Our research group investigates how to generate and maintain the stem cells in the hematopoietic system under physiological conditions but also how these processes are mimicked by the tumors for their perpetuation. We constantly improve our research by implementing novel technology to understand the process of normal and malignant hematopoietic development. Our research includes basic studies at the molecular level to understand cellular processes in the context of mouse models and human patients.
Our research comprises from basic biochemical research to the analysis of animal models that reproduce the pathologies of interest and allow us to study the functional relevance of new hypothesis. The ultimate goal is to confirm the importance of the findings and study possible therapeutic applications through the analysis of patient samples. In this sense we have devoted special efforts to understand the regulation of haematopoietic stem cells, as a tool to understand the mechanisms that regulate leukemia initiation and maintenance.Molecules that control both tumor initiation and progression, and tissue/stem cell homeostasis include those of the Notch, Wnt and NFκB signalling payhways. Studying these pathways in the hematopoietic, intestinal and skin tissues has also led to the identification of several interactions between them, which proved to be crucial for tissue homeostasis. We are currently working on several projects that deal with different functional aspects of normal haematopoietic stem cell regulation as well as leukemia initiating cells.
Generation of hematopoietic stem cells.
Our group was pioneer in revealing that specific elements of the Notch and Wnt/b-catenin pathways are required for the generation of hematopoietic stem cells during embryogenesis. Our current studies are focused on understanding the signals that the embryo uses to form these self-renewing cells that maintain the hematopoietic system throughout the life of the organism. We use genetically modified mouse strains combined with cutting edge imaging technologies, single cell genomics (scRNAseq, Cut&tag, ATAC seq), explant cell culture and “in mouse” hematopoietic transplantion assays to reveal how this process occurs. Our current challenge is to model the process of HSC specification in embryonic stem cells (ESC) in order to obtain functional cells for therapeutic applications.
Image 1: Hematopoietic cluster in the aorta
Understanding T Acute Lymphoblastic Leukemia (T-ALL) development and T-cell lymphoma.
We study the signals that regulate the generation and maintenance of normal and leukemic cells, as well as leukaemic stem cells (LSCS). With this aim we have developed in vitro and in vivo experimental models that complement the analysis of patient samples. In addition, we are now using several next-generation techniques to identify genetic drivers (Whole genome sequencing), gene expression patterns (RNA-seq), epigenetic patterns ( Chip-Seq or Cut&tag), CRISPR/Cas9 applications and specific multi-protein complexes (mass spectrometry) that define the populations of interest at the molecular level. These studies may reveal novel therapeutic targets for T-ALL and cutaneous T cell lymphoma (CTCL).
Image 2: Giemsa staining, leukemic blast
GATA2 deficiency syndrome
We are collaborating in an international consortium to understand the contribution of GATA2 mutations to pediatric Myelodysplastic syndrome and transformation to Acute Myeloid Leukemia (AML). We are developing humanized blood animal models of this syndrome.
Image 3: Progenitor colony (CFU-GM)
Understanding cell transformation
In addition, we work closely with the Research Group for Molecular Mechanisms of Cancer and Stemnessdirected by Dr. Lluís Espinosa and we take advantage of our discoveries in haematopoietic cells to understand epithelial tissues and vice versa. This long-standing partnership allows us to achieve a highest understanding of the biological problems and optimize resources.
Image 4: ChiP
Fundació Marató TV3
AECC (Spanish Cancer Association)
WCR (Worldwide Cancer Research).
Member of the National Cancer Network since 2008 and CIBERONC since 2017.
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Notch ligand Dll4 impairs cell recruitment into aortic clusters and limits hematopoietic stem cellsEMBO J . 2020 Apr 15;39(8):e104270 , .
Hematopoietic stem cells (HSCs) develop from the hemogenic endothelium in cluster structures that protrude into the embryonic aortic lumen. Although much is known about the molecular characteristics of the developing hematopoietic cells, we lack a complete understanding of their origin and the three-dimensional organization of the niche. Here, we use advanced live imaging techniques of organotypic slice cultures, clonal analysis, and mathematical modeling to show the two-step process of intra-aortic hematopoietic cluster (IACH) formation. First, a hemogenic progenitor buds up from the endothelium and undergoes division forming the monoclonal core of the IAHC. Next, surrounding hemogenic cells are recruited into the IAHC, increasing their size and heterogeneity. We identified the Notch ligand Dll4 as a negative regulator of the recruitment phase of IAHC. Blocking of Dll4 promotes the entrance of new hemogenic Gfi1+ cells into the IAHC and increases the number of cells that acquire HSC activity. Mathematical modeling based on our data provides estimation of the cluster lifetime and the average recruitment time of hemogenic cells to the cluster under physiologic and Dll4-inhibited conditions.More information
β-Catenin is required for T cell leucemia initiation and MYC transcription downstream of Notch1Leukemia . 2016 Oct;30(10):2002-2010 , .
Notch activation is instrumental in the development of most T-cell acute lymphoblastic leukemia (T-ALL) cases, yet Notch mutations alone are not sufficient to recapitulate the full human disease in animal models. We here found that Notch1 activation at the fetal liver (FL) stage expanded the hematopoietic progenitor population and conferred it transplantable leukemic-initiating capacity. However, leukemogenesis and leukemic-initiating cell capacity induced by Notch1 was critically dependent on the levels of β-Catenin in both FL and adult bone marrow contexts. In addition, inhibition of β-Catenin compromised survival and proliferation of human T-ALL cell lines carrying activated Notch1. By transcriptome analyses, we identified the MYC pathway as a crucial element downstream of β-Catenin in these T-ALL cells and demonstrate that the MYC 3' enhancer required β-Catenin and Notch1 recruitment to induce transcription. Finally, PKF115-584 treatment prevented and partially reverted leukemogenesis induced by active Notch1.More information
Notch signal strength controls cell fate in the haemogenic endotheliumNat Commun . 2015 Oct 14;6:8510 , .
Acquisition of the arterial and haemogenic endothelium fates concurrently occur in the aorta-gonad-mesonephros (AGM) region prior to haematopoietic stem cell (HSC) generation. The arterial programme depends on Dll4 and the haemogenic endothelium/HSC on Jag1-mediated Notch1 signalling. How Notch1 distinguishes and executes these different programmes in response to particular ligands is poorly understood. By using two Notch1 activation trap mouse models with different sensitivity, here we show that arterial endothelial cells and HSCs originate from distinct precursors, characterized by different Notch1 signal strengths. Microarray analysis on AGM subpopulations demonstrates that the Jag1 ligand stimulates low Notch strength, inhibits the endothelial programme and is permissive for HSC specification. In the absence of Jag1, endothelial cells experience high Dll4-induced Notch activity and select the endothelial programme, thus precluding HSC formation. Interference with the Dll4 signal by ligand-specific blocking antibodies is sufficient to inhibit the endothelial programme and favour specification of the haematopoietic lineage.More information
Hes repressors are essential regulators of Hematopoietic Stem Cell Development downstream of Notch signalingJ Exp Med . 2013 Jan 14;210(1):71-84 , .
Previous studies have identified Notch as a key regulator of hematopoietic stem cell (HSC) development, but the underlying downstream mechanisms remain unknown. The Notch target Hes1 is widely expressed in the aortic endothelium and hematopoietic clusters, though Hes1-deficient mice show no overt hematopoietic abnormalities. We now demonstrate that Hes is required for the development of HSC in the mouse embryo, a function previously undetected as the result of functional compensation by de novo expression of Hes5 in the aorta/gonad/mesonephros (AGM) region of Hes1 mutants. Analysis of embryos deficient for Hes1 and Hes5 reveals an intact arterial program with overproduction of nonfunctional hematopoietic precursors and total absence of HSC activity. These alterations were associated with increased expression of the hematopoietic regulators Runx1, c-myb, and the previously identified Notch target Gata2. By analyzing the Gata2 locus, we have identified functional RBPJ-binding sites, which mutation results in loss of Gata2 reporter expression in transgenic embryos, and functional Hes-binding sites, which mutation leads to specific Gata2 up-regulation in the hematopoietic precursors. Together, our findings show that Notch activation in the AGM triggers Gata2 and Hes1 transcription, and next HES-1 protein represses Gata2, creating an incoherent feed-forward loop required to restrict Gata2 expression in the emerging HSCs.More information
The Notch/Hes1 pathway sustains NFkB activation through CYLD repression in T cell leukemiaCancer Cell . 2010 Sep 14;18(3):268-81 , .
It was previously shown that the NF-κB pathway is downstream of oncogenic Notch1 in T cell acute lymphoblastic leukemia (T-ALL). Here, we visualize Notch-induced NF-κB activation using both human T-ALL cell lines and animal models. We demonstrate that Hes1, a canonical Notch target and transcriptional repressor, is responsible for sustaining IKK activation in T-ALL. Hes1 exerts its effects by repressing the deubiquitinase CYLD, a negative IKK complex regulator. CYLD expression was found to be significantly suppressed in primary T-ALL. Finally, we demonstrate that IKK inhibition is a promising option for the targeted therapy of T-ALL as specific suppression of IKK expression and function affected both the survival of human T-ALL cells and the maintenance of the disease in vivoMore information