Molecular and Genetic Basis of Tooth Development Flashcards Preview

Oral Histology > Molecular and Genetic Basis of Tooth Development > Flashcards

Flashcards in Molecular and Genetic Basis of Tooth Development Deck (65):
1

Neural Crest cells

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

2

Where are neural crest cells formed?

At the back of the neural tube

3

When doe neural crest cells migrate?

When the neural tube closes at week 4

4

What are the types of division that stem cells undergo?

Symmetric division
Asymmetric division

5

Symmetric division

Stem cells divide into 2 identical stem cells

6

Asymmetric division

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

7

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

Can interact with other cell layers
Embryonic development of the branchial arch structures relies on complicated but precise tissue-tissue interaction

8

NCC-ectoderm interaction

Regulates NCC cells during morphogenesis
Controls the position, size, and shape of organs

9

NCC-mesoderm interaction

Provides environment for NCC cells to populate

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NCC-endoderm interaction

Develops pharyngeal pouch-generated organs
(thyroid, parathyroid, and thymus)

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Rhombomeres

Segments of NCC on the neural crest

12

Where do r1-2 migrate?

Branchial arch I

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Where does r4 migrate?

Branchial arch II

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Where do r6-7 migrate?

Branchial arch III

15

What rhombomeres make up the Trigeminal nerve?

r1-3

16

What rhombomeres make up the facial nerve?

r4-5

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What rhombomeres make up the glossopharyngeal nerve?

r6-7

18

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

Even segments (but they collect from all segments)

19

Hox genes

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

20

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

A transcription factor, which controls other gene expression

21

Which NCCs are Hox free?

The ones that migrate to the first branchial arch (r1 and 2)
Hox genes are carried, but just not expressed

22

Which NCCs express Hox?

Ones that migrate to teh second branchial arch and further

23

D1x gene

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

24

D1x1/2 combination

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

25

D1x5/6 combination

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

26

D1x1/2 double mutants

Causes a lack of all maxillary molars - mandible is unaffected

27

D1x5/6 double mutants

Lower jaw mirrors the upper jaw

28

What drives the entire process of tooth development?

Interaction between epithelium and mesenchyme

29

What does the epithelium become during tooth development?

Ameloblasts

30

What does the mesenchyme become during tooth development?

Odontoblasts

31

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

All tooth structures except enamel

32

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

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

33

Enamel knots

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

34

Primary enamel knot

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

35

Secondary enamel knot

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

36

What does FGF determine?

Functions as a cusp activator

37

What does BMP determine?

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

38

What are important molecules produced by mesenchyme for tooth developemnt?

Signaling molecules
Transcription factors

39

What is the mechanism that determines tooth identity?

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

40

When does tooth innervation first occur?

Bell stage

41

What cranial nerve innervates teeth?

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

42

Sema3A

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

43

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

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

44

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

Lamini-5
TGF-beta

45

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

Nuclear factor IC (Nfic)

46

What are the fates of HERS

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

47

Ectodermal dysplasia cause

Mutation of transcription factor p63

48

Ectoderm dysplasia symptoms

Two or more ectodermal structures effected

49

Transcription Factor p63 normal function

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

50

Msx1 mutation symptoms

Lack of maxillary premolars and mandibular second premolars

51

Msx1 mutation cause

G-->C transversion mutaiton of the Msx1 gene

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Msx1 gene normal function

Transcription factor in the mesenchyme involved in tooth development

53

Pax9 mutation symptom

No molar development

54

Pax9 mutaiton cause

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

55

Pax9 normal function

Transcription factor

56

Axin2 mutation symptoms

More than 8 permanent teeth are underdeveloped

57

Axin2 mutation cause

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

58

Axin2 normal function

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

59

EDA mutation symptoms

Multiple missing anterior teeth

60

EDA mutation cause

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

61

EDA normal funciton

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

62

Celidocranial dysplasia syndrome

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

63

Cleidocranical dysplasia syndrome cause

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

64

Gardner's syndrome

Can cause supernumerary teeth, impacted teeth, and dentigerous cysts

65

Gardner's syndrome cause

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