Plum pudding random medium model of biological tissue toward remote microscopy from spectroscopic light scattering

Biological tissue has a complex structure and exhibits rich spectroscopic behavior. There is \emph{no} tissue model up to now able to account for the observed spectroscopy of tissue light scattering and its anisotropy. Here we present, \emph{for the first time}, a plum pudding random medium (PPRM) model for biological tissue which succinctly describes tissue as a superposition of distinctive scattering structures (plum) embedded inside a fractal continuous medium of background refractive index fluctuation (pudding). PPRM faithfully reproduces the wavelength dependence of tissue light scattering and attributes the "anomalous" trend in the anisotropy to the plum and the powerlaw dependence of the reduced scattering coefficient to the fractal scattering pudding. Most importantly, PPRM opens up a novel venue of quantifying the tissue architecture and microscopic structures on average from macroscopic probing of the bulk with scattered light alone without tissue excision. We demonstrate this potential by visualizing the fine microscopic structural alterations in breast tissue (adipose, glandular, fibrocystic, fibroadenoma, and ductal carcinoma) deduced from noncontact spectroscopic measurement

The new missense G376V-TDP-43 variant induces late-onset distal myopathy but not amyotrophic lateral sclerosis

TAR DNA binding protein of 43 kDa (TDP-43)-positive inclusions in neurons are a hallmark of several neurodegenerative diseases including familial amyotrophic lateral sclerosis (fALS) caused by pathogenic TARDBP variants as well as more common non-Mendelian sporadic ALS (sALS). Here we report a G376V-TDP-43 missense variant in the C-terminal prion-like domain of the protein in two French families affected by an autosomal dominant myopathy but not fulfilling diagnostic criteria for ALS.Patients from both families presented with progressive weakness and atrophy of distal muscles, starting in their fifth to seventh decade. Muscle biopsies revealed a degenerative myopathy characterized by accumulation of rimmed (autophagic) vacuoles, disruption of sarcomere integrity and severe myofibrillar disorganization. The G376V variant altered a highly conserved amino acid residue and was absent in databases on human genome variation. Variant pathogenicity was supported by in silico analyses and functional studies.The G376V mutant increased the formation of cytoplasmic TDP-43 condensates in cell culture models, promoted assembly into high molecular weight oligomers and aggregates in vitro, and altered morphology of TDP-43 condensates arising from phase separation. Moreover, the variant led to the formation of cytoplasmic TDP-43 condensates in patient-derived myoblasts and induced abnormal mRNA splicing in patient muscle tissue.The identification of individuals with TDP-43-related myopathy, but not ALS, implies that TARDBP missense variants may have more pleiotropic effects than previously anticipated and support a primary role for TDP-43 in skeletal muscle pathophysiology. We propose to include TARDBP screening in the genetic work-up of patients with late-onset distal myopathy. Further research is warranted to examine the precise pathogenic mechanisms of TARDBP variants causing either a neurodegenerative or myopathic phenotype. Zibold et al. identify a new TDP-43 missense variant (G376V) in two French families affected by late-onset distal myopathy but not ALS. The findings support a primary role for TDP-43 in skeletal muscle pathophysiology and suggest that TARDBP screening should be included in the genetic work-up of patients with distal myopathy

Non-canonical Wnt signalling regulates scarring in biliary disease via the planar cell polarity receptors

The number of patients diagnosed with chronic bile duct disease is increasing and in most cases these diseases result in chronic ductular scarring, necessitating liver transplantation. The formation of ductular scaring affects liver function; however, scar-generating portal fibroblasts also provide important instructive signals to promote the proliferation and differentiation of biliary epithelial cells. Therefore, understanding whether we can reduce scar formation while maintaining a pro-regenerative microenvironment will be essential in developing treatments for biliary disease. Here, we describe how regenerating biliary epithelial cells express Wnt-Planar Cell Polarity signalling components following bile duct injury and promote the formation of ductular scars by upregulating pro-fibrogenic cytokines and positively regulating collagen-deposition. Inhibiting the production of Wnt-ligands reduces the amount of scar formed around the bile duct, without reducing the development of the pro-regenerative microenvironment required for ductular regeneration, demonstrating that scarring and regeneration can be uncoupled in adult biliary disease and regeneration

Characterization of the planar cell polarity receptor Vangl2 in breast cancer

La polarité planaire ou PCP est un processus dans lequel les cellules et des structures apicales sedéveloppent et s’orientent dans le plan de l’épithélium. Cette polarité est régulée par un ensemble deprotéines incluant Vangl2. Un mutant murin de Vangl2 nommé looptail présente une forme sévèred’absence de fermeture du tube neural. Des pertes de fonctions de Vangl2 sont également retrouvées chezdes enfants atteints de défaut de fermeture du tube neural. Vangl2 possède un motif d’interaction pour desdomaines PDZ et s’organise en protéine à quatre domaines transmembranaires. Malgré de nombreusesdonnées génétiques disponibles concernant la perte de fonction de Vangl2, beaucoup reste à faire pourélucider les mécanismes moléculaires impliqués. Le locus du gène vangl2 humain est localisé dans unerégion fréquemment réarrangée dans différents cancers incluant les cancers du sein. Nous nous sommesintéressés à l’expression de Vangl2 dans les cancers du sein. Nous montrons que Vangl2 est surexprimédans des cancers du sein de sous-type basal (cancers du sein agressifs et de mauvais pronostic) danslesquels le locus génétique de Vangl2 est significativement amplifié et où le niveau d’expression del’ARNm et de la protéine est également élevé. De plus, par des études in vitro et in vivo, nous démontronsle rôle de Vangl2 dans la croissance tumorale et dans les processus de migration cellulaire. Ces effets sontdépendants de son motif d’interaction aux domaines PDZ et sont dépendants de Scrib, une autre protéinede la PCP, étudiée dans l’équipe et impliquée dans les processus de migration cellulaire. Par desexpériences de gain et de perte de fonction dans des cellules de cancers du sein, nous démontrons quel’expression de Vangl2 régule la signalisation JNK via l’activité des GTPases Rac1 et Cdc42 importantespour les processus de réorganisation du cytosquelette d’actine. L’ensemble de nos données indique un rôlerégulateur de Vangl2 dans les processus de tumorigenèse l’impliquant dans la croissance tumorale, laprolifération et migration cellulaires.Planar cell polarity (PCP) is a process by which cells and apical structures grow in a uniformorientation within the plane of the epithelium. This type of polarity is regulated by a set of “core” proteinsincluding Vangl2. A vangl2 mutant, known as looptail exhibits a severe form of neural tube defect.Mutations of vangl2 associated to neural tube defects were also described in human. Vangl2 possesses aPDZ binding motif and is potentially organized in a four transmembrane domain structure. While geneticdata has very well described the importance of Vangl2 in embryonic development, its molecular functionsare still unknown. The human vangl2 gene is localized in a region with frequent rearrangements involvedin multiple cancers, including breast cancer. We decided to explore the expression of Vangl2 in breastcancer and defined Vangl2 as a PCP “core” protein associated with a signature of poor prognosis basaltypebreast cancer. The Vangl2 genetic locus is amplified in breast cancers, and this amplificationcorrelates with high mRNA and protein levels. Moreover, in in vitro and in vivo studies, we demonstratethe role of Vangl2 in tumor growth and cell migration. These functions are dependent on its PDZ bindingmotif and implicates Scrib, a PCP protein containing PDZ domains and involved in cell migration. Finally,using gain-of-function and loss-of-function approaches in breast cancer cell lines, we demonstrate thatVangl2 modulates the JNK pathway activation via the Rac1 and Cdc42 GTPases which are important forcytoskeleton reorganization. Together, our data reveal that Vangl2 has a role in tumor growth, cellproliferation and cell migration

Regulation of Gene expression at the neuromuscular Junction

International audienc

Molecular characterisation of endogenous Vangl2/Vangl1 heteromeric protein complexes.

BACKGROUND: Mutations in the Planar Cell Polarity (PCP) core gene Vangl2 cause the most severe neural tube defects (NTD) in mice and humans. Genetic studies show that the Vangl2 gene genetically interacts with a close homologue Vangl1. How precisely Vangl2 and Vangl1 proteins interact and crosstalk has remained a difficult issue to address, with the main obstacle being the accurate discrimination of the two proteins, which share close sequence homology. Experimental evidence previously presented has been sparse and addressed with ectopically expressed proteins or with antibodies unable to biochemically discriminate Vangl1 from Vangl2, therefore giving rise to unclear results. METHODOLOGY AND MAIN FINDINGS: A highly specific monoclonal anti-Vangl2 antibody was generated and rigorously tested on both recombinant and extracted Vangl2 using surface plasmon resonance (SPR) analysis, western blot, and immunoprecipitation experiments. This antibody efficiently affinity-purified Vangl2 from cell lysates and allowed the unambiguous identification of endogenous Vangl2 by proteomic analysis. Vangl1 was also present in Vangl2 immunoprecipitates, establishing the first biochemical evidence for the existence of Vangl2/Vangl1 heterodimers at an endogenous level. Epitope-tagged Vangl2 and Vangl1 confirmed that both proteins interact and colocalize at the plasma membrane. The Vangl2 antibody is able to acutely assess differential expression levels of Vangl2 protein in culture cell lines, as corroborated with gene expression analysis. We characterised Vangl2 expression in the cochlea of homozygous and heterozygous Lp mutant mice bearing a point mutation within the C-terminal Vangl2 region that leads to profound PCP defects. Our antibody could detect much lower levels of Vangl2(Lp) protein in mutant mice compared to the wild type mice. CONCLUSION: Our results provide an in-depth biochemical characterisation of the interaction observed between Vangl paralogues

The CENP-A nucleosome: where and when it happens during the inner kinetochore's assembly

CENP-A is an essential histone variant that replaces the canonical H3 at the centromeres and marks these regions epigenetically. The CENP-A nucleosome is the specific building block of centromeric chromatin, and it is recognized by CENP-C and CENP-N, two components of the constitutive centromere-associated network (CCAN), the first protein layer of the kinetochore. Recent proposals of the yeast and human (h)CCAN structures position the assembly on exposed DNA, suggesting an elusive spatiotemporal recognition. We summarize the data on the structural organization of the CENP-A nucleosome and the binding of CENP-C and CENP-N. The latter posits an apparent contradiction in engaging the CENP-A nucleosome versus the CCAN. We propose a reconciliatory model for the assembly of CCAN on centromeric chromatin

H2A.Z is dispensable for both basal and activated transcription in post-mitotic mouse muscles

International audienceWhile the histone variant H2A.Z is known to be required for mitosis, it is also enriched in nucleosomes surrounding the transcription start site of active promoters, implicating H2A.Z in transcription. However, evidence obtained so far mainly rely on correlational data generated in actively dividing cells. We have exploited a paradigm in which transcription is uncoupled from the cell cycle by developing an in vivo system to inactivate H2A.Z in terminally differentiated post-mitotic muscle cells. ChIP-seq, RNA-seq and ATAC-seq experiments performed on H2A.Z KO post-mitotic muscle cells show that this histone variant is neither required to maintain nor to activate transcription. Altogether, this study provides in vivo evidence that in the absence of mitosis H2A.Z is dispensable for transcription and that the enrichment of H2A.Z on active promoters is a marker but not an active driver of transcription

Identification of p62/SQSTM1 as a component of non-canonical Wnt VANGL2-JNK signalling in breast cancer

Source: doi: 10.1038/ncomms10318The non-canonical Wnt/planar cell polarity (Wnt/PCP) pathway plays a crucial role in embryonic development. Recent work has linked defects of this pathway to breast cancer aggressiveness and proposed Wnt/PCP signalling as a therapeutic target. Here we show that the archetypal Wnt/PCP protein VANGL2 is overexpressed in basal breast cancers, associated with poor prognosis and implicated in tumour growth. We identify the scaffold p62/SQSTM1 protein as a novel VANGL2-binding partner and show its key role in an evolutionarily conserved VANGL2–p62/SQSTM1–JNK pathway. This proliferative signalling cascade is upregulated in breast cancer patients with shorter survival and can be inactivated in patient-derived xenograft cells by inhibition of the JNK pathway or by disruption of the VANGL2–p62/SQSTM1 interaction. VANGL2–JNK signalling is thus a potential target for breast cancer therapy