Biology subjects

Arato, K.

Publications and source records attributed to Arato, K..

5 recordsLinked to original sources

bioRxiv2025

Axial patterning of gastruloids via diverse cell type compositions

The formation of the germ layers and antero-posterior (AP) axial patterning are interlinked milestones of embryogenesis. Gastruloids, in vitro models from aggregated embryonic stem cells (ESCs), permit the study and deconstruction of these events. Gastruloids are successfully generated from ESCs of variable pluripotent states, but it remains unknown how the initial conditions influence cell type composition and to what degree resulting variations in spatial patterning can converge onto an elongated body axis. To address this, we comparatively study aggregates from varying proportions of primed and naive ESCs. Despite differences in AP symmetry-breaking dynamics and distinct trajectories toward either anterior mesodermal or neuro-ectodermal fates, all conditions produce elongated gastruloids. Furthermore, timed modulation of Activin/Nodal signaling in aggregates equalizes AP polarization modes and mixing of initial ESC pluripotent states generates gastruloids with enhanced tissue type diversity. This work therefore uncovers a previously unappreciated developmental flexibility underlying mammalian AP axial patterning.

developmental biology↗

bioRxiv2024

Cell-cell communication controls the timing of gastruloid symmetry-breaking

How cell fate decisions coordinate with tissue-scale morphogenesis remains a major challenge in developmental biology. Gastruloids, three-dimensional aggregates of pluripotent stem cells that self-organise and break symmetry via polarised Brachyury/T expression, provide an ideal system to address this question. By generating gastruloids with defined initial proportions of T-expressing cells we show that fate decisions occur collectively, with cell-fate proportions influencing the transition rates. Mechanical measurements reveal differences in surface tension between T-positive and T-negative tissues, consistent with radial cell sorting. Finally, incorporating fate dynamics and mechanics into a computational model recapitulates the sequential symmetry-breaking events observed in vitro. Our findings identify a mechanochemical mechanism underlying axis formation, and demonstrate how multicellular systems can robustly self-organise without external signalling cues.

biophysics↗

bioRxiv2023

Metabolic control of germ layer proportions through regulation of Nodal and Wnt signalling

During embryonic development, cells exit pluripotency to give rise to the three germ layers. Metabolic pathways influence cell fate decisions by modulating the epigenetic, transcriptional, and signalling states of cells. However, the interplay between metabolism and the major signalling pathways that drive the emergence of ectoderm, mesoderm, and endoderm remains poorly understood. Here, we demonstrate an instructive role of glycolytic activity in activating signalling pathways involved in mesoderm and endoderm induction. Using an in vitro model system for mouse gastrulation, we observed that inhibiting glycolysis prevents the upregulation of primitive streak markers, resulting in a significant increase in ectodermal cell fates at the expense of mesodermal and endodermal lineages. We demonstrate that this relationship is dose-dependent, enabling metabolic control of germ layer proportions through exogenous glucose levels. Mechanistically, we found that glycolysis inhibition leads to the downregulation of Wnt, Nodal, and Fgf signalling. Notably, this metabolic phenotype was rescued by Nodal or Wnt signalling agonists in the absence of glycolytic activity, suggesting that glycolytic activity acts upstream of both signalling pathways. Our work underscores the dependence of specific signalling pathways on metabolic conditions and provides mechanistic insight into the nutritional regulation of cell fate decision making.

developmental biology↗

bioRxiv2021

Dynamics of anteroposterior axis establishment in a mammalian embryo-like system

1.In the mammalian embryo, specification of the anteroposterior (AP) axis demarcates one of the first steps of body plan formation. While this process requires interactions with extra-embryonic tissues in the native embryo, minimal in vitro systems from embryonic stem cells (ESCs) undergo initial AP polarization in the absence of any localized, external cues. This self-organizing potential of stem cells remains not well understood. Here, we study such an initial symmetry breaking event in gastruloids, an established in vitro model for mammalian body plan formation, using the mesodermal marker gene Brachyury or T (Bra/T) to denote the onset of AP axis specification and concomitant germ layer formation. Through aggregate fusion experiments and manipulation of initial culture conditions as well as key developmental signalling pathways, we probe the dynamics of Bra/T polarization. We further conduct single-cell (sc) RNA sequencing of gastruloids at early stages to identify incipient molecular signatures of germ layer commitment and differences between Bra/T+ and Bra/T- populations during as well as after symmetry breaking. Moreover, we transcriptionally compare early development of gastruloids to the mouse embryo and conclude that gastruloids reproducibly undergo AP axis and germ layer specification in a parallel, but distinct manner: While their primed pluripotent cell populations adopt a more mesenchymal state in lieu of an epithelial epiblast-like transcriptome, the emerging mesendodermal lineages in vitro are nevertheless similar to their in vivo equivalents. Altogether, this study provides a comprehensive analysis of self-organized body plan establishment in a minimal in vitro system of early mammalian patterning and highlights the regulative capacity of mESCs, thereby shedding light on underlying principles of axial polarity formation.

developmental biology↗

bioRxiv2018

Impaired development of neocortical circuits contributes to the neurological alterations in DYRK1A haploinsufficiency syndrome

Autism spectrum disorders are early onset neurodevelopmental disorders characterized by deficits in social communication and restricted repetitive behaviors, yet they are quite heterogeneous in terms of their genetic basis and phenotypic manifestations. Recently, de novo pathogenic mutations in DYRK1A, a chromosome 21 gene associated to neuropathological traits of Down syndrome, have been identified in patients presenting a recognizable syndrome included in the autism spectrum. These mutations produce DYRK1A kinases with partial or complete absence of the catalytic domain, or they represent missense mutations located within this domain. Here, we undertook an extensive biochemical characterization of the DYRK1A missense mutations reported to date and show that most of them, but not all, result in enzymatically dead DYRK1A proteins. We also show that haploinsufficient Dyrk1a+/- mutant mice mirror the neurological traits associated with the human pathology, such as defective social interactions, stereotypic behaviors and epileptic activity. These mutant mice present altered proportions of excitatory and inhibitory neocortical neurons and synapses. Moreover, we provide evidence that alterations in the production of cortical excitatory neurons are contributing to these defects. Indeed, by the end of the neurogenic period, the expression of developmental regulated genes involved in neuron differentiation and/or activity is altered. Therefore, our data indicate that altered neocortical neurogenesis could critically affect the formation of cortical circuits, thereby contributing to the neuropathological changes in DYRK1A haploinsufficiency syndrome.

neuroscience↗