Chapter 14 Mesodermparaxial and intermediate

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Chapter 14- Mesoderm-paraxial and intermediate
Recall lineages
Notochord
Fig. 12.4
2
Chapter 14- Mesoderm-paraxial and intermediate
Fig. 14.3
1. Paraxial mesoderm
1. Paraxial
a. 4 components of somite formation

• __________________-

• somites form from ____________ in regular
  intervals

• total number of somites is __ in chicks, __ in
  mice

• Mechanism? Involves the _______ gene
• _____ gene expression correlates with
  positioning of somites
• This effect is _____________ of all surrounding
  tissue

2. __________________- mesenchyme is converted to
epithelium prior to final somite formation

• EM proteins fibronectin and N-cadherin link
  cells into clustered units

3
1. Paraxial mesoderm
4 components of somite formation (cont.)
3. ___________________________

• Distinct somites give rise to distinct __________

• Specific ___ gene expression predicts the type of
  vertebra formed

Somites
hox5
hox6
hox9
hox10
Fig. 11.40-Mouse somites mapped to vertebrate
regions and to specific_____ gene expression
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1. Paraxial mesoderm (cont.)
4 components of somite formation (cont.)

• 4. _____________________- somites form
• cartilage of ____________ and ribs
• ___________ of rib cage, limbs and back
• dermis of the dorsal _________

Some somite cells become mesenchymal cells again
to form ___________________- these will become
_____________ of vertebrae and ribs
5
1. Paraxial mesoderm (cont.)
4 components of somite formation
4. Differentiation- (continued)
Somites have three ________________ regions that
follow distinct fates
b. ______ muscles
a. _______
A
Fig. 14.9
c. Body wall __________
B
Sclerotome
What proteins are involved??
A
___________ produces NT-3 and ____ proteins that
influence somite cell fate
____________ produces ___________________ to
influence sclerotome fate
B
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Myogenesis
What dictates the muscle phenotype?
______ is a transcription factor that activates
transcription factors Myf5 and MyoD
Pax3
Wnt?
MyoD
Myf5
Muscle-specific genes
MyoD binding site
Signaling pathway to activate muscle-specific
genes (Figure not in text)
Introduction of ______ into other cell types
converts them to ______
Myoblasts fuse to form ___________ to produce
muscle ______
Fig. 14.10
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Osteogenesis (Bone development)
What dictates the bone development?

• There are three lineages that produce bone-
• ________ (vertebrae/ribs)
• ________________ (limbs)- Not yet discussed
• Cranial _____________ (head/face)

• Osteogenesis occurs by two mechanisms
• _______________ossification- bone without
  cartilage precursor
• _________________ ossification- cartilage
  converted to bone

1. Intramembrane ossification
Mesenchyme
___________cells
Cell _____________
Differentiate into _________ (secrete
collogen-proteoglycan matrix)
Differentiate into __________ (bone cell)
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1. Intramembrane ossification (cont.)
Mechanism of ___________________ ossification)
Transcription factor ________ plays a key role
BMP proteins also are important
_______
Mesenchyme
Differentiate into osteoblast
Activates expression of several _________________
genes
WT
CFB1A -/-
________ KO- all ossification prevented
Blue- cartilage Red- Bone
Fig. 14.12
Human disease- _____________________ (CCD)- due
to mutations in the ______ gene
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2. Endochondral ossification
A
B
C
Pax
Mesenchyme
_______
Differentiate into__________
E
D
Proliferation ceases, ______ is modified
__________ invade, Chondocytes die
Proliferate and form _____ of bone by producing
an EM
F
Adjacent cells (not chondrocytes) differentiate
into __________ to fill in bone
A
B
C
D
E
Fig. 14.13
F
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______________ - cells which hollow out bones to
form cavities

• Osteoclasts enter through _____________

• Osteoclasts are likely form blood-lineage
  ____________

The disease ___________ occurs if too ______
osteoclast activity- bones become brittle
The disease ___________ occurs if too ___________
osteoclast activity- bones are not hollowed out
enough
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Intermediate Mesoderm
Fig. 14.1- mesoderm lineages
Recall lineages
Lateral
Intermediate
Paraxial
Circulatory, Body cavity, extraembryonic
Kidney, gonads
Head
Somite
Fig. 12.4
Cartilage, skeletal, dermis
Kidney development
Three stages
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Kidney development
Three stages
1. ________________ arises from intermediate
mesoderm just ventral to anterior somites and
migrates toward tail
Pronephros
Nephric Duct
2. _________________ cells induce mesenchyme to
form ______________(tubules)
3. Pronephric tubules degenerate, but a new set
of _____________ tubules are formed (approx 30 in
humans) further down
Fig. 14.18
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Kidney development
Three stages
Pronephros
Stage 3. (cont.)
Nephric Duct

• The ________________produces
• ______________ stem cells
• __________ carrying tubes (In some mammals)

The ______________tubules are formed from
mesenchyme, which induces ____________ buds
(these become ureters that transport urine from
_______________)
Fig. 14.18
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Ureteric bud and metanephrogenic mesenchyme
interact to become the kidney- called
_______________________
Mechanism of ______________________
Fig. 14.19
3. Ureteric bud secretes ____ and _____ to
prevent _________ of MM
6. _______________ and growth of the ureteric
bud.