevant for early-stage detection strategies and translational cardiology.
In summary, this project sets the scene for a deeper understanding of how intracellular structural organisation contributes to heart function, addressing a critical scientific gap while aligning with broader political and societal needs to combat cardiovascular disease.
During the project, I carried out a comprehensive investigation into the molecular determinants of SR morphology and their impact on cardiomyocyte and heart function. The work combined genetic manipulation in Drosophila melanogaster, high-resolution imaging, and functional cardiac assays to address the central research question: which proteins are responsible for establishing and maintaining SR architecture in the heart?
The first phase of the work focused on establishing the experimental platform. I developed Drosophila cardiac-specific knockdown and overexpression lines for the four best-characterised ER-shaping proteins.
In the second phase, I characterised SR morphology in each genetic condition using confocal microscopy and fluorescent reporters of SR domains. This analysis revealed that all the four candidate proteins are essential for the correct organisation of both longitudinal SR (lSR) and junctional SR (jSR) domains, indicating their direct involvement in shaping SR architecture in cardiomyocytes.
The third phase focused on determining the functional relevance of these structural alterations. Using in vivo cardiac imaging and contractility assays in Drosophila, I demonstrated that disruption of two of these proteins leads to significant impairments in heart performance, including altered contraction dynamics and reduced pumping efficiency. These results show a clear mechanistic link between SR morphology and cardiac function.
Finally, by comparing the morphological alterations with the functional defects, I began to explore the possible cellular mechanisms underlying the phenotype. Due to its pivotal role in calcium handling, changes in SR structure could affect calcium handling and thereby influence excitation–contraction coupling. However, this remains an open question, and additional work will be required to clarify the molecular link between SR morphology and cardiac function.
Overall, the main achievements of the project include:
• the establishment of a robust Drosophila platform for SR-related cardiac studies;
• the identification of two key proteins required for SR domain formation in cardiomyocytes;
• the demonstration that disruption of these proteins leads to measurable cardiac dysfunction; and
• the generation of the first in vivo evidence linking ER-shaping proteins to heart performance.
These outcomes advance fundamental understanding of the molecular bases of cardiac function and open new avenues for the study of early mechanisms involved in heart disease.
The first phase of the work focused on establishing the experimental platform. I developed Drosophila cardiac-specific knockdown and overexpression lines for the four best-characterised ER-shaping proteins.
In the second phase, I characterised SR morphology in each genetic condition using confocal microscopy and fluorescent reporters of SR domains. This analysis revealed that all the four candidate proteins are essential for the correct organisation of both longitudinal SR (lSR) and junctional SR (jSR) domains, indicating their direct involvement in shaping SR architecture in cardiomyocytes.
The third phase focused on determining the functional relevance of these structural alterations. Using in vivo cardiac imaging and contractility assays in Drosophila, I demonstrated that disruption of two of these proteins leads to significant impairments in heart performance, including altered contraction dynamics and reduced pumping efficiency. These results show a clear mechanistic link between SR morphology and cardiac function.
Finally, by comparing the morphological alterations with the functional defects, I began to explore the possible cellular mechanisms underlying the phenotype. Due to its pivotal role in calcium handling, changes in SR structure could affect calcium handling and thereby influence excitation–contraction coupling. However, this remains an open question, and additional work will be required to clarify the molecular link between SR morphology and cardiac function.
Overall, the main achievements of the project include:
• the establishment of a robust Drosophila platform for SR-related cardiac studies;
• the identification of two key proteins required for SR domain formation in cardiomyocytes;
• the demonstration that disruption of these proteins leads to measurable cardiac dysfunction; and
• the generation of the first in vivo evidence linking ER-shaping proteins to heart performance.
These outcomes advance fundamental understanding of the molecular bases of cardiac function and open new avenues for the study of early mechanisms involved in heart disease.
This project has advanced current knowledge by uncovering previously unrecognised molecular components involved in the establishment and maintenance of SR morphology in cardiomyocytes. While the organisation of the ER has been extensively described in other cell types, little was known about the molecular determinants that specifically shape the SR in cardiac cells. The identification of two ER-shaping proteins as key contributors to SR architecture in Drosophila heart tissue therefore represents a significant step beyond the state of the art.
Furthermore, by combining genetic manipulation with high-resolution imaging and functional cardiac assays, this project provides in vivo evidence that alterations in SR structure are directly associated with measurable defects in heart performance. This link between subcellular architecture and physiological output has not been previously demonstrated in this model and opens new avenues for studying early mechanisms of cardiac dysfunction.
In addition to these scientific contributions, the project highlights important open questions that will shape future research. The potential connection between SR structural defects, impaired calcium handling, and altered excitation–contraction coupling requires further investigation to clarify the underlying molecular pathway. Additional work using complementary models and molecular tools will be essential to confirm the conservation of these mechanisms and to identify potential therapeutic targets.
Overall, the results generated during this project provide a solid foundation for a deeper understanding of intracellular structural determinants of heart function and establish a clear direction for future research with potential long-term impact.
Furthermore, by combining genetic manipulation with high-resolution imaging and functional cardiac assays, this project provides in vivo evidence that alterations in SR structure are directly associated with measurable defects in heart performance. This link between subcellular architecture and physiological output has not been previously demonstrated in this model and opens new avenues for studying early mechanisms of cardiac dysfunction.
In addition to these scientific contributions, the project highlights important open questions that will shape future research. The potential connection between SR structural defects, impaired calcium handling, and altered excitation–contraction coupling requires further investigation to clarify the underlying molecular pathway. Additional work using complementary models and molecular tools will be essential to confirm the conservation of these mechanisms and to identify potential therapeutic targets.
Overall, the results generated during this project provide a solid foundation for a deeper understanding of intracellular structural determinants of heart function and establish a clear direction for future research with potential long-term impact.