Dev Bio Final Flashcards
1
Q
Intermediate mesoderm derivatives?
A
Urogenital system (kidney, gonads)
2
Q
Lateral Plate Mesoderm derivatives?
A
heart, blood vessels, pelvic and limb skeleton origin of body cavity
3
Q
Intermediate mesoderm & lateral plate mesoderm are induced by
A
high levels of BMP
4
Q
High levels of BMP are located
A
further away from Neural Tube
5
Q
Neural Tube secretes
A
BMP inhibitor
6
Q
What genes may induce Intermediate & lateral plate mesoderm?
A
Fox genes
7
Q
Pax2 specifies
A
Intermediate mesoderm
8
Q
Stage 1 of kidney development
A
Pronephros (tubules of initial kidney)
9
Q
Pronephros establishes the
A
Wolffian duct
10
Q
Stage 2 of kidney development
A
Mesonephros
11
Q
Mesonephros grows out of
A
posterior region of Wolffian duct
12
Q
Stage 3 of kidney development
A
Metanephros
13
Q
Metanephros forms from
A
metanephric mesenchyme at the most posterior region of intermediate mesoderm
14
Q
Metanephros induces
A
ureteric bud & branching
15
Q
To form kidney, intermediate mesoderm must be in contact with?
A
Paraxial mesoderm
16
Q
Intermediate mesoderms interaction with paraxial mesoderm induces what?
A
Lim1, Pax2 & Pax8
17
Q
Lim1, Pax2 & Pax8 are sufficient to induce
A
kidney
18
Q
What limits the position of kidney formation & gives cells the competency to respond & express Lim1?
A
Hox genes (Hoxb4)
19
Q
What are the two ‘final’ kidney cell populations?
A
Ureteric bud & Metanephric mesenchyme
20
Q
Ureteric bud consists of
A
collecting ducts & ureter
21
Q
Metanephric mesenchyme consists of
A
nephron
22
Q
Reciprocal induction
A
each induces the other
23
Q
Ureteric bud branches into the
A
metanephric mesenchyme
24
Q
How does the Meta mesenchyme responds to the ureteric bud branching?
A
It condenses & forms nephron
25
What causes the 'final' kidney cell populations to differ?
the 'timing' of the cells migration through the primitive streak
26
Which cell population of the kidney migrates through the primitive streak early?
Ureteric
27
Which cell population of the kidney migrates through the primitive streak late?
Metanephric
28
Less Wnt + High Fgf/RA induces which kidney cell population?
Ureteric
29
More Wnt + Low Fgf/RA induces which kidney cell population?
Metanephric
30
Low Fgf/RA makes metanephric mesenchyme competent to respond to what?
Ureteric bud
31
Step 1 of kidney development
Metanephric mesenchyme signals ureteric bud to branch off Wolffian duct via GDNF secretion (ret receptor)
32
Step 2 of kidney development
Ureteric bud signals (Fgf2, Fgf9, BMP7) mesenchyme to 'survive' = stem cell pool
33
Step 3 of kidney development
Mesenchyme induces ureteric bud to branch further, creating the ureteric bud tip cells & mesenchyme cap cells
34
Step 4 of kidney development
ureteric bud induces mesenchyme to condense and develop nephron
Wnt signals from bud cells induce MET in condensed cap cells, which causes the epithelium to undergo morphogenesis & tubulation. Process dependent on Notch expression
35
Ureter must connect to what to complete the filtration system?
bladder
36
Which pathway does the ureter used to connect to the bladder?
Eph-ephrin pathway
37
What is furthest from the notochord & NT?
lateral plate mesoderm
38
What two layers does the lateral plate mesoderm split into?
Somatic mesoderm (dorsal) & Splanchnic mesoderm (ventral)
39
The space between somatic mesoderm and splanchnic mesoderm is called what?
coelom
40
Dermis & body wall muscles would originate from which layer?
the 'outer' mesodermal layer
41
The inner layers of lateral plate mesoderm make up what?
organs & surround endoderm (digestive tract)
42
What is the first functional system to develop in embryo from splanchnic mesoderm?
circulatory system
43
Heart progenitor cells migrate through what?
primitive streak
44
The heart progenitor cells migrating through the primitive streak anteriorly & joining the lateral plate mesoderm creates what?
heart fields (cardiogenic mesoderm)
45
The first heart fields consists of what?
scaffold of heart & left ventricle (Mesp1 & Nkx2.5)
46
The second heart field consists of what?
all other parts of heart (not scaffold & left ventricle) & jaw muscles & lung mesenchyme (Mesp1, Nkx2.5, Tbx1)
47
What contributes to heart development?
Neural crest cells
48
what end of the embryo does the heart form at?
anterior end, starting in the 'neck' region
49
What specifies the anterior lateral plate mesoderm?
pharyngeal endoderm & notochord; requires BMP & Fgf8
50
What induces blood formation & prevents heart development in the posterior?
Wnt & BMP inhibitors
51
Developing heart cells migrate posterior along what?
gut endoderm
52
What gradient do heart cells follow along the gut endoderm?
fibronectin gradient
53
When do the heart fields merge together?
occurs as Lateral plate mesoderm folds to surround embryo; 7 somite stage
54
Mutations that prevent heart field fusion result in what?
two hearts
55
What cells can make all the cell types of the heart?
Cardiac progenitor cells
56
What are some of the cell types of the heart?
endocardium, endothelium, smooth muscle & cardiac muscle
57
Cardiac progenitor cells express what pioneer factors?
Nkx2.5 & Mesp1
58
Cardiac progenitor cells are derived from what?
earlier mesoderm precursor
59
hemanigoblasts are
blood vessels & blood cells
60
Vasculogenesis is the
creation of vessels from mesoderm (hemangioblast) cells
61
Vasculogenesis requires what signals?
Starts job: Fgfs & VEGF-A
62
Angiogenesis is when
existing vessels are remodeled and branched
63
Angiogenesis requires what signals?
Finishes job: VEGF-A (secreted by developing organs to recruit vessels to form capillary network)
64
What are the three major functions of endoderm?
(1) pattern mesodermal tissues
(2) form epithelial layers of digestive & respiratory tubes
(3) Form epithelial layers of certain glands (tonsils, thymus, thyroid, parathyroid)
65
Majority of endoderm initiates as what?
a bulk structure (tube) that systematically branches out into specific structures; stretches mouth to anus
66
What must cells express when entering the primitive streak to become endoderm?
Sox17
67
What must cells express when entering the primitive streak to become mesoderm?
brachyrury & TbxT
68
High [Nodal] from visceral endoderm induces the expression of what?
Sox17
69
High [BMP] & [FGF] induces the expression of what?
TbxT
70
Once the endoderm is induced, it is patterned along the A-P axis via what?
Wnt/Bmp/fgf (high in posterior) & Hox genes
71
Anterior region of endoderm gives rise to what?
pharynx, lung, thryoid
72
Middle region of endoderm gives rise to what?
liver, pancreas
73
Posterior region of endoderm gives rise to what?
intestine
74
Endoderm starts as what?
a sheet & folds into a tube (like NT)
75
Folding initiates in two locations (anterior & posterior) then what?
It fuses in the middle (like NT closure)
76
What two sites of the mammalian gut tube migrate toward each other and fuse?
Anterior intestinal portal (AIP) & Caudal intestinal portal (CIP)
77
As the anterior intestinal portal & caudal intestinal portal migrate towards the middle, what slowly shrinks & disappears?
the yolk sac
78
What part of the endoderm is the only region that contacts the ectoderm directly?
the ends
79
What is the anterior region that contacts the ectoderm?
oral plate (stomodeum)
80
What is the posterior region that contacts the ectoderm?
anorectal junction
81
What is the digestive tube anterior to where respiratory starts?
pharynx
82
What are the ectoderm derivatives in the very anterior mouth?
teeth, tastebuds
83
What region of the mouth is endoderm?
posterior
84
The pharynx has what?
pharyngeal arches (mesoderm/ectoderm) & pharyngeal pouches (endoderm)
85
What do the pharyngeal pouches give rise to?
specific glands: tonsil, thyroid, parathyroid, thymus
86
Where does the respiratory system start developing?
between the 4th pair of pharyngeal pouches
87
Shh from endoderm is known as what?
survival factor
88
The digestive tube stretches from where to where?
esophagus to rectum
89
The digestive tube consists of what?
endoderm surrounded by lateral plate mesoderm
90
The endoderm of the digestive tube forms what?
lining of tube
91
The lateral plate mesoderm of the digestive tube forms what?
connective tissues and smooth muscles
92
Patterning of the digestive tube is dependent on what?
A-P axis
93
What is critical for endoderm identity?
Sox17
94
What is the default state of the digestive tube (in terms of differentiation)?
anterior/stomach like endoderm
95
Wnt expression in the posterior of the digestive tube induces what?
Cdx1 & Cdx2
96
High expression of [Cdx1] & [Cdx2] induces what?
large intestine
97
Low expression of [Cdx1] & [Cdx2] induces what?
small intestine
98
Cdx2 inhibits what?
stomach, liver, & pancreas
99
What blocks wnt in the anterior?
Barx1
100
When Wnt is blocked by Barx1 in the anterior, what forms?
stomach (mesenchymal signals)
101
Endoderm secretes what?
graded Shh
102
Graded Shh secretion via the endoderm induces what?
differential Hox expression
103
Once the digestive tube is patterned, what occurs along the A-P axis?
synchronized differentiation
104
What is formed through buckling of tissues via interactions between smooth muscle & endoderm?
Villi of intestine
105
The buckling of tissues positions stem cells away from what?
villus tip (facing lumen)
106
B-catenin & Sox9 expression induce what?
intestinal stem cell
107
The other digestive organs form as what?
buds off of endoderm in the posterior region
108
Buds interact with what to direct development of the liver & pancreas?
mesenchyme
109
Liver bud branches to form what?
gallbladder
110
Early in development endoderm patterns what?
cardiogenic mesoderm
111
Later, cardiac mesoderm induces what?
liver and pancreas
112
Any endoderm near cardiac mesoderm will express what?
liver genes (a-fetoprotein & albumin)
113
What signals are needed to express liver genes?
Fgfs (cardiac mesoderm) & BMP (lateral plate mesoderm)
114
Liver is repressed by what?
notochord
115
Why is liver repressed by the notochord?
the notochord inhibits Shh in the area
116
The endoderm (liver) must be competent for what?
to respond to fgf
117
What factors open chromatin near liver genes?
Foxa1 & Foxa2
118
The liver bud grows into what?
mesenchyme & is induced to differentiate into multiple cell types
119
The pancreas develops from what two separate origins?
dorsal & ventral diverticula (outgrowth)
120
The pancreas is induced by what?
notochord
121
The pancreas is inhibited by what?
cardiogenic mesoderm
122
The notochord secrets what to inhibit Shh in endoderm?
Fgf2 & activin
123
The notochord secretion of fgf2 & activin allows endoderm to respond to what?
blood vessels
124
What is induced at the foreguts 3 contact points with the endothelium of vessel?
Pdx1 & ptf1a
125
No vessels =
no pancreas
126
extra vessels =
large pancreatic tissue
127
What sets up the pathway to insulin-secreting cells?
Pdx1
128
Pancreatic stem cells are regulated by what levels?
Ptf1a
129
high [Ptf1a] induces what?
exocrine (digestive enzymes)
130
low [Ptf1a] induces what?
endocrine (insulin, glucagon)
131
Notch signaling plays a role in what?
determining cell types of the foregut
132
+ Notch induces what?
exocrine (keeps Ptf1a on)
133
(-) Notch induces what?
endocrine (shuts off Ptf1a, activates Ngn3)
134
What foregut cell type has another choice after Notch specification?
endocrine cells
135
The respiratory tube forms from what?
a separation off of the foregut endoderm; i.e. lungs are derived from the digestive system
136
At the level of 4th pharyngeal pouch, what begins to extend ventrally?
laryngotracheal groove or respiratory diverticulum
137
The foregut tube becomes what in the digestive system?
esophagus
138
The laryngotracheal tube becomes what in the respiratory system?
trachea
139
Separation of the foregut tube and laryngotracheal tube requires what?
interactions with surrounding mesenchyme
140
Wnt from the ventral mesenchyme induces what?
increased B-catenin in endoderm
141
Increased B-catenin in endoderm instructs what in the respiratory system?
lung/trachea
142
If B-catenin is expressed in gut tube then what happens?
ectopic lungs
143
Dorsal mesenchyme expresses what?
Barx1
144
Barx1 induces cells to what?
secrete wnt inhibitors
145
Cells secreting wnt inhibitors induces what?
esophageal development
146
When the trachea hits the thorax what occurs?
instructed to branch
147
What induces further branching of the trachea after the thorax is reached?
mesenchyme in the region
148
lung mesoderm =
branches (right)
149
If lung mesoderm is replaced by tracheal mesoderm what occurs?
less branching (left)
150
What are the three steps of bronchial branching?
(1) Domain branching
(2) Planar bifurcation
(3) orthogonal bifurcation
151
Domain branching
proximal-distal outgrows in dorsal, ventral, medial, & lateral positions (spiraling comb)
152
Planar bifurcation
tip of each new branch split at midline along A-P axis
153
Orthogonal bifurcation
tip of branch splits at 90 rotation
154
Each alveolus can be traced back to what?
original bronchus
155
Branching can be caused
externally or internally
156
External (mammalian lungs)
smooth muscle develops in surrounding mesoderm & compresses the bud into two forks (bifurcation)
157
Internal (avian lungs)
branch bud induced by localized apical constriction along parental branch (domain branching)
158
In both cases (internal & external) branching is induced by what?
Fgf signaling from mesenchyme
159
Alveolar cells secrete what?
surfactant
160
surfactant
keeps alveolar cells from sticking together
161
Surfactant triggers what?
mothers immune system
162
Macrophages migration from fetus to uterine lining triggers what?
a cascade of IL1B to prostaglandins, which induces contraction
163
Limbs forms at predefined along
A-P axis
164
Limb Bud
forms and grows outwards
165
Thumb =
anterior
166
Pinkie =
posterior
167
Proximal-Distal axis of limbs
Shoulder to fingers or hip to toes
168
Stylopod
most proximal (connected to girdle)
169
Zeugopod
middle
170
Autopod
most distal
171
Each segment is regulated genetically by
Hox genes
172
First identifiable sign of limb development
limb bud
173
limb bud arises from what?
limb field
174
All cells are capable of making a limb where?
in limb field
175
Limb bud is derived from what?
- LPM (skeletal)
- Somites (muscle)
- Overlying ectoderm (epidermis)
176
Limb bud grows what?
proximal-distal (limited in A-P & D-V growth)
177
Limb bud is organized into three domains. What are these domains?
1) Progress Zone (PZ)
2) Zone of polarizing activity (ZPA)
3) Apical Ectodermal Ridge (AER)
178
Progress Zone (PZ)
high proliferation; making cells that will contribute to the limb
179
Zone of polarizing activity (ZPA)
posterior region; patterns the A-P axis
180
Apical ectodermal ridge (AER)
thickening of ectoderm; critical signaling center (all axes of the limb)
181
What patterns the mesoderm to initiate a specific pathway?
Hox genes
182
What is later used for the P-D identity within the limb?
Hox genes
183
Hox expression follows what?
3' to 5' expression
184
3' hox genes =
more proximal
185
Hox9/10
stylopod
186
5' hox genes =
more distal
187
Hox12/13
autopod
188
What happens if Hox10 is knocked down in a mouse?
Hox9 in the forelimb would be enough to give some stylopod in the forelimb but no hindlimb would form due to lack of Hox9 expression
189
Hox gene expression along the P-D axis contributed to the evolution of what?
tetrapod limb development
190
Tiktaalik =
' fish with fingers'
- first tetrapod-like fossil; had joints that allowed flexion
191
Regional specification of mesoderm for forelimb?
Hoxc6 near the cervical- thoracic transition
192
Regional specification of mesoderm for hindlimb?
Hoxd9 near the lumbar-sacral transition
193
Expanding the Hox6 region (forelimb) mesoderm leads to what?
expanded limb bud
194
Decreasing Hoxc6 region (forelimb) mesoderm leads to what?
reduced limb bud
195
What allows an entire limb to be developed experimentally or "naturally"?
potency
196
RA represses what?
fgf8
197
RA represses fgf8 in specific regions leads to what?
forelimb positioning
198
RA expression in what?
trunk mesoderm
199
Fgf8 expression in what?
anterior & posterior
200
Loss of RA leads to what?
expanded fgf8; leads to loss of Tbx5; leads to hindlimb
201
RA is not necessary for what?
hindlimb development
202
Limb types are specific to what?
Tbx expression
203
If an ectopic limb is induced what is key?
position
204
Tbx5 =
forelimb
205
Loss of Tbx5 =
no forelimb
206
Pitx1, Tbx4, Islet1 =
hindlimb
207
Loss of Tbx4 =
outcome is species dependent
- chick = no hindlimb
- mouse = initial growth; premature arrest
208
If an fgf10 bead is placed between the forelimb & hindlimb what happens?
bud will express both Tbx5 & Tbx4; leads to chimera limb; ectopic limb will have both identities
209
Loss of Islet1 leads to what?
no hindlimb (formation of limb bud)
210
Loss of Pitx1 leads to what?
abnormal patterning
211
Islet1
hindlimb initiation
212
Pitx1
hindlimb patterning
213
Tbx4
hindlimb outgrowth
214
Islet1, Pitx1, & Tbx4 converge on what?
fgf10 (induces proliferation of limb)
215
What happens once the limb field is induced? what is it induced by?
lateral plate mesoderm undergoes EMT
- Tbx5
216
specified fields set up two gradients. What induces these gradients?
Wnt signaling
- fields maintain each others expression via 2 positive feedback loops
- keeps proliferation high so the limb bud will grow
217
Fgf10 in messenchyme induces what?
ectoderm to express fgf8
218
Apical ectodermal ridge (AER) induces what?
Fgf8 expression
219
Apical ectodermal ridge (AER) does what?
- patterns all axes of the developing limb
- Proliferation in underlying mesenchyme (progress zone - PR)
- maintains gene expression for the A-P axis
- directs differentiation across axes
220
Extra AER =
extra/duplicate limb
221
No AER =
no limb
222
AER over the wrong mesenchyme =
fate of mesenchyme takes priority
223
AER replaced with fgf8 bead =
same as having AER (normal)
224
AER directs mesenchyme to grow BUT what?
the mesenchyme retains its patterned identity
225
Mesenchyme what as it grows proximal to distal?
ages
226
Early mesenchyme is not as what as late mesenchyme?
differentiated
227
What is critical for proper bone development?
balance between opposing P-D gradients
228
What signals come from distal?
Fgf/Wnt
229
More fgf/wnt exposure
more autopod/distal phenotype
230
What signals come from proximal?
RA
231
More RA exposure
more stylopod/proximal phenotype
232
Graft limb: If left untreated
bones will develop as the age of the mesenchyme indicates
233
Graft limb: If RA is added
bones become more proximal because proximal genes are induced
234
Graft limb: If fgf/wnt is added
bones become more distal because distal genes are induced
235
RA and fgf are what?
mutually antagonistic
236
As AER moves distal, more what can be expressed?
fgf8
237
Fgf8 upregulates what?
Cyp26
238
Cyp26
degrades RA
239
RA and fgf8 differentially regulate what?
P-D axis
240
Limb fields are what?
pre-set
241
RA from trunk mesoderm induces what?
Meis1/2 expression; stylopod
242
As AER moves distal what is activated?
Hox11 with the RA-fgf8 threshold
243
At the most distal area what is open & expressed?
Hox13
244
How do the cells know what type of bone to make?
the cell types are the same, but spatially different
245
Alan turing
mathematical model of self-organizinng pattterns
246
Activators (A) and Inhibitors (I) are initially what?
uniform will eventually create a pattern
247
If A induces A and I then what?
I will turn and inhibit A
248
Local diffusion rates will establish what?
specific gradients & patterns
249
AER divides the limb into what?
2 active domains & 1 inhibitory zone
250
Inhibitory zone (apical zone/ most distal mesenchyme)
chondrogenesis is repressed here
251
Active zone (most proximal to inhibitory zone)
chondrogenesis occurs
252
Active zone has what?
activators and inhibitors of cartilage formation
253
Active zone formed aggregates makes what?
cartilage & repress other cells from making it
254
Frozen zone (further from the inhibitory zone)?
cartilage is already formed here
255
In the early bud
only room from one condnensate
256
In later bud
room for 2 (radius & ulna)
257
In latest bud
room for many (wrist & digits)
258
Zone of polarizing activity (ZPA)
posterior region of the limb bud
259
ZPA is potent enough to produce what when transplanted to the anterior limb bud?
new A-P axis
260
ZPA secretes what from posterior to anterior?
Shh gradient
261
Expressing Shh in the anterior has the same effect as what?
transplanting the entire ZPA
262
What is Shh doing?
Shh-expressing cells do not undergo apoptosis & contribute to bone and cartilage of the posterior limb
- Digits 4 & 5 (ring finger + thumb)
263
Digit identity (4 or 5) dependent on what?
time of Shh expression, not amount
264
what is independent of Shh?
thumb
265
What is the default digit in the absence of Shh?
thumb
266
Shh has 2 functions
1) pattern digits as a morphogen
2) promote proliferation as a mitogen
267
Shh TxF induces what?
Gli1
268
How does Shh pattern digit identity?
Cell cycle control & BMP pathway
269
Gli1 regulates what? promotes what?
- regulates cell proliferation of cartilage precursor
- promotes cartilage formation
270
Division slows through what?
decreased Cdk6
271
Gli1 inhibits what?
Gremlin (BMP antagonists); thus, active BMP
272
Graded BMP expression across the limb bud leads to what?
digit identity (which is then further specified by the webbing between digits)
273
Web mesoderm patterns the digits what to it?
anterior
- default is to become 1
274
Gradients are set up through interaction between the what?
AER & ZPA
275
What forms a feedback loop from AER?
Fgf10 & fgf8
276
BMPs inhibits what?
fgfs
277
In the ZPA what induces Gremlin (BMP inhibitor) , which blocks BMPs in limb mesoderm ?
Shh
278
Gremlin helps to maintain what?
Fgf expression
- fgf inhibits Shh repressors (Etv4/5)
279
Interactions between AER and ZPA creates what?
Shh-Fgf feedback loop
280
In anterior what blocks Shh?
fgf
281
Eventually, what levels will get really high, inhibiting gremlin, leading to BMP activity increase & fgf ultimate shut down?
fgf
282
AER continues to grows what? so what becomes spatially distanced?
distally; signaling centers
283
Mutual activation (and repression) stops
AER & ZPA disappears
284
Phased Hox expression for limbs; first phase:
P-D axis for stylopod and zeugopod
285
Phased Hox expression for limbs; second phase
A-P axis for autopod
286
Hox activated by what?
'phased' enhancers
287
What sets up the 3' to 5' hox expression
early limb control regulatory (ECLR)
288
ECLR is activated by what?
ZRS (ZPA regulatory sequence)
289
Shh flips the script for what?
phase 2
290
What Hox is expressed first?
5' hox (Hox13 is most anterior = thumb)
291
Hoxd13
most highly expressed
292
D-V axis is determied by what?
overlaying ectoderm
293
Swapping the ectoderm in the limb bud does what?
reversed D-V axis
294
Wnt7a
dorsal ectoderm expression
- first known D-V gene in the limb bud
295
Loss of Wnt7a
ventral identity in dorsal (foot pads on top of the foot)
296
Wnt7a induces what?
Lmx1b in mesenchyme
297
Lmx1b in mesenchyme specifies what?
dorsal expression of Lmx1b in ventral, converts to dorsal (including the underlying tissues (i.e. tendons))
298
Loss of Lmx1b
ventralizes the limb
299
human Lmx1b mutations
nail-patella syndrome
300
D-V identity is critical for what?
the innervation of the tissue
301
Axon pathfinding requires what?
D-V cues
302
Ventral ectoderm expresses what?
engrailed-1 (En1)
303
Engrailed-1 (En1) represses what? Induces what?
- Represses Wnt in the ectoderm
- Induced by BMP in ventral mesenchyme
304
What phenotype would you expect in a BMP null mutant here?
nail all around
305
D-V axis is coordinated with what?
A-P & P-D axis
306
Wnt7a mutants lose what?
posterior digits due to reduced Shh expression
307
Wnt7a + Fgf4 induces what?
Shh
308
BMPs
stops growth and patterning in all 3 axis
- shut down AER as the limb extends
- Shut down ZPA indirectly
- block wnt in the D-V axis
309
Exogenous BMP in AER induces what?
epithelialization of tissue
310
Loss of BMPs in AER
limb will continue to grow beyond normal
311
All forming digits have what?
tissue between them
312
Other organisms lose the tissue between the digits through apoptosis
interdigital necrotic zone
313
Apoptosis is required for what?
the separation of zeugopod bones & other shaping of the limbs
314
Separation of digits is signaled by what?
BMP (induced by RA expression in these tissue)
315
BMPs are inhibited in what?
'non-apoptotic regions'
316
Cartilage-producing cells express what?
Noggin (BMP inhibitor)
317
What happens if Noggin is expressed throughout the limb bud?
keep the webbing between digits
318
BMP means?
bone morphogenetic protein (first decribed as inducers of bone development)
319
Apoptosis vs bone is based on what?
context dependency
320
before cartilage condensation
BMPs induce apoptosis
321
After cartilage condensation
surrounding cells express BMP & induce more cartilage formations
322
Noggin limits what?
amount of cartilage induced
323
What is expressed between bones and is required for instruction of joint tissue?
GDF5 (BMP)
324
Limb structure/differences are shaped through what?
differential regulation of same genes (BMPs, fgfs, Shh)
325
Ducks express what between digits, inhibiting apoptosis?
Gremlin (gives them webbed feet)
326
Cetaceans reduce what in hindlimbs?
Shh (reduces limb)
327
Snakes lost what?
ZRA = no ZPA = no Shh = no limbs
328
Cetaceans increased what in AER leads to longer digits?
fgf
