Biology subjects

de Celis, J. F.

Publications and source records attributed to de Celis, J. F..

4 recordsLinked to original sources

bioRxiv2025

Signaling by RasG12V depends on EGFR activity in vivo

Ras proteins are key regulators of signaling pathways initiated by transmembrane tyrosine kinase receptors, and activating Ras mutations are drivers in cancer and RASophaties. The development of effective therapies against these diseases requires a profound understanding of how Ras mutations modify pathway output and interact with other pathway components. In this work we generated G12V activating mutations in the Drosophila Ras1 locus and used Ras1G12V and human KRASBG12V to analyze in vivo the consequences of endogenous RasG12V expression and its interplay with other components of the EGFR/Raf/MAPK pathway. We find that RasG12V alters the timing but not the spatial pattern of ERK activation. Consistently, RasG12V mutant proteins respond to EGFR stimulation and can partially compensates for EGFR loss to generate basal levels of ERK activity. However, full pathway activation is still strictly dependent on EGFR function. Altogether, our results suggest that RasG12V mutant proteins act as an amplifier of EGFR stimulation accelerating and raising baseline ERK activity but requiring EGFR signaling for maximal activation. This mechanistic framework supports the use of combined inhibition of both Ras and EGFR to maximize therapeutic efficacy in RasG12V tumors.

genetics↗

bioRxiv2024

A function of Spalt proteins in heterochromatin organization and maintenance of genomic DNA integrity

The phylogenetically conserved Spalt proteins regulate gene expression and participate in a variety of cell fate choices during multicellular development, generally acting as transcriptional repressors in different gene regulatory networks. Paradoxically, besides their roles as DNA sequence-specific transcription factors, Spalt proteins show a consistent localization to heterochromatic regions. They can act through interactions with the Nucleosome remodeling and deacetylase complex (NuRD) to promote closing of open chromatin domains, but their activities as epigenetic regulators also rely on interactions with DNA Methyltransferases or with the Lysine-specific histone demethylase LSD1, suggesting that they can participate in multiple regulatory mechanisms. Here we describe several major consequences of loss of spalt function in Drosophila cells, including changes in chromatin accessibility affecting mostly pericentromeric heterochromatin, the generation of DNA damage, alterations in the localization of chromosomes within the nucleus in polyploid cells of the salivary glands and miss-expression of transposable elements. We suggest that most of these effects are related to roles of Spalt proteins in the regulation of heterochromatin formation. We propose that Drosophila Spalt proteins have two complementary functions, acting as sequence-specific transcriptional repressors on specific target genes and regulating more global gene silencing through the generation or maintenance of heterochromatic domains.

developmental biology↗

bioRxiv2023

A function of Spalt major as a sequence-specific DNA binding transcription factor mediates repression of knirps in the Drosophila wing imaginal disc

The Spalt transcriptional regulators participate in a variety of cell fate decisions during multicellular development. Vertebrate Spalt proteins have been mostly associated to the organization of heterochromatic regions, but they also contribute regulatory functions through binding to A/T rich motives present in their target genes. The developmental processes in which the Drosophila spalt genes participate are well known through genetic analysis, but the mechanism by which the Spalt proteins regulate transcription are still unknown. Furthermore, despite the prominent changes in gene expression associated to mutations in the spalt genes, the specific DNA sequences they bind are also unknow. In this contribution we describe the analysis of a DNA fragment present in the regulatory region of the knirps gene. Spalt proteins are candidate repressors of knirps expression during the formation of the venation pattern in the wing disc, and here we identify a minimal conserved 30bp sequence that binds to Spalt major both in vivo and in vitro. This sequence mediates transcriptional repression in the central region of the wing blade, constituting the first confirmed case of a direct regulatory interaction between Spalt major and its target DNA in Drosophila.

developmental biology↗

bioRxiv2018

A refutation to ‘A new A-P compartment boundary and organizer in holometabolous insect wings.’

We respond to a recent report by Abbasi and Marcus who present two main findings: first they argue that there is an organiser and a compartment boundary within the posterior compartment of the butterfly wing. Second, they present evidence for a previously undiscovered lineage boundary near wing vein 5 in Drosophila, a boundary that delineates a \"far posterior\" compartment. Clones of cells were marked with the yellow mutation and they reported that these clones always fail to cross a line close to vein 5 on the Drosophila wing. In our hands yellow proved an unusable marker for clones in the wing blade and therefore we reexamined the matter. We marked clones of cells with multiple wing hairs or forked and found a substantial proportion of these clones cross the proposed lineage boundary near vein 5, in conflict with their findings and conclusion. As internal controls we showed that these same clones respect the other two well established compartment boundaries: the anteroposterior compartment boundary is always respected. The dorsoventral boundary is mostly respected, and is crossed only by clones that are induced early in development, consistent with many reports. We question the validity of Abbasi and Marcus conclusions regarding the butterfly wing but present no new data.\n\nArising from: R. Abbasi and J. M. Marcus Sci. Rep. 7, 16337 (2017); https://doi.org/10.1038/s41598-017-16553-5

developmental biology↗