Publications by authors named "Laurel M Johnstone"

3 Publications

  • Page 1 of 1

Gibbon genome and the fast karyotype evolution of small apes.

Nature 2014 Sep;513(7517):195-201

Max Delbrück Center for Molecular Medicine, Berlin 13125, Germany.

Gibbons are small arboreal apes that display an accelerated rate of evolutionary chromosomal rearrangement and occupy a key node in the primate phylogeny between Old World monkeys and great apes. Here we present the assembly and analysis of a northern white-cheeked gibbon (Nomascus leucogenys) genome. We describe the propensity for a gibbon-specific retrotransposon (LAVA) to insert into chromosome segregation genes and alter transcription by providing a premature termination site, suggesting a possible molecular mechanism for the genome plasticity of the gibbon lineage. We further show that the gibbon genera (Nomascus, Hylobates, Hoolock and Symphalangus) experienced a near-instantaneous radiation ∼5 million years ago, coincident with major geographical changes in southeast Asia that caused cycles of habitat compression and expansion. Finally, we identify signatures of positive selection in genes important for forelimb development (TBX5) and connective tissues (COL1A1) that may have been involved in the adaptation of gibbons to their arboreal habitat.
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http://dx.doi.org/10.1038/nature13679DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4249732PMC
September 2014

Cellular basis of neurogenesis in the brain of crayfish, Procambarus clarkii: Neurogenic complex in the olfactory midbrain from hatchlings to adults.

Arthropod Struct Dev 2009 Jul 23;38(4):339-60. Epub 2009 Feb 23.

Neuroscience Institute and Department of Biology, Georgia State University, P.O. Box 5030, Atlanta, GA 30302-5030, USA.

Neurogenesis in the central olfactory pathway of decapod crustaceans persists throughout life. Here we describe the structural basis of neurogenesis within the olfactory deutocerebrum of the crayfish Procambarus clarkii from hatchlings to adults. Using a proliferation marker and immunostaining, we found that throughout development each hemibrain contains a neurogenic complex consisting of five parts: two proliferation zones, each within the neuronal soma clusters containing local or projection interneurons, a tail of proliferating cells extending from each proliferation zone, and an elongated clump of cells where the two tails meet. The clump of cells comprises two subdivisions joined at a nucleus-free central area. Each subdivision consists of a dense group of clump cells with small, spindle-shaped nuclei and is connected to one of the proliferation zones by a strand of fibrous material encompassing the tail of proliferating cells extending from it. We identify one proliferating cell with a large nucleus in each subdivision as a putative neuroblast. Its daughter cells migrate through the strands to the associated proliferation zones, but in the strand leading to the soma cluster of local interneurons this is masked by local proliferation. We conclude that neurogenesis in the olfactory deutocerebrum of juvenile and adult P. clarkii is based on a few neuroblasts that are associated with unique clumps of cells likely representing stem cell niches.
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http://dx.doi.org/10.1016/j.asd.2008.12.004DOI Listing
July 2009

Social domination increases neuronal survival in the brain of juvenile crayfish Procambarus clarkii.

J Exp Biol 2007 Apr;210(Pt 8):1311-24

Department of Biology, Program in Brains and Behavior, and Center for Behavioral Neuroscience, Georgia State University, Atlanta, GA 30302-4010, USA.

Olfactory cues are among the sensory inputs that crayfish use in establishing dominance hierarchies. Throughout their lives, new neurons are continuously added into brain cell clusters 9 and 10, which contain somata of olfactory local and projection interneurons, respectively. Using markers for DNA synthesis (bromodeoxyuridine) and mitosis (phospho-histone-3), we tested juvenile crayfish (Procambarus clarkii) to examine effects of pairwise social experience on proliferation and survival of cells in these brain regions. Proliferating and mitotic cells appeared within restricted neurogenic areas in both clusters and in ;tails' extending from them. These tails, embedded in tubulin-positive strands, are linked by a patch of cells. Neither cell proliferation nor mitotic activity was affected by social dominance. Cell survival of neuronal precursors was affected by dominance: compared to dominants, subordinates had fewer newborn cells surviving in cluster 9 after 14 days of social experience. Social experience also affected body growth rate, but the effect of social experience on neurogenesis remained when differences in body growth rate were statistically controlled. We conclude that social domination enhances survival of new olfactory interneuronal precursors compared to social subordination but not compared to social isolation.
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http://dx.doi.org/10.1242/jeb.02758DOI Listing
April 2007