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 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/

Explorando la inhibición de p73 como diana terapéutica frente a células troncales de glioblastoma

91 p.[ES] El Glioblastoma Multiforme (GBM) es el tumor más prevalente y letal de todos los que afectan al sistema nervioso central. El gen TP73 es un factor de transcripción que pertenece a la familia de p53. Este gen tiene 2 promotores, a partir de los cuales puede dar lugar a 2 isoformas, la isoforma TAp73, que contiene un dominio de transactivación, y la isoforma DNp73, que carece de este dominio. En este proyecto de tesis doctoral se plantea la hipótesis de que TAp73 es una diana terapéutica en glioblastoma. El objetivo general analiza el papel de TAp73 en Glioblastoma Stem Cells (GSC) e identifica y caracteriza posibles compuestos candidatos activos frente a GSC que modulen los niveles de TAp73.Ministerio de Economía y CompetitividadJunta de Castilla y Leó