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.
What are the components of each pharygeal arch?
an aortic arch artery, a specific cranial nerve and associated muscles and a cartilage skeleton.
What does 1st pharyngeal groove give rise to?
external auditory meatus
What do each pharyngeal pouch give rise to?
pouch 1: paryngotympanic tube and middle ear cavity.
pouch 2: middle ear cavity and palatine tonsil.
pouch 3: thymus, inferior parathyroid glands.
pouch 4: superior parathyroid glands and ultimobranchial bodies of the thyroid gland.
What are the four types of cells found in pharyngeal arches and what are their roles?
1) ectoderm - lines external surfaces and the depressions between the pharyngeal arches called pharyngeal grooves.
2) endoderm - lines internal surfaces at foregut, endoderm ally lined depressions are called pharyngeal pouches.
3) mesoderm
4) neural crest cells
What is the major difference between cephalic neural crest and trunk neural crest?
cephalic neural crest can form mesenchyme (embryonic connective tissue), and a much broader set of tissues, including fibroblasts, chondrocytes, osteocytes, and cells that form dental tissues.
What are rhombomeres?
eight segments of the neural tube located in the hindbrain = rhombencephalon. rhombomeres produce neural crest cells.
What does pharyngeal pouch 1 produce?
ventral surface: nothing
dorsal surface: pharyngotympanic tube and middle ear cavity.
What does pharyngeal pouch 2 produce?
ventral surface: palatine tonsil
dorsal surface: contributes to pharyngotympanic tube.
What does pharyngeal pouch 3 produce?
ventral: thymus
dorsal: inferior parathyroid gland
What does pharyngeal pouch 4 produce?
ventral: ultimobranchial bodies (C-cells of thyroid gland)
dorsal: superior parathyroid gland.
