University:
Amherst College
Course:
BIOL 220 | Developmental Biology
Academic year:

2020
Views:

171

Pages:

18
Author:

efelenni46y

Fish What are the Characteristics of Fish Development? • • • • • Meroblastic Discoidal Transparent eggs Fertilization through micropyle Transcription (zygote genes) begins in midblastula (transition) • Specification at late blastula (fate map) What Good Are Transparent Embryos? • GFP (green fluorescent protein) gene linked to other genes show where expressed in living cells Hedgehog promoterGFP: notochord 24hr Fish Blastula • Deep cells become embryo • EVL is protective • YSL Zebrafish Fate Map of Deep Cells Blastula to Neurula • Epiboly of blastoderm over yolk – force provided by syncitial layer • progresses via microtubles • pulls deep cells with it – thicker end ( embryonic shield) dorsal side – dorsal mesoderm forms chordamesoderm notochord – neural cells go to midline keel Zebrafish Development: Time Lapse Films Zebrafish Gastrulation I 30% 50% Zebrafish Gastrulation II 90% 100% The Fish Organizer Transplantation induces secondary axis What are the Signals for DV Axis Formation? • Dorsal-ventral – – – – from embryonic shield induction signals like amphibians ectoderm + BMP2B epidermis chordamesoderm chordino (chordin) • blocks BMP allowing neural development – other extracellular regulators A-P and L-R Axes • A-P axis set in oocyte – anterior = animal cap – stabilizes at gastrulation – two centers • anterior neural cells • posterior mesodermal cells • L-R – nodal-related protein (nr-2) What Induces Shield Mesoderm? • Nuclei of YSL under future embryonic shield accumulate b-catenin • Activates squint and bozozok (like nodal and siamois) • Bozozok – represses bmp2B and wnt8 ventralizing genes – suppresses vega1 Induction of Shield • Squint and bozozak – activate chordino – activate goosecoid, noggin, dickkopf of neural ectoderm that block wnt and bmp • Again similar to Xenopus – Conservation of signals and pathways Zebrafish Axis Formation Zebrafish Axis Formation Are Developmental Signals Conserved in Vertebrates? • b-catenin • • • • • • • Veg factors Bmp and Wnt antagonism Chordino = chordin Noggin Dickkopf Bozozok = siamois Goosecoid Conservation of Signals: Vertebrate-Invertebrate Dorsal-Ventral Reversed ventral in frog dorsal in fly

Fish Development

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