Molecular Genetics and Early Embryonic Development Flashcards
Paradigm of Development
• In every species and at every level of
organization, complex structures are made
by repeating a few basic themes with
variations.
Stages of Embryonic Development (3)
differentiation
growth
patterning
Differentiation:
cells begin to form specific
and specialized structures.
Growth:
cell divisions that form more cells
with identical functions as the parental cell.
Patterning:
cells produced by cleavage get
organized into layers and groups of cell
masses through what is known as
gastrulation.
Patterning needs to occur in 3 dimensions (3)
– Anterior-Posterior (top-bottom)
– Dorsal-Ventral (left-right)
– Proximal-Distal (front-back)
Malocclusion syndromes (3)
– Pierre-Robin
– Treacher Collins
– Marfan syndrome
skipped Craniofacial malformations (4)
– Crouson
– Apert
– Pfeiffer
– Clefting syndromes (lip and palate)
skipped
• Bone Mass Traits (3)
– Sclerosteosis and van Buschem’s
– High Bone Mass and OPPG
– Paget’s Disease
Tooth Development Disorders (2)
– Dentinogenesis Imperfecta
– Amelogenesis Imperfecta
Craniofacial Anomalies Account for ~— of
All Congenital Defects
1/3
Important Concepts of Embryonic
Development (4)
• Universal Mechanisms of Animal Development • Proteins can be substituted across species • Inductive signaling • Regional Determination
Multicellular animals are enriched in proteins mediating (2)
cell interactions and gene regulation
Regulatory DNA defines the
development
program
Asymmetric versus Symmetric Cell
Division
sister cells born different
sister cells become different as result of influences acting on them after their birth
Inductive Signaling and Morphogens (2)
– Gradients reflective of a balance between
positive and inhibitory inductive signals
– Sequential Induction
Inductive Signaling (4)
- Starting Point (cell or cell cluster)
- Cell – cell signaling
- Cell signaling cascades
- Acts over great distances
Gastrulation
• Early developmental process in which the embryo (week 3
in humans) transforms from a single cell layer (blastula)
into the three primary germ layers
Gastrulation
• Early developmental process in which the embryo (week 3
in humans) transforms from a single cell layer (blastula)
into the three primary germ layers:
– Ectoderm
– Endoderm
– Mesoderm
Craniofacial Syndromes • >--- distinct syndromes • Significant cause of --- --- • --% of all live births exhibit some form of minor or major abnormality
700
infant mortality
3
skipped
Craniofacial Development
- Neural tube development and closure
- Formation of ectoderm, somites, mesoderm and other cell masses
- Neural crest cell development, differentiation and migration
- Tissue-tissue interactions
- Tissue specific patterns of gene expression
- Reciprocal Induction
- Growth and mineralization of bones and teeth
- Neural development
- Muscle development
Neural Crest Cells
• Embryonic cell population that is localized between the
developing neural tube and the epidermis. (there are also
adult neural crest cell like cells that have been identified in
many tissues)
Some neural crest cell exhibit “stemness” in that they can
give rise to multiple differentiated cell types
In the formation of the craniofacial structures (and many
other structures) the neural crest cells migrate through
restricted pathways to form the
developing structures.
Cell migration is a tightly regulated processes and the
NCCs receive cues such as (2)
that restrict their movement and determine fate.
morphogens and growth factors
Over — genes identified that have
mutations associated with tooth patterning,
morphogenesis defects and cell
differentiation defects
300
As a collective group — genetic
diseases are the most common
craniofacial
Ectodermal dysplasias (2)
– >100 different disorders
– Commonly involves one or more of teeth, nails, skin, sweat glands
and/or hair
Tooth Agenesis
– Hypodontia:
– Oligodontia:
– Anodontia:
missing only a few teeth
missing more than 6 teeth, excluding third molars
absence of teeth
skipped
Genetic Diseases of the Dentition (5)
Ectodermal dysplasias Tooth Agenesis Supernumerary Teeth Cleft Lip/Palate (OMIM lists 565 entries) Skeletal Diseases and the Dentition
Microdontia:
one or more teeth appear smaller
Macrodontia:
one or more teeth grow faster and
exceed average size
The prevalence of genetics diseases
involving the — skeleton present a
high likelihood that as a dentist you will
encounter one these challenging cases in
your practice. Especially, if you practice in
an academic setting, the chances are high
that you may consult on the treatment and
management of these cases.
craniofacial
