Flashcards in Molecular and Genetic Basis of Tooth Development Deck (65):
Neural Crest cells
Stem cells that migrate through defined paths to reach the branchial arches
Where are neural crest cells formed?
At the back of the neural tube
When doe neural crest cells migrate?
When the neural tube closes at week 4
What are the types of division that stem cells undergo?
Stem cells divide into 2 identical stem cells
Can divide into 1 differentiated cell, and 1 identical stem cell
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
Regulates NCC cells during morphogenesis
Controls the position, size, and shape of organs
Provides environment for NCC cells to populate
Develops pharyngeal pouch-generated organs
(thyroid, parathyroid, and thymus)
Segments of NCC on the neural crest
Where do r1-2 migrate?
Branchial arch I
Where does r4 migrate?
Branchial arch II
Where do r6-7 migrate?
Branchial arch III
What rhombomeres make up the Trigeminal nerve?
What rhombomeres make up the facial nerve?
What rhombomeres make up the glossopharyngeal nerve?
What segments do nerves exit from to innervate peripheral target structures?
Even segments (but they collect from all segments)
A group of homeobox genes, which possess a unique homeobox (DNA sequence), which encodes a conservative homeodomain (protein segment)
What is the protein product if a Hox gene is expressed?
A transcription factor, which controls other gene expression
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
Which NCCs express Hox?
Ones that migrate to teh second branchial arch and further
Family of homeobox genes that produce differences between the maxilla and the mandible
Required for the development of the proximal portion of the first branchial arch (maxillary process)
Required for the development of the distal portion of the first branchial arch (mandibular process
D1x1/2 double mutants
Causes a lack of all maxillary molars - mandible is unaffected
D1x5/6 double mutants
Lower jaw mirrors the upper jaw
What drives the entire process of tooth development?
Interaction between epithelium and mesenchyme
What does the epithelium become during tooth development?
What does the mesenchyme become during tooth development?
What tooth structures are contributed by NCC that migrate to the first branchial arch?
All tooth structures except enamel
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)
Epithelial aggregates that function as signal centers for tooth morphogenesis and odontoblast differentiation
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
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
What does FGF determine?
Functions as a cusp activator
What does BMP determine?
May function as an inhibitor to regulate the formation of inter-cusp distance
What are important molecules produced by mesenchyme for tooth developemnt?
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
When does tooth innervation first occur?
What cranial nerve innervates teeth?
Pioneer trigeminal axons are in the dental pulp after the start of enamel formation
Expressed in mesenchyme when tooth innervation is forming.
Serves as a chemorepelent for axons to control timing and pattern
What induces the dental papilla cells to differentiate into apical odontobalsts?
Hetwig's Epithelial rooth sheath is in close proximity to the dnetal fillicle
What molecule(s) is secreted by HERS to differentiate apical odontobalsts?
What molecule is essential for root dentin formation, but not grown dentin
Nuclear factor IC (Nfic)
What are the fates of HERS
Become the epithelial rest of Malassez
Incorporated into the cementum
Migration to PDL
Differentiation into cementoblasts
Ectodermal dysplasia cause
Mutation of transcription factor p63
Ectoderm dysplasia symptoms
Two or more ectodermal structures effected
Transcription Factor p63 normal function
Required for the normal function of FGF, BMP, and SHH (critical signaling pathways involved in epithelial-mesenchyme interactions)
Msx1 mutation symptoms
Lack of maxillary premolars and mandibular second premolars
Msx1 mutation cause
G-->C transversion mutaiton of the Msx1 gene
Msx1 gene normal function
Transcription factor in the mesenchyme involved in tooth development
Pax9 mutation symptom
No molar development
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
Pax9 normal function
Axin2 mutation symptoms
More than 8 permanent teeth are underdeveloped
Axin2 mutation cause
Missense (C-->T) or
Both cause premature stop codon to Axin2
Axin2 normal function
Expressed in mesenchyme
Loss of function disrupts Wnt signals (but Axin2 is not a transcription factor)
EDA mutation symptoms
Multiple missing anterior teeth
EDA mutation cause
Missense (C-->G), resulting in a Q to E substitution in the gene
EDA normal funciton
Transmembrane signaling molecule that is in the TNF pathway (it's not a transcription factor)
Celidocranial dysplasia syndrome
Autosomal-dominant disease causing supernumerary teeth, delayed eruption, and impaction of permanent teeth
Cleidocranical dysplasia syndrome cause
Runx2 mutation - it encodes a trancription factor essential for tooth development
Can cause supernumerary teeth, impacted teeth, and dentigerous cysts