Molecular and Genetic Mechanisms of Tooth Development (Larsen 3)

Question 1

Cell fate depends of _____ and ______.

Answer 1

• Origin

- Temporal-spatial history

Question 2

Cell fate is determined by _____ and ______.

Answer 2

-Genes
-Environment
(Autonomous or intrinsic) (Non-autonomous or extrinsic)

Question 3

What combination of epithelium and neural crest cells results in tooth formation?

Answer 3

• Neural crest

- Mandibular epithelium

Question 4

Prior to day 12, the _____ initiates odontogenesis.

Answer 4

Epithelium

Question 5

After day 12, the mandibular/first arch epithelium _____ odontogenic potential and _______ directs the development of the tooth.

Answer 5

• Loses

- Ectomesenchyme

Question 6

Growth factors are _____.

Answer 6

Peptides

Question 7

Growth factors bind to _____ in membrane which initiates a cascade of specific protein-protein interactions.

Answer 7

Receptors

Question 8

Transcription factors bind to ______ and a gene is transcribed to make mRNA allowing specific proteins to be translated.

Answer 8

DNA

Question 9

Initiation (_____) –> Morphogenesis (____, ____) –> Cytodifferentiation (____)

Answer 9

• Dental lamina
• Bud, Cap
• Bell

Question 10

Undifferentiated ectomesenchymal cells become ______ when in contact with _____.

Answer 10

• Odontoblasts

- Growth factor

Question 11

Co-linear-spatial relationship on the chromosome is the same as the embryo anteroposterior axis. These genes are called ______.

Answer 11

Hox genes

Question 12

Each Hox gene contains a ________.

Answer 12

Homeodomain

Question 13

Hox family genes establish regional diversity within the ________.

Answer 13

Brachial arch system

Question 14

What are the homeobox genes associated with the neural crest cells migrating from the midbrain and rhombomeres 1 and 2

Answer 14

• Msx
• Dlx
• Barx

Question 15

The formation of the dental lamina occurs in the overlap region of the _____ that expresses _____, _____, and _____.

Answer 15

• Ectomesenchyme
• Msx-1
• Msx-2
• Dlx-2

Question 16

During the formation of the dental lamina, expression is induced by _____ and repressed by _____ from epithelium.

Answer 16

• Fgf-8

- Bmp-4

Question 17

Homeobox Expression: Incisor

Answer 17

• Msx-1

- Msx-2

Question 18

Homeobox Expression: Canine

Answer 18

• Msx-1
• Msx-2
• Dlx-2

Question 19

Homeobox Expression: Molar

Answer 19

• Dlx-2

- Barx-1

Question 20

_____ gene expression occurs at sites where tooth germs appear.

Answer 20

Co-localized

Question 21

What controls the number and marks the position of teeth? (Epithelium)

Answer 21

• Fgf-8 induces
• Bmp-2 and Bmp-4 restricts
• FGF does not overlap with BMPs location (how placode forms)

Question 22

What controls the number and marks the position of teeth? (Ectomesenchyme)

Answer 22

• Pax-9

- Depends on ligands early and independent from bud stage on

Question 23

Roles of epithelium and ectomesenchyme ______ during tooth development.

Answer 23

• Change
• Early: epithelium is in control
• Once mesenchyme specification is established, the mesenchyme takes over

Question 24

Initiation: Epithelial Signals

Answer 24

Shh (sonic hedgehog) a secreted protein
-Shh soaked beads applied to oral epithelium causes invaginations that resemble tooth buds
(Direction of Signals E–>M)

Question 25

Bud Stage: Condensing Mesenchyme Signals

Answer 25

The switching of the expression of BMP-4 indicates the control shift of tooth development from the epithelium to the connective tissue (Direction of Signals M-->E)

Question 26

Dental lamina expresses _____ where teeth will develop during the initiation stage, down growth of the dental lamina.

Answer 26

BMP-4

Question 27

During the morphogenic (bud) stage, BMP-4 expression is switched to the _______.

Answer 27

Connective tissue

Question 28

Changes in BMP-4 expression precedes changes in _____ expression which becomes more localized.

Answer 28

Msx-1

Question 29

In the Cap Stage (Enamel Knot Signaling), ______ is required to induce the enamel knot.

Answer 29

Mesenchymal Bmp4 | Direction of Signals E-->M

Question 30

In the Cap Stage (Enamel Knot Signaling), specific inner enamel epithelium cells express ____, ____, and ____.

Answer 30

- SHH - BMP4 - FGF4

Question 31

A layer of non-dividing ______ at the surface of the developing _____ controls the crown shape

Answer 31

- Epithelium | - Cusp tips

Question 32

What is involved in formation of crown shape?

Answer 32

- Primary enamel knot - Secondary enamel knot - Express p21 (cell cycle related gene) - Signaling factors: BMP, FGF, SHH, WNT

Question 33

Gene name and function: Msx

Answer 33

- Msh-like genes | - Transcription factor

Question 34

Gene name and function: Dlx

Answer 34

- Distaless homologue | - Transcription factor

Question 35

Gene name and function: Barx

Answer 35

- Barh1 homologue | - Transcription factor

Question 36

Gene name and function: Bmp-4

Answer 36

- Bone morphogenetic protein | - Secreted protein

Question 37

Gene name and function: Shh

Answer 37

- Sonic hedgehog | - Secreted protein