EX1; Molecular and Genetic Basis of Tooth Development Flashcards
(97 cards)
1
Q
Where are cranial neural crest (NCC) cells formed
A
at the back of the neural tube and begin to migrate when the neural tube closes
2
Q
Where do NCC cells migrate to
A
branchial arches
3
Q
What specifically are NCC cells
A
stem cells
4
Q
When do the branchial arches form
A
week 4
5
Q
In which branchial arch are teeth derived from
A
arch 1
6
Q
What can stem cells replicate to become
A
copies of itself or differentiate into other cell types
7
Q
What are the two divisions of stem cells
A
symmertric (same)
asymmetric (different)
8
Q
What cells concerning tooth development are differentiated from NCCs
A
odontoblasts
cementoblasts
9
Q
Structure development, including odontogenesis at the right location and time, is through what
A
tissue-tissue interaction
10
Q
This tissue-tissue interaction regulates NCC cells during morphogenesis and controls the position, size, and shape of organs
A
ectoderm - NCC
11
Q
This tissue-tissue interaction provides environment for NCC cells to populate
A
mesoderm - NCC
12
Q
This tissue-tissue interaction developed pharyngeal pouch generated organs; thyroid, parathyroids, and thymus
A
endoderm - NCC
13
Q
NCCs form well-organized what
A
migratory streams to the branchial arches
14
Q
NCCs for the first branchial arch are formed from which hindbrain rhmobomeres
A
1 and 2
15
Q
Hindbrain-derived neural crest cells migrate into what three streams
A
first branchial arch; 1 and 2
second branchial arch; 4
third branchial arch; 6 and 7
16
Q
The branchiomotor nerves collect axons from cell bodies but exit the hindbrain only from what to innervate their peripheral target structures
A
the even numbered segments
17
Q
What cranial nerve is associated with r1-3; 1st branchial arch structures including teeth
A
trigeminal (V)
18
Q
What cranial nerve is associated with r4-5
A
facial (VII)
19
Q
What cranial nerve is associated with r6-7
A
glossopharyngeal (IX)
20
Q
NCCs in each migratory stream express specific what
A
Hox gene codes
21
Q
This is a group of homeobox genes, which possess a unique homeobox (DNA sequence) which encodes a conservative homeodomain (protein segment)
A
Hox genes
22
Q
If a Hox gene is expressed, its protein products functions as what
A
a transcription factor; controling gene expression
23
Q
True or False
In specific NCC streams, there is a specific Hox gene profile
A
True
24
Q
What becomes of r3 and r5
A
they undergo apoptosis
25
What is unique about the NCCs that migrate to the first branchial arch regarding the Hox genes
the first branchial arch is Hox free; it carries the genes, but does not express them
26
NCCs involved in tooth development do or do not express Hox genes
DO NOT
27
Within each branchial arch, these genes are expressed to produce regional differences, such as between the maxillae and mandible
specific D1x gene codes
28
True or False
| D1x genes are not homeobox
False; they are
29
True or False
| D1x genes are not transcription factors
False; they are
30
How many members compose the D1x family
7
| 7, 8, 9 are actually the same gene
31
For branchial arch 1, D1x 1/2 combination is required for what
development of the proximal portion (maxillary process)
32
What do D1x 1/2 mutants lack
all maxillary molars;
| mandibular structures are not affected
33
For branchial arch 1, D1x 5/6 combination is required for what
development of the distal portion (mandibular process)
34
What do Dx1 5/6 mutants look like
the lower jaw looks like a mirror image of the upper jaw
35
Normal tooth development is a process with precisely arranged/regulated what
cell and tissue interactions
36
The interaction between the epithelium and the mesenchyme is through what
numerous molecules
37
What is the entire process of tooth development initiated by
epithelium followed by epithelium-mesencyhme interaction
38
What are the four major signaling pathways for the ectoderm-derived epithelium
BMP; bone morphogenic protein
FGF; fibroblast growth factor
Wnt; wingless (drosophila) and int (mouse)
SHH; sonic hedgehog
39
The four major singling pathways bind to what
cell membrane receptors
40
The four major signaling pathways eventually impact on gene regulation through what
varied intracellular pathways
41
The four major signaling pathways are also important for the development of what
other ectodermal organs such as hair, nails, and glands
42
These are epithelial aggregates that function as signal centers for tooth morphogenesis and odontoblast differentiation
enamel knots
43
Which enamel knot appears at the end of the bud stage and which one appears at the locations of future molar cusps at the bell stage
primary EK
| secondary EK
44
Which enamel knot closely interacts with the mesenchyme
primary EK
45
Which enamel knot stimulates terminal differentiation of odontoblasts at the end of the bud stage, which always occurs first at the location of future cusps/cusps tips
secondary EK
46
Which enamel knot strongly stimulates proliferation of adjacent cells
primary EK
47
Which enamel knot is essential for bud to cap transition and without it, tooth development will be arrested
primary EK
48
Which enamel knot determines the number of cusps and locations of the molar cusps
secondary EK
49
Which enamel know disappears by cell apoptosis
primary EK
50
Which enamel knot is not present in incisors
secondary EK
51
This signaling molecule signaling molecule as a cusp activator
FGF
52
This signaling molecule functions as a cusp inhibitor
BMP (and possibly SHH)
53
What do FGF and BMP (and possibly SHH) regulate in terms of the cusps
the formation of inter-cusp distance
54
All tooth structures except for what are directly contributed by NCCs migrated to the first branchial arch
enamel
| dentin, pulp, periodontal ligament, and cementum
55
What are the important signaling molecules produced by the mesenchymal cells for tooth development
BMP, FGF, Wnt, and their inhibitors
56
What are the important transcription factors produced by the mesenchymal cells for tooth development
Ms x1/2, D1x 1/2, Pax9, Gli 2/3, Runx2, Barx1, etc.
57
At the cell and molecular level, the development of a tooth crown can be divided into what three major stages
1. initiation
2. morphogenesis
3. differentiation and mineralization
58
What occurs through all of the tooth crown development stages
intense molecular interaction
59
Which signaling molecules are present at the anterior sites which control the development of incisors
BMP4 Msx1, Msx2
60
Which signaling molecules are present at the posterior sites which control the development of molars
FGF Barx1, D1x2, Lhx6/7
61
Innervation of the tooth is from beaches of which cranial nerve
trigeminal
62
When do pioneer trigeminal axons penetrate into the dental pulp after what
the start of enamel formation
63
Through the epithelial-mesenchymal interation, the epithelium expresses what into mesenchyme
Sema3A
64
Sema3A serves as what
chemorepellent for the axons, thus controlling the timing and patterning of tooth innervation
65
After the crown development is nearly complete, this grows apically between two mesenchymal regions; dental papilla and dental follicle
Hertwig's root sheath (HERS)
66
Immediately after HERS formation, these appear adjacent to the HERS on the papilla side
apical odontoblasts
67
This is required for root development
induction from the enamel epithelium
68
HERS induces dental papilla cells to do what
differentiate into odontoblasts
69
Recent evidence shows that this may be secreted by HERS to induce odontoblast differentiation
lamini-5 and transforming growth factor-beta (TGF-β)
70
What is different about the odontoblasts in the root region compared to the crown region
they are much less elongated in the root region than the crown region
71
This is essential for root dentin formation but not for crown dentin formation; without it, odontoblasts cannot normally form even when the HERS appear normal
nuclear factor Ic (Nfic)
72
Cementum formation starts when
HERS and dental follicle are in close proximity
73
Both epithelial HERS and mesenchymal (dental follicle) cells participate in what, but their contribution remain unclear
cementum formation
74
What are the molecules involved in epithelial-mesenchyme interaction
HERS; TGF-β, Nfic, insulin-like growth factors, Wnts, FGF
| Mesenchyme; BMP and FGF
75
What do the HERS cells determine regarding the roots
the number of roots; however many groups of HERS cells equals number of roots
76
What can happen for HERS after root development
```
Become the epithelial rest of Malassez
Apoptosis
Incorporated into cementum front
Epithelial-mesenchyme transformation
Migration to the periodontal ligament
Differentiation into cementoblasts
```
77
This is when two or more ectodermal structures are affected
ectodermal dysplasia
78
A mutation in this, required for normal function of FGF, BMP, and SHH, critical signaling pathways involved in epithelial-mesenchymal interaction cause ectodermal dysplasia
transcription factor p63
79
This mutation results in a family with multiple members lacking bot maxillary premolars and mandibular 2nd premolars
Msx1 mutation
80
What is the genetic basis for a Msx1 mutation
G to C transversion in the Msx1 homeodomain region, affecting its normal transcription factor function
81
This mutation results in member having no molar development
Pax9 mutation
82
What is the genetic basis for a Pax9 mutation
guanine insertion causing frame shift in the DNA-binding domain which affects normal transcription factor function
83
This mutation results in member all having more than 8 permanent teeth undeveloped
Axin2
84
What is the genetic basis for an Axin2 mutation
missence (C to T) or insertion (G) inducing a premature stop codon resulting in the disruption of Wnt signaling (not a TF)
85
What are patients with an Axin2 mutation prone to
colorectal polyps and cancer
86
This mutation results in members having multiple missing anterior teeth (X-linked)
EDA
87
What is the genetic basis of an EDA mutation
missence (C to G) mutation disrupting the transmembrane signaling molecule belonging to the TNF pathway (not a TF)
88
What are some theories for the etiology of supernumerary teeth
atavism (evolutionary throwback)
tooth germ dichotomy
hyperactivity of dental lamina
genetic/environmental factors
89
Most supernumerary teeth are what kind of cases
isolated cases; multiple supernumerary teeth are rare
90
This is an autosomal-dominant skeletal displasia in clavicles, patent sutures, and fontanels, formation of Wormian bones and short stature results in supernumerary teeth and delay eruption of permanent teeth
cleidocranial dysplasia
91
What mutation causes cleidocranial dysplasia
Runx2
92
What does Runx2 encode
a transcription factor in the mesenchyme essential for tooth development; a negative regulator for secondary teeth
93
Identical Runx2 mutations showed what in supernumerary tooth formation
wide variaion; suggesting epigenetic and environmental factors
94
This causes adenomatours polyps of the GI tract, demoed tumors, osteomas, and dentally; supernumerary teeth, impacted teeth, dentigerous cysts, etc.
Gardner's syndrome
95
What is the mutation that causes Gardner's syndrome
APC gene mutation
96
What APC deficiency mediated by
β-catenin (Wnt pathway)
97
Does APC encode a transcription factor
No
