Neurons migrate from their birthplaces to the destinations, and extending axons navigate to their synaptic targets by sensing various extracellular cues in spatiotemporally controlled manners. These evolutionally conserved guidance cues and their receptors regulate multiple aspects of neural development to establish the highly complex nervous system by mediating both short- and long-range cell-cell communications. Neuronal guidance genes (encoding cues, receptors, or downstream signal transducers) are critical not only for development of the nervous system but also for synaptic maintenance, remodeling, and function in the adult brain. One emerging theme is the combinatorial and complementary functions of relatively limited classes of neuronal guidance genes in multiple processes, including neuronal migration, axonal guidance, synaptogenesis, and circuit formation. Importantly, neuronal guidance genes also regulate cell migration and cell-cell communications outside the nervous system. We are just beginning to understand how cells integrate multiple guidance and adhesion signaling inputs to determine overall cellular/subcellular behavior and how aberrant guidance signaling in various cell types contributes to diverse human diseases, ranging from developmental, neuropsychiatric, and neurodegenerative disorders to cancer metastasis. We review classic studies and recent advances in understanding signaling mechanisms of the guidance genes as well as their roles in human diseases. Furthermore, we discuss the remaining challenges and therapeutic potentials of modulating neuronal guidance pathways in neural repair.
Humans ; Axon Guidance/genetics* ; Neurons ; Axons/metabolism* ; Signal Transduction/genetics* ; Cell Communication

Aberrant regulation of miRNA genes contributes to pathogenesis of a wide range of human diseases, including cancer. The TAR DNA binding protein 43 (TDP-43), a RNA/DNA binding protein associated with neurodegeneration, is involved in miRNA biogenesis. Here, we systematically examined miRNAs regulated by TDP-43 using RNA-Seq coupled with an siRNA-mediated knockdown approach. TDP-43 knockdown affected the expression of a number of miRNAs. In addition, TDP-43 down-regulation led to alterations in the patterns of different isoforms of miRNAs (isomiRs) and miRNA arm selection, suggesting a previously unknown role of TDP-43 in miRNA processing. A number of TDP-43 associated miRNAs, and their candidate target genes, are associated with human cancers. Our data reveal highly complex roles of TDP-43 in regulating different miRNAs and their target genes. Our results suggest that TDP-43 may promote migration of lung cancer cells by regulating miR-423-3p. In contrast, TDP-43 increases miR-500a-3p expression and binds to the mature miR-500a-3p sequence. Reduced expression of miR-500a-3p is associated with poor survival of lung cancer patients, suggesting that TDP-43 may have a suppressive role in cancer by regulating miR-500a-3p. Cancer-associated genes LIF and PAPPA are possible targets of miR-500a-3p. Our work suggests that TDP-43-regulated miRNAs may play multifaceted roles in the pathogenesis of cancer.
Animals ; Cells, Cultured ; DNA-Binding Proteins ; metabolism ; Electrophoretic Mobility Shift Assay ; Humans ; Immunoprecipitation ; Mice ; MicroRNAs ; genetics ; metabolism ; Neoplasms ; genetics ; metabolism

Axonal transport of mitochondria is critical for neuronal survival and function. Automatically quantifying and analyzing mitochondrial movement in a large quantity remain challenging. Here, we report an efficient method for imaging and quantifying axonal mitochondrial transport using microfluidic-chamber-cultured neurons together with a newly developed analysis package named "MitoQuant". This tool-kit consists of an automated program for tracking mitochondrial movement inside live neuronal axons and a transient-velocity analysis program for analyzing dynamic movement patterns of mitochondria. Using this method, we examined axonal mitochondrial movement both in cultured mammalian neurons and in motor neuron axons of Drosophila in vivo. In 3 different paradigms (temperature changes, drug treatment and genetic manipulation) that affect mitochondria, we have shown that this new method is highly efficient and sensitive for detecting changes in mitochondrial movement. The method significantly enhanced our ability to quantitatively analyze axonal mitochondrial movement and allowed us to detect dynamic changes in axonal mitochondrial transport that were not detected by traditional kymographic analyses.
Animals ; Axonal Transport ; physiology ; Cerebral Cortex ; cytology ; metabolism ; Drosophila melanogaster ; cytology ; metabolism ; Embryo, Mammalian ; Gene Expression ; Lab-On-A-Chip Devices ; Microscopy, Confocal ; Mitochondria ; metabolism ; ultrastructure ; Motor Neurons ; metabolism ; ultrastructure ; Movement ; Mutation ; Primary Cell Culture ; RNA-Binding Protein FUS ; genetics ; metabolism ; Rats ; Rats, Sprague-Dawley ; Software

MicroRNAs (miRNAs) are critical for both development and function of the central nervous system. Significant evidence suggests that abnormal expression of miRNAs is associated with neurodevelopmental disorders. MeCP2 protein is an epigenetic regulator repressing or activating gene transcription by binding to methylated DNA. Both loss-of-function and gain-of-function mutations in the MECP2 gene lead to neurodevelopmental disorders such as Rett syndrome, autism and MECP2 duplication syndrome. In this study, we demonstrate that miR-130a inhibits neurite outgrowth and reduces dendritic spine density as well as dendritic complexity. Bioinformatics analyses, cell cultures and biochemical experiments indicate that miR-130a targets MECP2 and down-regulates MeCP2 protein expression. Furthermore, expression of the wild-type MeCP2, but not a loss-of-function mutant, rescues the miR-130a-induced phenotype. Our study uncovers the MECP2 gene as a previous unknown target for miR-130a, supporting that miR-130a may play a role in neurodevelopment by regulating MeCP2. Together with data from other groups, our work suggests that a feedback regulatory mechanism involving both miR-130a and MeCP2 may serve to ensure their appropriate expression and function in neural development.
Animals ; Dendrites ; genetics ; metabolism ; Dendritic Spines ; genetics ; metabolism ; Down-Regulation ; physiology ; Methyl-CpG-Binding Protein 2 ; biosynthesis ; genetics ; MicroRNAs ; genetics ; metabolism ; Rats

Ubiquitin specific protease 33 (USP33) is a multifunctional protein regulating diverse cellular processes. The expression and role of USP33 in lung cancer remain unexplored. In this study, we show that USP33 is down-regulated in multiple cohorts of lung cancer patients and that low expression of USP33 is associated with poor prognosis. USP33 mediates Slit-Robo signaling in lung cancer cell migration. Downregulation of USP33 reduces the protein stability of Robo1 in lung cancer cells, providing a previously unknown mechanism for USP33 function in mediating Slit activity in lung cancer cells. Taken together, USP33 is a new player in lung cancer that regulates Slit-Robo signaling. Our data suggest that USP33 may be a candidate tumor suppressor for lung cancer with potential as a prognostic marker.
Blotting, Western ; Cell Line, Tumor ; Cell Movement ; genetics ; physiology ; Cohort Studies ; Down-Regulation ; Female ; Gene Expression Regulation, Neoplastic ; HEK293 Cells ; Humans ; Immunohistochemistry ; Intercellular Signaling Peptides and Proteins ; metabolism ; Kaplan-Meier Estimate ; Lung Neoplasms ; genetics ; metabolism ; pathology ; Male ; Middle Aged ; Nerve Tissue Proteins ; metabolism ; Prognosis ; RNA Interference ; Receptors, Immunologic ; metabolism ; Reverse Transcriptase Polymerase Chain Reaction ; Signal Transduction ; genetics ; physiology ; Ubiquitin Thiolesterase ; genetics ; metabolism

Chronic constipation (CC) may impact on quality of life. There is substantial patient dissatisfaction; possible reasons are failure to recognize underlying constipation, inappropriate dietary advice and inadequate treatment. The aim of these practical guidelines intended for primary care physicians, and which are based on Asian perspectives, is to provide an approach to CC that is relevant to the existing health-care infrastructure. Physicians should not rely on infrequent bowel movements to diagnose CC as many patients have one or more bowel movement a day. More commonly, patients present with hard stool, straining, incomplete feeling, bloating and other dyspeptic symptoms. Physicians should consider CC in these situations and when patients are found to use laxative containing supplements. In the absence of alarm features physicians may start with a 2-4 week therapeutic trial of available pharmacological agents including osmotic, stimulant and enterokinetic agents. Where safe to do so, physicians should consider regular (as opposed to on demand dosing), combination treatment and continuous treatment for at least 4 weeks. If patients do not achieve satisfactory response, they should be referred to tertiary centers for physiological evaluation of colonic transit and pelvic floor function. Surgical referral is a last resort, which should be considered only after a thorough physiological and psychological evaluation.
Asia ; Asian Continental Ancestry Group ; Colon ; Constipation ; Health Resorts ; Humans ; Pelvic Floor ; Physicians, Primary Care ; Primary Health Care ; Quality of Life ; Referral and Consultation ; Sprains and Strains

Down syndrome cell adhesion molecule (DSCAM) acts as a netrin-1 receptor and mediates attractive response of axons to netrin-1 in neural development. However, the signaling mechanisms of netrin-DSCAM remain unclear. Here we report that AMP-activated protein kinase (AMPK) interacts with DSCAM through its γ subunit, but does not interact with DCC (deleted in colorectal cancer), another major receptor for netrin-1. Netrin-treatment of cultured cortical neurons leads to increased phosphorylation of AMPK. Both AMPK mutant with dominant-negative effect and AMPK inhibitor can significantly suppress netrin-1 induced neurite outgrowth. Together, these findings demonstrate that AMPK interacts with DSCAM and plays an important role in netrin-1 induced neurite outgrowth. Our study uncovers a previously unknown component, AMPK, in netrin-DSCAM signaling pathway.
AMP-Activated Protein Kinases ; antagonists & inhibitors ; genetics ; metabolism ; Animals ; Cell Adhesion Molecules ; genetics ; metabolism ; Cells, Cultured ; HEK293 Cells ; Humans ; Mice ; Nerve Growth Factors ; pharmacology ; Netrin-1 ; Neurites ; physiology ; Neurons ; cytology ; drug effects ; metabolism ; Phosphorylation ; Protein Binding ; Protein Kinase Inhibitors ; pharmacology ; RNA Interference ; RNA, Small Interfering ; Recombinant Fusion Proteins ; biosynthesis ; genetics ; Signal Transduction ; drug effects ; Transfection ; Tumor Suppressor Proteins ; pharmacology

The nervous system is one of the most complicated organ systems in invertebrates and vertebrates. Down syndrome cell adhesion molecule (DSCAM) of the immunoglobulin (Ig) superfamily is expressed widely in the nervous system during embryonic development. Previous studies in Drosophila suggest that Dscam plays important roles in neural development including axon branching, dendritic tiling and cell spacing. However, the function of the mammalian DSCAM gene in the formation of the nervous system remains unclear. Here, we show that Dscam ( del17 ) mutant mice exhibit severe hydrocephalus, decreased motor function and impaired motor learning ability. Our data indicate that the mammalian DSCAM gene is critical for the formation of the central nervous system.
Animals ; Cell Adhesion Molecules ; genetics ; metabolism ; Corpus Callosum ; metabolism ; pathology ; Genotype ; Hydrocephalus ; genetics ; metabolism ; pathology ; Mice ; Mice, Knockout ; Motor Activity ; genetics ; physiology ; Mutation

Mutations in the Fused in sarcoma/Translated in liposarcoma gene (FUS/TLS, FUS) have been identified among patients with amyotrophic lateral sclerosis (ALS). FUS protein aggregation is a major pathological hallmark of FUS proteinopathy, a group of neurodegenerative diseases characterized by FUS-immunoreactive inclusion bodies. We prepared transgenic Drosophila expressing either the wild type (Wt) or ALS-mutant human FUS protein (hFUS) using the UAS-Gal4 system. When expressing Wt, R524S or P525L mutant FUS in photoreceptors, mushroom bodies (MBs) or motor neurons (MNs), transgenic flies show age-dependent progressive neural damages, including axonal loss in MB neurons, morphological changes and functional impairment in MNs. The transgenic flies expressing the hFUS gene recapitulate key features of FUS proteinopathy, representing the first stable animal model for this group of devastating diseases.
Aged ; Aging ; genetics ; metabolism ; pathology ; Amyotrophic Lateral Sclerosis ; genetics ; metabolism ; pathology ; Animals ; Animals, Genetically Modified ; Disease Models, Animal ; Drosophila melanogaster ; genetics ; metabolism ; Gene Expression ; Humans ; Microscopy, Electron, Scanning ; Motor Neurons ; metabolism ; pathology ; Mushroom Bodies ; metabolism ; pathology ; Mutant Proteins ; genetics ; metabolism ; Mutation ; Photoreceptor Cells, Invertebrate ; metabolism ; pathology ; Plasmids ; RNA-Binding Protein FUS ; genetics ; metabolism ; Recombinant Fusion Proteins ; genetics ; metabolism ; Retinal Degeneration ; pathology ; physiopathology ; Transfection