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LECTURE 11: MAKING EYES IN MICE AND MEN

LECTURE 11: MAKING EYES IN MICE AND MEN. Gastrulation of A Frog Embryo. Formation of the Vertebrate Eye. Comparative Eye Development. Fly. Vertebrate. Squid. Eye. Wild-type Wing. Wing Mis-expressing Human pax6 gene. Is Eyeless/Pax6 a Master Gene for Eye Development?.

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LECTURE 11: MAKING EYES IN MICE AND MEN

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  1. LECTURE 11: MAKING EYES IN MICE AND MEN

  2. Gastrulation of A Frog Embryo

  3. Formation of the Vertebrate Eye

  4. Comparative Eye Development Fly Vertebrate Squid

  5. Eye Wild-type Wing Wing Mis-expressing Human pax6 gene Is Eyeless/Pax6 a Master Gene for Eye Development? Arguments in Favor: Decreased activity of pax6 genes results in reduced eye size in flies, mice, and humans. 2) pax6 genes are expressed in the early eye primordia of flies, humans, and squid, in which eyes were thought to have evolved independently. 3) Mis-expression of fly or human pax6 genes in certain fly tissues (e.g. wing) result in formation of ectopic eyes.

  6. Jesper Kronhamn, Erich Frei, Michael Daube, Renjie Jiao, Yandong Shi, Markus Noll, and Åsa Rasmuson-Lestander Headless flies produced by mutations in the paralogous Pax6 genes eyeless and twin of eyeless Development 2002 129: 1015-1026. Normal Fly head Fly Lacking eyeless Function Is Eyeless/Pax6 a Master Gene for Eye Development? Arguments Against: Elimination of eyeless or pax6 gene function results in loss of more brain structures than eyes (e.g. completely headless flies). 2) Several other genes (sine oculus, eyes absent,daschund) play roles similar to pax6 in eye development - Loss-of-function results in loss of eyes - Ectopic expression induces ectopic eyes. 3) The regulatory relationships between eye determining genes are different in flies versus vertebrates.

  7. Evolutionary Conservation of Hox Expression Patterns

  8. Evolutionary Conservation of Neural Induction Inverted-brate Hypothesis

  9. Comparative Eye Development Fly Vertebrate Squid

  10. Eyespot? Sensory Appendages? Head Abdomen Tail Anus/ Genitals Mouth Gills? A/P Axis D/V Axis Dpp/BMP4 Non-neural Ectoderm Photosensitive Protrusions or Neural Ectoderm Hox genes Sog/Chd organs appendages Reconstructing the Common Ancestor of Flies and Humans

  11. What Was So Great About Our the Common Ancestor? The Question: The common ancestor of humans and flies must have lived in a complex eco-system with many other species, some of which it ate and others of which it ate. 2) The creature and its decedents somehow displaced all other animal forms. 3) Why?? What was so great about this animal?? Possible Answers: The ancestor evolved a mechanism for extracting low levels of oxygen from the atmosphere and delivering them to internal tissues. 2) The ancestor evolved HOX genes, which allowed for the subsequent diversification of individual body parts.

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