Molecular and Genetic Basis of Tooth Development

Question 1

Neural Crest cells

Answer 1

Stem cells that migrate through defined paths to reach the branchial arches

Question 2

Where are neural crest cells formed?

Answer 2

At the back of the neural tube

Question 3

When doe neural crest cells migrate?

Answer 3

When the neural tube closes at week 4

Question 4

What are the types of division that stem cells undergo?

Answer 4

Symmetric division

Asymmetric division

Question 5

Symmetric division

Answer 5

Stem cells divide into 2 identical stem cells

Question 6

Asymmetric division

Answer 6

Can divide into 1 differentiated cell, and 1 identical stem cell

Question 7

What does it mean for Neural crest cells to be Multipotent stem cells? Why is it important?

Answer 7

Can interact with other cell layers

Embryonic development of the branchial arch structures relies on complicated but precise tissue-tissue interaction

Question 8

NCC-ectoderm interaction

Answer 8

Regulates NCC cells during morphogenesis

Controls the position, size, and shape of organs

Question 9

NCC-mesoderm interaction

Answer 9

Provides environment for NCC cells to populate

Question 10

NCC-endoderm interaction

Answer 10

Develops pharyngeal pouch-generated organs

thyroid, parathyroid, and thymus

Question 11

Rhombomeres

Answer 11

Segments of NCC on the neural crest

Question 12

Where do r1-2 migrate?

Answer 12

Branchial arch I

Question 13

Where does r4 migrate?

Answer 13

Branchial arch II

Question 14

Where do r6-7 migrate?

Answer 14

Branchial arch III

Question 15

What rhombomeres make up the Trigeminal nerve?

Answer 15

r1-3

Question 16

What rhombomeres make up the facial nerve?

Answer 16

r4-5

Question 17

What rhombomeres make up the glossopharyngeal nerve?

Answer 17

r6-7

Question 18

What segments do nerves exit from to innervate peripheral target structures?

Answer 18

Even segments (but they collect from all segments)

Question 19

Hox genes

Answer 19

A group of homeobox genes, which possess a unique homeobox (DNA sequence), which encodes a conservative homeodomain (protein segment)

Question 20

What is the protein product if a Hox gene is expressed?

Answer 20

A transcription factor, which controls other gene expression

Question 21

Which NCCs are Hox free?

Answer 21

The ones that migrate to the first branchial arch (r1 and 2)

Hox genes are carried, but just not expressed

Question 22

Which NCCs express Hox?

Answer 22

Ones that migrate to teh second branchial arch and further

Question 23

D1x gene

Answer 23

Family of homeobox genes that produce differences between the maxilla and the mandible

Question 24

D1x1/2 combination

Answer 24

Required for the development of the proximal portion of the first branchial arch (maxillary process)

Question 25

D1x5/6 combination

Answer 25

Required for the development of the distal portion of the first branchial arch (mandibular process

Question 26

D1x1/2 double mutants

Answer 26

Causes a lack of all maxillary molars - mandible is unaffected

Question 27

D1x5/6 double mutants

Answer 27

Lower jaw mirrors the upper jaw

Question 28

What drives the entire process of tooth development?

Answer 28

Interaction between epithelium and mesenchyme

Question 29

What does the epithelium become during tooth development?

Answer 29

Ameloblasts

Question 30

What does the mesenchyme become during tooth development?

Answer 30

Odontoblasts

Question 31

What tooth structures are contributed by NCC that migrate to the first branchial arch?

Answer 31

All tooth structures except enamel

Question 32

What are the 4 major signaling pathways for ectoderm-derived epithelium?

Answer 32

BMP (bone morphogenic protein) FGF (fibrobalst growth factor) Wnt (wingless and int) SHH (sonic hedgehog)

Question 33

Enamel knots

Answer 33

Epithelial aggregates that function as signal centers for tooth morphogenesis and odontoblast differentiation

Question 34

Primary enamel knot

Answer 34

Appear at the end of the bud stage Closely interact with the Mesenchyme Essential for bud-to-cap transition Dissapperas by apoptosis

Question 35

Secondary enamel knot

Answer 35

Appears at the locations of future molar cusps at the bell stage Determines the number and locations of the molar cusps Not present in incisors

Question 36

What does FGF determine?

Answer 36

Functions as a cusp activator

Question 37

What does BMP determine?

Answer 37

May function as an inhibitor to regulate the formation of inter-cusp distance

Question 38

What are important molecules produced by mesenchyme for tooth developemnt?

Answer 38

Signaling molecules | Transcription factors

Question 39

What is the mechanism that determines tooth identity?

Answer 39

It's not clear | Some evidence suggests there are different molecular interactions in anterior and posterior regions

Question 40

When does tooth innervation first occur?

Answer 40

Bell stage

Question 41

What cranial nerve innervates teeth?

Answer 41

Pioneer trigeminal axons are in the dental pulp after the start of enamel formation

Question 42

Sema3A

Answer 42

Expressed in mesenchyme when tooth innervation is forming. | Serves as a chemorepelent for axons to control timing and pattern

Question 43

What induces the dental papilla cells to differentiate into apical odontobalsts?

Answer 43

Hetwig's Epithelial rooth sheath is in close proximity to the dnetal fillicle

Question 44

What molecule(s) is secreted by HERS to differentiate apical odontobalsts?

Answer 44

Lamini-5 | TGF-beta

Question 45

What molecule is essential for root dentin formation, but not grown dentin

Answer 45

Nuclear factor IC (Nfic)

Question 46

What are the fates of HERS

Answer 46

``` Become the epithelial rest of Malassez Apoptosis Incorporated into the cementum Epithelial-mesenchyme transformation Migration to PDL Differentiation into cementoblasts ```

Question 47

Ectodermal dysplasia cause

Answer 47

Mutation of transcription factor p63

Question 48

Ectoderm dysplasia symptoms

Answer 48

Two or more ectodermal structures effected

Question 49

Transcription Factor p63 normal function

Answer 49

Required for the normal function of FGF, BMP, and SHH (critical signaling pathways involved in epithelial-mesenchyme interactions)

Question 50

Msx1 mutation symptoms

Answer 50

Lack of maxillary premolars and mandibular second premolars

Question 51

Msx1 mutation cause

Answer 51

G-->C transversion mutaiton of the Msx1 gene

Question 52

Msx1 gene normal function

Answer 52

Transcription factor in the mesenchyme involved in tooth development

Question 53

Pax9 mutation symptom

Answer 53

No molar development

Question 54

Pax9 mutaiton cause

Answer 54

``` Guanine insertion (causing a frameshift) of the Pax9 gene The mutaiton is at the DNA-binding domain, which affects Pax9 normal function ```

Question 55

Pax9 normal function

Answer 55

Transcription factor

Question 56

Axin2 mutation symptoms

Answer 56

More than 8 permanent teeth are underdeveloped

Question 57

Axin2 mutation cause

Answer 57

Missense (C-->T) or Insertion (G) Both cause premature stop codon to Axin2

Question 58

Axin2 normal function

Answer 58

Expressed in mesenchyme | Loss of function disrupts Wnt signals (but Axin2 is not a transcription factor)

Question 59

EDA mutation symptoms

Answer 59

Multiple missing anterior teeth

Question 60

EDA mutation cause

Answer 60

Missense (C-->G), resulting in a Q to E substitution in the gene

Question 61

EDA normal funciton

Answer 61

Transmembrane signaling molecule that is in the TNF pathway (it's not a transcription factor)

Question 62

Celidocranial dysplasia syndrome

Answer 62

Autosomal-dominant disease causing supernumerary teeth, delayed eruption, and impaction of permanent teeth

Question 63

Cleidocranical dysplasia syndrome cause

Answer 63

Runx2 mutation - it encodes a trancription factor essential for tooth development

Question 64

Gardner's syndrome

Answer 64

Can cause supernumerary teeth, impacted teeth, and dentigerous cysts

Question 65

Gardner's syndrome cause

Answer 65

APC gene mutation - causing an issue of the Wnt signaling pathway