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Oliver hobert

Eduardo Leyva-Díaz, Nikolaos Stefanakis, Inés Carrera, Lori Glenwinkel, Guoqiang Wang, Monica Driscoll, Oliver Hobert
Repetitive DNA sequences are subject to gene silencing in various animal species. Under specific circumstances repetitive DNA sequences can escape such silencing. For example, when exogenously added, extrachromosomal DNA sequences that are stably inherited in multicopy repetitive arrays in the nematode Caenorhabditis elegans are frequently silenced in the germline, whereas such silencing often does not occur in the soma. This indicates that somatic cells might utilize factors that prevent repetitive DNA silencing...
August 11, 2017: Genetics
Esther Serrano-Saiz, Laura Pereira, Marie Gendrel, Ulkar Aghayeva, Abhishek Battacharya, Kelly Howell, L Rene Garcia, Oliver Hobert
The nervous system of most animals is sexually dimorphic but such dimorphisms are generally poorly mapped on an anatomical, cellular, and molecular level. The adult nervous system of the nematode Caenorhabditis elegans displays a number of clearly defined anatomical sexual dimorphisms, but molecular features of sexually dimorphic neurons remain sparse. In this resource paper, we provide a comprehensive atlas of neurotransmitters used in the nervous system of the male and compare it to that of the hermaphrodite...
July 2017: Genetics
Paschalis Kratsios, Sze Yen Kerk, Catarina Catela, Joseph Liang, Berta Vidal, Emily A Bayer, Weidong Feng, Estanisla Daniel De La Cruz, Laura Croci, G Giacomo Consalez, Kota Mizumoto, Oliver Hobert
A core principle of nervous system organization is the diversification of neuron classes into subclasses that share large sets of features but differ in select traits. We describe here a molecular mechanism necessary for motor neurons to acquire subclass-specific traits in the nematode Caenorhabditis elegans. Cholinergic motor neuron classes of the ventral nerve cord can be subdivided into subclasses along the anterior-posterior (A-P) axis based on synaptic connectivity patterns and molecular features. The conserved COE-type terminal selector UNC-3 not only controls the expression of traits shared by all members of a neuron class, but is also required for subclass-specific traits expressed along the A-P axis...
July 5, 2017: ELife
Kelly Howell, Oliver Hobert
Cilia on dendritic endings of sensory neurons organize distinct types of sensory machinery [1]. Ciliated endings display neuron-type-specific patterns of membrane elaborations [1-3], but it is not well understood how such neuron-type-specific morphologies are generated and whether they are coupled to the specification of other identity aspects of a terminally differentiated sensory neuron. In the course of a genome-wide analysis of members of a small family of immunoglobulin domain proteins, we found that OIG-8, a previously uncharacterized transmembrane protein with a single immunoglobulin (Ig) domain, instructs the distinct, neuron-type-specific elaboration of ciliated endings of different olfactory neuron types in the nematode C...
June 19, 2017: Current Biology: CB
Tulsi Patel, Oliver Hobert
The acquisition of a specific cellular identity is usually paralleled by a restriction of cellular plasticity. Whether and how these two processes are coordinated is poorly understood. Transcription factors called terminal selectors activate identity-specific effector genes during neuronal differentiation to define the structural and functional properties of a neuron. To study restriction of plasticity, we ectopically expressed C. elegans CHE-1, a terminal selector of ASE sensory neuron identity. In undifferentiated cells, ectopic expression of CHE-1 results in activation of ASE neuron type-specific effector genes...
April 19, 2017: ELife
Esther Serrano-Saiz, Meital Oren-Suissa, Emily A Bayer, Oliver Hobert
Functional and anatomical sexual dimorphisms in the brain are either the result of cells that are generated only in one sex or a manifestation of sex-specific differentiation of neurons present in both sexes. The PHC neuron pair of the nematode C. elegans differentiates in a strikingly sex-specific manner. In hermaphrodites the PHC neurons display a canonical pattern of synaptic connectivity similar to that of other sensory neurons, but in males PHC differentiates into a densely connected hub sensory neuron/interneuron, integrating a large number of male-specific synaptic inputs and conveying them to both male-specific and sex-shared circuitry...
January 23, 2017: Current Biology: CB
Sze Yen Kerk, Paschalis Kratsios, Michael Hart, Romulo Mourao, Oliver Hobert
A common organizational feature of nervous systems is the existence of groups of neurons that share common traits but can be divided into individual subtypes based on anatomical or molecular features. We elucidate the mechanistic basis of neuronal diversification processes in the context of C.elegans ventral cord motor neurons that share common traits that are directly activated by the terminal selector UNC-3. Diversification of motor neurons into different classes, each characterized by unique patterns of effector gene expression, is controlled by distinct combinations of phylogenetically conserved, class-specific transcriptional repressors...
January 4, 2017: Neuron
Oliver Hobert, Lori Glenwinkel, John White
We revisit the classification of neuronal cell types in the nervous system of the nematode Caenorhabditis elegans. Based on anatomy and synaptic connectivity patterns, the 302 neurons of the nervous system of the hermaphrodite were categorized into 118 neuron classes more than 30 years ago. Analysis of all presently available neuronal gene expression patterns reveals a remarkable congruence of anatomical and molecular classification and further suggests subclassification schemes. Transcription factor expression profiles alone are sufficient to uniquely classify more than 90% of all neuron classes in the C...
November 21, 2016: Current Biology: CB
Marie Gendrel, Emily G Atlas, Oliver Hobert
Neurotransmitter maps are important complements to anatomical maps and represent an invaluable resource to understand nervous system function and development. We report here a comprehensive map of neurons in the C. elegans nervous system that contain the neurotransmitter GABA, revealing twice as many GABA-positive neuron classes as previously reported. We define previously unknown glia-like cells that take up GABA, as well as 'GABA uptake neurons' which do not synthesize GABA but take it up from the extracellular environment, and we map the expression of previously uncharacterized ionotropic GABA receptors...
October 14, 2016: ELife
Meital Oren-Suissa, Emily A Bayer, Oliver Hobert
Whether and how neurons that are present in both sexes of the same species can differentiate in a sexually dimorphic manner is not well understood. A comparison of the connectomes of the Caenorhabditis elegans hermaphrodite and male nervous systems reveals the existence of sexually dimorphic synaptic connections between neurons present in both sexes. Here we demonstrate sex-specific functions of these sex-shared neurons and show that many neurons initially form synapses in a hybrid manner in both the male and hermaphrodite pattern before sexual maturation...
May 12, 2016: Nature
Oliver Hobert
Our present day understanding of nervous system development is an amalgam of insights gained from studying different aspects and stages of nervous system development in a variety of invertebrate and vertebrate model systems, with each model system making its own distinctive set of contributions. One aspect of nervous system development that has been among the most extensively studied in the nematode Caenorhabditis elegans is the nature of the gene regulatory programs that specify hardwired, terminal cellular identities...
July 2016: Wiley Interdisciplinary Reviews. Developmental Biology
Oliver Hobert
The analysis of the developmental programs that define many different neuron types in the nematode Caenorhabditis elegans has revealed common themes in how distinct terminal differentiation programs are controlled. Rather than being controlled in a piece-meal manner, terminal identity features of a mature neuron are often coregulated by so-called terminal selector transcription factors. Here, I summarize the terminal selector concept and emphasize core features of this concept in the C. elegans system such as coregulation of terminal effector batteries, combinatorial control mechanisms, and the coupling of initiation and maintenance of neuronal identity...
2016: Current Topics in Developmental Biology
Kelly Howell, Oliver Hobert
The integrity of neural circuits must be maintained throughout the lifetime of an organism. In this issue of Neuron, Cherra and Jin (2016) characterize a small, two-Ig domain protein, ZIG-10, and its role in maintaining synaptic density in a specific set of C. elegans neurons.
January 20, 2016: Neuron
Paola Arlotta, Oliver Hobert
Homeosis is classically defined as the transformation of one body part into something that resembles another body part. We propose here to broaden the concept of homeosis to the many neuronal cell identity transformations that have been uncovered over the past few years upon removal of specific regulatory factors in organisms from Caenorhabditis elegans to Drosophila, zebrafish, and mice. The concept of homeosis provides a framework for the evolution of cell type diversity in the brain.
December 2015: Trends in Neurosciences
Amel Alqadah, Yi-Wen Hsieh, Berta Vidal, Chieh Chang, Oliver Hobert, Chiou-Fen Chuang
Diversification of neuron classes is essential for functions of the olfactory system, but the underlying mechanisms that generate individual olfactory neuron types are only beginning to be understood. Here we describe a role of the highly conserved HMG-box transcription factor SOX-2 in postmitotic specification and alternative differentiation of the Caenorhabditis elegans AWC and AWB olfactory neurons. We show that SOX-2 partners with different transcription factors to diversify postmitotic olfactory cell types...
October 14, 2015: EMBO Journal
Nikolaos Stefanakis, Ines Carrera, Oliver Hobert
While neuronal cell types display an astounding degree of phenotypic diversity, most if not all neuron types share a core panel of terminal features. However, little is known about how pan-neuronal expression patterns are genetically programmed. Through an extensive analysis of the cis-regulatory control regions of a battery of pan-neuronal C. elegans genes, including genes involved in synaptic vesicle biology and neuropeptide signaling, we define a common organizational principle in the regulation of pan-neuronal genes in the form of a surprisingly complex array of seemingly redundant, parallel-acting cis-regulatory modules that direct expression to broad, overlapping domains throughout the nervous system...
August 19, 2015: Neuron
Berta Vidal, Anthony Santella, Esther Serrano-Saiz, Zhirong Bao, Chiou-Fen Chuang, Oliver Hobert
Neurogenesis involves deeply conserved patterning molecules, such as the proneural basic helix-loop-helix transcription factors. Sox proteins and specifically members of the SoxB and SoxC groups are another class of conserved transcription factors with an important role in neuronal fate commitment and differentiation in various species. In this study, we examine the expression of all five Sox genes of the nematode C. elegans and analyze the effect of null mutant alleles of all members of the SoxB and SoxC groups on nervous system development...
July 15, 2015: Development
Patricia M Gordon, Oliver Hobert
Neuron identity transformations occur upon removal of specific regulatory factors in many different cellular contexts, thereby revealing the fundamental principle of alternative cell identity choices made during nervous system development. One common molecular interpretation of such homeotic cell identity transformations is that a regulatory factor has a dual function in activating genes defining one cellular identity and repressing genes that define an alternative identity. We provide evidence for an alternative, competition-based mechanism...
July 27, 2015: Developmental Cell
Kelly Howell, John G White, Oliver Hobert
Synapse formation is a process tightly controlled in space and time. How gene regulatory mechanisms specify spatial and temporal aspects of synapse formation is not well understood. In the nematode Caenorhabditis elegans, two subtypes of the D-type inhibitory motor neuron (MN) classes, the dorsal D (DD) and ventral D (VD) neurons, extend axons along both the dorsal and ventral nerve cords. The embryonically generated DD motor neurons initially innervate ventral muscles in the first (L1) larval stage and receive their synaptic input from cholinergic motor neurons in the dorsal cord...
July 2, 2015: Nature
Sabrina Murgan, Willi Kari, Ute Rothbächer, Magali Iché-Torres, Pauline Mélénec, Oliver Hobert, Vincent Bertrand
Transcription factors of the TCF family are key mediators of the Wnt/β-catenin pathway. TCF usually activates transcription on cis-regulatory elements containing TCF binding sites when the pathway is active and represses transcription when the pathway is inactive. However, some direct targets display an opposite regulation (activated by TCF in the absence of Wnt), but the mechanism behind this atypical regulation remains poorly characterized. Here, we use the cis-regulatory region of an opposite target gene, ttx-3, to dissect the mechanism of this atypical regulation...
June 22, 2015: Developmental Cell
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