Neurons show the path: tip-to-nucleus communication in filamentous fungal development and pathogenesis

44 p.-7 fig.Multiple fungal species penetrate substrates and accomplish host invasion through the fast, permanent and unidirectional extension of filamentous cells known as hyphae. Polar growth of hyphae results, however, in a significant increase in the distance between the polarity site, which also receives the earliest information about ambient conditions, and nuclei, where adaptive responses are executed. Recent studies demonstrate that these long distances are overcome by signal transduction pathways which convey sensory information from the polarity site to nuclei, controlling development and pathogenesis. The present review compares the striking connections of the mechanisms for long-distance communication in hyphae with those from neurons, and discusses the importance of their study in order to understand invasion and dissemination processes of filamentous fungi, and design strategies for developmental control in the future.Work at the UPV/EHU lab was funded by the University of the Basque Country (grant EHUA15/08) and the Basque Government (grant IT599-13). Work at CIB-CSIC was funded by MINECO (BFU2015-66806-R).Peer reviewe

Apical Control of Conidiation in Aspergillus nidulans

21 p.-2 fig.The infection cycle of filamentous fungi consists of two main stages: invasion (growth) and dispersion (development). After the deposition of a spore on a host, germination, polar extension and branching of vegetative cells called hyphae allow a fast and efficient invasion. Under suboptimal conditions, genetic reprogramming of hyphae results in the generation of asexual spores, allowing dissemination to new hosts and the beginning of a new infection cycle. In the model filamentous fungus Aspergillus nidulans, asexual development or conidiation is induced by the upstream developmental activation (UDA) pathway. UDA proteins transduce signals from the tip, the polarity site of hyphae, to nuclei, where developmental programs are transcriptionally activated. The present review summarizes the current knowledge on this tip-to-nucleus communication mechanism, emphasizing its dependence on hyphal polarity. Future approaches to the topic will also be suggested, as stimulating elements contributing to the understanding of how apical signals are coupled with the transcriptional control of development and pathogenesis in filamentous fungi.Work at the UPV/EHU was funded by the UPV/EHU (Grant EHUA15/08) and the Basque Government (Grant IT599-13). Work at CIB-CSIC was funded by MINECO (BFU2012-33142).Peer reviewe

Transcriptional changes in the transition from vegetative cells to asexual development in the model fungus Aspergillus nidulans

32 p.-6 fig.-2 tab.Morphogenesis encompasses programmed changes in gene expression that lead to the development of specialized cell types. In the model fungus Aspergillus nidulans, asexual development involves the formation of characteristic cell types, collectively known as the conidiophore. With the aim of determining the transcriptional changes that occur upon induction of asexual development, we have applied massive mRNA sequencing to compare the expression pattern of 19-h-old submerged vegetative cells (hyphae) with that of similar hyphae after exposure to the air for 5 h. We found that the expression of 2,222 (20.3%) of the predicted 10,943 A. nidulans transcripts was significantly modified after air exposure, 2,035 being downregulated and 187 upregulated. The activation during this transition of genes that belong specifically to the asexual developmental pathway was confirmed. Another remarkable quantitative change occurred in the expression of genes involved in carbon or nitrogen primary metabolism. Genes participating in polar growth or sexual development were transcriptionally repressed, as were those belonging to the HogA/SakA stress response mitogen-activated protein (MAP) kinase pathway. We also identified significant expression changes in several genes purportedly involved in redox balance, transmembrane transport, secondary metabolite production, or transcriptional regulation, mainly binuclear-zinc cluster transcription factors. Genes coding for these four activities were usually grouped in metabolic clusters, which may bring regulatory implications for the induction of asexual development. These results provide a blueprint for further stage-specific gene expression studies during conidiophore development. © 2013, American Society for Microbiology. All Rights Reserved.This work has been supported by the Basque Government through grant (IT393-10) and the Ministerio de Economía y Competitividad (formerly Ministerio de Ciencia e Innovación) through grant (BFU2010-17528) to U.U., grant (BFU2009- 08701) to E.A.E. and grants from the German Science Foundation (DFG Fi 459), the Fonds der Chemischen Industrie, the Baden-Württemberg Stiftung, and the Centre for Functional Nanostructures to R.F. A. G. is now a contract researcher from The University of The Basque Country. J.R. was a postdoctoral fellow of the Ministerio de Ciencia e Innovación. O.E is a contract researcher associated to grant BFU2010- 17528.Peer Reviewe

Patient-specific iPSC-derived cellular models of LGMDR1

Limb-girdle muscular dystrophy recessive 1 (LGMDR1) represents one of the most common types of LGMD in the population, where patients develop a progressive muscle degeneration. The disease is caused by mutations in calpain 3 gene, with over 500 mutations reported to date. However, the molecular events that lead to muscle wasting are not clear, nor the reasons for the great clinical variability among patients, and this has so far hindered the development of effective therapies. Here we generate human induced pluripotent stem cells (iPSCs) from skin fibroblasts of 2 healthy controls and 4 LGMDR1 patients with different mutations. The generated lines were able to differentiate into myogenic progenitors and myotubes in vitro and in vivo, upon a transient PAX7 overexpressing protocol. Thus, we have generated myogenic cellular models of LGMDR1 that harbor different CAPN3 mutations within a human genetic background, and which do not derive from muscular biopsies. These models will allow us to investigate disease mechanisms and test therapies. Despite the variability found among iPSC lines that was unrelated to CAPN3 mutations, we found that patient-derived myogenic progenitors and myotubes express lower levels of DMD, which codes a key protein in satellite cell regulation and myotube maturation

Preclinical models for prediction of immunotherapy outcomes and immune evasion mechanisms in genetically heterogeneous multiple myeloma

The historical lack of preclinical models reflecting the genetic heterogeneity of multiple myeloma (MM) hampers the advance of therapeutic discoveries. To circumvent this limitation, we screened mice engineered to carry eight MM lesions (NF-κB, KRAS, MYC, TP53, BCL2, cyclin D1, MMSET/NSD2 and c-MAF) combinatorially activated in B lymphocytes following T cell-driven immunization. Fifteen genetically diverse models developed bone marrow (BM) tumors fulfilling MM pathogenesis. Integrative analyses of ∼500 mice and ∼1,000 patients revealed a common MAPK-MYC genetic pathway that accelerated time to progression from precursor states across genetically heterogeneous MM. MYC-dependent time to progression conditioned immune evasion mechanisms that remodeled the BM microenvironment differently. Rapid MYC-driven progressors exhibited a high number of activated/exhausted CD8+ T cells with reduced immunosuppressive regulatory T (Treg) cells, while late MYC acquisition in slow progressors was associated with lower CD8+ T cell infiltration and more abundant Treg cells. Single-cell transcriptomics and functional assays defined a high ratio of CD8+ T cells versus Treg cells as a predictor of response to immune checkpoint blockade (ICB). In clinical series, high CD8+ T/Treg cell ratios underlie early progression in untreated smoldering MM, and correlated with early relapse in newly diagnosed patients with MM under Len/Dex therapy. In ICB-refractory MM models, increasing CD8+ T cell cytotoxicity or depleting Treg cells reversed immunotherapy resistance and yielded prolonged MM control. Our experimental models enable the correlation of MM genetic and immunological traits with preclinical therapy responses, which may inform the next-generation immunotherapy trials

Aspergillus nidulans in the post-genomic era: a top-model filamentous fungus for the study of signaling and homeostasis mechanisms

18 p.-4 fig.The accessibility to next-generation sequencing (NGS) techniques has enabled the sequencing of hundreds of genomes of species representing all kingdoms. In the case of fungi, genomes of more than a thousand of species are publicly available. This is far from covering the number of 2.2–3.8 million fungal species estimated to populate the world but has significantly improved the resolution of the fungal tree of life. Furthermore, it has boosted systematic evolutionary analyses, the development of faster and more accurate diagnostic analyses of pathogenic strains or the improvement of several biotechnological processes. Nevertheless,the diversification of the nature of fungal species used as model has also weakened research in other species that were traditionally used as reference in the pre-genomic era. In this context, and after more than 65 years since the first works published by Pontecorvo, Aspergillus nidulans remains as one of the most referential model filamentous fungus in research fields such as hyphal morphogenesis, intracellular transport, developmental programs, secondary metabolism, or stress response. This minireview summarizes how A. nidulans has contributed to the progress in these fields during the last years, and discusses how it could contribute in the future, assisted by NGS and new-generation molecular, microscopy, or cellular tools.Work at the UPV/EHU lab was funded by the University of the Basque Country (grant EHUA15/08). Work at CIBCSIC was funded by the MINECO/FEDER/EU (grant BFU2015-66806-R).Peer reviewe

Defining the transcriptional responses of Aspergillus nidulans to cation/alkaline pH stress and the role of the transcription factor SltA

18 p.-7 fig.Fungi have developed the ability to overcome extreme growth conditions and thrive in hostile environments. The model fungus Aspergillus nidulans tolerates, for example, ambient alkalinity up to pH 10 or molar concentrations of multiple cations. The ability to grow under alkaline pH or saline stress depends on the effective function of at least three regulatory pathways mediated by the zinc-finger transcription factor PacC, which mediates the ambient pH regulatory pathway, the calcineurin-dependent CrzA and the cation homeostasis responsive factor SltA. Using RNA sequencing, we determined the effect of external pH alkalinization or sodium stress on gene expression. The data show that each condition triggers transcriptional responses with a low degree of overlap. By sequencing the transcriptomes of the null mutant, the role of SltA in the above-mentioned homeostasis mechanisms was also studied. The results show that the transcriptional role of SltA is wider than initially expected and implies, for example, the positive control of the PacC-dependent ambient pH regulatory pathway. Overall, our data strongly suggest that the stress response pathways in fungi include some common but mostly exclusive constituents, and that there is a hierarchical relationship among the main regulators of stress response, with SltA controlling pacC expression, at least in A. nidulans.Work at CIB-CSIC was funded by MINECO (BFU2015-66806-R to E. A.E) and MICIU/AEI (RTI2018-094263-B-100) to E. A. E (both partially supported by FEDER, EU). Work at the UPV/EHU lab was funded by UPV/EHU grants PPGA19/08 and GIU19/014 to O. E and the Basque Government grant Elkartek19/72 (to Professor María Teresa Dueñas).I. P and E. R. held research contracts associated with grants RTI2018-094263-B-100 and BFU2015-66806-R,respectively.We acknowledge the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI) for enabling this open access publication through a Publish and Read deal with the Microbiology Society.Peer reviewe

Elucidation of functional markers from Aspergillus nidulans developmental regulator FlbB and their phylogenetic distribution

Aspergillus nidulans is a filamentous fungus widely used as a model for biotechnological and clinical research. It is also used as a platform for the study of basic eukaryotic developmental processes. Previous studies identified and partially characterized a set of proteins controlling cellular transformations in this ascomycete. Among these proteins, the bZip type transcription factor FlbB is a key regulator of reproduction, stress responses and cell-death. Our aim here was the prediction, through various bioinformatic methods, of key functional residues and motifs within FlbB in order to inform the design of future laboratory experiments and further the understanding of the molecular mechanisms that control fungal development. A dataset of FlbB orthologs and those of its key interaction partner FlbE was assembled from 40 members of the Pezizomycotina. Unique features were identified in each of the three structural domains of FlbB. The N-terminal region encoded a bZip transcription factor domain with a novel histidine-containing DNA binding motif while the dimerization determinants exhibited two distinct profiles that segregated by class. The C-terminal region of FlbB showed high similarity with the AP-1 family of stress response regulators but with variable patterns of conserved cysteines that segregated by class and order. Motif conservation analysis revealed that nine FlbB orthologs belonging to the Eurotiales order contained a motif in the central region that could mediate interaction with FlbE. The key residues and motifs identified here provide a basis for the design of follow-up experimental investigations. Additionally, the presence or absence of these residues and motifs among the FlbB orthologs could help explain the differences in the developmental programs among fungal species as well as define putative complementation groups that could serve to extend known functional characterizations to other speciesThis work was supported by the Basque Government(http://www.hezkuntza.ejgv.euskadi.net) through grant IT393-10 to U.U. and by the Spanish Ministerio de Educacio´n y Ciencia (www.mec.es) through grant BFU2009-08701 to E.A.E. M.S.C. was a contract researcher of the Ikerbasque program of the Basque Government (www.ikerbasque.net). O.E. was a contract researcher of the University of the Basque Country (www.ehu.es). A.G. held a predoctoral fellowship frommthe Basque Government.Peer reviewe