Chapter 32-2 Mammals. 32-2 Diversity of Mammals Mammals: Monotremes.
Chapter 11- Fish and mammals
description
Transcript of Chapter 11- Fish and mammals
Chapter 11- Fish and mammals• Zebrafish are becoming the sweetheart of developmental
biologists
Fig. 11.1
• Large broods• Breed year-round• Easy and cheap• Transparent embryos• Develop outside mother• Early development complete in 24 hours
1
6
Blastoderm is perched on a
large ________
1st 12 divisions are sychronous to form _____________
3. ____________ layer (YSL)
Three cell populations1. __________
_____ (EL)
2. ____layer- gives rise to embryo proper
Fig. 11.2
A. Cleavage
Fig. 11.3
B. Gastrulation
EpibolyDeep cells migrate to outside then encase entire yolk
Movement not by crawling, but by YSL cells expansion and pulling EL cells along
• A ________ is formed either by _________ of superficial cells or by _______• These combine with superficial epiblast cells to form the _______________ (function equivalent of the dorsal lip in amphibians)
1. Enveloping layer (EL)
2. Deep cells
3. YSL cells
hypoblast
epiblastEmbryonic shield
6 hrs post-fertilization
YSL
Recall Epiboly from Ch 9
Fig. 11.3
B. Gastrulation (cont.)
The hypoblast cells extend in both directions to form the notochord precursor
Animal
Vegetal
Ventral Dorsal
Head
TailTrunk
Fig. 11.2 -A zebrafish fate map
Ectoderm
Mesoderm
Endoderm
C. Axis formation1. Dorsal ventral axis-
1. Establishes the _______________ axis• Converts lateral/ventral medoderm to
dorsal mesoderm (notochord)• Convert ectoderm to neural rather
than epidermal
2. Forms the ______________ precursor
As with the amphibian __________ (Organizer), the embryonic shield:
B-catenin
samois
goosecoid
BMP inhibitors
e.g. Chordino
C. Axis formation
Fig. 11.6
1. Dorsal ventral axis-
As with the amphibian dorsal lip (Organizer), the embryonic shield:
4. Acquires its function from _________ accumulation in nearby cells
•B-catenin accumulates in _____ cells •______________is activated
BMP2
3. Secretes proteins to inhibit BMP from inducing ectoderm to become epidermis
•This inhibiting molecule is called ___________• If mutate ________, no neural tube is formed
Chordino
Embryonic shield
B-catenin
samois
goosecoid
BMP inhibitors
e.g. Chordino
C. Axis formation (cont.)
Fig. 11.6
3. ________________ axis -
In amphibians , the anterior-posterior axis is formed during oogenesisThis axis is stabilized during gastrulation by _____________ ________________________.
_________ neural inducing signal (from ectoderm cells)
__________ neural-inducing signal ( from mesoderm cells)
2. _________________ axis-
Not much known, but involves ______ family signaling molecules
Mammalian Development
• ______ diameter (1/1000th volume of frog egg!)• Few in number ___________• Develops within mother• Cleavage events take _____ hours each• Development occurs en route to ___________
Tough to study!!
1. Egg released from _____
2. fertilization
3. Cleavage during migration down _________
4. Implant in ______
Fig. 11.20
Mammalian Development
1. Slow- ______ hrs per cleavage2. 2nd cleavage is ______________3. Marked __________ in early cell
division4. Cleavage at 2nd division requires
newly made ________ from zygote
Distinctions of mammalian cleavage
Fig. 11.21-rotational cleavage in mammals
Fig. 11.23- Compaction at 8 cell stage (______ in humans)compaction
5. ____________ (marked cell huddling) occurs at 8 cell stage
A. Cleavage
Amphibians Mammals
16 cell embryo is termed “_______”
•external cells will become ___________, which will become the _________•Internal cells will become _____________ (ICM), or the ______________
A. Cleavage (cont.)
This marks 1st differentiation event in mammalian development
At 64 cell stage, an internal cavity appears and the embryo is termed a ___________, ready for implantation onto uterus wall
The ______________ (recall ch. 7) must be shed in order to implant• Blastocyst ____ a small hole in zona using the enzyme _______
Note- attachment of embryo to oviduct wall is called a ______________.
Similar to __________ and birds
•Mammalian embryo relies on __________ for nutrients, not yolk•Thus, the embryo must have a specialized organ to accept nutrients- called the ___________•The chorion induces uterine cells to become a _________ (rich in blood vessels)
B. Gastrulation
Fig. 11.28- Day 15 human embryo
Hypoblasts (from ICM) line the ________- these give rise to ______________________.
Epiblasts form ______________
blastocoel
hypoblasts
epiblasts
Mammalian ______ and ______ cells arise from epiblasts that migrate through primitive streak
E-cadherin attachment is mechanism
Fig.11.11- Chick gastrulation- similar to mammalian
Fig. 11.28- Day 16 in human
_____________ _____________
Those cells that migrate through the ____________ will become the _________________.
B. Gastrulation (cont.)
Direction of migration
Extraembryonic membrane FormationTrophoblast cells (originally termed “cytotrophoblast”) gives rise to multinucleated ____________________
These syncytiotrophoblasts: • secrete proteolytic enzyme to invade
__________________• Digest uterine tissueMothers blood vessels contact the
syncytiotrophoblast cellsEmbryo produces its own blood vessels
Uterine wall
Fig. 11.27-Blastocyst invading uterus
Blood vessels feed embryo, but blood cells do not mix
Mothers blood vessels
Embryo chorion
Mother’s Placenta
Chorion Villi
Embryo’s blood vessels
Fig. 11.31
B. Gastrulation (cont.)
C. Anterior-posterior axis formation
Two signaling centers1. _______________________ (AVE)2. _________ (Organizer)
Fig. 11.34 These are on opposite sides of a “cup” structure
These work together to form
___________.
Node produces _____ and ________
AVE produces ______ and Otx-1Knock-out of one of these results no
_________
The Hox genes specify _________________ polarityThese are homologous to _________ gene complex (Hom-C) of __________
Recall that the Hom-C genes are arranged in the same order as their expression pattern on anterior-posterior axis
Mammalian counterparts are clustered on____________________ .
Equivalent genes (Hoxb-4 and hoxd-4) are called a ____________ _________.
C. Anterior-posterior axis formation
Fig. 11.36- Hox genes are organized in a linear sequences that concurs with posterior to anterior structures
This is referred to as the ___________
C. Anterior-posterior axis formation (cont.)
Hoxa-3 KO- thymus, ______________ malformed
Hoxa-2 KO- _______ missing, duplicate incus
Incus
Stapes
1. Different sets of Hox genes are required for __________ of any region of the _____________________ axis
Hoxd-3 KO = deformed ______ (1st vertebra)
Hoxa-3/Hoxd-3 _______ KO- atlas and neck cartilage nearly absent
2. Different members of a paralogous group may specify different ___________ in a given region
Hox gene rules
3. A hox gene KO causes defects in the _____________ of that gene’s expression
Example
Retinoic Acid has a profound effect on development
Structure of retinoic acid (not in textbook)Fig. 10.41
Recall amphibian development (Ch. 10)
RA
Retinoic acid activates mammalian _____ genes
Wild-type mouse embryo
RA-treated mouse embryo
Lacks all distal
vertebra
Retinoic acid is likely produced in the _____, and perhaps more time
spent in the node dictates more ___________
specification
Hox geneRetinoic acid bind a receptor,
then the complex binds promoter of a hox gene
D. Dorsal-ventral axis formation
Inner cell mass (ICM)
Dorsal axis forms from ICM cells near _____________
Ventral axis forms from ICM cells near _____________
Blastocoel
Fig. 11.32
Trophoblast
E. Left-right axis formation
Note that mammals are ___________
Fig. 11.42
Two levels of regulation-1. Global- an ____ gene defect results
in all ______ on the wrong side
2. Organ-specific- an ___gene defect causes the axis of an organ to change
Organs are located in specific locations