Biology subjects

Nahaboo, W.

Publications and source records attributed to Nahaboo, W..

3 recordsLinked to original sources

bioRxiv2021

Keratin dynamics govern the establishment of the maternal-fetal interface.

After implantation, the mouse embryo undergoes gastrulation and forms mesoderm and endoderm. Mesoderm participates in embryonic and extra-embryonic tissues including the amnion, yolk sac, chorion and allantois, the umbilical cord precursor. Extra-embryonic mesoderm is rich in intermediate filaments. Two-photon live imaging of keratin 8-eYFP knock-in embryos allowed recording nucleation and elongation of keratin filaments, which formed apical cables coordinated across multiple cells in amnion, allantois, and blood islands. Embryos lacking all keratins displayed a deflated exocoelomic cavity, a narrow thick amnion, and a short allantois, indicating a hitherto unknown role for keratin filaments in post-implantation extra-embryonic membranes morphogenesis. Single-cell RNA sequencing of mesoderm cells, microdissected amnion, chorion, and allantois provided an interactive atlas of transcriptomes with germ layer and regional information. Keratin 8high mesenchymal cells in contact with the exocoelom shared a cytoskeleton and adhesion expression profile that might explain the adaptation of extra-embryonic structures to the increasing mechanical pressure. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=199 SRC="FIGDIR/small/438772v1_ufig1.gif" ALT="Figure 1"> View larger version (47K): org.highwire.dtl.DTLVardef@30dfe4org.highwire.dtl.DTLVardef@bb19d6org.highwire.dtl.DTLVardef@19d6758org.highwire.dtl.DTLVardef@ebd3a5_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental biology↗

bioRxiv2020

An asymmetry in the frequency and position of mitosis in the epiblast precedes gastrulation and suggests a role for mitotic rounding in cell delamination during primitive streak epithelial-mesenchymal transition.

The epiblast, a pseudostratified epithelium, is the precursor for the three main germ layers required for body shape and organogenesis: ectoderm, mesoderm, and endoderm. At gastrulation, a subpopulation of epiblast cells constitutes a transient posteriorly located structure called the primitive streak, where cells that undergo epithelial-mesenchymal transition make up the mesoderm and endoderm lineages. In order to observe the behavior of individual cells, epiblast cells were labeled ubiquitously or in a mosaic fashion using fluorescent membrane reporters. The cell shapes of individual cells and the packing and behaviour of neighbouring cells during primitive streak formation were recorded through live time-lapse imaging. Posterior epiblast displayed a higher frequency of rosettes, a signature of cell rearrangements, prior to primitive streak initiation. A third of rosettes were associated with a central cell undergoing mitosis. Interestingly, cells at the primitive streak, in particular delaminating cells, underwent mitosis twice more frequently than other epiblast cells, suggesting a role for cell division in epithelial-mesenchymal transition. Pseudostratified epithelia are characterized by interkinetic nuclear migration, where mitosis occurs at the apical side of the epithelium. However, we found that exclusively on the posterior side of the epiblast, mitosis was not restricted to the apical side. Non-apical mitosis was apparent as early as E5.75, just after the establishment of the anterior-posterior axis, and prior to initiation of epithelial-mesenchymal transition. Non-apical mitosis was associated with primitive streak morphogenesis, as it occurred specifically in the streak even when ectopically located. Most non-apical mitosis resulted in one or two daughter cells leaving the epiblast layer to become mesoderm. Furthermore, in contrast to what has been described in other pseudostratified epithelia such as neuroepithelium, the majority of cells dividing apically detached completely from the basal pole in the epiblast. Cell rearrangement associated with mitotic cell rounding in the posterior epiblast during gastrulation, in particular when it occurs on the basal side, might thus facilitate cell ingression through the PS and transition to a mesenchymal phenotype. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=105 SRC="FIGDIR/small/959080v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@18530b2org.highwire.dtl.DTLVardef@1400a63org.highwire.dtl.DTLVardef@169f688org.highwire.dtl.DTLVardef@1b87931_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental biology↗

bioRxiv2018

Distinct mesoderm migration phenotypes in extra-embryonic and embryonic regions of the early mouse embryo

In the gastrulating mouse embryo, epiblast cells delaminate at the primitive streak to form mesoderm and definitive endoderm, through an epithelial-mesenchymal transition.\n\nMosaic expression of a membrane reporter in nascent mesoderm enabled recording cell shape and trajectory through live imaging. Upon leaving the streak, cells changed shape and extended protrusions of distinct size and abundance depending on the neighboring germ layer, as well as the region of the embryo. Embryonic trajectories were meandrous but directional, while extra-embryonic mesoderm cells showed little net displacement.\n\nEmbryonic and extra-embryonic mesoderm transcriptomes highlighted distinct guidance, cytoskeleton, adhesion, and extracellular matrix signatures. Specifically, intermediate filaments were highly expressed in extra-embryonic mesoderm, while live imaging for F-actin showed abundance of actin filaments in embryonic mesoderm only. Accordingly, RhoA or Rac1 conditional deletion in mesoderm inhibited embryonic, but not extra-embryonic mesoderm migration.\n\nOverall, this indicates separate cytoskeleton regulation coordinating the morphology and migration of mesoderm subpopulations.

developmental biology↗