{"101441":{"#nid":"101441","#data":{"type":"news","title":"Scientists Alter Developing Brain to Resemble that of Another Species","body":[{"value":"\u003Cp\u003EBy David Terraso\n\u003C\/p\u003E\n\u003Cp\u003EScientists at the Georgia Institute of Technology have found that by applying chemicals to manipulate genes in a developing embryo, they\u0027ve been able to change the brain of one type of cichlid fish to resemble that of another.  The researchers also discovered differences in the general patterning of the brain very early in development before functional neurons form in a process known as neurogenesis. This finding is at odds with a well-held theory known as \u0022late equals large.\u0022 The research appears in the Proceedings of the National Academy of Sciences Online Early Edition beginning May 3, 2010.\n\u003C\/p\u003E\n\u003Cp\u003EIn the mid 1990s, the hypothesis called \u0022late equals large\u0022 was put forth to explain the way brains evolve across species. The brain begins as a blank slate. In early development, the anterior, or front, part of the brain is specified from the posterior, or back, part. After that, neurogenesis occurs as precursor cells mature to become neurons. These precursors can replicate endlessly, but once they become functional neurons, replication ends. The later the switch from precursors to mature neurons, the larger the brain, or brain region, becomes. The \u0022late equals large\u0022 model holds that the brains of different species, for example humans vs. mice, are similar early in development and differ because of the later process of neurogenesis.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022We found differences in the general patterning of the brain as early as 48 hours after fertilization, before neurogenesis begins,\u0022 said J. Todd Streelman, associate professor in Georgia Tech\u0027s School of Biology.\n\u003C\/p\u003E\n\u003Cp\u003EStreelman, Ph.D. student Jonathan Sylvester, and their colleagues studied brain development in six species of cichlid from Lake Malawi stock, three species from the rock-dwelling lineage and three species of their sand-dwelling cousins.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022We repeated our tests from two to four days after fertilization and found that sand\u00e2\u0080\u0022dwelling cichlids exhibited a larger expression domain of the gene wnt1, known to be an important factor in the development of the posterior brain. This correlates with a larger thalamus, a posterior forebrain structure used in the processing of vision,\u0022 said Sylvester.\n\u003C\/p\u003E\n\u003Cp\u003EThe sand-dwelling cichlids use their vision to detect plankton prey, so their brains are heavily devoted to integrating visual signals. However, the rock-dwelling species feed by scraping algae from rocks and possess larger cerebra, or telencephala, perhaps to aid in navigating their complex 3D environments.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022The genomes of these species are very similar,\u0022 said Streelman, \u0022almost as similar as those of any two humans, and yet their brains vary as much as some mammal groups, one from each other.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EMost of the data supporting the \u0022late equals large\u0022 hypothesis hasn\u00e2\u0080\u0099t been drawn from species that are as closely related as these cichlids, added Streelman.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022Among primates, for example, most of the links between species have been severed long ago. So, it is difficult to study developmental patterning because subtle differences are often confounded by large differences in brain size,\u0022 said Streelman.\n\u003C\/p\u003E\n\u003Cp\u003EIn another part of the study, the team wanted to see if they could use chemicals to change the patterns of gene expression and hence the brain development of the embryos. Could they, in fact, alter the brain of a rock-dwelling embryo to that of a sand-dwelling embryo? Turns out they could.\n\u003C\/p\u003E\n\u003Cp\u003ESylvester treated the embryos with lithium chloride for three to five hours during an early stage of anterior-posterior patterning. After treatment, he returned the embryos to fish water and then took samples for study at different developmental stages. He found that each time he checked, treatment with lithium chloride up-regulated Wnt signaling, which led to a reallocation of brain precursors to the posterior thalamus.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022Neurogenesis is still a very important process in brain development and evolution,\u0022 said Streelman. \u0022We,ve just shown that there are differences in the developmental process much earlier than previously suspected and that these changes are also relevant for brain diversity.\u0022\n\u003C\/p\u003E\n\u003Cp\u003E\u0022We\u00e2\u0080\u0099re interested in what these early differences have to say about early behavior,\u0022 said Streelman. \u0022Because if we think in terms of the \u0027late equals large\u0027 model, it means that early in development, brains don\u0027t differ that much. But now that we know species possess divergent brains early on, we can begin to assess how early behaviors may differ as well.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EOther members of the team include former Georgia Tech undergradate Constance Rich, current Biology PhD candidate Eddie Loh, former post-doc toral fellow in Streelman\u0027s lab Gareth Fraser and Moira van Staaden from Bowling Green University. The research was supported by funding from the National Science Foundation, National Institutes of Health and the Alfred P. Sloan Foundation.\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"Scientists at the Georgia Institute of Technology have found that by applying chemicals to manipulate genes in a developing embryo, they\u00e2\u0080\u0099ve been able to change the brain of one type of cichlid fish to resemble that of another.","format":"limited_html"}],"field_summary_sentence":[{"value":"Scientists Alter Developing Brain to Resemble that of Another Sp"}],"uid":"27245","created_gmt":"2010-05-04 00:00:00","changed_gmt":"2016-10-08 03:11:09","author":"Troy Hilley","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2010-05-04T00:00:00-04:00","iso_date":"2010-05-04T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"101451":{"id":"101451","type":"image","title":"Cichlid Embryo","body":null,"created":"1449178166","gmt_created":"2015-12-03 21:29:26","changed":"1475894720","gmt_changed":"2016-10-08 02:45:20"}},"media_ids":["101451"],"related_links":[{"url":"http:\/\/www.biology.gatech.edu\/faculty\/todd-streelman\/","title":"Todd Streelman"},{"url":"http:\/\/www.biology.gatech.edu\/","title":"School of Biology"}],"groups":[{"id":"1275","name":"School of Biological Sciences"}],"categories":[],"keywords":[],"core_research_areas":[],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cstrong\u003ESchool of Biology\u003C\/strong\u003E\u003Cbr \/\u003EBiology\u003Cbr \/\u003E\u003Ca href=\u0022mailto:admin@biology.gatech.edu\u0022\u003EContact School of Biology\u003C\/a\u003E\u003Cbr \/\u003E\u003Cstrong\u003E404-894-3700\u003C\/strong\u003E","format":"limited_html"}],"email":["admin@biology.gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}