发育生物学：Ciona intestinalis (玻璃海鞘),

1、Ciona intestinalis (玻璃海鞘), a new chordate system for developmental biologyTo think and learn as a biologistFacts, ideas, conceptsFacts, ideas, concepts DNA structure, base composition, etc.How to identify problemsHow to identify problems Nucleic acid is the genetic material, the bacterial transforma

2、tion experimentHow to solve problemsHow to solve problems X-ray crystallography Logic and critical thinking, the fundamentals of biomedical researchNecessary vs. sufficientNecessary vs. sufficient Necessary: If A does not happen, neither will B Sufficient: If A happens, B will always happen Example:

3、 continue on viral transformation, DNA is both necessary and sufficient for bacterial re-activation Logic and critical thinking, the fundamentals of biomedical research (cont.)Causation vs. correlationCausation vs. correlation When A and B happen together, is it because there is causality between th

4、e two, or because they are both the result from a upstream event? How is typical biological research done?The quest for diversity of life formsWhy do we study developmental biology?Why do we study developmental biology? from single cell to multicellularity, signal transduction, cell-cell interaction

5、Why do we study a specific model organism?Why do we study a specific model organism? vertebrates, invertebrates, non-traditional systemsHow similar/different are developmental programs How similar/different are developmental programs in different organisms?in different organisms? Why do living thing

6、s look so different? What is the biological basis for such differences?Basic questions for developmental biologyWhy do we study developmental biology?Why do we study developmental biology? from single cell to multicellularity, signal transduction, cell-cell interactionWhy do we study a specific mode

7、l organism?Why do we study a specific model organism? vertebrates, invertebrates, non-traditional systemsHow similar/different are developmental programs How similar/different are developmental programs in different organisms?in different organisms? Why do living things look so different? What is th

8、e biological basis for such differences?Developmental biology conceptsRegulative vs. mosaic developmentRegulative vs. mosaic development animal cloning, only possible if regulative development mosaic development, what is the advantage?Developmental biology concepts (cont.)Cell autonomous vs. non-aut

9、onomousCell autonomous vs. non-autonomous how is it related to different modes of development? what is the basis for these two types of developmental program?The central questions of developmental biologyDifferentiation: how are different cell types generated from a single fertilized egg?Morphogenes

10、is: collective movement of different cell types shapes the embryo, how are different cell behaviors produced?How do organisms reproduce?Ciona intestinalis is a solitary ascidian speciesRevised chordate phylogenyConserved chordate body plan and developmental featuresAscidian is an old model organismA

11、lexander Kovalevsky(1840-1901)ascidians are chordates as the larvae have notochordThomas Morgan(1866-1945)ascidian self-incompatibilityEdwin Conklin(1863-1952)ascidian fate map and muscle determinantFunction of vertebrate T geneNature 364:582-583 (1993)Mechanism of self-sterility in a hermaphroditic

12、 chordateScience 320:548-550 (2007)macho-1 encodes a localized mRNA in ascidian eggsNature 409:724-729 (2001)Embryonic stages of CionaMetamorphosis: from larvae to adultsAdult anatomy of CionaCiona embryonic lineages show strict mosaic mode of developmentMuscle determinant in ascidiansIn 1905, Conkl

13、in observed in ascidian embryos, a yellowish cytoplasmic region segregates into the muscle lineage, hence termed muscle determinantMuscle determinant in ascidiansIn 2001, the gene was cloned and named macho-1, a Zic family transcription factor necessary and sufficient for muscle fate developmentmach

14、o-1 in situHow did they do it?Subtractive hybridizationDetermination of embryonic lineages in CionaHRP tracingDye tracingReporter assayThe power of the Ciona systemSimplified genome (120M, 16k genes) and reduced regulatory gene setElectroporation to create transient transgenicsGenomics tools: sequen

15、ced genome, EST collection, in situ databaseConserved developmental mechanisms in vertebrates for comparative studiesLabeling of specific embryonic lineage for lineage tracing, live imaging and whole genome studyBasic concepts of electroporationShi et al, 2005Main topics of the lectureSpecification

16、of early embryonic cell fatesTissue morphogenesis: notochord convergent extension and heart cell migrationEvo-devo, the chordate origin of secondary heart field, from fossils to embryosLineage restriction of early blastomere fatesWhat is maternal determinant?mRNA or protein, localized to special reg

17、ions in the oocyte, What is required to make cells different?Cell-cell interaction, asymmetric segregation of cell fate determinantsHow to determine whether a cell fate has been committed?Transplantation, cell isolation, inhibition of cell divisionGene regulatory networks control lineage specific ce

18、ll fatesA complex interplay between maternal factors and zygotic genesMorphogenesis: from specific cell fates to unique cell behavior and pattern formationCell behaviors are determined by their fates: endoderm invaginates, mesoderm converges, neural crest migrates, etc.Cell behavior is tightly regul

19、ated: when to start, where to go, at which point to stop, etc.Cell-cell communication and cell-matrix interactions are required for constructing fine 3-D structuresCell movements as the basis for embryonicpattern formationSolnica-Krezel 2005Zebrafish gastrulation movementsConvergent extension (C/E),

20、 the major morphogenetic event shaping chordate embryosConvergent extension (C/E), the major morphogenetic event shaping chordate embryosCiona notochord morphogenesisWhat is notochord?What is the basic structure of notochord?What function does notochord play?How does notochord form?Notochord cell be

21、haviorNotochord plate time lapseIsolated notochord cell behaviorFGF signal gradient specifies notochord polarity Shi et al, 2009Heart cell migrationCiona heart consists of a single chambered beating muscular structureIt is specified by MAPK signaling to separate from its tail muscle sibling fateIt u

22、ndergoes anterior migrationHeart gene regulatory networksHeart migration can be separated from fate specificationWild type heart mutant heart positioned at tailEvolutionary developmental (evo-devo) biology, the study of changes of developmental programs in different animalsHomology vs. convergence, whether genes, cells o