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

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

Isolation and characterization of myogenic precursor cells from human cremaster muscle

Human myogenic precursor cells have been isolated and expanded from a number of skeletal muscles, but alternative donor biopsy sites must be sought after in diseases where muscle damage is widespread. Biopsy sites must be relatively accessible, and the biopsied muscle dispensable. Here, we aimed to histologically characterize the cremaster muscle with regard number of satellite cells and regenerative fibres, and to isolate and characterize human cremaster muscle-derived stem/precursor cells in adult male donors with the objective of characterizing this muscle as a novel source of myogenic precursor cells. Cremaster muscle biopsies (or adjacent non-muscle tissue for negative controls; N=19) were taken from male patients undergoing routine surgery for urogenital pathology. Myosphere cultures were derived and tested for their in vitro and in vivo myogenic differentiation and muscle regeneration capacities. Cremaster-derived myogenic precursor cells were maintained by myosphere culture and efficiently differentiated to myotubes in adhesion culture. Upon transplantation to an immunocompromised mouse model of cardiotoxin-induced acute muscle damage, human cremaster-derived myogenic precursor cells survived to the transplants and contributed to muscle regeneration. These precursors are a good candidate for cell therapy approaches of skeletal muscle. Due to their location and developmental origin, we propose that they might be best suited for regeneration of the rhabdosphincter in patients undergoing stress urinary incontinence after radical prostatectomy.We thank patients and medical personnel for their generous involvement in the study. We also acknowledge the help of Biodonostia Animal and Experimental Operations Facility. This work was supported by grants from Ministerio de Economia y Competitividad (RTC-2015-3750-1) and Instituto de Salud Carlos III (PI13/02172, PI16/01430) to A.I., co-funded by the European Union (ERDF/ESF, 'Investing in your future'). N.N.-G. received a studentship from the Department of Education, University and Research of the Basque Government (PRE2013-1-1168). A.L.M. was funded by grants from FIS (PI17/01841 and PI14/00436), CIBERNED and the Basque Government (2015/11038, RIS3 2017222021 and BIO16/ER/022). M.F.L.-C. was supported by the Servicio Andaluz de Salud from the Consejeria de Salud de la Junta de Andalucia, grant PI 0222-2014, co-funded by the European Union (ERDF/ESF). I.M.A was funded by grants from Ministerio de Economia y Competitividad (PEJ-2014-P-01215 and FJCI-2016-28121)

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality

New insights into the genetic etiology of Alzheimer's disease and related dementias

Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele

Multiancestry analysis of the HLA locus in Alzheimer’s and Parkinson’s diseases uncovers a shared adaptive immune response mediated by HLA-DRB1*04 subtypes

Across multiancestry groups, we analyzed Human Leukocyte Antigen (HLA) associations in over 176,000 individuals with Parkinson’s disease (PD) and Alzheimer’s disease (AD) versus controls. We demonstrate that the two diseases share the same protective association at the HLA locus. HLA-specific fine-mapping showed that hierarchical protective effects of HLA-DRB1*04 subtypes best accounted for the association, strongest with HLA-DRB1*04:04 and HLA-DRB1*04:07, and intermediary with HLA-DRB1*04:01 and HLA-DRB1*04:03. The same signal was associated with decreased neurofibrillary tangles in postmortem brains and was associated with reduced tau levels in cerebrospinal fluid and to a lower extent with increased Aβ42. Protective HLA-DRB1*04 subtypes strongly bound the aggregation-prone tau PHF6 sequence, however only when acetylated at a lysine (K311), a common posttranslational modification central to tau aggregation. An HLA-DRB1*04-mediated adaptive immune response decreases PD and AD risks, potentially by acting against tau, offering the possibility of therapeutic avenues

Estudio del papel de p73 en la ciliogénesis y el establecimiento de la polaridad celular planar en células ependimarias = Role of P73 in ependymal cell ciliogenesis and planar cell polarity establishment

163 p.La Polaridad Cellular Planar (PCP) describe la orientación coordinada de las células en el plano del tejido y es una característica fundamental de los tejidos epiteliales. En las células multiciliadas, la orientación individual y coordinada de los cilios es esencial para el correcto funcionamiento de las mismas. En el cerebro del ratón, donde los ventrículos están tapizados por células multiciliadas denominadas células ependimarias, los fallos en la formación de los cilios y/o en el establecimiento de la PCP da lugar a una pérdida de función de los cilios e hidrocefalia. Las células ependimarias presentan dos tipos de polaridad, la polaridad translacional (tPCP) y la polaridad rotacional (rPCP), que son fundamentales para el movimiento coordinado de los cilios. Ambas se establecen durante el periodo perinatal, cuando las células de la glía radial (RGCs) monociliadas se transforman en células ependimarias multiciliadas (ECs). La regulación de la tPCP en células ependimarias es llevado a cabo, al menos en parte, por la activación de la miosina no muscular II (NMII), una proteína de unión a actina que es esencial para el control de la adhesión celular y la arquitectura tisular. La activación de NMII mediante la kinasa MLCK (myosin light chain kinase) es esencial para el establecimiento de la polaridad translacional en las células ependimarias. La regulación de la rPCP se lleva a cabo mediante la localización asimétrica de las proteínas pertenecientes a la vía de señalización PCP, que se mueven de manera diferencial dentro de la célula para establecer asimetrías moleculares. Esta asimetría se traducirá en cambios en el citoesqueleteto celular que orientará los cilios para su movimiento coordinado. El factor de transcripción p73, que pertenece a la familia de factores de transcripción p53, es un importante regulador del desarrollo del Sistema Nervioso Central y es necesario para el establecimiento de la arquitectura del nicho neurogénico que se localiza en la pared lateral de los ventrículos. En esta tesis doctoral se ha llevado a cabo el estudio del papel de p73 en el desarrollo de las células ependimarias, la formación de los cilios y su organización en la membrana apical

Immunohistochemistry subtyping of urothelial carcinoma is feasible in the daily practice

The preferred treatment of choice in muscle-invasive bladder cancer (MIBC) is usually transurethral resection followed by cystectomy, with neoadjuvant chemotherapy being a second option. As the treatment is associated with relevant side effects, a great effort is being made to improve the selection of patients, with molecular subtyping being one of the main strategies. Our aim was to develop an immunohistochemical algorithm for subtyping MIBCs. After a literature review, we have developed a simple algorithm to subtype MIBCs based on their morphology and three common antibodies: GATA3, CK5/6, and p16. We applied it to 113 muscle-invasive carcinomas. The positivity threshold for GATA3 and CK5/6 was 20% with at least moderate intensity, while p16 was 70% with moderate to intense nuclear and cytoplasmic staining. Cases GATA3 + CK5/6 − were considered luminal, while cases GATA3 − CK5/6 + were classified as nonluminal/basal squamous. Luminal p16 + cases were labeled as genomically unstable and luminal p16 − as Uro-like. Cases GATA3 + CK5/6 + with a predominantly basal pattern were labeled luminal, while diffuse cases were labeled nonluminal/basal squamous. All GATA3-CK5/6 − cases were considered nonluminal and were divided into mesenchymal-like or neuroendocrine, depending on the morphology. We were able to classify the 113 cases as: 82 (72.57%) were luminal, being 47 Uro-like (41.59%) and 35 (30.97%) genomically unstable; 31 (27.43%) were nonluminal, being 24 basal/squamous (21.24%), two (1.76%) mesenchymal-like, and five (4.42%) neuroendocrine like. We have achieved a feasible and cost-effective algorithm to subtype MIBCs from morphological features and the use of three common antibodies. Further studies in external cohorts are necessary to validate these results