Biology subjects

Costantini, E.

Publications and source records attributed to Costantini, E..

3 recordsLinked to original sources

bioRxiv2023

Clonal neural tube organoids self-organise floorplate through BMP-mediated cluster competition

The neural tube (NT) has been a hallmark example of embryonic induction and patterning whereby the notochord induces an organiser, the floorplate, that secretes Sonic Hedgehog (SHH) to pattern the surrounding field of neural progenitors. On the other hand, NT organoids (NTOs) formed from embryonic stem cells (ESCs) undergo spontaneous floorplate formation and patterning in the absence of their normal embryonic inducers. Understanding how stem cells undergo regulative organiser formation is a central challenge in biology. Here, we investigated the self-organisation of a SHH-expressing floorplate organiser using clonal NTOs. Expression of FOXA2, a floorplate transcription factor, was initially spatially scattered before resolving into multiple clusters. These FOXA2+ clusters underwent competition and physical sorting, resulting in a stable "winning" floorplate. We identified BMP signalling as a key governor of long-range cluster competition. FOXA2+ clusters expressed BMP4 ligand suppressing FOXA2 in receiving cells, while simultaneously expressing the BMP-inhibitor NOGGIN to secure FOXA2+ cluster survival. Genetic mutation of Noggin perturbed the floorplate not only in NTOs but also in vivo at the mid-hindbrain region of the mouse NT. These results demonstrate how the floorplate can form autonomously without its well-known inducer, the notochord, suggesting redundant mechanisms ensuring robustness. Defining molecular pathways that govern organiser self-organisation is critical in harnessing the developmental plasticity of stem cells toward directed tissue engineering.

developmental biology↗

bioRxiv2022

Perturbation of protein homeostasis brings plastids at the crossroad between repair and dismantling

The chloroplast proteome is a dynamic mosaic of plastid- and nuclear-encoded proteins. Plastid protein homeostasis is maintained through the balance between de novo synthesis and proteolysis. Intracellular communication pathways, including the plastid-to-nucleus signalling and the protein homeostasis machinery, made of stromal chaperones and proteases, shape chloroplast proteome based on developmental and physiological needs. However, the maintenance of fully functional chloroplasts is costly and under specific stress conditions the degradation of damaged chloroplasts is essential to the maintenance of a healthy population of photosynthesising organelles while promoting nutrient redistribution to sink tissues. In this work, we have addressed this complex regulatory chloroplast- quality-control pathway by modulating the expression of two nuclear genes encoding plastid ribosomal proteins PRPS1 and PRPL4. By transcriptomics, proteomics and transmission electron microscopy analyses, we show that the increased expression of PRPS1 gene leads to chloroplast degradation and early flowering, as an escape strategy from stress. On the contrary, the overaccumulation of PRPL4 protein is kept under control by increasing the amount of plastid chaperones and components of the unfolded protein response (cpUPR) regulatory mechanism. This study advances our understanding of molecular mechanisms underlying chloroplast retrograde communication and provides new insight into cellular responses to impaired plastid protein homeostasis.

plant biology↗

bioRxiv2022

Developmental cell fate choice employs two distinct cis regulatory strategies

In many developing tissues the patterns of gene expression that assign cell fate are organised by secreted signals functioning in a graded manner over multiple cell diameters. Cis Regulatory Elements (CREs) interpret these graded inputs to control gene expression. How this is accomplished remains poorly understood. In the neural tube, a gradient of the morphogen Sonic hedgehog allocates neural progenitor identity. Here, we uncover two distinct ways in which CREs translate graded Shh signaling into differential gene expression. In the majority of ventral neural progenitors a common set of CREs are used to control gene activity. These CREs integrate cell type specific inputs to control gene expression. By contrast, the most ventral progenitors use a unique set of CREs. These are established by the pioneer factor FOXA2, paralleling the role of FOXA2 in endoderm. Moreover, FOXA2 binds a subset of the same sites in neural and endoderm cells. Together the data identify distinct cis regulatory strategies for the interpretation of morphogen signaling and raise the possibility of an evolutionarily conserved role for FOXA2-mediated regulatory strategy across tissues.

developmental biology↗