Isabel Rodriguez

Control of compartmental affinity boundaries by Hedgehog

In Drosophila, each segmental primordium is subdivided into two cell populations, the anterior (A) and posterior (P) compartments by the selective activity of the transcription factor Engrailed (En) in P cells. Under En control, P cells secrete, but cannot respond to, the signalling protein Hedgehog (Hh). In contrast, and by default, A cells are programmed to respond to Hh by expressing other signalling molecules, such as Decapentaplegic (Dpp) and Wingless (Wg), which organize growth and patterning in both compartments,. Cells of the A and P compartments do not intermix, apparently as a consequence of their having distinct cell affinities that cause them to maximize contact with cells of the same compartment, while minimizing contact with cells from the other compartment. This failure to mix has previously been ascribed to an autonomous and direct role for En in specifying a P, as opposed to an A, cell affinity,. However, an alternative hypothesis is that Hh secreted by P cells induces A cells to acquire a distinct cell affinity, ensuring that a stable ‘affinity boundary’ forms wherever P and A cells meet. Here we show that the affinity boundary that segregates A and P cells into adjacent but immiscible cell populations is to a large extent a consequence of local Hh signalling, rather than a reflection of an intrinsic affinity difference between A and P cells.

Preparation and characterization of whey protein hydrolysates: applications in industrial whey bioconversion processes.

A whey protein hydrolysate was prepared by incubation of reconstituted whey or a whey protein concentrate with Alcalase 0.6L. The proteolytic degradation of alpha-lactalbumin and beta-lactoglobulin initially resulted in 6-kDa and, later, 2.5-kDa degradation products, quickly followed by the appearance of multiple peptides of 1 kDa or smaller. The hydrolysate showed a steady increase in solubility and a biphasic change in foaming characteristics with decreasing peptide size. At the highest degree of hydrolysis achieved (22%), the majority of the peptides were smaller than 1 kDa and could be efficiently assimilated by the yeast Kluyveromyces marxianus growing in a defined medium.

Synergistic Potentials of Coffee on Injured Pancreatic Islets and Insulin Action via KATP Channel Blocking in Zebrafish.

Pancreatic islets (PIs) are damaged under diabetic conditions, resulting in decreased PI size. This study examined the regenerative effects of coffee and its components (caffeine, CFI; trigonelline, TRG; chlorogenic acid, CGA) on zebrafish larval PIs and β-cells damaged by administration of alloxan (AX). In addition, the influence of coffee and its active components on KATP channels was investigated using diazoxide (DZ) as a KATP channel activator. PI size and fluorescence intensity were significantly increased in the coffee-treated group relative to the no-treatment group (P < 0.0001). In addition, coffee exerted significant regenerative effects on pancreatic β-cells (p = 0.006). Treatment with TRG and CGA rescued PI damage, and the combination of TRG/CGA had a synergistic effect. In conclusion, the results indicate that coffee has beneficial effects on AX-damaged PIs and may also be useful as a blocker of pancreatic β-cell K(+) channels.

Drosophila TIEG is a modulator of different signalling pathways involved in wing patterning and cell proliferation

Acquisition of a final shape and size during organ development requires a regulated program of growth and patterning controlled by a complex genetic network of signalling molecules that must be coordinated to provide positional information to each cell within the corresponding organ or tissue. The mechanism by which all these signals are coordinated to yield a final response is not well understood. Here, I have characterized the Drosophila ortholog of the human TGF-β Inducible Early Gene 1 (dTIEG). TIEG are zinc-finger proteins that belong to the Krüppel-like factor (KLF) family and were initially identified in human osteoblasts and pancreatic tumor cells for the ability to enhance TGF-β response. Using the developing wing of Drosophila as “in vivo” model, the dTIEG function has been studied in the control of cell proliferation and patterning. These results show that dTIEG can modulate Dpp signalling. Furthermore, dTIEG also regulates the activity of JAK/STAT pathway suggesting a conserved role of TIEG proteins as positive regulators of TGF-β signalling and as mediators of the crosstalk between signalling pathways acting in a same cellular context.

Silicon particles as trojan horses for potential cancer therapy

BackgroundPorous silicon particles (PSiPs) have been used extensively as drug delivery systems, loaded with chemical species for disease treatment. It is well known from silicon producers that silicon is characterized by a low reduction potential, which in the case of PSiPs promotes explosive oxidation reactions with energy yields exceeding that of trinitrotoluene (TNT). The functionalization of the silica layer with sugars prevents its solubilization, while further functionalization with an appropriate antibody enables increased bioaccumulation inside selected cells.ResultsWe present here an immunotherapy approach for potential cancer treatment. Our platform comprises the use of engineered silicon particles conjugated with a selective antibody. The conceptual advantage of our system is that after reaction, the particles are degraded into soluble and excretable biocomponents.ConclusionsIn our study, we demonstrate in particular, specific targeting and destruction of cancer cells in vitro. The fact that the LD50 value of PSiPs-HER-2 for tumor cells was 15-fold lower than the LD50 value for control cells demonstrates very high in vitro specificity. This is the first important step on a long road towards the design and development of novel chemotherapeutic agents against cancer in general, and breast cancer in particular.

Lipid Composition and Chloroplast Ultrastructure in Triazine Resistant Biotypes of Amaranthus Species

Summary A study was made of thylakoid membrane polar lipid composition and of chloroplast ultrastructure in triazine resistant (R) and susceptible (S) biotypes of four Amaranthus species. R biotypes showed higher values for MGDG/DGDG (monogalactosyl-diacylglycerides/digalactosyl-diacylglycerides) and MGDG/PL (monogalactosyl-diacylglycerides/phospholipids) ratios. For fatty acid composition, when R were compared with S biotypes, they showed higher trans-hexadecenoic acid content in the PL fraction, higher linolenic acid content in TL, MGDG and DGDG, and lower linoleic acid content in TL, MGDG and DGDG. Studies of chloroplast ultrastructure revealed no appreciable difference between RandS biotypes with regard to the chlorophyll a/b ratio or the extent of thylakoid appression.

Spatio-temporal regulation of Dachsous proteins expressed during Drosophila development

Transcriptional regulation is one of the main mechanisms involved in tissue morphogenesis to give rise to functional organs with characteristic shapes. The Drosophila dachsous (ds) gene plays a key role in tissue development and tumorigenesis by controlling planar cell polarity (PCP), tissue growth, patterning and mitochondrial activity, among other processes. Disturbance of ds expression during Drosophila development results in alterations of the function and morphology of a wide range of embryonic and larval tissues. Similarly, in humans, mutations in the DCHS1 gene cause severe congenital malformations due to a global impairment affecting the normal formation of many tissues and organs. However, the transcriptional mechanism governing the expression of ds gene remains poorly understood. Here, we perform transcriptional analysis of ds expression and identify novel embryonic Ds proteins not expressed in larvae. The comparative analysis of Ds proteins and the exon expression pattern in/of two regulatory alleles such as dsD36 and ds38K further suggests the existence of specific transcriptional ds variants at different stages. Furthermore, a search for regulatory elements that control the spatial and temporal pattern of ds revealed the presence of cis-regulatory elements located in the intronic regions, which regulate the expression of these Ds proteins. Finally, using the Drosophila wing as model to perform a functional analysis, we show that wing growth and PCP are differentially regulated by Ds proteins expressed in different regions of wing disc. The present findings reveal that the complex regulation of the ds gene ensures the expression of specific Ds protein isoforms at different developmental stages in order to activate the cell-specific molecular programs required for tissue morphogenesis.

Transcriptional analysis of the dachsous gene uncovers novel isoforms expressed during development in Drosophila

The Drosophila cadherin‐related protein Dachsous (Ds) plays a prominent role in planar cell polarity (PCP) and growth. The regulation of these two processes is based on the interaction between Ds and Fat proteins, generating an intracellular response required for tissue polarization and modulation of Hippo pathway activity. Here we have performed a comprehensive molecular study of the ds gene during larval development that has shown an unexpected complexity in its transcriptional regulation and revealed the expression of hitherto unsuspected transcripts. Also, knockdown of several isoforms provides new evidence on the importance of the cytoplasmic domain in the mechanism of action of Ds during development.

11-P003 Searching for the components of the Ds/Ft pathway in Drosophila and their orthologs in mouse

Specification of the mammalian left–right (L–R) axis is controlled by fluid flows in the embryonic node, a ciliated pit like structure located at the distal tip of the mouse embryo. Nodal cilia rotate so as to cause a leftward fluid flow-this has been experimentally demonstrated to control embryonic sidedness. How the embryo interprets this flow remains the subject of debate. The two cilia hypothesis argues that immotile cilia are deformed by flow, causing a Pkd2-dependent left sided Ca2+ signal. Other hypotheses argue that morphogens become asymmetrically localised in response to flow. Rikishi (rks), an ENU-derived point mutant, displays striking defects in L-R patterning that phenocopy the Pkd2 mutant. While Pkd1 interacts with Pkd2 in the kidney to produce a stress induced Ca2+ channel, Pkd1 has no role in L–R patterning. The rks mutation is in a conserved residue in a Pkd1 related gene. We therefore, propose that rks interacts with Pkd2 in L–R patterning in the node, supporting the two cilia hypothesis. However, when we examined cilia motility in Pkd2 and rks mutant embryos, we found that while Pkd2 / nodal cilia were motile, rks mutant nodal cilia were immotile. The rks and Pkd2 phenotypes are distinct from immotile cilia phenotypes, revealing a dual role for rks: in combination with Pkd2 in flow detection as well as a previously unrecognised role for Ca2+ signalling in cilia motility in the mouse node.