Embryogenesis Genes - Embryology

Gene

Function

Sonic hedgehog (SHH)

Involved in patterning along anterior-posterior axis

Embryonic development of limbs, somites, gut formation and establishment of midline CNS
- produced in zone of polarizing activity (ZPA: collection of mesoderm cells at posterior border of apical ectodermal ridge on developing limb)
- secreted by notochord to control neural tube patterning

Mutation in SHH pathway and/or haploinsufficiency can lead to holoprosencephaly, a developmental defect characterized by a failure of the early forebrain vesicle to divide into distinct halves

WNT-7

 
                        Necessary for proper organization alongdorsal-ventral axis
                    
                        Development of midbrain and limb patterning
                    
                        produced at dorsal apical ectodermal ridge (AER: thickened ectoderm at distal end of each developing limb)

FGF

 
                        Stimulates mitosis and differentiation of underlying mesoderm
                    
                        provides for lengthening of limbsby maintainingprogress zone(progress zone: proliferating mesenchymal cells proximal to AER)
                    
                        produced atapical ectodermal ridge
                    
                        Controls anterior-posterior neural tube patterning
                    
                        Plays a role in somite segmentation, angiogenesis, and axon growth

Homeobox(HOX)

 
                        Involved in segmental organization in cranio-caudal direction
                    
                        production depends on combinatorial expression of SHH, WNT-7, and FGF 
                    
                        controls rib development, cardiac patterning, and radioulnar differentiation of the upper extremity

Action	Numeric Key	Letter Key	Function Key
Show Bullets		S	Enter (frontside only)
20%	1	N
40%	2	H
60%	3	F	Enter (backside only)
80%	4	E
100%	5	M
Toss	0	T