EX1; Molecular and Genetic Basis of Tooth Development Flashcards Preview

May14 Oral Histology > EX1; Molecular and Genetic Basis of Tooth Development > Flashcards

Flashcards in EX1; Molecular and Genetic Basis of Tooth Development Deck (97):
1

Where are cranial neural crest (NCC) cells formed

at the back of the neural tube and begin to migrate when the neural tube closes

2

Where do NCC cells migrate to

branchial arches

3

What specifically are NCC cells

stem cells

4

When do the branchial arches form

week 4

5

In which branchial arch are teeth derived from

arch 1

6

What can stem cells replicate to become

copies of itself or differentiate into other cell types

7

What are the two divisions of stem cells

symmertric (same)
asymmetric (different)

8

What cells concerning tooth development are differentiated from NCCs

odontoblasts
cementoblasts

9

Structure development, including odontogenesis at the right location and time, is through what

tissue-tissue interaction

10

This tissue-tissue interaction regulates NCC cells during morphogenesis and controls the position, size, and shape of organs

ectoderm - NCC

11

This tissue-tissue interaction provides environment for NCC cells to populate

mesoderm - NCC

12

This tissue-tissue interaction developed pharyngeal pouch generated organs; thyroid, parathyroids, and thymus

endoderm - NCC

13

NCCs form well-organized what

migratory streams to the branchial arches

14

NCCs for the first branchial arch are formed from which hindbrain rhmobomeres

1 and 2

15

Hindbrain-derived neural crest cells migrate into what three streams

first branchial arch; 1 and 2
second branchial arch; 4
third branchial arch; 6 and 7

16

The branchiomotor nerves collect axons from cell bodies but exit the hindbrain only from what to innervate their peripheral target structures

the even numbered segments

17

What cranial nerve is associated with r1-3; 1st branchial arch structures including teeth

trigeminal (V)

18

What cranial nerve is associated with r4-5

facial (VII)

19

What cranial nerve is associated with r6-7

glossopharyngeal (IX)

20

NCCs in each migratory stream express specific what

Hox gene codes

21

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

Hox genes

22

If a Hox gene is expressed, its protein products functions as what

a transcription factor; controling gene expression

23

True or False
In specific NCC streams, there is a specific Hox gene profile

True

24

What becomes of r3 and r5

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