Lecture 1 - Limb development Flashcards
What embryonic tissues give rise to the fore/hind limbs?
Ectoderm, dermatome, hypaxial portion of myotome, and somatic of lateral plate mesoderm
What gene is responsible for the timing of limb development?
Hox genes
What direction do things develop?
Proximal to distal
What gene is responsible for limb identity?
T-box
What are the three axes limbs develop in?
Proximodistal, dorsoventral, and crainocaudal
What proteins are active on the proximodistal axis?
Fgf 10, fgf 8m at AER
What is the AER?
Apical ectodermal ridge
What proteins are active on the crainocaudal axis?
Shh at ZPA
What is the ZPA?
Zone of polarizing activity
What protein/region is related to the dorsoventral axis?
Dorsal ectoderm/Wnt7a
What direction do the forelimbs rotate?
Dorsally
What direction do the hindlimbs rotate?
Venterally
What two specific things are the HOX genes responsible for?
Where the limb buds form and development at the specific location
What hox genes are responsible for different bones?
Hoxa and hoxd
How do Hox genes regulate bone growth in general?
overlap of expression
What are the two primary limb structures, in order?
Limb field - limb bud
What signal occurs during the induction of limb development?
Fgf8 induces fgf10
What is involved in the establishment of AER and ZPA centers?
Fgf10 induces Fgf8 (which induces Shh)
What are Fgf’s responsible for during AER and ZPA development?
Maintaining cell proliferation
What does Shh induce during outgrowth of the limb bud?
Fgf14
What are the main Fgf’s in early limb development?
Fgf8, 10, 14, and Shh
What are FGF10 and TBX5 responsible for together?
Induce epithelium to mesenchyme transition inducing the formation of the limb bud
What is the order of ridge development (fore vs hind)?
Forbud ridge appears 1-2 days before hindbud ridge
Where do limb buds originate from?
Ridges in ventrolateral body wall