Biology subjects

Marzullo, M.

Publications and source records attributed to Marzullo, M..

10 recordsLinked to original sources

bioRxiv2025

Distinct Cellular Effects of Myotonic Dystrophy type 2 RAN Tetrapeptides in Drosophila melanogaster

Myotonic dystrophy type 2 (DM2) is an autosomal dominant, multisystemic disorder caused by the expansion of CCTG repeats in the first intron of the CNBP gene. Repeat-associated non-AUG (RAN) translation of the expanded CCTG RNA may produce two tetrapeptide repeat proteins (TPRs), poly-QAGR and poly-PACL, whose roles in DM2 pathogenesis remain poorly understood. To investigate their individual contributions, we expressed codon-optimized QAGR and PACL peptides with ATG start codon in Drosophila melanogaster. Expression of QAGR and PACL TPRs significantly compromised fly viability and lifespan, induces eye degeneration and locomotor defects. We found that QAGR accumulated in the nucleolus, disrupted nucleolar integrity, and compromised rRNA processing. Moreover, QAGR expression interfered with autophagy, leading to the accumulation of Atg8a- and Ref(2)P-positive aggregates. Genetic interaction studies showed that overexpression of Atg8a or Ref(2)P mitigated QAGR-induced eye-toxicity, while knockdown of autophagy genes exacerbated it. Conversely, PACL repeats promoted stress granule formation, as indicated by their colocalization with TIAR in human cells and their epistatic interaction with the Drosophila orthologue Rox8. Notably, cytoplasmic PACL aggregates were observed in myoblasts of DM2 patient. Together these findings demonstrate that QAGR and PACL peptides exert distinct toxic effects, impairing nucleolar function and autophagy, or altering stress granule dynamics, respectively. Both mechanisms likely converge to drive DM2 pathogenesis and represent promising therapeutic targets.

genetics↗

bioRxiv2025

Microcephaly-Associated Genes asp and Sas4 Control Chromatin Organization and Nuclear Lamina Structure in Drosophila melanogaster

Autosomal recessive primary microcephaly (MCPH) is a neurodevelopmental disorder characterized by reduced brain size and non-progressive intellectual disability. Mutations in over 30 genes have been linked to MCPH. Nearly a half of the genes identified by these mutations encode proteins involved in centrosome biogenesis or microtubule (MT) dynamics, suggesting a central role for mitotic spindle organization and division plane orientation in disease aetiology. However, it has been suggested that disruptions in spindle positioning alone are not sufficient to lead to microcephaly. Here, we investigate the contribution of the Drosophila orthologs of ASPM/MCPH5 (asp) and CENPJ/MCPH6 (Sas4) to nuclear architecture, chromatin organization, and genome stability. We show that loss of either Sas4 or Asp leads to aberrant microtubule architecture, mislocalization of the LINC complex, and deformation of the nuclear lamina. These defects are accompanied by reduced levels of both lamin and HP1 and impaired centromere clustering in interphase cells. Sas4 and asp mutants also exhibit a global reduction in heterochromatin-associated histone marks (H3K9me2/3 and H3K27me3) and increased levels of the euchromatin-associated mark H3K4me3. Remarkably, treatment with Methylstat, a demethylase inhibitor, reduced nuclear invaginations by partially restoring H3K9me3 levels. Additionally, Sas4 or Asp depletion leads to DNA damage, increased sensitivity to genotoxic stress, and delayed DNA repair. Together, these findings reveal a previously underappreciated role for Asp and Sas4 in preserving nuclear architecture and chromatin integrity, offering new insight into the pathogenesis of MCPH. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/666102v1_ufig1.gif" ALT="Figure 1"> View larger version (79K): org.highwire.dtl.DTLVardef@bfdfbborg.highwire.dtl.DTLVardef@f983eaorg.highwire.dtl.DTLVardef@143857borg.highwire.dtl.DTLVardef@1f0895b_HPS_FORMAT_FIGEXP M_FIG C_FIG

genetics↗

bioRxiv2025

Caspase-8 is a novel modulator of Homologous Recombination Repair in response to ionizing radiations

Caspase-8 is a cysteine protease historically regarded as anti-neoplastic protein, thanks to its role in apoptosis. However, Caspase-8 expression is retained or even enhanced in several tumors, including glioblastoma (GBM), where it plays pro-tumor functions. We previously reported that it is a negative prognostic factor and contributes to resistance against DNA damaging agents, such as ionizing radiations (IR) and Temozolomide, commonly used in standard GBM treatment. We therefore investigated whether Caspase-8 may sustain DNA repair pathways proficiency in GBM. Here we uncover a novel role of Caspase-8 as promoter of the Homologous Recombination Repair (HRR). Importantly, IR promote Caspase-8 transient nuclear translocation and its recruitment to the chromatin. Moreover, Caspase-8 sustains the expression and the recruitment to the chromatin upon IR of RAD51 and CtIP, two key players of the HRR. Consistently, we identify a synthetically lethal interaction between Caspase-8 and PARP inhibition, that may ameliorate GBM response to IR. Remarkably, by using Caspase-8-/- murine embryo fibroblasts and a Drosophila melanogaster Caspase-8 mutant, we demonstrate that Caspase-8 plays an evolutionary conserved role in DNA repair. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=149 HEIGHT=200 SRC="FIGDIR/small/656091v1_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@1016001org.highwire.dtl.DTLVardef@145ed73org.highwire.dtl.DTLVardef@1e847d5org.highwire.dtl.DTLVardef@c417e1_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2024

cGAS-STING is responsible for aging of telomerase deficient zebrafish.

Telomere shortening occurs in multiple tissues throughout aging. When telomeres become critically short, they trigger DNA damage responses and p53 stabilization, leading to apoptosis or replicative senescence. In vitro, cells with short telomeres activate the cGAS-STING innate immune pathway resulting in type I interferon inflammation and senescence. However, the consequences of these events to the organism are not yet understood. Here, we show that sting is responsible for premature aging of telomerase-deficient zebrafish. We generated sting-/- tert-/- double mutants and observed a thorough rescue of tert-/- phenotypes. At the cellular level, lack of cGAS-STING in ter t mutants resulted in reduced senescence, increased cell proliferation, and low inflammation despite similar short telomeres. Critically, absence of sting function resulted in dampening of the DNA damage response and low p53 levels. At the organism level, sting-/- tert-/- zebrafish regained fertility, delayed cachexia, and cancer incidence, resulting in increased healthspan and lifespan of telomerase mutants.

cell biology↗

bioRxiv2023

Su(var)3-9 mediates age-dependent increase in H3K9 methylation on TDP-43 promoter triggering neurodegeneration

Aging progressively modifies the physiological balance of the organism increasing susceptibility to both genetic and sporadic neurodegenerative diseases. These changes include epigenetic chromatin remodeling events that may modify gene transcription. However, how aging interconnects with disease-causing genes is not well known. Here, we found that Su(var)3-9 causes increased methylation of histone H3K9 in the promoter region of TDP-43, the most frequently altered factor in amyotrophic lateral sclerosis (ALS), affecting the mRNA and protein expression levels of this gene through epigenetic modifications in chromatin organization that appear to be conserved in aged Drosophila brains, mouse and human cells. Remarkably, augmented Su(var)3-9 activity causes a decrease in TDP-43 expression followed by early defects in locomotor activities. In contrast, decreasing Su(var)3-9 action promotes higher levels of TDP-43 expression and reinvigorates motility parameters in old flies, uncovering a novel role of this enzyme in regulating TDP-43 expression and locomotor senescence. The data indicate how conserved epigenetic mechanisms may link aging with neuronal diseases and suggest that Su(var)3-9 may play a role in the pathogenesis of ALS.

molecular biology↗

bioRxiv2022

Novel cell- and stage-specific transcriptional signatures defining Drosophila neurons, glia and hemocytes

Cell types can be now defined at unprecedented resolution using high throughput assays. We analyzed the transcriptional signatures of Drosophila neurons, glia and hemocytes, as examples of cell types that are related by position (glia/neurons) or function (glia/hemocytes) or that are unrelated (neurons/hemocytes). The most related cells display the highest similarity level (neurons and glia), the least related ones, the lowest (neurons and hemocytes), however, cells can show plastic features. Glia are much more similar to neurons than to hemocytes in the embryo, but are equally similar to the two cell types in the larva, when hemocytes acquire more immune functions. Larval glia and hemocytes display common as well as specific immune features, such as the glia-specific NimA receptor, in agreement with the different environment faced by each cell types. Surprisingly, time represents a key identity parameter, as neurons, hemocytes and glia group more significantly by the stage than by the cell type and larval cells show upregulation of genes involved in chromatin organization and in DNA repair. This latter group of genes is linked to changes in gene expression levels and chromatin organization, revealing a function of these genes beyond DNA repair. Finally, the metabolic profiles reveal cell type-specific signatures and an overall shift from an embryonic, anabolic state to a larval, catabolic state.

developmental biology↗

bioRxiv2021

Translational control of polyamine metabolism by CNBP is required for Drosophila locomotor function

Microsatellite expansions of CCTG repeats in the CNBP gene leads to accumulation of toxic RNA and have been associated to DM2. However, it is still unclear whether the dystrophic phenotype is also linked to CNBP decrease, a conserved CCHC-type zinc finger RNA binding protein that regulates translation and is required for mammalian development. Here we show that depletion of Drosophila CNBP in muscles causes age-dependent locomotor defects that are correlated with impaired polyamine metabolism. We demonstrate that the levels of ornithine decarboxylase (ODC) and polyamines are significantly reduced upon dCNBP depletion. Of note, we show a reduction of the CNBP-polyamine axis in muscle from DM2 patients. Mechanistically, we provide evidence that dCNBP controls polyamine metabolism through binding dOdc mRNA and regulating its translation. Remarkably, the locomotor defect of dCNBP-deficient flies is rescued by either polyamine supplementation or dOdc1 overexpression. We suggest that this dCNBP function is evolutionarily conserved in vertebrates with relevant implications for CNBP-related pathophysiological conditions. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=195 SRC="FIGDIR/small/441910v2_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@a8c31corg.highwire.dtl.DTLVardef@1a18260org.highwire.dtl.DTLVardef@76a3d4org.highwire.dtl.DTLVardef@fdd041_HPS_FORMAT_FIGEXP M_FIG C_FIG CNBP controls muscle function by regulating the polyamine metabolism O_LILack of dCNBP impairs locomotor function through ODC-polyamine downregulation C_LIO_LIdCNBP binds dOdc mRNA and regulates its translation C_LIO_LIPolyamine supplementation or dOdc1 reconstitution rescues locomotor defects C_LIO_LICNBP-ODC-polyamine levels are reduced in muscle of DM2 patients C_LI

genetics↗

bioRxiv2020

Akt/Foxo pathway activation switches apoptosis to senescence in short telomere zebrafish

Progressive telomere shortening during lifespan is associated with increased genome instability, block to cell proliferation and aging. Apoptosis and senescence are the two main cellular outcomes upon irreversible cell damage. In this study, we show a transition between apoptosis to senescence in cells of two independent tissues in telomerase zebrafish mutants. In young mutants, proliferative tissues exhibit defects in cell proliferation and p53-dependent apoptosis, but no senescence. Progressively, these tissues display signs of tissue dysfunction, loss of cellularity and increased senescence. These alterations are accompanied by an activation of pro-proliferative stimulus mediated by AKT. Consequently, FoxO1 and FoxO4 transcriptional factors are inactivated, reducing SOD2 levels, causing an increase in ROS. These alterations elicit the activation of the zebrafish p16/15 and senescence. Thus, upon telomere shortening in aging, early apoptosis induces compensatory proliferation. However, progressive decline in cell proliferation results in tissue damage and proliferative signals, promoting a switch to senescence.

cell biology↗

bioRxiv2019

Telomere shortening produces an inflammatory environment that promotes tumor invasiveness in zebrafish

Cancer incidence increases exponentially with age, when human telomeres are shorter. Similarly, telomerase mutant zebrafish (tert) have premature short telomeres and anticipate cancer incidence to younger ages. However, because short telomeres constitute a road block to cell proliferation, telomere shortening is currently viewed as a tumor suppressor mechanism and should protect from cancer. This conundrum is not fully understood. In our current study, we report that telomere shortening promotes cancer in a non-cell autonomous manner. Using zebrafish chimeras, we show increased incidence of invasive melanoma when WT tumors are generated in tert mutant zebrafish. tert zebrafish show increased levels of senescence (cdkn2a and ink4a/b) and inflammation (TNF-). In addition, we transferred second generation tert blastula cells into WT to produce embryo chimeras. Cells with very short telomeres induced senescence and increased neutrophil numbers in surrounding larval tissues in a non-cell autonomous manner, creating an inflammatory environment. Considering that inflammation is pro-tumorigenic, we transplanted melanoma-derived cells into second generation tert zebrafish embryos and observed that tissue environment with short telomeres leads to increased micrometastasis. To test if inflammation was necessary for this effect, we treated melanoma transplants with non-steroid anti-inflammatory drugs and show that higher melanoma invasiveness can be averted. Thus, apart from the cell autonomous role of short telomeres in contributing to genome instability, we propose that telomere shortening with age causes systemic chronic inflammation leading to increased tumor incidence. Significance StatementCancer incidence increases exponentially in human midlife. Even though mutation accumulation in somatic tissues results in increased tumorigenesis, it is currently not understood how aging contributes to cancer. Telomeres, the ends of eukaryotic linear chromosomes, shorten with each cell division. Here we show that telomere shortening contributes to cancer in a non-cell autonomous manner. Using embryo chimeras of telomerase deficient zebrafish generated from melanoma-prone fish, we show that tumors arise more frequently and become more invasive in animals with shorter telomeres. Telomere shortening gives rise to increased senescence and systemic inflammation. We observed increased melanoma metastasis dissemination in zebrafish larvae with very short telomeres. Thus, telomere shortening similar to human aging, generates a chronic inflammatory environment that increases cancer incidence.

cancer biology↗

bioRxiv2017

Lhr and Hmr are required for sister chromatid detachment during anaphase but not for centromere function

Crosses between Drosophila melanogaster females and Drosophila simulans males produce hybrid sons that die at the larval stage. This hybrid lethality is suppressed by loss-of-function mutations in the D. melanogaster Hybrid male rescue (Hmr) or in the D. simulans Lethal hybrid rescue (Lhr) genes. Previous studies have shown that Hmr and Lhr interact with heterochromatin proteins and suppress expression of transposable elements within D. melanogaster. It also has been proposed that Hmr and Lhr function at the centromere. We examined mitotic divisions in larval brains from Hmr and Lhr single mutants and Hmr; Lhr double mutants in D. melanogaster. In none of the mutants did we observe defects in metaphase chromosome alignment or hyperploid cells, which are hallmarks of centromere or kinetochore dysfunction. In addition, we found that Hmr-HA and Lhr-HA do not localize to centromeres either during interphase or mitotic division. However, all mutants displayed anaphase bridges and chromosome aberrations resulting from the breakage of these bridges, predominantly at the euchromatin-heterochromatin junction. The few dividing cells present in hybrid males showed irregularly condensed chromosomes with fuzzy and often closely apposed sister chromatids. Despite this defect in condensation, chromosomes in hybrids managed to align on the metaphase plate and undergo anaphase. We conclude that there is no evidence for a centromeric function of Hmr and Lhr within D. melanogaster nor for a centromere defect causing hybrid lethality. Instead we find that Hmr and Lhr are required in D. melanogaster for detachment of sister chromatids during anaphase.

genetics↗