Fibronectin, Mesoderm Migration, and Gastrulation in Xenopus
Biology 624 - Developmental Genetics Lecture #4 – Gastrulation Movements.
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Transcript of Biology 624 - Developmental Genetics Lecture #4 – Gastrulation Movements.
GASTRULATION is a complex series of cell movements that:
--rearranges cells, giving them new neighbors--results in the formation of 3 GERM LAYERS that will
form the subsequent embryo: ectoderm, endoderm and mesoderm
--forms the main body axes of the embryo (they were specified earlier but not formed)
16h0h 6h1.5h
cleavage GASTRULATION organogenesis*
4.5d24h
first cleavage GASTRULATION
segmentation* organogenesis
6.5d 20d14d
implantation
4d24h
cleavageGASTRULATION
segmentation* organogenesis
7d 21d
0h 10h2.5h 24h
cleavage GASTRULATIONorganogenesis* dorsal closure
5h2.8h
cleavage GASTRULATIONsegmentation* organogenesis
24h48-72h
10h
18h3.5h
cleavage GASTRULATION neurulation* organogenesis
36h
Convergent extension- the lengthening of a group of cells in the long axis while shortening in the perpendicular axis
Convergent Extension
GERM BAND EXTENDED PROCESSES:
--organogenesis – e.g. nervous system forms by neuroblast ingression from ectoderm
--segmentation – A-P segment unique identity set up
--imaginal disc specification – cells set aside that will survive pupation
(Gryzik and Muller, 2004)
WildType
Stage 7 Stage 9Stage 8
earlygastrulation
extendedgerm band
mid-gastrulation
Neurotactin, membrane markerTwist, mesoderm marker
Mutant
FGF Signaling is Critical to Gastrulation in Drosophila
Convergent extension- the lengthening of a group of cells in the long axis while shortening in the perpendicular axis
Convergent Extension
Blastocoel Roof Explants deposit matrix thatdirects the migration of mesoderm
from Nagel et al, 2004
Wnt Signaling Mediates Two Distinct Aspects of Gastrulation
(Huelsken and Birchmeier, 2001)
Convergent Extension Tissue Separation
CE in Zebrafish Requires Oriented Cell Division
(Gong et al, 2004) This is the dorsal ectoderm of embryos ingastrulation, Xdd is a Disheveled mt, animalpole is up
At the end of gastrulation--
--the basic body plan is set up--the three germ layers have formedand will produce all embryonicstructures except the germline
ECTODERM----skin, nervous system, neural crest
MESODERM----muscle, bones, blood and vessels, kidney,gonads, connective tissue
ENDODERM----gut, liver, lungs, pancreas