75 research outputs found

    Limb diversity and digit reduction in reptilian evolution

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    Journal ArticleThe study of morphological rules, or trends, offered classical biologists the opportunity to address the mechanisms underlying the evolution of anatomical designs. Regularities in evolution suggested that common functional or developmental rules governed the transformation of structures. Parallelism is one such example

    Commencement of the Class of 2016

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    It’s amazing how fast three years passes. And in the end, IMSA is so much more than just a building. Others may never truly understand what it means to be a part of this community, but we will know. Years from now, we’ll remember the thrill of Clash or the nostalgic warmth of Carnival. We’ll remember late nights spent laughing with best friends, and we’ll remember what it felt like to belong here. It’s true, IMSA gave us the building blocks for academic and professional success. But it also gave us each other. And as we stand here as a class for the last time, I thank IMSA for bringing us together. Class of 2016, never stop learning and growing. Never lose that drive or that passion, and never forget what you have gained from IMSA. As we move on to another chapter of our lives, we will continue to expand our brick-and-mortar walls. We will gain countless more chances, and we will learn countless more things. It is my hope that we, as a class, will continue to seek out new opportunities, and I hope that we continue to find better ways of cementing it all together. Yet no matter how far we go, part of us will always belong in a residence hall at 1500 Sullivan Road. And no matter how far apart we may end up, we can find comfort in knowing that we have built something beautiful together Heidi Dong, Student Council Presiden

    A conserved Shh cis-regulatory module highlights a common developmental origin of unpaired and paired fins

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    Despite their evolutionary, developmental, and functional importance the origin of vertebrate paired appendages remains uncertain. In mice, a single enhancer termed ZRS is solely responsible for Shh expression in limbs. Here, zebrafish and mouse transgenic assays trace the functional equivalence of ZRS across the gnathostome phylogeny. CRISPR/Cas9-mediated deletion of the medaka-ZRS and enhancer assays reveal the existence of ZRS shadow enhancers in both teleost and human genomes. Deletion of both ZRS and shadow ZRS abolish shh expression and completely truncate pectoral fin formation. Strikingly, deletion of ZRS results in an almost complete ablation of the dorsal fin. This finding indicates that a ZRS-Shh regulatory module is shared by paired and median fins, and that paired fins likely emerged by the co‐option of developmental programs established in the median fins of stem gnathostomes. Shh function was later reinforced in pectoral fin development with the recruitment of shadow enhancers, conferring additional robustness

    The spotted gar genome illuminates vertebrate evolution and facilitates human-teleost comparisons

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    To connect human biology to fish biomedical models, we sequenced the genome of spotted gar (Lepisosteus oculatus), whose lineage diverged from teleosts before teleost genome duplication (TGD). The slowly evolving gar genome has conserved in content and size many entire chromosomes from bony vertebrate ancestors. Gar bridges teleosts to tetrapods by illuminating the evolution of immunity, mineralization and development (mediated, for example, by Hox, ParaHox and microRNA genes). Numerous conserved noncoding elements (CNEs; often cis regulatory) undetectable in direct human-teleost comparisons become apparent using gar: functional studies uncovered conserved roles for such cryptic CNEs, facilitating annotation of sequences identified in human genome-wide association studies. Transcriptomic analyses showed that the sums of expression domains and expression levels for duplicated teleost genes often approximate the patterns and levels of expression for gar genes, consistent with subfunctionalization. The gar genome provides a resource for understanding evolution after genome duplication, the origin of vertebrate genomes and the function of human regulatory sequences

    Your inner fish: the amazing discovery of our 375-million-year-old ancestor

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