Biology subjects

de Boer, T.

Publications and source records attributed to de Boer, T..

4 recordsLinked to original sources

bioRxiv2026

Reciprocal repression between Isl1 and Nkx2-5 defines the zebrafish embryonic cardiac pacemaker domain

The cardiac pacemaker initiates each heartbeat and is essential for normal cardiac function. Although the gene regulatory network controlling pacemaker development has been extensively studied in mammals, it remains unclear whether the same regulatory hierarchy governs pacemaker development in other vertebrates. Here, we combined high-speed optical mapping with genetic analysis to define the gene regulatory network that establishes and maintains pacemaker identity in the zebrafish embryo. We show that the LIM-homeodomain transcription factor Isl1 is essential for maintaining pacemaker identity of venous pole cardiomyocytes. Loss of Isl1 causes pacemaker cells to acquire chamber-like characteristics through ectopic nkx2-5 expression, resulting in loss of a dominant pacemaker site and severe bradyarrhythmia. Reducing Nkx2-5 activity largely restores regular rhythm despite persistent loss of other Isl1-dependent markers, indicating that inappropriate Nkx2-5 activity contributes substantially to the electrophysiological defects in isl1 mutants. In contrast, genetic disruption of shox2 does not impair embryonic pacemaker development or alter isl1 expression, suggesting that Shox2 is not an essential component of the zebrafish pacemaker gene regulatory network. Together, our findings establish a zebrafish-specific transcriptional hierarchy in which Isl1 safeguards pacemaker identity by restricting Nkx2-5 independently of Shox2. These results show that a conserved boundary between pacemaker and chamber myocardium can be maintained by distinct upstream factors during vertebrate heart development.

developmental biology↗

bioRxiv2023

Habitat selection during dispersal reduces the energetic cost of transport when making large displacements

Dispersal is energetically costly. However, there is now growing evidence that dispersing animals can express distinct movement strategies that allow them to mitigate most of the energetic costs of displacing over large distances. Whilst to date we know that these strategies involve changes in how dispersing animals move, it is unclear whether these changes in movement are facilitated by other components of behaviour--namely changes in habitat selection. Here, we combine step-selection analyses with models of the energetic costs of movement to high-resolution GPS tracking data in terrestrially dispersing vulturine guineafowl (Acryllium vulturinum) to test the hypothesis that dispersing animals should select for habitats that facilitate more energetically efficient movements during dispersal. We find that actively dispersing individuals exhibit increased positive selection for open habitats, especially roads. We then show that moving along roads facilitates straighter, faster movements and results in a more than 33% reduction in the energetic cost of transport relative to other habitat types. Our results confirm that fine-scale differences in habitat selection expressed by dispersers facilitate more energetically efficient movement, expanding our understanding of how animals exhibit adaptive movement strategies across different axes of decision-making (e.g., where and how to move) to overcome ecological challenges.

ecology↗

bioRxiv2022

Leak current, even with gigaohm seals, can cause misinterpretation of stem-cell derived cardiomyocyte action potential recordings

Human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) have become an essential tool to study arrhythmia mechanisms. Much of the foundational work on these cells, and the computational models built from the resultant data, has overlooked the contribution of seal-leak current on the immature and heterogeneous phenotype that has come to define these cells. Here, we use in silico and in vitro studies to demonstrate how seal-leak current depolarises action potentials (APs), substantially affecting their morphology, even with seal resistances (Rseal) above 1 G{Omega}. We show that compensation of this leak current is difficult due to challenges with recording accurate measures of Rseal during an experiment. Using simulation, we show that Rseal measures: 1) change during an experiment, invalidating the use of pre-rupture values, and 2) are polluted by the presence of transmembrane currents at every voltage. Finally, we posit the background sodium current in baseline iPSC-CM models imitates the effects of seal-leak current and is increased to a level that masks the effects of seal-leak current on iPSC-CMs. Based on these findings, we make three recommendations to improve iPSC-CM AP data acquisition, interpretation, and model-building. Taking these recommendations into account will improve our understanding of iPSC-CM physiology and the descriptive ability of models built from such data. Key pointsO_LIHuman induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) are an essential tool in the study of cardiac arrhythmia mechanisms. C_LIO_LITheir immature and heterogeneous action potential phenotype complicates the interpretation of experimental data, and has slowed their acceptance in industry and academia. C_LIO_LIWe suggest that a leak current caused by an imperfect pipette-membrane seal during single-cell patch-clamp experiments is partly responsible for inducing this phenotype. C_LIO_LIUsing in vitro experiments and computational modelling, we show that this seal-leak current affects iPSC-CM AP morphology, even under ideal experimental conditions. C_LIO_LIBased on these findings, we make recommendations that should be considered when interpreting, analysing and fitting iPSC-CM data. C_LI

physiology↗

bioRxiv2020

Istaroxime treatment ameliorates calcium dysregulation in a zebrafish model for Phospholamban R14del cardiomyopathy

The heterozygous phospholamban (PLN) p.Arg14del (R14del) mutation is found in patients with dilated or arrhythmogenic cardiomyopathy. The PLN R14del mutation triggers cardiac contractile dysfunction and arrhythmogenesis by affecting intracellular Ca2+ dynamics. Little is known about the physiological processes preceding PLN R14del induced cardiomyopathy, which is characterized by sub-epicardial accumulation of fibrofatty tissue, and a specific drug treatment is currently lacking. Here, we addressed these issues using a knock-in PLN R14del zebrafish model. Hearts from adult zebrafish with the R14del mutation display age-related remodeling with sub-epicardial inflammation and fibrosis. Echocardiography revealed contractile pulsus alternans before overt structural changes occurred, which correlated at the cellular level with action potential duration (APD) alternans. These functional alterations are preceded by diminished Ca2+ transient amplitudes in embryonic hearts. We found that istaroxime treatment ameliorates the in vivo Ca2+ dysregulation, rescues the cellular APD alternans, while it improves cardiac relaxation. Thus, we present novel insight into the pathophysiology of PLN R14del cardiomyopathy and identify istaroxime as a potential novel drug for its treatment.

cell biology↗