Novel role of p73 as a regulator of developmental angiogenesis: implication for cancer therapy

[EN] Information regarding the role of p73 in the regulation of angiogenesis has been incomplete and quite controversial. Remarkably, several groups, including ours, have recently demonstrated that TP73 plays a fundamental role in angiogenesis regulation and that differential expression of TP73 could have important consequences in tumor angiogenesis. Here, we discuss a possible model for p73 function in the regulation of developmental angiogenesis and tumor angiogenesisS

La búsqueda del sensor celular del oxígeno, un camino al Nobel

El premio Nobel de Medicina y Fisiología ha sido otorgado este año a los investigadores William Kaelin Jr., Sir Peter Ratcliffe y Gregg Semenza por descubrir los mecanismos moleculares mediante los cuales las células detectan los cambios en los niveles de oxígeno y se adaptan a ellos. Las células de un organismo requieren oxígeno para oxidar los nutrientes y generar energía. Sin embargo, los tejidos pueden verse temporalmente privados de oxígeno (hipoxia). Por ello, durante la evolución las células han adquirido mecanismos que les permiten detectar cambios en los niveles de oxígeno y responder a ellos adaptando el metabolismo celular. Estos procesos adaptativos son fundamentales durante el desarrollo embrionario y el mantenimiento de la homeostasis en adultos. Además, su desregulación juega un papel fundamental en el desarrollo de enfermedades como la diabetes, el ictus o el cáncer. En este artículomecentraré en el trabajo que realizó uno de los galardonados, William Kaelin, el cual fue mi jefe y mentor en mi etapa posdoctoral. El Dr. Kaelin descubrió los mecanismos subyacentes a la respuesta a hipoxia estudiando una enfermedad rara que se caracteriza por la aparición de tumores altamente vascularizados, el síndrome de Von Hippel-Lindau. En la actualidad, centra sus esfuerzos en el diseño de terapias dirigidas contra dianas múltiples que, usadas en combinación, permitan en un futuro curar enfermedades complejas como el cáncer

p73 as a Tissue Architect

Sec. Molecular and Cellular Pathology[EN] The TP73 gene belongs to the p53 family comprised by p53, p63, and p73. In response to physiological and pathological signals these transcription factors regulate multiple molecular pathways which merge in an ensemble of interconnected networks, in which the control of cell proliferation and cell death occupies a prominent position. However, the complex phenotype of the Trp73 deficient mice has revealed that the biological relevance of this gene does not exclusively rely on its growth suppression effects, but it is also intertwined with other fundamental roles governing different aspects of tissue physiology. p73 function is essential for the organization and homeostasis of different complex microenvironments, like the neurogenic niche, which supports the neural progenitor cells and the ependyma, the male and female reproductive organs, the respiratory epithelium or the vascular network. We propose that all these, apparently unrelated, developmental roles, have a common denominator: p73 function as a tissue architect. Tissue architecture is defined by the nature and the integrity of its cellular and extracellular compartments, and it is based on proper adhesive cell-cell and cell-extracellular matrix interactions as well as the establishment of cellular polarity. In this work, we will review the current understanding of p73 role as a neurogenic niche architect through the regulation of cell adhesion, cytoskeleton dynamics and Planar Cell Polarity, and give a general overview of TAp73 as a hub modulator of these functions, whose alteration could impinge in many of the Trp73–/– phenotypesSIThis work was supported by Grant PID2019-105169RB-I00 from Spanish Ministerio de Ciencia e Innovación cofinanced by FEDER funds (to MCM). LM-A was a holder of a predoctoral scholarship from the Asociación Española contra el Cáncer (AECC) and was funded by a postdoctoral contract from Junta de Castilla y León

Células troncales y reprogramación celular

A partir de diferentes estadios del desarrollo embrionario murino, es posible establecer in vitro cultivos de células troncales que presentan dos rasgos distintivos: su capacidad para proliferar indefinidamente, dando lugar a nuevas células troncales (auto-renovación), y su capacidad de diferenciación a todos los tipos celulares que forman el organismo adulto (pluripotencia). Durante décadas, el tránsito del estado pluripotente al estado de diferenciación terminal fue considerado irreversible; sin embargo, en la actualidad es posible revertir este proceso e inducir la pluripotencia en células somáticas mediante la expresión de factores de transcripción que regulan la identidad de las células troncales embrionarias. Este proceso, denominado reprogramación celular, da lugar a la generación de células troncales pluripotentes inducidas (iPSCs), que presentan características moleculares y funcionales similares a las de células troncales embrionarias (ESCs). Por ello, las células reprogramadas son una valiosa herramienta en Biomedicina, y están siendo empleadas para modelar enfermedades humanas o para la búsqueda de nuevos tratamientos en patologías que no responden a los enfoques clínicos tradicionale

The Trp73 Mutant Mice: A Ciliopathy Model That Uncouples Ciliogenesis From Planar Cell Polarity

Sec. Genetics of Common and Rare Diseases[EN] p73 transcription factor belongs to one of the most important gene families in vertebrate biology, the p53-family. Trp73 gene, like the other family members, generates multiple isoforms named TA and DNp73, with different and, sometimes, antagonist functions. Although p73 shares many biological functions with p53, it also plays distinct roles during development. Trp73 null mice (p73KO from now on) show multiple phenotypes as gastrointestinal and cranial hemorrhages, rhinitis and severe central nervous system defects. Several groups, including ours, have revisited the apparently unrelated phenotypes observed in total p73KO and revealed a novel p73 function in the organization of ciliated epithelia in brain and trachea, but also an essential role as regulator of ependymal planar cell polarity. Unlike p73KO or TAp73KO mice, tumor-prone Trp53−/− mice (p53KO) do not present ependymal ciliary or planar cell polarity defects, indicating that regulation of ciliogenesis and PCP is a p73-specific function. Thus, loss of ciliary biogenesis and epithelial organization might be a common underlying cause of the diverse p73KO-phenotypes, highlighting Trp73 role as an architect of the epithelial tissue. In this review we would like to discuss the data regarding p73 role as regulator of ependymal cell ciliogenesis and PCP, supporting the view of the Trp73-mutant mice as a model that uncouples ciliogenesis from PCP and a possible model of human congenital hydrocephalusSIThis work was supported by Grants SAF2015-71381-R from Spanish Ministerio de Economía y Competitividad co-financed by FEDER funds (to MCM) and LE021P17 from Junta de Castilla y Leon. JV-F and SF-A are holders of predoctoral fellowships from the Junta de Castilla y León. LM-A is supported by a pre-doctoral scholarship from the Asociación Española contra el Cáncer (AECC

Deciphering the Nature of Trp73 Isoforms in Mouse Embryonic Stem Cell Models: Generation of Isoform-Specific Deficient Cell Lines Using the CRISPR/Cas9 Gene Editing System

This article belongs to the Special Issue The Isoforms of the p53 Gene Family and Their Role in Cancer and Aging：Selection Papers from International p53/p63/p73 Isoforms Workshop[EN] The p53 family has been widely studied for its role in various physiological and pathological processes. Imbalance of p53 family proteins may contribute to developmental abnormalities and pathologies in humans. This family exerts its functions through a profusion of isoforms that are generated by different promoter usage and alternative splicing in a cell type dependent manner. In particular, the Trp73 gene gives rise to TA and DN-p73 isoforms that confer p73 a dual nature. The biological relevance of p73 does not only rely on its tumor suppression effects, but on its pivotal role in several developmental processes. Therefore, the generation of cellular models that allow the study of the individual isoforms in a physiological context is of great biomedical relevance. We generated specific TA and DN-p73-deficient mouse embryonic stem cell lines using the CRISPR/Cas9 gene editing system and validated them as physiological bona fide p73-isoform knockout models. Global gene expression analysis revealed isoform-specific alterations of distinctive transcriptional networks. Elimination of TA or DN-p73 is compatible with pluripotency but prompts naïve pluripotent stem cell transition into the primed state, compromising adequate lineage differentiation, thus suggesting that differential expression of p73 isoforms acts as a rheostat during early cell fate determinationSIThis work was supported by Grants PID2019-105169RB-I00 from Spanish Ministerio de Ciencia e Innovación cofinanced by FEDER funds (to M.C.M.) and LE021P17 from Junta de Castilla y Leon. L.L.-F. was a holder of a postdoctoral contract “Juan de de la Cierva-Incorporacion” from Ministerio de Ciencia e Innovación. N.M.-G. and H.A.-O. are supported by a predoctoral scholarship from the Asociación Española contra el Cáncer (AECC). M.M.-L. was a recipient of a Torres Quevedo contract from Ministerio de Ciencia e Innovación at Biomar Microbial Technologies. Á.D.-M., J.V.-F. and L.M.-A. are funded by Junta de Castilla y Leó

p73 deficiency results in impaired self renewal and premature neuronal differentiation of mouse neural progenitors independently of p53

[EN] The question of how neural progenitor cells maintain its self-renewal throughout life is a fundamental problem in cell biology with implications in cancer, aging and neurodegenerative diseases. In this work, we have analyzed the p73 function in embryonic neural progenitor cell biology using the neurosphere (NS)-assay and showed that p73-loss has a significant role in the maintenance of neurosphere-forming cells in the embryonic brain. A comparative study of NS from Trp73-/-, p53KO, p53KO;Trp73-/- and their wild-type counterparts demonstrated that p73 deficiency results in two independent, but related, phenotypes: a smaller NS size (related to the proliferation and survival of the neural-progenitors) and a decreased capacity to form NS (self-renewal). The former seems to be the result of p53 compensatory activity, whereas the latter is p53 independent. We also demonstrate that p73 deficiency increases the population of neuronal progenitors ready to differentiate into neurons at the expense of depleting the pool of undifferentiated neurosphere-forming cells. Analysis of the neurogenic niches demonstrated that p73-loss depletes the number of neural-progenitor cells, rendering deficient niches in the adult mice. Altogether, our study identifies TP73 as a positive regulator of self-renewal with a role in the maintenance of the neurogenic capacity. Thus, proposing p73 as an important player in the development of neurodegenerative diseases and a potential therapeutic targetSILGC is beneficiary of a predoctoral fellowship from Consejo de Educación de la Junta de Castilla y León and RFA from Spanish Ministerio de Ciencia e Innovación. This work was supported by Grants SAF2009-07897 from Spanish Ministerio de Ciencia e Innovacion (to MCM), Grant from Cajas de Ahorro de Castilla y León (to MCM), and Grants LE030A07 (to MMM) and LE015A10-2 (to MCM) from the Junta de Castilla y Leó

p73 regulates ependymal planar cell polarity by modulating actin and microtubule cytoskeleton

[EN]Planar cell polarity (PCP) and intercellular junctional complexes establish tissue structure and coordinated behaviors across epithelial sheets. In multiciliated ependymal cells, rotational and translational PCP coordinate cilia beating and direct cerebrospinal fluid circulation. Thus, PCP disruption results in ciliopathies and hydrocephalus. PCP establishment depends on the polarization of cytoskeleton and requires the asymmetric localization of core and global regulatory modules, including membrane proteins like Vangl1/2 or Frizzled. We analyzed the subcellular localization of select proteins that make up these modules in ependymal cells and the effect of Trp73 loss on their localization. We identify a novel function of the Trp73 tumor suppressor gene, the TAp73 isoform in particular, as an essential regulator of PCP through the modulation of actin and microtubule cytoskeleton dynamics, demonstrating that Trp73 is a key player in the organization of ependymal ciliated epithelia. Mechanistically, we show that p73 regulates translational PCP and actin dynamics through TAp73-dependent modulation of non-musclemyosin-II activity. In addition, TAp73 is required for the asymmetric localization of PCP-core and global signaling modules and regulates polarized microtubule dynamics, which in turn set up the rotational PCP. Therefore, TAp73 modulates, directly and/or indirectly, transcriptional programs regulating actin and microtubules dynamics and Golgi organization signaling pathways. These results shed light into the mechanism of ependymal cell planar polarization and reveal p73 as an epithelial architect during development regulating the cellular cytoskeletonSIThis work was supported by Grants SAF2015-71381-R from Spanish Ministerio de Economía y Competitividad co-financed by FEDER funds (to M.C.M.) and LE021P17 from Junta de Castilla y Leon, and from the Queen Elisabeth Medical Foundation to F.T. J.V.-F. and S.F.-A. are holders of predoctoral fellowships from the Junta de Castilla y León. L.M.-A. is supported by a predoctoral scholarship from the Asociación Española contra el Cáncer (AECC). F.T. is a Research Director of the FNRS. M.W. and M.L. are funded by the Deutsche Forschungsgemeinschaft (DFG) under grant number LI 2405/

p73 is required for appropriate BMP-induced mesenchymal-to-epithelial transition during somatic cell reprogramming

[EN] The generation of induced pluripotent stem cells (iPSCs) by somatic cell reprogramming holds great potential for modeling human diseases. However, the reprogramming process remains very inefficient and a better understanding of its basic biology is required. The mesenchymal-to-epithelial transition (MET) has been recognized as a crucial step for the successful reprogramming of fibroblasts into iPSCs. It has been reported that the p53 tumor suppressor gene acts as a barrier of this process, while its homolog p63 acts as an enabling factor. In this regard, the information concerning the role of the third homolog, p73, during cell reprogramming is limited. Here, we derive total Trp73 knockout mouse embryonic fibroblasts, with or without Trp53, and examine their reprogramming capacity. We show that p73 is required for effective reprogramming by the Yamanaka factors, even in the absence of p53. Lack of p73 affects the early stages of reprogramming, impairing the MET and resulting in altered maturation and stabilization phases. Accordingly, the obtained p73-deficient iPSCs have a defective epithelial phenotype and alterations in the expression of pluripotency markers. We demonstrate that p73 deficiency impairs the MET, at least in part, by hindering BMP pathway activation. We report that p73 is a positive modulator of the BMP circuit, enhancing its activation by DNp73 repression of the Smad6 promoter. Collectively, these findings provide mechanistic insight into the MET process, proposing p73 as an enhancer of MET during cellular reprogramming.S