【正文】 Developmental Biology Chapter 5: Patterning the body plan in animals Vertebrates Patterning the body plan in animals 1 Development of the Drosophila body plan Specification of the anteroposterior and dorsoventral axis in Drosophila oocyte Setting up the body axes in Drosophila Patterning the Drosophila embryo 2 Patterning the vertebrate body plan Specification and setting up of the body axes in amphibians (Xenopus) Somite formation and anteroposterior patterning Patterning the vertebrate nervous system Specifying the leftright axis (leftright asymmetry of internal ans) All vertebrates, despite their many outward differences, have a similar basic body plan The skeleton of a mouse embryo illustrates the vertebrate body plan The AP axis: head, trunk with paired appendages (vertebral column脊柱 ) and the postanal tail The vertebral column is divided into cervical (neck), thoracic (chest), lumbar (lower back), and sacral (hip and lower) regions The DV axis: the mouth defining the ventral side and the spinal cord the dorsal side Patterning the body plan in vertebrates ? Early development in Drosophila is largely under the control of maternal factors that sequentially activate a different sets of the embryo’s own genes (zygotic genes) to pattern the body plan. ? Vertebrate axes do not form from localized determinants, as in Drosophila. Rather, they arise progressively through a sequence of inductive interactions between neighboring cells. Amphibian axis formation is an example of this regulative development. ? The experiments of Hans Spemann and his students showed there exists an embryonic anizer, Spemann anizer that determines the amphibian axis formation and patterns the embryo along the body axes through inducing such inductive interactions. Patterning the body plan in animals 1 Development of the Drosophila body plan Specification of the anteroposterior and dorsoventral axis in Drosophila oocyte Setting up the body axes in Drosophila Patterning the Drosophila embryo 2 Patterning the vertebrate body plan Specification and setting up of the body axes in amphibians (Xenopus) Somite formation and anteroposterior patterning Patterning the vertebrate nervous system Specifying the leftright axis (leftright asymmetry of internal ans) In the transplantation experiments, Hans Spemann and Hilde Mangold showed that the dorsal lip of the blastopore can induce the host’s ventral tissues to form a second embryo with clear anteroposterior and dorsoventral body axes. Spemann refered the dorsal lip as the anizer. The discovery of the Spemann anizer Dr Hans Spemann the Nobel Laureate in Physiology or Medicine 1935 For his discovery of the anizer effect in embryonic development Mechanisms underlying role of the Spemann anizer in development of the body plan ? How was the anizer specified and formed? What caused the dorsal blastopore lip to differ from any other region of the embryo? ? What factors were being secreted from the anizer to create the anteroposterior and dorsoventral axes? ? How did the patterning of the embryo along the body axes bee acpanied? Mechanisms underlying role of the Spemann anizer in development of the body plan ? How was the anizer specified and formed? What caused the dorsal blastopore lip to differ from any other region of the embryo? ? What factors were being secreted from the anizer to create the anteroposterior and dorsoventral axes? ? How did the patterning of the embryo along the body axes bee acpanied? The developmentally important maternal factors are differentially localized along the animalvegetal axis in the Xenopus unfertilized eggs The Xenopus egg possesses a distinct animalvegetal axis, with most of the developmentally important maternal products (mRN