Biology subjects

Mongera, A.

Publications and source records attributed to Mongera, A..

4 recordsLinked to original sources

bioRxiv2022

Activity-driven extracellular volume expansion drives vertebrate axis elongation

The vertebrate bauplan is primarily established via the formation of embryonic tissues in a head-to-tail progression. The biomechanics of this elongation, which requires the presomitic mesoderm (PSM), remains poorly understood. Here, we find that avian PSM explants can elongate autonomously when physically confined in vitro, producing a pushing force that can largely account for the posterior elongation of the embryo. Tissue elongation results from volumetric expansion that is driven by cellular activity and accompanied by inhomogeneous increase of the extracellular fraction along the AP axis. We show that FGF signaling promotes glycolysis-dependent production of Hyaluronic Acid (HA), which is required for expansion of the posterior PSM. Our findings link body axis elongation to tissue expansion through the metabolic control of extracellular matrix production downstream of FGF signaling. One-Sentence SummaryActive tissue expansion propels body elongation independent of cell proliferation-driven growth

developmental biology↗

bioRxiv2022

Chitin utilization by marine picocyanobacteria and the evolution of a planktonic lifestyle

Marine picocyanobacteria (Prochlorococcus and Synechococcus), the most abundant photosynthetic cells in the oceans, are generally thought to have a primarily single-celled and free-living lifestyle. However, we find that genes for breaking down chitin - an abundant source of organic carbon that primarily exists as particles - are widespread in this group. We further show that cells with a chitin degradation pathway display chitin degradation activity, attach to chitin particles and show enhanced growth under low light conditions when exposed to chitosan, a partially deacetylated form of chitin. Marine chitin is largely derived from arthropods, whose roots lie in the early Phanerozoic, 520-535 million years ago, close to when marine picocyanobacteria began colonizing the ocean. We postulate that attachment to chitin particles allowed benthic cyanobacteria to emulate their mat-based lifestyle in the water column, initiating their expansion into the open ocean, seeding the rise of modern marine ecosystems. Transitioning to a constitutive planktonic life without chitin associations along a major early branch within the Prochlorococcus tree led to cellular and genomic streamlining. Our work highlights how coevolution across trophic levels creates metabolic opportunities and drives biospheric expansions.

ecology↗

bioRxiv2022

Reconstruction and deconstruction of human somitogenesis in vitro

The body of vertebrates displays a segmental organization which is most conspicuous in the periodic organization of the vertebral column and peripheral nerves. This metameric organization is first implemented when somites, which contain the precursors of skeletal muscles and vertebrae, are rhythmically generated from the presomitic mesoderm (PSM). Somites then become subdivided into anterior and posterior compartments essential for vertebral formation and segmental patterning of the peripheral nervous system1-4. How this key somitic subdivision is established remains poorly understood. Here we introduce novel tridimensional culture systems of human pluripotent stem cells (PSCs), called Somitoids and Segmentoids, which can recapitulate the formation of epithelial somite-like structures with antero-posterior (AP) identity. Using these systems, we identified a key organizing function of the segmentation clock in converting temporal rhythmicity into the spatial regularity of anterior and posterior somitic compartments. We show that an initial salt-and-pepper expression pattern of the segmentation gene MESP2 in the newly formed segment is transformed into defined compartments of anterior and posterior identity via an active cell sorting mechanism. Moreover, we demonstrate a large degree of independence of the various patterning modules involved in somitogenesis including the segmentation clock, somite epithelialization and AP polarity patterning. Together we put forward a novel framework accounting for the symmetry breaking process initiating somite polarity patterning. Our work provides a valuable platform to decode general principles of somitogenesis and advance knowledge of human development.

developmental biology↗

bioRxiv2021

Mechanics of the cellular microenvironment as perceived by cells in vivo

Tissue morphogenesis and repair, as well as organ homeostasis, require cells to constantly monitor their 3D microenvironment and adapt their behaviors in response to local biochemical and mechanical cues1-6. In vitro studies have shown that substrate stiffness and stress relaxation are important mechanical parameters in the control of cell proliferation and differentiation, stem cell maintenance, cell migration 7-11, as well as tumor progression and metastasis12,13. Yet, the mechanical parameters of the microenvironment that cells perceive in vivo, within 3D tissues, remain unknown. In complex materials with strain- and time-dependent material properties, the perceived mechanical parameters depend both on the strain and timescales at which the material is mechanically probed14. Here, we quantify in vivo and in situ the mechanics of the cellular microenvironment that cells probe during vertebrate presomitic mesoderm (PSM) specification. By analyzing the magnitude and dynamics of endogenous, cell-generated strains, we show that individual cells preferentially probe the stiffness associated with deformations of the supracellular, foam-like tissue architecture. We reveal how stress relaxation leads to a perceived microenvironment stiffness that decreases over time, with cells probing the softest regime. While stress relaxation timescales are spatially uniform in the tissue, most mechanical parameters, including those probed by cells, vary along the anteroposterior axis, as mesodermal progenitors commit to different lineages. Understanding the mechanical parameters that cells probe in their native 3D environment is important for quantitative studies of mechanosensation in vivo2-4,6,15 and can help design scaffolds for tissue engineering applications16-18.

biophysics↗