Lecture 18 Flashcards
The thickened area on the side of a salamander that gives rise to the limb is the?
Limb disc
What is the peripheral region around the disc called that can give rise to the limb if the disc is removed?
Morphogenetic field (if removed no limb will form)
Remove half the limb disc?
Remaining half will form a complete limb
Vertically divide disc into 2 halves?
each half will form a normal limb
fuse two discs together?
a single normal limb will form
this gene initiates future forelimb
Tbx5*
this gene initiates future hindlimb
Tbx4* and Pitx-1
the three axes that define the vertebrate limb are?
dorsoventral, anterior-posterior, proximodistal
what happens if you transplant a limb disc to the opposite side?
AP axis is reversed but not the DV axis.
what happens if you rotate a limb disc 180 degrees?
Both the AP and the Dv axis will be reversed.
Regarding asymmetry in the vertebrate limb, this gene determines the position of ZPA via its highest concentration and is induced by RA?
Hoxb8
Regarding asymmetry in the vertebrate limb, this genes signal is produced by ZPA, maintains AER, induces expression of gremlin
sonic hedgehog
Regarding asymmetry in the vertebrate limb, this gene inhibits the expression of shh in ANTERIOR part of limb bud
Gli-3
the AER is located at the border between dorsal and ventral ectoderm, what does the dorsal ectoderm express? ventral?
radical fringe, engrailed-1 (En-1)
cells in the distal limb bud express what genes?
Msx-1
this gene is involved in pattern formation in the proximodistal limb axis?
Hoxd
cartilage formation is restricted to the central core of the limb bud and produces what gene
Wnt-7a
mesenchymal pre-cartilage condensations express what genes
Bmp-2 and Bmp-4
this gene is necessary to maintain cartilage development in the formation of joints
BMP
this gene inhibits BMP in the region of the future joint cavity
noggin
in limb muscle development, proximal cells of the limb bud produce what
scatter factor
in limb muscle development, premuscle cells in the somite express what
c-met (receptor for scatter factor)
in limb muscle development, migrating pre-muscle cells express what gene
Pax-3 and N-cadherin
differentiation of premuscle cells within the limb bud depend on what gene expressed by the limb bud ectoderm
Wnt-6
in limb development, this gene is expressed by the CT associated with the muscle masses
Tcf-4
major axons originate from the spinal cold during what week?
5
axons originating from the medial locations in the spinal cord grow into the __ muscle mass
ventral
axons originating from the lateral locations in the spinal cord grow into the __ muscle mass
dorsal
if the forelimb rudiment of a salamander embryo is removed and the limb fails to develop what happens?
the nerves of the brachial plexus remain smaller (thinner)
if an additional limb rudiment is transplanted to the flank of a salamander embryo what happens?
local nerves increase in thickness
if the normal path of nerves is blocked what happens?
nerves will form loops around the mica plate and still rich hindlimb rudiments
