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1.  Guidelines for the Nomenclature of Genetic Elements in Tunicate Genomes 
Tunicates are invertebrate members of the chordate phylum, and are considered to be the sister group of vertebrates. Tunicates are composed of ascidians, thaliaceans, and appendicularians. With the advent of inexpensive high-throughput sequencing, the number of sequenced tunicate genomes is expected to rise sharply within the coming years. To facilitate comparative genomics within the tunicates, and between tunicates and vertebrates, standardized rules for the nomenclature of tunicate genetic elements need to be established. Here we propose a set of nomenclature rules, consensual within the community, for predicted genes, pseudogenes, transcripts, operons, transcriptional cis-regulatory regions, transposable elements, and transgenic constructs. In addition, the document proposes guidelines for naming transgenic and mutant lines.
PMCID: PMC4308547  PMID: 25220678
tunicates; genome annotation; gene; transposable element; cis-regulatory sequences
2.  Coincident Generation of Pyramidal Neurons and Protoplasmic Astrocytes in Neocortical Columns 
The Journal of Neuroscience  2012;32(14):4762-4772.
Astrocytes, one of the most common cell types in the brain, are essential for processes ranging from neural development through potassium homeostasis to synaptic plasticity. Surprisingly, the developmental origins of astrocytes in the neocortex are still controversial. To investigate the patterns of astrocyte development in the neocortex we examined cortical development in a transgenic mouse in which a random, sparse subset of neural progenitors undergoes CRE/lox recombination, permanently labeling their progeny. We demonstrate that neural progenitors in neocortex generate discrete columnar structures that contain both projection neurons and protoplasmic astrocytes. Ninety-five percent of developmental cortical columns labeled in our system contained both astrocytes and neurons. The astrocyte to neuron ratio of labeled cells in a developmental column was 1:7.4, similar to the overall ratio of 1:8.4 across the entire gray matter of the neocortex, indicating that column-associated astrocytes account for the majority of protoplasmic astrocytes in neocortex. Most of the labeled columns contained multiple clusters of several astrocytes. Dividing cells were found at the base of neuronal columns at the beginning of gliogenesis, and later within the cortical layers, suggesting a mechanism by which astrocytes could be distributed within a column. These data indicate that radial glia are the source of both neurons and astrocytes in the neocortex, and that these two cell types are generated in a spatially restricted manner during cortical development.
PMCID: PMC3643505  PMID: 22492032
3.  Genetic and Genomic Toolbox of the Chordate Ciona intestinalis 
Genetics  2012;192(1):55-66.
The experimental malleability and unique phylogenetic position of the sea squirt Ciona intestinalis as part of the sister group to the vertebrates have helped establish these marine chordates as model organisms for the study of developmental genetics and evolution. Here we summarize the tools, techniques, and resources available to the Ciona geneticist, citing examples of studies that employed such strategies in the elucidation of gene function in Ciona. Genetic screens, germline transgenesis, electroporation of plasmid DNA, and microinjection of morpholinos are all routinely employed, and in the near future we expect these to be complemented by targeted mutagenesis, homologous recombination, and RNAi. The genomic resources available will continue to support the design and interpretation of genetic experiments and allow for increasingly sophisticated approaches on a high-throughput, whole-genome scale.
PMCID: PMC3430545  PMID: 22964837
ascidian; development; transgenesis; electroporation
4.  Coordinated regulation of cholinergic motor neuron traits through a conserved terminal selector gene 
Nature Neuroscience  2011;15(2):205-214.
Cholinergic motor neurons are defined by the co-expression of a battery of genes which encode proteins that act sequentially to synthesize, package and degrade acetylcholine and reuptake its breakdown product, choline. How expression of these critical motor neuron identity determinants is controlled and coordinated is not understood. We show here that in the nematode Caenorhabditis elegans all members of the cholinergic gene battery, as well as many other markers of terminal motor neuron fate, are co-regulated by a shared cis-regulatory signature and a common trans-acting factor, the phylogenetically conserved COE (Collier/Olf/EBF)-type transcription factor UNC-3. UNC-3 initiates and maintains expression of cholinergic fate markers and is sufficient to induce cholinergic fate in other neuron types. UNC-3 furthermore operates in negative feedforward loops to induce the expression of transcription factors that repress individual, UNC-3-induced terminal fate markers resulting in diversification of motor neuron differentiation programs in specific motor neuron subtypes. A chordate ortholog of UNC-3, Ciona intestinalis COE, is also both required and sufficient for inducing a cholinergic fate. Thus, UNC-3 is a terminal selector for cholinergic motor neuron differentiation whose function is conserved across phylogeny.
PMCID: PMC3267877  PMID: 22119902
5.  Genetic Labeling of Neuronal Subsets through Enhancer Trapping in Mice 
PLoS ONE  2012;7(6):e38593.
The ability to label, visualize, and manipulate subsets of neurons is critical for elucidating the structure and function of individual cell types in the brain. Enhancer trapping has proved extremely useful for the genetic manipulation of selective cell types in Drosophila. We have developed an enhancer trap strategy in mammals by generating transgenic mice with lentiviral vectors carrying single-copy enhancer-detector probes encoding either the marker gene lacZ or Cre recombinase. This transgenic strategy allowed us to genetically identify a wide variety of neuronal subpopulations in distinct brain regions. Enhancer detection by lentiviral transgenesis could thus provide a complementary method for generating transgenic mouse libraries for the genetic labeling and manipulation of neuronal subsets.
PMCID: PMC3369840  PMID: 22685588
6.  High resolution, plasmid-driven cell lineage tracing reveals developmental variability in leech 
Knowing the normal patterns of embryonic cell proliferation, migration and differentiation is a cornerstone for understanding development. Yet for most species, the precision with which embryonic cell lineages can be determined is limited by technical considerations (the large numbers of cells, extended developmental times, opacity of the embryos), and these are exacerbated by the inherent variability of the lineages themselves. Here we present an improved method of cell lineage tracing in the leech Helobdella, driving the expression of a nuclearly localized histone H2B:GFP fusion protein in selected lineages by microinjection of a plasmid vector. This construct generates a long lasting and minimally mosaic signal with single cell resolution, and does not disrupt the development of most lineages tested. We have validated this technique by elucidating details of cell lineages contributing to segmental and prostomial tissues that could not be observed with standard dextran lineage tracers.
PMCID: PMC3086637  PMID: 19924812
Leech; Helobdella; plasmid injection; cell lineage variability

Results 1-6 (6)