Ectoderm

Question 1

Fgf function in mesoderm

Answer 1

(Fibroblast Growth Factor)

acts as a mesoderm-inducing factor, patterning the anterior-posterior axis and regulating various mesodermal cell fates and movements.

Question 2

Chordin function in mesoderm

Answer 2

acting as a BMP antagonist. It specifically blocks the binding of bone morphogenetic proteins (BMPs) to their receptors, thereby preventing BMP signaling, which would otherwise promote ventral fates. This inhibition allows for the formation of dorsal mesodermal structures and neural tissue.

Question 3

Noggin function in mesoderm

Answer 3

antagonizing Bone Morphogenetic Protein (BMP) signaling. This antagonism is essential for dorsalizing the mesoderm, promoting neural tissue formation, and influencing the development of cartilage, bone, and muscle.

Question 4

BMP function in xenopus embryo

Answer 4

Bone Morphogenetic Proteins (BMPs), particularly BMP4, play a crucial role in establishing and maintaining the ventral-dorsal axis, a key aspect of early development.

Question 5

Activin/Nodal function in mesoderm and endoderm

Answer 5

High levels of Nodal signaling promote endoderm formation, while lower levels direct cells towards a mesoderm fate.

Question 6

VegT function in mesoderm and endoderm

Answer 6

VegT is localized in the vegetal hemisphere of the egg and early embryo. It induces endoderm both cell-autonomously and by activating TGF-beta signaling, which in turn contributes to mesoderm formation.

Question 7

Wnt/β-catenin function in mesoderm and endoderm

Answer 7

involved in the formation of the primitive streak, which is essential for gastrulation and the establishment of the body axis.

Question 8

Mixer function in endoderm

Answer 8

act as a key determinant in specifying the endodermal germ layer during embryonic development. Essentially, Mixer drives cells into the endoderm lineage, ensuring they become the cells that will eventually form the digestive tract and other internal organs.

Question 9

Cer function in endoderm

Answer 9

Cerberus (Cer) acts as a head-inducing and Wnt/Nodal/BMP pathway inhibitor. It’s a secreted protein that’s expressed in the anterior endoderm and plays a crucial role in the formation of the head and anterior structures.

Question 10

Central to mesendoderm induction, activated downstream of VegT* and Wnt signals.

Answer 10

Activin/Nodal

Question 11

What can be observed in the 17 dpf gastrula in humans

Answer 11

1. Amnion
2. Oropharyngeal membrane
3. Notochord
4. Node
5. Primitive streak
6. Cloacal membrane

Question 12

What can be observed in the 19 dpf gastrula in humans

Answer 12

1. Amnion
2. Neural plate
3. Node
4. Primitive streak

Question 13

What can be observed in the 20 dpf gastrula in humans

Answer 13

1. Neural fold
2. Neural groove
3. Somites
4. Neurenteric canal
5. Primitive streak

Question 14

Between 3.5 and 4.5 dpc, the embryo, now known as a________, consists of 2 cell populations: An outer _______ (expressing Cdx2), and a mosaic inner ____________ population

Answer 14

Blastocyst; multipotent trophectoderm (TE); pluripotent inner cell mass (ICM)

Question 15

Together the remaining cells of the ICM (the epiblast) and the hypoblast form the _________ by 5.0 dpc.

Answer 15

bilaminar disc

Question 16

Hypoblast cells that remain in close contact with the epiblast differentiate into ___________ while those that migrate along the basement membrane of the TE form the tPA+ parietal endoderm (PaE), resulting in the formation of the_______.

Answer 16

visceral endoderm (VE); yolk sac

Question 17

At 5.5 dpc the embryo is known as the_________.

Answer 17

egg cylinder

Question 18

TE -> Polar TE -> EXE (Extraembryonic endoderm

Question 19

ICM -> Epiblast (Nanog/Oct4) or Hypoblast (Gata6/Sox17)

Epiblast -> PrEct (FGF5/Nanog/Oct4) [Primitive Ectoderm]

Hypoblast -> VE (Hnf4) [Visceral Endoderm] or PaE (tPA) [Parietal Endoderm]

Question 20

Early pre- and post-implantation in mouse embryonic development
1. 4.0 dpc = Blastocyst
2. 4.5 dpc = Implantation
3. 5.0 dpc
4. 5.5 dpc = Egg Cylinder

Question 21

ICM becomes …

Answer 21

Primitive endoderm – Hypoblast
Primitive ectoderm – Epiblast

Question 22

Primitive endoderm forms…

Answer 22

Visceral endoderm
Parietal endoderm

Question 23

Primitive ectoderm becomes… (after gastrulation)

Answer 23

Definitive ectoderm

(EMT – Epithelial-mesenchymal transition) Primitive streak

Question 24

Primitive streak becomes…

Answer 24

Definitive mesoderm (forms Muscle. Bone, Connective tissue, Blood, Vasculature)

Definitive endoderm (forms GIT – gastrointestinal tract, RT – respiratory tract, Endocrine)

Question 25

Definitive ectoderm becomes…

Answer 25

Neurectoderm Surface ectoderm (forms Epidermal)

Question 26

Neurectoderm becomes…

Answer 26

Neural crest (forms PNS, ENS – enteric nervous system, Facial cartilage & bone, Melanocytes) CNS (High levels of BMP specify the cells to become epidermis. Very low levels specify the cells to become neural plate. Intermediate levels effect the formation of the neural crest cells.)

Question 27

The _______ is a pluripotent population of cells that arises between 3.5 and 4.5 dpc within the blastocyst.

Answer 27

inner cell mass (ICM)

Question 28

At 6.5 dpc, the primitive ectoderm undergoes gastrulation in response to various signals including Nodal, resulting in a subset of cells undergoing an epithelial-to-mesenchymal transition (EMT), allowing them to ingress through the primitive streak and form the definitive mesoderm and definitive endoderm germ layers.

Question 29

The remaining primitive ectoderm cells (which see little or no Nodal) do not move through the streak and give rise to the definitive ectoderm germ layer, which further differentiates into the surface ectoderm and neurectoderm in response to the presence and absence of BMP4 signaling, respectively.

Question 30

Derivatives of the Ectoderm

Answer 30

1. Surface ectoderm 2. Neural crest 3. Neural tube

Question 31

Surface ectoderm gives rise to the following:

Answer 31

- Epidermis - Hair - Nails - Sebaceous glands - Olfactory epithelium - Mouth epithelium - Lens, cornea - Anterior pituitary - Tooth enamel - Cheek epithelium

Question 32

Neural crest gives rise to the following:

Answer 32

- PNS - Adrenal medulla - Melanocytes - Facial cartilage - Dentine of teeth - Schwann cells - Neuroglial cells - Sympathetic nervous system - Parasympathetic nervous system

Question 33

Neural tube gives rise to the following:

Answer 33

- Brain - Neural pituitary - Spinal cord - Motor neurons - Retina

Question 34

Parts of somite

Answer 34

- Dermatome - Myotome - Sclerotome

Question 35

Neural crest cells migrates to dermis

Question 36

Development of (Surface) Ectodermal Organs

Answer 36

1. Epithelial placode 2. Bud 3. Morphogenesis 4. Adult organ

Question 37

basal unit of ectodermal organogenesis

Answer 37

Placode

Question 38

is the formation of the vertebrate nervous system in embryos.

Answer 38

Neurulation

Question 39

Development of CNS (Neurulation)

Answer 39

The notochord induces the dorsal ectoderm to become neural tissue through signaling molecules like Noggin, Chordin, and Follistatin. This leads to the formation of the neural plate, which folds to form the neural tube, the structure that gives rise to the brain and spinal cord. 1. Notochord 2. Ectoderm (Dorsal) - Noggin, Chordin, Follistatin 3. Neural Plate 4. Neural Tube 5. Brain & Spinal Cord

Question 40

During gastrulation, a population of the dorsal ectoderm is specified to become __________

Answer 40

neural ectoderm

Question 41

During gastrulation, a population of the dorsal ectoderm is specified to become neural ectoderm which involves the following signals:

Answer 41

Noggin Chordin Follistatin

Question 42

What is the appearance of cells in Neural Plate

Answer 42

Columnar

Question 43

What morphogenetic movement is at work during neurulation

Answer 43

Convergence

Question 44

Neurulation a. Neural plate b. Medial Hingepoint Formation c. Dorso-Lateral Hingepoint Formation d. Neural Folds Fusion

Question 45

Formation of the Neural Tube * 2 mechanisms

Answer 45

* Primary Neurulation – Cells that flank neural plate induce the neural plate to proliferate, invaginate, pinch off to form neural tube * Secondary Neurulation –Mesenchyme cells of the ectoderm coalesce to form a solid cord – Cord then hollows – This happens further posteriorly

Question 46

Primary Neurulation * The neural plate is induced to form by signals from the underlying mesoderm (notochord) * Occurs in a _______ (anterior posterior) direction * Involves convergence

Answer 46

rostro-caudal

Question 47

2 points of closure initiation during neural tube formation:

Answer 47

at the future midbrain at the hindbrain-cervical boundary

Question 48

Xenopus embryos exhibit closure almost simultaneously along the entire body axis

Question 49

In _______ there is no formation of neural folds at all; rather, the NP cells coalesce to form a ______ and the NT lumen opens subsequently within this structure.

Answer 49

teleost fish; neural keel

Question 50

Mediated by the expression of adhesion molecules - N-cadherin is expressed in neural plate - E-cadherin is expressed in the remaining ectoderm Thus, the surface ectoderm and neural plate can not adhere to each other

Question 51

If N-cadherin is over-expressed in the surrounding surface ectoderm, ________ – This is achieved by injecting N-cadherin mRNA into the embryo at the 2-cell stage

Answer 51

neural tube closure is impeded

Question 52

Neurulation in Mammals * Neural tube closes in several places along axis (not in A to P direction) * If any one of those closures fails, neural defects result

Question 53

Mammalian Neural Tube defects:

Answer 53

Spina Bifida Anencephaly

Question 54

– Posterior neural tube does not fuse; Spinal cord remains exposed

Answer 54

Spina bifida

Question 55

– Anterior neural tube does not fuse; Forebrain ceases to develop; Lethal – Occur in 1 of 500 births in humans (Preventable through diet, folic acid)

Answer 55

Anencephaly

Question 56

Secondary Neurulation

Answer 56

1. Occurs beyond the caudal neuropore - lumbar and tail region 2. Exclusive mechanism for fish 3. Starts with formation of medullary cord 4. Cavitation of cord to form hollow tube

Question 57

Differentiation of the Neural Tube * Neural tube must maintain dorsal-ventral polarity * Accomplished by “inductive cascades”

Answer 57

– Sensory neurons- dorsal – Motor neurons- ventral – Dorsal: BMPs from epidermis -> Roof plate cells in neural tube -> TGF-B cascade -> Cell differentiation – Ventral: Sonic hedgehog from notochord and retinoic acid from somites -> Floor plate cells of neural tube -> shh gradient -> Cell differentiation

Question 58

Neurulation in chick embryo Subdivided into primary and secondary - Neural plate boundary will separate to the neural ectoderm to become components of the surface ectoderm and to give rise to the surface of the skin - Neural plate will become the neural tube. Gradually, neural plate will elevate, that's why we can see the formation of the neural fold. Neural fold will undergo closure to accomplish the closed neural tube

Question 59

Neural Crest Cells (NCCs) * Originate in ________ * Migrate extensively to populate the body with a variety of cell types –Neurons, glia, adrenal medulla, pigment cells of the skin (melanocytes), skeletal components of head

Answer 59

dorsal neural tube

Question 60

Cranial NC gives rise to the bone and cartilage Cardiac NC contributes to the aorticopulmonary septum and conotruncal cushions of the heart Vagal NC will give rise to the enteric ganglia of the gut Trunk NC will give rise to neurons, which will contribute to the PNS

Question 61

form at the junction of the neural plate and the epidermal ectoderm

Answer 61

Neural crest cells

Question 62

– Neural Plate expresses ____ – Epidermal ectoderm expresses __ – At the boundary, cells are induced to express neural crest specific transcription factors: ____, ______

Answer 62

BMPs; Wnt6; Slug, FoxD3

Question 63

– If inhibited, no neural crest cells form – Necessary for neural crest specification

Answer 63

FoxD3

Question 64

– If inhibited, neural crest cells cannot migrate – Necessary for neural crest migration

Answer 64

Slug

Question 65

Aid in defining neural plate border region

Answer 65

Notch signaling

Question 66

NCCs distribution in mouse at E9.5 Cranial - Chondrocytes - Osteocytes - Cranial sensory ganglia - Ciliary ganglia - Odontoblasts - Thyroid cells Vagal (Cardic 3) - Smooth muscle cells - Cardiac septa - Pericytes - Ganglia - Mesenchyme - Pericytes Trunk - Dorsal root ganglia - Sympathetic ganglia - Adrenal medulla - Schwann cells - Melanocytes Sacral - Enteric ganglia - Sympathetic ganglia

Question 67

Trunk NCCs Migration Ventral pathway: * cells move through anterior portion of somite toward ventral side of embryo * Cells become: sensory neurons, sympathetic ganglia, medulla of adrenal gland Dorsolateral pathway: * cells move between epidermis and somite * Cells become: melanocytes

Question 68

Sacral NCCs Migration The sacral NCC migrates ventrally and colonizes the gut after the vagal crest. The dorsal location of the gut in the posterior end of the embryo allows the sacral NCC to take a more direct route to the gut, populating the enteric mesenchyme at the right developmental window.

Question 69

Issues that arise during the formation and migration of neural crest cells are known as ______, with varying effects depending on the location of the dysfunction.

Answer 69

neurocristopathies

Question 70

is a prototypic facial dysostosis and NCP of cranial neural crest origin. This syndrome was first described in 1900 by Edward Treacher Collins, an English ophthalmologist. It affects one in 50 000 live births. More than 90% of --- cases are caused by autosomal dominant mutations of the TCOF1 gene located on chromosome 5. Up to 60% of cases result from sporadic mutations. TCOF1 encodes the treacle protein, which is essential for proliferation and formation of cranial NCCs. Mutations of TCOF1 result in abnormal development of the first and second pharyngeal arches.

Answer 70

Treacher Collins Syndrome

Question 71

Formation and patterning during Neurulation A. Neural plate B. Elevation C. Folding D. Convergence, closure, and patterning

Question 72

Primitive gut

Answer 72

Archenteron

Question 73

Primary Neurulation: Stages

Answer 73

1. Elongation and folding of the neural plate. 2. Bending of neural plate. 3. Convergence of neural folds. 4. Closure of neural tube.

Question 74

The cellular dynamics of neural tube formation

Answer 74

Convergent extension with actomyosin and apical constriction 1. Tailbud elongation 2. Cell confinement and lineage restriction 3. Lumen initiation 4. Lumen resolution Secondary neural tube - mesenchyme - notochord

Question 75

The regulation of hinge points revolves around BMP as an antagonist to both DLHP and MHP formation. Apical constriction occurs only in those cells experiencing low enough concentrations of both BMP (MHP and DLHP) and Shh (DLHP) morphogens.

Question 76

During gastrulation, endoderm is the first to invaginate

Question 77

primitive endoderm differentiates into definitive endoderm during embryonic development

Question 78

Tube is hollow to accommodate spinal cord

Question 79

Notochord = distinguishing factor of vertebrates