A little winning streak: The reptilian-eye view of gastrulation in birds

Authors

  • Federica Bertocchini,

    Corresponding author
    • Instituto de Biomedicina y Biotecnologia de Cantabria (IBBTEC), CSIC-SODERCAN-Universidad de Cantabria, Facultad de Medicina, Santander, Spain
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  • Cantas Alev,

    1. Lab for Early Embryogenesis, RIKEN Center for Developmental Biology, Chuo-Ku, Kobe, Hyogo, Japan
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  • Yukiko Nakaya,

    1. Lab for Early Embryogenesis, RIKEN Center for Developmental Biology, Chuo-Ku, Kobe, Hyogo, Japan
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  • Guojun Sheng

    Corresponding author
    1. Lab for Early Embryogenesis, RIKEN Center for Developmental Biology, Chuo-Ku, Kobe, Hyogo, Japan
    • Instituto de Biomedicina y Biotecnologia de Cantabria (IBBTEC), CSIC-SODERCAN-Universidad de Cantabria, Facultad de Medicina, Santander, Spain
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Authors to whom all correspondence should be addressed.

Email: federica.bertocchini@unican.es; sheng@cdb.riken.jp

Abstract

The primitive streak is where the mesoderm and definitive endoderm precursor cells ingress from the epiblast during gastrulation. It is often described as an embryological feature common to all amniotes. But such a feature has not been associated with gastrulation in any reptilian species. A parsimonious model would be that the primitive streak evolved independently in the avian and mammalian lineages. Looking beyond the primitive streak, can one find shared features of mesoderm and endoderm formation during amniote gastrulation? Here, we survey the literature on reptilian gastrulation and provide new data on Brachyury RNA and laminin protein expression in gastrula-stage turtle (Pelodiscus sinensis) embryos. We propose a model to reconcile the primitive streak-associated gastrulation in birds and the blastopore-associated gastrulation in extant reptiles.

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