Embryology Flashcards

Terms Definitions
2 molecules for PGC specification
BMP4 - initiates expression of genes for specifying PGC. AND Blimp1 - stops cell from becoming somatic cell
The neural tube will form....
Brain and spinal cord
Neuralation
Morphogenesis of neural plate to form neural tube
Neural induction
Interaction between axial mesoderm and ectoderm. Ectoderm forms neural plate
Direction of neural plate formation
Cranial to caudal
Cell type in neural plate
Pseudo stratified columnar neuroepithelial cells
Days for formation of neural plate
17-22
Day of start of neural folding (and location and direction)
Starts on day 22 in the cervical level and goes in both cranial and caudal directions
Process of secondary neurulation
Neural eminence cells first form solid neural cord, which then hollows out, and then connects to neural tube at week 8
Neural tube closing
Closes at first on day 22 at cervical level. Closes at Cranial level at day 24 and at Claudal level at day 26
Cells in the ventricular layer of the neural tube give rise to...
Neurons, glial cells, ependymal cells
Cells in intermediate (mantle) layer of the neural tube give rise to....
Neural and glial cells have migrated here. It makes up the gray matter of spinal cord
Cells in marginal zone of neural tube give rise to...
Neuron processes (axons and dendrites) and some glial cells. This is white matter
Meninges
Cell layers of mesoderm and neural crest origin that cover spinal cord
Mitotically active zone in the neural tube
The ventricular zone
Dorsal ventral patterning of spinal cord
Sulcus limitans forms and divides spinal cord into the dorsal alar plates (dorsal horns) and the basal plates (ventral horn)
What connects the left and right alar plates?
Thin roof plate
What connects the two basal plates?
Floor plate
Motor component of spinal cord
Basal plates- axons exit through the ventral roots
Sensory component of the spinal cord
The alar plates. Sensory axons enter as dorsal roots and synapse with neurons in the dorsal horn
What things influence organization of sensory and motor function of spinal cord?
Dorsal ectoderm induces dorsal cell types via BMP. Notochord induces floor plate and ventral cell types (motor neurons) via Shh
Spina Bifida
Vertebral arch defect
Spina Bifida Occulta
Usually just one vetebra doesn't form correctly. Just see tuft of hair.
Spina Bifida cystic
The more severe forms of spina Bifida - meningocele, meningomyelocele, myeloschisis
Klippel-Feil Syndrome (Brevicollis)
Fusion of two or more cervical vertebrae. Short neck and limited movement
Chordoma
Remnants of notochord become malignant tumor
Somite patterning depends on...
Inductive signals for neural tube, notochord, and surface ectoderm
Genes involved in somite segregation
Mesp2 and genes related to Notch signaling pathway
Axial skeleton
Skull, vertebral column, ribs, sternum
Somites form.....
Most of the axial skeleton of the trunk and all skeletal muscles in the body
Somite formation
On day 20, somitomeres 8-10 form somites 1-3. This progresses in a cranial caudal direction with 3-4 somite pairs developing per day. Makes 42 pairs, end with 37
Sclerotome gives rise to
Vertebral columns and ribs
Myotome
Forms most skeletal muscle on body
Dermatome
Dermis of the trunk
Embryonic induction
One region interacts with second region to influence development of second region
First step of somite maturation
Sclerotome undergo E TO M transition after signals for neural tube and notochord. Dermamyotome displaced laterally.
Bone formation
Mesenchyme to cartilage to bone
Start of vertebral body
Somite 6
Formation of vertebral arch depends on signals from....
Neural tube and and surface ectoderm
Formation of vertebral body depends on signals from
Notochord (which then disappears once inside body)
Reasons for somite resegmentation
Need opening for cranial nerves. Also this way, muscle attaches to two vertebrae
Formation of intervertebral disc
Sclerotome cells at segmental position surround NOTOCHORD, forms annulus fibrosus. Notochord forms nucleus pulposus
How many ribs?
12. Only 7 top ones contact sternum
How do ribs form.
In thoracic region starting on day 35. Costal processes lengthen. Then costovertebral joints form. Then upper ribs contact the ventral sternal bars, which fuse to become sternum
Myotome divides into....
Dorsal epimere and ventral hypomere
Epimere makes
Deep muscles of the back - erector spinal and the transversospinalis
Failure of neural tube closure affects
Vertebral arches, muscle and skin,
Meningocele
Spinal meninges protrude
Meningomyelocele
Both neural tissue and meninges protrude
Meroanencephaly
Partial absence of brain. Causes by failure of cranial neuropore to close
Neural tube defects- environ factors
Vitamin A, frolic acid, valproic acid
Pax 3
Transcription factor - mutations here could affect neural tube closing
Three primary brain vesicles
Forebrain, midbrain, hindbrain
5 secondary brain vesicles
The cephalons
Myeloschisis
Failure of neural tube closing and separating from surface ectoderm
As neural tube is closing, neural crest cells...
Undergo E to M transition and delaminates from dorsal neural tube.
FOXD3
Necessary and sufficient for neural crest induction
Induction of neural crest cells
From BMP gradient and other molecular signals
5 major regions of neural crest cells
Cranial (cephalic), cardiac, vagal, trunk, sacral
What determines what neural crest cells turn into
The environment where they migrate to
Cranial neural crest cells
Face, thymus , tooth, bones of ear and jaw
Vagal and sacral neural crest
Enteric ganglia of gut - control peristaltic movement of gut
Cardiac neural crests
Can form different types of cardiac cells. Migrate to outflow tract and form the septum between aorta and pulmonary artery. Also form smooth muscle that line aortic arch arteries
Trunk neural crest cells
Dorsal root ganglia and adrenal gland medulla, parasympathetic and sympathetic ganglia (ventrolaterally) and melanocytes (dorsolateral path)
Neural crest cell experiments
Used quail and check embryo cells. Fate mapping and ablation experiments
DiGeorge syndrome
Defect in cranial and cardiac neural crest cells. May be due to mutations in T-box transcription factor (Tbx1)
Hirschsprung
Defects in vagal and sacral crest cells leads to no enteric ganglion in distal part of colon. Genes: c-Ret, SOX10, EDN3, EDNRB
Neurofibromatosis type 1 (NF1)
Tumors from over proliferation of neural crest cells
Neural crest derived from what kind of cell?
Ectoderm
BMP antagonists that determine neural crest
Follistatin, chordin, noggin
Neural cret formed by interaction of these two tissues
Neural plate and the non-neural ectoderm
BMP level that gives rise to neural crest
Intermediate level. (Low level is neural plate, high level is non-neural ectoderm)
Signaling molecules that affect neural crest formation
WNT and FGF and Notch secreted by paraxial mesoderm under the neural crest region. BMP in ectoderm is inhibited by axial mesoderm
Function of the notochord
Patterns neural tube, somites, and gut tube
Cause of caudal regression
Failure of mesoderm to grow or migrate. Due to mutation in T, also called Brachyury
Oocyte atresia
Reduction in number of oocytes during fetal period (from 7 million to 2 million)
Spermiogenesis
Golgi turns to Acrosome, DNA condenses, lose cytoplasm, get sperm tail (with cilia)
Molecule that promotes spermatogonia self renewal
Glial derived neurotrophic factor (GDNF) - binds to GFRA1 and RET. secreted by Sertoli cells
FoxD3
Necessary and sufficient for neural crest cell formulation
Pax3
Important for neural crest migration from epithelium. Leads to Waardenburg syndrome - mutant for one copy of Pax3 - have patches of skin lacking pigmentation because neural crest cells didn't migrate there.
Waardenburg Syndrome
Leads to Waardenburg syndrome - mutant for one copy of Pax3 - have patches of skin lacking pigmentation because neural crest cells didn't migrate there.
Single most important decider of neural crest cell fate
Location along anterior posterior axis. A
Rhombomeres
Faint segmentation - distinct compartments- that transiently show in hindbrain. Identity of each rhombomere controlled by Hox genes
BMPs are involved in...
Specifying PGC, patterning the dorsal horns of the spinal cord, specifying the neural crest cells (which have intermediate BMP levels)
What controls regional identity of vertebrae column - ie only thoracic has ribs?
The HOX genes, which encode transcription factors. These are influenced by vitamin A
Neural crest cells migrate from rhombomeres to...
Pharyngeal arches - makes part of face
First pathway for trunk neural crests
Ventrolateral - through the anterior part of somite but not the posterior part
Second pathway for trunk neural crest
Dorsolaterally - between somites and epithelium - creates melanocytes
If you don't have vagal or sacral neural crest...
No enteric ganglia cells in gut. Gut gets constricted. Adjacent parts of gut get distended. Yikes.
Defects in cardiac neural crest
Defects in outflow tract and aortic arch arteries and also in locations close to the heart.
Why ppl used quail donor and chick host
Can easily tell difference between cells using histology staining or antibody
Neural crest cell potential
Transplanted neural crest cells will take on fate of their new axial position. So neural crest cells have greater developmental potential than their fate!!!! Exception - cranial neural crest cells
Fate mapping in mice
Look at lecturer
Fate vs potential of neural crest
Potential > developmental fate
Neurocristopathies
Group of diverse diseases having common origin of defective neural crest cell development. Could be problem with cell or environment
Hirschsprung disease
Abensen
Congenital melanocytic naevi
Moles from too much neural crest cells. Higher chance of skin cancer
SOX10
Required for normal development of melanocytes. Also promotes moles and skin cancer
Timeframe for PGC migration
weeks 3-5
SLex
Sperm binds to Slex on egg ZP
Phospholipase c-zeta
Secreted by sperm after fertilization. Causes calcium release which promotes release of cortical granules which changes ZP
Dysgerminomia
PGC left on midline and don't die - makes tumors
Why are spermatids connected by cytoplasmic bridges
Because a some has X and some has Y and you need both
Functions of Sertoli cells
Nutrition and support, phagocytose bad sperm cells, form tight junctions to divide the cells, secret GDNF
Defective or absence GDNF
Causes all spermatogonia to differentiate. Loses germline. Become infertile
Cumulus cells location and function
Next to oocyte. Support the oocyte
C-kit receptor roles
1 migration of PGC and survival. 2. In the developments of follicles
TGFbeta subfamilies
Promotes maturation of oocytes
What forms corpus luteum
The mural granulosa
Izumo
Protein on the sperm. Helps with fertilization
CD9
Protein on the egg- helps with fertilization
You don't produced any primary oocytes after....
20 weeks!
ZP3
Glycoprotein on the ZP that can initiate Acrosome reaction
Function of capacitation
Makes sperm more motile. Allows for acrosomal reaction.
Rise of calcium after fertilization
Causes release of cortical granules and finishing of meosis II for the egg
Definition of infertility
Can't conceive after a year of unprotected sex
Uvomorulin
E-cadherins which plays a role in compaction
Morula stage
Cells are determined (by location) but not differentiated
HB-EGF
Heparin binding EGF-like growths factor. Secreted by moms epithelium before blastocyst attachment
Leukemia inhibitory factor
Secreted by mother. Needed for implantation. Mice lacking this cant implant their blastocysts.
L selectin
After blastocyst hatches , starts to express L selectin, which helps it make initial interaction with uterine lining
Hypoblast -what type of cells.
Cuboidal
Epiblast-what type of cells
Columnar
What is measured for pregnancy test?
HCG
Three roles of placenta
Metabolism, transport of gases and nutrients, endocrine (HCG)
Deciduous basalis
Forms maternal part of placenta
Conjoined twins
Formed after formation of the amniotic sac
FGF8
Necessary and sufficient for limb formation
FGF10
Necessary for limb formation
fgf10
necessary for limb bud formation
mols. involved in PD patterning of limbs
retinoic acid, fgf8, and HOX code
hormone involved in anterior/posterior patterning of limbs
Shh from the zone of polarizing activity (in the posterior mesoderm)
en-1
Found in ventral ectoderm. Inhibits WNT-7a to denote ventral fate.
Wnt-7a
Found in dorsal ectoderm. Specifies dorsal identity by upregulating LMX-1 (transcription factor in dorsal mesoderm)
LMX-1
in dorsal mesoderm. It's a transcription factor upregulated by WIN-7a. It turns on genes to lead to dorsal fate
Loss of LMX-1
Loss of dorsal structures (like fingernails or knee caps).
BMP in digit formation
mediates the cell death of soft tissue between the digital rays
What molecule specifies the hindlimb?
Pitx-1, which induces TBx4 expression
what molecule specifies the forelimb?
Tbx5, which inhibits Tbx4 expression
amelia
complete absence of limbs - defect in week 4
mesomelia
partial absence of limbs (defect in week 5)
polydactyly
extra digits
syndactyly
fusion of one or more digits. Can be caused in mutations in HOX genes
cutaneous syndactyly
fusion of soft tissue between digits
osseous syndactyly
fusion of bones of one or more digits
Two aspects of Shh that determine anterior/posterior patterning
the time and concentration of Shh
Mullerian inhibiting substance
expressed at the genital ridge - suppressing development of female genitalia
candidate mesoderm inducers
Fgs, nodal, BMP
MyoD
needed for muscle cell determination (myoblast development)
Myf-5
needed for muscle cell determination (myoblast formation)
Myogenin
needed for muscle cell differentiation (fusion of myoblast)
MRF-4
needed to create muscle cells
Mesp2 and Notch
involved in somite segmentation
what controls regional identity of vertebral column?
HOX genes
What three molecules influence somite muturation?
BMPs, wnt, Shh
How to ribs form?
costal processes form and extend, costovertebral joint forms, top 7 ribs connect to bilateral sternum bars, the bars fuse to form sternum
epimere forms
the muscle of the deep back
hypomere forms
the intercostal and abdominal muscles
melingomyelocele
both meninges and neural tissue protrude
prosencephalon
forebrain
rhombencephalon
hindbrain
what controls the identity of rhombomeres?
hox genes
mesencephalon
midbrain
exencephaly
skull doesn't form - brain is exposed
primary neural induction - purpose of axial mesoderm
to inhibit BMP expression in ectoderm and thus promote ectoderm to be neural plate
BMP inhibitors
chordin, noggin, follistatin
If you remove 2 or more BMP inhibitors from axial mesoderm...
lack of CNS
Definition of neural plate
portion of the ectoderm without BMP
signaling from paraxial mesoderm in neural crest induction
Wnt, Fgf, Notch
list neural crest cells and their fate
see list
TFs used to make iPSC
SOCK = Sox2, Oct4, C-myc, Klf4
Four ways to test ESC
1. in vitro differentiation; 2. teratoma; 3. chimera; 4. tetraploid complement
Three descriptions of adult stem cells
1. limited differential potential; 2. hard to expand outside the body; 3. rare.
what is the organizer?
future axial mesoderm
Pitx-1
in the hindlimbs - induces Tbx4
Tbx5
specifies forelimbs - inhibits Tbx4
Thalidomide
a teratogene -- leads to limb defects. But now could be important as a cancer treatment for mylenoma
cardiac neural crest cells are next to somites
1-3
vagral neural crest cells are next to somites
1-7
sacral neural crest cells are next to somites
28+
Primary brain vesicles form in
Week 4
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