Class Notes (835,759)
Canada (509,376)
5-350 (38)

Limb Development

4 Pages
Unlock Document

Biological Sciences
Asish Mukhopadhyay

Limb Development Timeline – buds appear at 26d – somites 8-12 lower buds at 28d – somites 24-29 complete at 56d Embryological Origins of limb components: skin = surface ectoderm melanocytes = NCC sensory neurons = NCC motor neurons = neural tube myotome (somites) = muscle somatic lateral plate mesoderm + ectoderm = limb buds (bones, tendons, ligaments, dermis) AER – apical ectodermal ridge AER divides limb bud into dorsal-ventral transplanted ectoderm can form new AER induced by mesenchyme **both need to be functioning for proper limb-bud development PROGRESS ZONE – actively dividing cells adjacent to AER Progress Zone mesenchyme here determines proximal/distal patterning “rejacketing experiments” – late mesenchyme + early cap  only distal elements form **age of mesenchyme determines proximal/distal fate** Limb Development LIMB POSITIONING along anterior/posterior body axis FGF-8 induces limb bud formation (which leads to AER FGF-8 formation) FGF-soaked beads can induce an entire ectopic limb - however, polarity is reversed (mirror-image limb forms) FGF-10 is initially expressed broadly throughout mesoderm FGF-10 localized FGF expression is necessary for limb bud formation localized FGF levels are also higher concentration Hox, Wnt genes likely candidates for positioning FGF-10 knockouts  no limbs mesoderm FGF-10 induces AER FGF-8 expression FGF-8: positive feedback to underlying mesenchyme (FGF-10 expression) FGF-8 in mesenchyme also induces SHH expression SHH for anterior/posterior limb patterning Limb Development LIMB BUD OUTGROWTH: PROXIMAL/DISTAL PATTERN prox/dist fate depends on how long mesenchyme is under influence of the AER (which is secreting FGF) BMP2 inhibits cell division in limb buds (antagonizes FGF)BMP-2 necessary for apoptotic signals in digit formation
More Less

Related notes for 5-350

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.