Cell coupling compensates for changes in single-cell Her6 dynamics and provides phenotypic robustness.

This paper investigates the effect of altering the protein expression dynamics of the bHLH transcription factor Her6 at the single-cell level in the embryonic zebrafish telencephalon. Using a homozygote endogenous Her6:Venus reporter and 4D single-cell tracking, we show that Her6 oscillates in neural telencephalic progenitors and that the fusion of protein destabilisation (PEST) domain alters its expression dynamics, causing most cells to downregulate Her6 prematurely. However, counterintuitively, oscillatory cells increase, with some expressing Her6 at high levels, resulting in increased heterogeneity of Her6 expression in the population.

Sequential and additive expression of miR-9 precursors control timing of neurogenesis.

MicroRNAs (miRs) have an important role in tuning dynamic gene expression. However, the mechanism by which they are quantitatively controlled is unknown. We show that the amount of mature miR-9, a key regulator of neuronal development, increases during zebrafish neurogenesis in a sharp stepwise manner.

Differential phase register of Hes1 oscillations with mitoses underlies cell-cycle heterogeneity in ER breast cancer cells.

Here, we study the dynamical expression of endogenously labeled Hes1, a transcriptional repressor implicated in controlling cell proliferation, to understand how cell-cycle length heterogeneity is generated in estrogen receptor (ER) breast cancer cells. We find that Hes1 shows oscillatory expression with ∼25 h periodicity and during each cell cycle has a variable peak in G1, a trough around G1-S transition, and a less variable second peak in G2/M. Compared to other subpopulations, the cell cycle in CD44CD24 cancer stem cells is longest and most variable.

A dynamic, spatially periodic, micro-pattern of HES5 underlies neurogenesis in the mouse spinal cord.

Ultradian oscillations of HES Transcription Factors (TFs) at the single-cell level enable cell state transitions. However, the tissue-level organisation of HES5 dynamics in neurogenesis is unknown. Here, we analyse the expression of HES5 ex vivo in the developing mouse ventral spinal cord and identify microclusters of 4-6 cells with positively correlated HES5 level and ultradian dynamics.

Dynamic properties of noise and Her6 levels are optimized by miR-9, allowing the decoding of the Her6 oscillator.

Noise is prevalent in biology and has been widely quantified using snapshot measurements. This static view obscures our understanding of dynamic noise properties and how these affect gene expression and cell state transitions. Using a CRISPR/Cas9 Zebrafish her6::Venus reporter combined with mathematical and in vivo experimentation, we explore how noise affects the protein dynamics of Her6, a basic helix-loop-helix transcriptional repressor.

A secretory cell type develops alongside multiciliated cells, ionocytes and goblet cells, and provides a protective, anti-infective function in the frog embryonic mucociliary epidermis.

The larval epidermis of Xenopus is a bilayered epithelium, which is an excellent model system for the study of the development and function of mucosal and mucociliary epithelia. Goblet cells develop in the outer layer while multiciliated cells and ionocytes sequentially intercalate from the inner to the outer layer. Here, we identify and characterise a fourth cell type, the small secretory cell (SSC).

ERK and phosphoinositide 3-kinase temporally coordinate different modes of actin-based motility during embryonic wound healing.

Embryonic wound healing provides a perfect example of efficient recovery of tissue integrity and homeostasis, which is vital for survival. Tissue movement in embryonic wound healing requires two functionally distinct actin structures: a contractile actomyosin cable and actin protrusions at the leading edge. Here, we report that the discrete formation and function of these two structures is achieved by the temporal segregation of two intracellular upstream signals and distinct downstream targets.

Inositol kinase and its product accelerate wound healing by modulating calcium levels, Rho GTPases, and F-actin assembly.

Wound healing is essential for survival. We took advantage of the Xenopus embryo, which exhibits remarkable capacities to repair wounds quickly and efficiently, to investigate the mechanisms responsible for wound healing. Previous work has shown that injury triggers a rapid calcium response, followed by the activation of Ras homolog (Rho) family guanosine triphosphatases (GTPases), which regulate the formation and contraction of an F-actin purse string around the wound margin.

C/EBPalpha initiates primitive myelopoiesis in pluripotent embryonic cells.

The molecular mechanisms that underlie the development of primitive myeloid cells in vertebrate embryos are not well understood. Here we characterize the role of cebpa during primitive myeloid cell development in Xenopus. We show that cebpa is one of the first known hematopoietic genes expressed in the embryo.

spib is required for primitive myeloid development in Xenopus.

Vertebrate blood formation occurs in 2 spatially and temporally distinct waves, so-called primitive and definitive hematopoiesis. Although definitive hematopoiesis has been extensively studied, the development of primitive myeloid blood has received far less attention. In Xenopus, primitive myeloid cells originate in the anterior ventral blood islands, the equivalent of the mammalian yolk sac, and migrate out to colonize the embryo.

xRic-8 is a GEF for Gsalpha and participates in maintaining meiotic arrest in Xenopus laevis oocytes.

Immature stage VI Xenopus oocytes are arrested at the G(2)/M border of meiosis I until exposed to progesterone, which induces meiotic resumption through a non-genomic mechanism. One of the earliest events produced by this hormone is inhibition of the plasma membrane enzyme adenylyl cyclase (AC), with the concomitant drop in intracellular cAMP levels and reinitiation of the cell cycle. Recently Gsalpha and Gbetagamma have been shown to play an important role as positive regulators of Xenopus oocyte AC, maintaining the oocyte in the arrested state.

Galphaq negatively regulates the Wnt-beta-catenin pathway and dorsal embryonic Xenopus laevis development.

The non-canonical Wnt/Ca2+ signaling pathway has been implicated in the regulation of axis formation and gastrulation movements during early Xenopus laevis embryo development, by antagonizing the canonical Wnt/beta-catenin dorsalizing pathway and specifying ventral cell fate. However, the molecular mechanisms involved in this antagonist crosstalk are not known. Since Galphaq is the main regulator of Ca2+ signaling in vertebrates and from this perspective probably involved in the events elicited by the non-canonical Wnt/Ca2+ pathway, we decided to study the effect of wild-type Xenopus Gq (xGalphaq) in dorso-ventral axis embryo patterning.

Epidemiological surveillance of ovine hydatidosis in Tierra del Fuego, Patagonia Argentina, 1997-1999.

Cystic echinococcosis is the most prevalent zoonosis in Tierra del Fuego province, Argentina, with important economic, productive and public health consequences. The present work was performed to determine the ovine prevalence in Tierra del Fuego, Argentina, as well as to evaluate the quality of diagnostic systems in slaughterhouses. Moreover, genetic analyses to characterize the strain of Echinococcus granulosus involved in the region were done.

A Gbetagamma stimulated adenylyl cyclase is involved in Xenopus laevis oocyte maturation.

Xenopus laevis oocyte maturation is induced by the steroid hormone progesterone through a nongenomic mechanism that implicates the inhibition of the effector system adenylyl cyclase (AC). Recently, it has been shown that the G protein betagamma heterodimer is involved in oocyte maturation arrest. Since AC is the proposed target for Gbetagamma action, we considered of importance to identify and characterize the Gbetagamma regulated AC isoform(s) that are expressed in the Xenopus oocyte.

Modulation of glycine-activated ion channel function by G-protein betagamma subunits.

Glycine receptors (GlyRs), together with GABA(A) and nicotinic acetylcholine (ACh) receptors, form part of the ligand-activated ion channel superfamily and regulate the excitability of the mammalian brain stem and spinal cord. Here we report that the ability of the neurotransmitter glycine to gate recombinant and native ionotropic GlyRs is modulated by the G protein betagamma dimer (Gbetagamma). We found that the amplitude of the glycine-activated Cl- current was enhanced after application of purified Gbetagamma or after activation of a G protein-coupled receptor.

Human brain synembryn interacts with Gsalpha and Gqalpha and is translocated to the plasma membrane in response to isoproterenol and carbachol.

Heterotrimeric G-proteins transduce signals from heptahelical transmembrane receptors to different effector systems, regulating diverse complex intracellular pathways and functions. In brain, facilitation of depolarization-induced neurotransmitter release for synaptic transmission is mediated by Gsalpha and Gqalpha. To identify effectors for Galpha-proteins, we performed a yeast two-hybrid screening of a human brain cDNA library, using the human Galphas protein as a bait.

S111N mutation in the helical domain of human Gs(alpha) reduces its GDP/GTP exchange rate.

G-protein alpha subunits consist of two domains: a Ras-like domain also called GTPase domain (GTPaseD), structurally homologous to monomeric G-proteins, and a more divergent domain, unique to heterotrimeric G-proteins, called helical domain (HD). G-protein activation, requires the exchange of bound GDP for GTP, and since the guanine nucleotide is buried in a deep cleft between both domains, it has been postulated that activation may involve a conformational change that will allow the opening of this cleft. Therefore, it has been proposed, that interdomain interactions are playing an important role in regulating the nucleotide exchange rate of the alpha subunit.