Basic Developmental Biology Deck 2 Flashcards
What factor causes ectoderm to differentiate into epidermal cell fate?
BMP promotes epidermal fate, secreted at the margins of the neural plate.
What is spina bifida occulta?
neural tube closure defect, vertebrae affected but no major protrusion of cord contents.
What is meningocele?
extrusion of meninges without protrusion of cord.
What is myelomeningocele?
protrusion of cord and meninges.
What is myeloschisis?
protrusion of spinal cord in which the cord itself is exposed.
What are the divisions of the forebrain, midbrain and hindbrain?
forebrain: telencelphalon, diencelphalon.
midbrain: tectum and tegmentum.
hindbrain: metencephalon and myelencelphalon.
What does the metencelphalon develop into?
pons and cerebellum.
What does the myencephalon develop into?
medulla.
What factors are secreted:
1) caudally from the telencelphalon
2) rostrally from the hindbrain
3) ventrally from the ectoderm of the diencephalon and midbrain regions.
4) dorsally from the notochord.
1) FGF
2) Wnt
3) BMP
4) SHH
Within the ventricular zone, what factors lead stem cells to become neurons?
pro neural basic Helix-loop-helix TFs, FGFs and neurotrophins.
Within the ventricular zone, what factors lead stem cells to become glial cells?
BMPs, Notch signaling and CNTF.
In pathway selection, what cues signal the specialized actin-rich structure at the distal tip of the developing axons:
1) long range attractive cues
2) short range permissive ECM cues?
3) short range repulsive cues?
4) Long range repulsive cues?
1) Netrins -> DCC receptor.
2) Laminin -> laminin receptor
3) ephrins and semaphorins -> EphR, PlexinsR
4) Slits -> Robo receptors.
What factor causes ectoderm to differentiate into neural tissue?
Sox2 - BMP secreted by margins of neural plate is inhibited by BMP antagonists secreted by the node / primitive streak.
At what point during development does the neural tube close?
4th week in humans.
What are examples of intrinsic and extrinsic influences on brain development along the A-P axis?
intrinsic influence: Hox gens, Hox1 (rostral) - Hox13 (caudal).
extrinsic influence: RA/FGF gradient - RA produced caudally in the brain, lower concentration rostrally. FGF secreted rostrally at midbrain-hindbrain boundary and from caudal tail bud.
What are examples of extrinsic influences on spinal cord development along the dorso-ventral axis?
Notochord (axial mesoderm) releases SHH, inducing SHH in floor-plate ventrally. Gradient of BMP is released from ectoderm. SHH / BMP gradient controls target genes that specify distinct cell fates.
What is holoprosencephaly, when does it occur, and what is the molecular mechanism?
Ventral patterning defect that obliterates the division between the cerebral hemispheres. Arises 4-6 weeks into gestation, caused by deficit in SHH signaling in ventral forebrain.
Where are melanocytes derived from?
dorsal neural crest via ectoderm.
Where are Merkel cells derived, what do they do and where are they located?
derived from ectoderm, differentiate from keratinocytes, sit on basal layer, are touch receptors and are sensory innervated.
What are Langerhans, from where are they derived?
professional antigen presenting Cells in the skin, mesodermal in origin. Uniformly spaced out in the skin.
What signals cause ectoderm progenitors to become embryonic epidermis?
Wnt and BMP.
What signal inhibits hair bud formation and what is the mechanism?
DKK inhibits Wnt10b, is expressed in the dermis lateral to each dermal papilla.
What signal triggers hair follicle formation and what is the mechanism?
EDA-ectodysplasin induces Wnt10b expression in the placed condensate (mesenchymal cells). SHH drives proliferation in the placode, downstream of Wnt10b.
What is Gorlin Syndrome and what causes it?
Genetic predisposition to basal cell cancer, a hyper proliferation of keratinocytes. Caused by inactivating mutations in Ptch, SHH signaling is hyperactive via Gli transcription factors.
