Biology subjects

Martin-Blanco, E.

Publications and source records attributed to Martin-Blanco, E..

4 recordsLinked to original sources

bioRxiv2017

Contractility, Differential Tension and Membrane Removal direct zebrafish Epiboly Biomechanics

Precise tissue remodeling during development is essential for shaping embryos and for optimal organ function. Epiboly is an early gastrulation event by which the blastoderm expands around the yolk to engulf it. Three different layers are involved, an epithelial layer (the enveloping layer, EVL), the embryo proper, constituted by the deep cells (DCs), and the yolk cell. Although teleost epiboly has been studied for many years, a clear understanding of its mechanics was still missing. Here we present new information on the cellular, molecular and mechanical elements involved in epiboly that, together with some other recent data and upon comparison with previous biomechanical models, lets conclude that the expansion of the epithelia is passive and driven by cortical contraction and membrane removal in the adjacent layer, the External Yolk Syncytial Layer (E-YSL). The isotropic actomyosin contraction of the E-YSL generates an anisotropic stress pattern and a directional net movement as a result of the differences in the deformation response of two opposites adjacent domains (the EVL and the Yolk Cytoplasmic Layer - YCL). Contractility is accompanied by the local formation of membrane folds and the membrane removal by Rab5ab dependent macropinocytosis. The increase in area of the epithelia during the expansion is achieved by cell-shape changes (flattening) responding to spherical geometrical cues. The counterbalance between the geometry of the embryo and forces dissipation is therefore essential for epiboly global coordination.

developmental biology↗

bioRxiv2016

Rab5-mediated Yolk Endocytosis modulates Zebrafish Epiboly Biomechanics and Tissue Movements

Morphogenetic processes demand the coordinated allocation of cells and tissues to their final destination in a spatio-temporal controlled way. Identifying how these morphogenetic movements are directed and implemented is essential for understanding morphogenesis. Topographical and scalar differences in adhesion and contractility within and between cells are essential, yet, the role that membrane remodeling may play remains less clear. To clarify how surface turnover and dynamics may modulate tissue arrangements we studied epiboly in the zebrafish. During epiboly the blastoderm expands as a result of an asymmetry of mechanical tension along the embryo surface. In this scenario, we found that the membrane removal by macropinocytosis of the external yolk cell syncytial layer (E-YSL) ahead of the blastoderm is key for epiboly progression In early zebrafish embryos, the activity of the GTPase Rab5ab was essential for endocytosis, and interference in its expression exclusively in the yolk cell resulted in the reduction of yolk cell actomyosin contractility, the disruption of cortical and internal yolk flows, a disequilibrium in force balance and as a result epiboly impairment. We conclude that regulated membrane remodeling is crucial for directing cell and tissue mechanics and coordinating morphogenetic movements during epiboly.

developmental biology↗

bioRxiv2016

The Dachsous/Fat/Four-jointed pathway implements axial long-range cell orientation

Despite a cumulative body of knowledge describing short-range cell interactions in morphogenetic processes, relatively little is known on the mechanism involved in the long-range spatial and temporal coordination of cells to build functional and structurally organized tissues. In particular, the attainment of a functionally optimized epithelia must require directional cues to instruct cell movements and cell orientations throughout the tissue field. In Drosophila, the adult epidermis of the abdominal segments is created de novo by the replacement of obsolete larval epidermal cells (LECs) by histoblasts (imaginal founder cells). As these proliferate, expand and fuse, they uniformly organize orienting on the surface along the antero-posterior axis. We found that the coordinated, axially oriented changes in shape of histoblasts respond to a dynamic, yet stereotyped redesign of the epithelial field mediated by the Dachsous/Fat/Four-jointed (Ds/Ft/Fj) pathway. The establishment and refinement of the expression gradients of the atypical cadherins Ds and Ft result in their axial polarization across cell interfaces and differential adhesiveness. We suggest that the role of Ds/Ft/Fj in long-range axially oriented planar cell alignment is a general function and that the regulation of the expression of its components would be crucial in the achievement of tissue uniformity in many other morphogenetic models or during tissue repair.

developmental biology↗

bioRxiv2016

The architectural balance of the Ventral Nerve Cord depends on the level of JNK signaling activity

Central Nervous System (CNS) organogenesis is a complex process that obeys precise architectural rules. The impact that nervous system architecture may have on its functionality remains, however, relatively unexplored. To clarify this problem, we analyzed the development of the Drosophila embryonic Ventral Nerve Cord (VNC). VNC morphogenesis requires the tight control of Jun kinase (JNK) signaling, exerted in part via a negative feedback loop mediated by the dual specificity phosphatase Puckered, in a subset of pioneer neurons. Here we show that the JNK pathway autonomously regulates neuronal electrophysiological properties without affecting synaptic vesicle transport. Manipulating, during early embryogenesis, JNK signaling activity in pioneer neurons, directly influences their function as organizers of VNC architecture and, moreover, uncovers a role in the coordination of the embryonic motor circuitry that is required for hatching. Together, our data reveal critical links, mediated by the control of the JNK signaling cascade by Puckered, between the structural organization of the VNC and its functional optimization.

developmental biology↗