Intronic expansion of a hexanucleotide GGGGCC repeat in the chromosome 9 open reading frame 72 (C9ORF72) gene is the major cause of familial amyotrophic lateral sclerosis (ALS) and frontotemporal dementia. However, the cellular function of the C9ORF72 protein remains unknown. Here, we demonstrate that C9ORF72 regulates endosomal trafficking. C9ORF72 colocalized with Rab proteins implicated in autophagy and endocytic transport: Rab1, Rab5, Rab7 and Rab11 in neuronal cell lines, primary cortical neurons and human spinal cord motor neurons, consistent with previous predictions that C9ORF72 bears Rab guanine exchange factor activity. Consistent with this notion, C9ORF72 was present in the extracellular space and as cytoplasmic vesicles. Depletion of C9ORF72 using siRNA inhibited transport of Shiga toxin from the plasma membrane to Golgi apparatus, internalization of TrkB receptor and altered the ratio of autophagosome marker light chain 3 (LC3) II:LC3I, indicating that C9ORF72 regulates endocytosis and autophagy. C9ORF72 also colocalized with ubiquilin-2 and LC3-positive vesicles, and co-migrated with lysosome-stained vesicles in neuronal cell lines, providing further evidence that C9ORF72 regulates autophagy. Investigation of proteins interacting with C9ORF72 using mass spectrometry identified other proteins implicated in ALS; ubiquilin-2 and heterogeneous nuclear ribonucleoproteins, hnRNPA2/B1 and hnRNPA1, and actin. Treatment of cells overexpressing C9ORF72 with proteasome inhibitors induced the formation of stress granules positive for hnRNPA1 and hnRNPA2/B1. Immunohistochemistry of C9ORF72 ALS patient motor neurons revealed increased colocalization between C9ORF72 and Rab7 and Rab11 compared with controls, suggesting possible dysregulation of trafficking in patients bearing the C9ORF72 repeat expansion. Hence, this study identifies a role for C9ORF72 in Rab-mediated cellular trafficking.

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are overlapping, fatal neurodegenerative disorders in which the molecular and pathogenic basis remains poorly understood. Ubiquitinated protein aggregates, of which TDP-43 is a major component, are a characteristic pathological feature of most ALS and FTD patients. Here we use genome-wide linkage analysis in a large ALS/FTD kindred to identify a novel disease locus on chromosome 16p13.3. Whole-exome sequencing identified a CCNF missense mutation at this locus. Interrogation of international cohorts identified additional novel CCNF variants in familial and sporadic ALS and FTD. Enrichment of rare protein-altering CCNF variants was evident in a large sporadic ALS replication cohort. CCNF encodes cyclin F, a component of an E3 ubiquitin–protein ligase complex (SCFCyclin F). Expression of mutant CCNF in neuronal cells caused abnormal ubiquitination and accumulation of ubiquitinated proteins, including TDP-43 and a SCFCyclin F substrate. This implicates common mechanisms, linked to protein homeostasis, underlying neuronal degeneration.

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Phosphoprotein driven cellular signaling events represent most of the new molecular targets for cancer treatment. Application of reverse-phase protein microarray technology for the study of ongoing signaling activity within breast tumor specimens holds great potential for elucidating and profiling signaling activity in real-time for patient-tailored therapy. Analysis of laser capture microdissection primary human breast tumors and metastatic lesions reveals pathway specific profiles and a new way to classify cancer based on functional signaling portraits. Moreover, the data demonstrate the requirement of laser capture microdissection for analysis and reveal the metastasis-specific changes that occur within a new microenvironment. Analysis of biopsy material from clinical trials for targeted therapeutics demonstrates the feasibility and utility of comprehensive signal pathway activation profiling for molecular analysis.

Oocyte maturation and egg fertilization in both vertebrates and invertebrates are marked by orchestrated cytoplasmic translocation of secretory vesicles known as cortical granules. It is thought that such redistribution of cellular content is critical for asymmetrical cell division during early development, but the mechanism and regulation of the process is poorly understood. Here we report the identification, purification and cDNA cloning of a C-type lectin from oocytes of a freshwater fish species gibel carp (Carassius auratus gibelio). The purified protein has been demonstrated to have lectin activity and to be a Ca(2+)-dependent C-type lectin by hemagglutination activity assay. Immunocytochemistry revealed that the lectin is associated with cortical granules, gradually translocated to the cell surface during oocyte maturation, and discharged to the egg envelope upon fertilization. Interestingly, the lectin becomes phosphorylated on threonine residues upon induction of exocytosis by fertilization and returns to its original state after morula stage of embryonic development, suggesting that this posttranslational modification may represent a critical molecular switch for early embryonic development.

Background Pathological forms of TAR DNA-binding protein 43 (TDP-43) are present in motor neurons of almost all amyotrophic lateral sclerosis (ALS) patients, and mutations in TDP-43 are also present in ALS. Loss and gain of TDP-43 functions are implicated in pathogenesis, but the mechanisms are unclear. While the RNA functions of TDP-43 have been widely investigated, its DNA binding roles remain unclear. However, recent studies have implicated a role for TDP-43 in the DNA damage response. Methods We used NSC-34 motor neuron-like cells and primary cortical neurons expressing wildtype TDP-43 or TDP-43 ALS associated mutants (A315T, Q331K), in which DNA damage was induced by etoposide or H2O2 treatment. We investigated the consequences of depletion of TDP-43 on DNA repair using small interfering RNAs. Specific non homologous end joining (NHEJ) reporters (EJ5GFP and EJ2GFP) and cells lacking DNA-dependent serine/threonine protein kinase (DNA-PK) were used to investigate the role of TDP-43 in DNA repair. To investigate the recruitment of TDP-43 to sites of DNA damage we used single molecule super-resolution microscopy and a co-immunoprecipitation assay. We also investigated DNA damage in an ALS transgenic mouse model, in which TDP-43 accumulates pathologically in the cytoplasm. We also examined fibroblasts derived from ALS patients bearing the TDP-43 M337V mutation for evidence of DNA damage. Results We demonstrate that wildtype TDP-43 is recruited to sites of DNA damage where it participates in classical NHEJ DNA repair. However, ALS-associated TDP-43 mutants lose this activity, which induces DNA damage. Furthermore, DNA damage is present in mice displaying TDP-43 pathology, implying an active role in neurodegeneration. Additionally, DNA damage triggers features typical of TDP-43 pathology; cytoplasmic mis-localisation and stress granule formation. Similarly, inhibition of NHEJ induces TDP-43 mis-localisation to the cytoplasm. Conclusions This study reveals that TDP-43 functions in DNA repair, but loss of this function triggers DNA damage and is associated with key pathological features of ALS.

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