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

Molecular and Genetic Basis of Tooth Development Flashcards

1
Q

Neural Crest cells

A

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

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2
Q

Where are neural crest cells formed?

A

At the back of the neural tube

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3
Q

When doe neural crest cells migrate?

A

When the neural tube closes at week 4

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4
Q

What are the types of division that stem cells undergo?

A

Symmetric division

Asymmetric division

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5
Q

Symmetric division

A

Stem cells divide into 2 identical stem cells

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6
Q

Asymmetric division

A

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

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7
Q

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

A

Can interact with other cell layers

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

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8
Q

NCC-ectoderm interaction

A

Regulates NCC cells during morphogenesis

Controls the position, size, and shape of organs

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9
Q

NCC-mesoderm interaction

A

Provides environment for NCC cells to populate

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10
Q

NCC-endoderm interaction

A

Develops pharyngeal pouch-generated organs

thyroid, parathyroid, and thymus

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11
Q

Rhombomeres

A

Segments of NCC on the neural crest

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12
Q

Where do r1-2 migrate?

A

Branchial arch I

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13
Q

Where does r4 migrate?

A

Branchial arch II

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14
Q

Where do r6-7 migrate?

A

Branchial arch III

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15
Q

What rhombomeres make up the Trigeminal nerve?

A

r1-3

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16
Q

What rhombomeres make up the facial nerve?

A

r4-5

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17
Q

What rhombomeres make up the glossopharyngeal nerve?

A

r6-7

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18
Q

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

A

Even segments (but they collect from all segments)

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19
Q

Hox genes

A

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

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20
Q

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

A

A transcription factor, which controls other gene expression

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21
Q

Which NCCs are Hox free?

A

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

Hox genes are carried, but just not expressed

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22
Q

Which NCCs express Hox?

A

Ones that migrate to teh second branchial arch and further

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23
Q

D1x gene

A

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

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24
Q

D1x1/2 combination

A

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

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25
Q

D1x5/6 combination

A

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

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26
Q

D1x1/2 double mutants

A

Causes a lack of all maxillary molars - mandible is unaffected

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27
Q

D1x5/6 double mutants

A

Lower jaw mirrors the upper jaw

28
Q

What drives the entire process of tooth development?

A

Interaction between epithelium and mesenchyme

29
Q

What does the epithelium become during tooth development?

A

Ameloblasts

30
Q

What does the mesenchyme become during tooth development?

A

Odontoblasts

31
Q

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

A

All tooth structures except enamel

32
Q

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

A

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

33
Q

Enamel knots

A

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

34
Q

Primary enamel knot

A

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

35
Q

Secondary enamel knot

A

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
Q

What does FGF determine?

A

Functions as a cusp activator

37
Q

What does BMP determine?

A

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

38
Q

What are important molecules produced by mesenchyme for tooth developemnt?

A

Signaling molecules

Transcription factors

39
Q

What is the mechanism that determines tooth identity?

A

It’s not clear

Some evidence suggests there are different molecular interactions in anterior and posterior regions

40
Q

When does tooth innervation first occur?

A

Bell stage

41
Q

What cranial nerve innervates teeth?

A

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

42
Q

Sema3A

A

Expressed in mesenchyme when tooth innervation is forming.

Serves as a chemorepelent for axons to control timing and pattern

43
Q

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

A

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

44
Q

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

A

Lamini-5

TGF-beta

45
Q

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

A

Nuclear factor IC (Nfic)

46
Q

What are the fates of HERS

A 
Become the epithelial rest of Malassez
Apoptosis
Incorporated into the cementum
Epithelial-mesenchyme transformation
Migration to PDL
Differentiation into cementoblasts
47
Q

Ectodermal dysplasia cause

A

Mutation of transcription factor p63

48
Q

Ectoderm dysplasia symptoms

A

Two or more ectodermal structures effected

49
Q

Transcription Factor p63 normal function

A

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

50
Q

Msx1 mutation symptoms

A

Lack of maxillary premolars and mandibular second premolars

51
Q

Msx1 mutation cause

A

G–>C transversion mutaiton of the Msx1 gene

52
Q

Msx1 gene normal function

A

Transcription factor in the mesenchyme involved in tooth development

53
Q

Pax9 mutation symptom

A

No molar development

54
Q

Pax9 mutaiton cause

A 
Guanine insertion (causing a frameshift) of the Pax9 gene
The mutaiton is at the DNA-binding domain, which affects Pax9 normal function
55
Q

Pax9 normal function

A

Transcription factor

56
Q

Axin2 mutation symptoms

A

More than 8 permanent teeth are underdeveloped

57
Q

Axin2 mutation cause

A

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

58
Q

Axin2 normal function

A

Expressed in mesenchyme

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

59
Q

EDA mutation symptoms

A

Multiple missing anterior teeth

60
Q

EDA mutation cause

A

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

61
Q

EDA normal funciton

A

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

62
Q

Celidocranial dysplasia syndrome

A

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

63
Q

Cleidocranical dysplasia syndrome cause

A

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

64
Q

Gardner’s syndrome

A

Can cause supernumerary teeth, impacted teeth, and dentigerous cysts

65
Q

Gardner’s syndrome cause

A

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

Oral Histology (12 decks)

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