Teneurins in development and disease

The teneurins are a novel type II transmembrane protein family originally discovered in Drosophila and highly conserved between invertebrates and vertebrates. Studies in invertebrates suggest important functions for the teneurins in many processes during development. However, still very little is known about the biological function and mechanism of action of the vertebrate teneurin family, which consists of four paralogs called teneurin-1 to -4. In the first part of my thesis, I analyzed the expression pattern and signaling mechanism of teneurin-1 during chick development. Teneurin-1 was prominently expressed in specific regions of the brain, and often complementary to teneurin-2. The presence of teneurin-1 and -2 in interconnected regions of the brain implies a role for teneurins in the establishment of appropriate neuronal connectivity. Using a novel antibody recognizing the teneurin-1 intracellular domain (ICD), N-terminal processing products were detected and nuclear staining was observed in specific neurons and tissues. This provides evidence for our working hypothesis, according to which teneurins can be processed by a mechanism called regulated intramembrane proteolysis, resulting in the release and nuclear translocation of the ICD. Similar results were obtained for teneurin-4 during chick development. In the second part of my thesis, I investigated the implication of teneurins in two human diseases. X-linked mental retardation: Teneurin-1 was analyzed as an X-linked mental retardation (XLMR) candidate gene in 23 XLMR patients. No mutation that is likely to cause the disease was found the coding region or splice sites of the teneurin-1 gene in these patients. Brain tumors: Teneurin-4 was found to be upregulated in a microarray analysis of human brain tumors including astrocytomas, oligodendrogliomas and glioblastomas (GBMs). The overexpression of teneurin-4 was confirmed on protein level in brain tumor lysates. Immunohistochemistry (IHC) revealed strong staining around tumors cells in some brain tumors whereas in others teneurin-4 restricted to blood vessels

Teneurin-1 is expressed in interconnected regions of the developing brain and is processed in vivo

<p>Abstract</p> <p>Background</p> <p>Teneurins are a unique family of transmembrane proteins conserved from <it>C. elegans </it>and <it>D. melanogaster </it>to mammals. In vertebrates there are four paralogs (teneurin-1 to -4), all of which are expressed prominently in the developing central nervous system.</p> <p>Results</p> <p>Analysis of teneurin-1 expression in the developing chick brain by in situ hybridization and immunohistochemistry defined a unique, distinct expression pattern in interconnected regions of the brain. Moreover we found complementary patterns of teneurin-1 and-2 expression in many parts of the brain, including the retina, optic tectum, olfactory bulb, and cerebellum as well as in brain nuclei involved in processing of sensory information. Based on these expression patterns, we suspect a role for teneurins in neuronal connectivity.</p> <p>In contrast to the cell-surface staining of the antibody against the extracellular domain, an antibody recognizing the intracellular domain revealed nuclear staining in subpopulations of neurons and in undifferentiated mesenchyme. Western blot analysis of brain lysates showed the presence of N-terminal fragments of teneurin-1 containing the intracellular domain indicating that proteolytic processing occurs. Finally, the teneurin-1 intracellular domain was found to contain a nuclear localization signal, which is required for nuclear localization in transfected cells.</p> <p>Conclusion</p> <p>Teneurin-1 and -2 are expressed by distinct interconnected populations of neurons in the developing central nervous system. Our data support the hypothesis that teneurins can be proteolytically processed leading to the release of the intracellular domain and its translocation to the nucleus.</p

Human teneurin-1 is a direct target of the homeobox transcription factor EMX2 at a novel alternate promoter

<p>Abstract</p> <p>Background</p> <p>Teneurin-1 is a member of a family of type II transmembrane proteins conserved from <it>C.elegans </it>to vertebrates. Teneurin expression in vertebrates is best studied in mouse and chicken, where the four members teneurin-1 to -4 are predominantly expressed in the developing nervous system in area specific patterns. Based on their distinct, complementary expression a possible function in the establishment of proper connectivity in the brain was postulated. However, the transcription factors contributing to these distinctive expression patterns are largely unknown. Emx2 is a homeobox transcription factor, known to be important for area specification in the developing cortex. A study of Emx2 knock-out mice suggested a role of Emx2 in regulating patterned teneurin expression.</p> <p>Results</p> <p>5'RACE of human teneurin-1 revealed new alternative untranslated exons that are conserved in mouse and chicken. Closer analysis of the conserved region around the newly identified transcription start revealed promoter activity that was induced by EMX2. Mutation of a predicted homeobox binding site decreased the promoter activity in different reporter assays <it>in vitro </it>and <it>in vivo </it>in electroporated chick embryos. We show direct <it>in vivo </it>binding of EMX2 to the newly identified promoter element and finally confirm that the endogenous alternate transcript is specifically upregulated by EMX2.</p> <p>Conclusions</p> <p>We found that human teneurin-1 is directly regulated by EMX2 at a newly identified and conserved promoter region upstream of the published transcription start site, establishing teneurin-1 as the first human EMX2 target gene. We identify and characterize the EMX2 dependent promoter element of human teneurin-1.</p

Integrative genomic analysis reveals widespread enhancer regulation by p53 in response to DNA damage

The tumor suppressor p53 has been studied extensively as a direct transcriptional activator of protein-coding genes. Recent studies, however, have shed light on novel regulatory functions of p53 within noncoding regions of the genome. Here, we use a systematic approach that integrates transcriptome-wide expression analysis, genome-wide p53 binding profiles and chromatin state maps to characterize the global regulatory roles of p53 in response to DNA damage. Notably, our approach identified conserved features of the p53 network in both human and mouse primary fibroblast models. In addition to known p53 targets, we identify many previously unappreciated mRNAs and long noncoding RNAs that are regulated by p53. Moreover, we find that p53 binding occurs predominantly within enhancers in both human and mouse model systems. The ability to modulate enhancer activity offers an additional layer of complexity to the p53 network and greatly expands the diversity of genomic elements directly regulated by p53

A Large Intergenic Noncoding RNA Induced by p53 Mediates Global Gene Repression in the p53 Response

Recently, more than 1000 large intergenic noncoding RNAs (lincRNAs) have been reported. These RNAs are evolutionarily conserved in mammalian genomes and thus presumably function in diverse biological processes. Here, we report the identification of lincRNAs that are regulated by p53. One of these lincRNAs (lincRNA-p21) serves as a repressor in p53-dependent transcriptional responses. Inhibition of lincRNA-p21 affects the expression of hundreds of gene targets enriched for genes normally repressed by p53. The observed transcriptional repression by lincRNA-p21 is mediated through the physical association with hnRNP-K. This interaction is required for proper genomic localization of hnRNP-K at repressed genes and regulation of p53 mediates apoptosis. We propose a model whereby transcription factors activate lincRNAs that serve as key repressors by physically associating with repressive complexes and modulate their localization to sets of previously active genes.National Institutes of Health (U.S.) (New Innovator Award)Smith Family FoundationDamon Runyon Cancer Research FoundationSearle Scholars ProgramNational Institutes of Health (U.S.) (1R01CA119176-01

Missense mutations in TENM4, a regulator of axon guidance and central myelination, cause essential tremor

Essential tremor (ET) is a common movement disorder with an estimated prevalence of 5% of the population aged over 65 years. In spite of intensive efforts, the genetic architecture of ET remains unknown. We used a combination of whole-exome sequencing and targeted resequencing in three ET families. In vitro and in vivo experiments in oligodendrocyte precursor cells and zebrafish were performed to test our findings. Whole-exome sequencing revealed a missense mutation in TENM4 segregating in an autosomal-dominant fashion in an ET family. Subsequent targeted resequencing of TENM4 led to the discovery of two novel missense mutations. Not only did these two mutations segregate with ET in two additional families, but we also observed significant over transmission of pathogenic TENM4 alleles across the three families. Consistent with a dominant mode of inheritance, in vitro analysis in oligodendrocyte precursor cells showed that mutant proteins mislocalize. Finally, expression of human mRNA harboring any of three patient mutations in zebrafish embryos induced defects in axon guidance, confirming a dominant-negative mode of action for these mutations. Our genetic and functional data, which is corroborated by the existence of a Tenm4 knockout mouse displaying an ET phenotype, implicates TENM4 in ET. Together with previous studies of TENM4 in model organisms, our studies intimate that processes regulating myelination in the central nervous system and axon guidance might be significant contributors to the genetic burden of this disorde

Život iz reklame za pivo. Ivan Balenović – Boris Svrtan, Metastaze, Satiričko kazalište Kerempuh

He olfactory bulb (A), there is a strong hybridization signal in the mitral cell layer (mcl). The ganglion cell layer (gcl) is also positive, but the external plexiform layer (epl) is not. In the retina (B), the ganglion cell layer (gcl) is labelled intensely, and there is a faint signal in neurons of the inner nuclear layer (inl) adjacent to the inner plexiform layer (ipl). The pigment retina (pr) has dark melanosomes. The nucleus rotundus (C) contains large, scattered neurons that are positive for teneurin-1 mRNA. In the optic tectum (D) teneurin-1 mRNA is widespread, but is seen most clearly in the large neurons of the stratum griseum centrale (sgc). In the hindbrain (E) the nucleus laminaris (La) and nucleus magnocellularis (MCC) are labelled, as are Purkinje cells (Pcl) and other neurons in the cerebellum (F).<p><b>Copyright information:</b></p><p>Taken from "Teneurin-1 is expressed in interconnected regions of the developing brain and is processed in vivo"</p><p>http://www.biomedcentral.com/1471-213X/8/30</p><p>BMC Developmental Biology 2008;8():30-30.</p><p>Published online 25 Mar 2008</p><p>PMCID:PMC2289808.</p><p></p