This PPT is a simplified introduction for molecular embryology. It includes molecular regulation of Heart, GIT, Liver, Pancreas, Kidney and somites Development. This will be followed by another PPT with molecualr regulation of other important organs as Brain and spinal cord. I hope that I could make it as simple as possible, waiting for your valuable comments. Enjoy my dear friends.

1. Molecular Embryology
By:
Dr. Khaled El Masry
Assistant Lecturer of Human Anatomy &
Embryology
Mansoura Faculty of Medicine, Mansoura University,
Mansoura , Egypt.
2013

2. Molecular Regulation of
Cardiac
Development

3. BMP 2, 4 + Inhibitors of WNT genes (In Endoderm & Lateral Plate
Mesoderm )
Stimulate Production of Signals from
Anterior Cranial Endoderm
Expre
ss
NKX 2.5
Specify Cardiogenic
Field in Overlying
Mesoderm.
Role in Cardiac
Septation.
Role in Conducting System Development.
TBX-5 ( another Expressed later than NKX
transcriptional factor) 2.5
contain T- Box.
Role in Cardiac
Septation

4. Molecular Regulation of
SomitE
Differentiation

5. Limb & body wall
Epaxial muscles
Activate Myogenin & MRF-5 muscles
WNT proteins MYF-5 MYOD
( from Neural Tube) Myotubes &
Myofibrils
DM Midpart
NT-3 (from Neural
Tube)
VM SHH Dermis
D
Scleroto
me
PAX 1
Initiate cascade of cartilage & bone forming genes
Vertebral
formation
L
BY:
Interaction ( ) BMP-4 ( from lateral plate mesoderm) & WNT proteins ( from
Dr. Khaled El Epidermis)
WNT proteins PAX 3 Specify Dermomyotome Region of Somites
Masry ( from Neural Tube)

6. Molecular Regulation of
Gut
Development

7. Differentiation of different regions of gut & its derivatives is dependent
upon
Reciprocal interaction ( ) Endoderm of GUT & Surrounding Splanchnic
Mesoderm.
SHH ( Expressed throughout gut
endoderm)
Induce expression
HOX genes in
Mesoderm
Once expressed & Mesoderm specified by
HOX genes
Mesoderm instruct Endoderm to form various regions of
Midgut & Hindgut
Similar Interactions are responsible for Partitioning of
Foregut.

8. Molecular Regulation of
LIVER
Development

9. All Foregut Endoderm has the ability to express liver-specific genes & to
differentiate into Liver tissue
But
This expression is blocked by factors produced from
surrounding tissues including: Ectoderm, non- cardiac
mesoderm & Notochord.
Liver Development occurs
when:
Cardiac Mesoderm FGF4 Block the inhibitory signals in
prospective hepatic Region
This process is partially Cells differentiate into
regulated by HNF 3,4 hepatocytes & Biliary cell
(Hepatocyte Nuclear lineage
Transcription Factors 3 & 4 )

10. Molecular Regulation of
Pancreas
Development

11. Notochord FGF & Suppress SHH ( in
Activin gut endoderm that
form the will
pancreas
Upregulate PDX genes
( Pancreatic & Duodenal
Homeobox genes)
PAX 4,6 Specify
expression endocrine cell
lineage
Cells expressing
Cells expressing PAX 6
PAX 4 & 6
only
α
β Cells δ Cells γ Cells Cells
( glucagon)
(Insulin) (Pancreatic
(Somatostat polypeptide)

12. Molecular Regulation of
Kidney
Development

13. Differentiation of the kidney involves interaction between the epithelium of
Ureteric Bud & the mesenchyme of Metanephric Cap.
FGF 2
BMP
Ureteric Bud 7 Metanephric Cap
RE
T
MET
GDNF
( Glial Derived Neurotrophic Factor )
HGF
( Hepatocyte Growth Factor )
Thus, Signaling Pathway is established between these

14. Block Apoptosis
Stimulate proliferation of
Metanephric Cap
FGF Maintain WT 1
2 production
BMP 7
Ureteric Metanephri
Bud GDN c Cap
F
HGF
Make the metanephric Cap competent to WT
respond to induction by Ureteric Bud 1
Stimulate growth Regulate production
of Ureteric Bud of GDNF & HGF

15. TO BE CONTINUED
ISA …