Embryonic Genes B&B Flashcards
what are the 2 key roles in embryonic development of SHH gene?
- CNS development - required for establishing midline of forebrain (L/R sides)
- limb patterning - required for development of anterior-posterior plane
what is the effect of SHH mutation on CNS development?
SHH required for establishing midline of forebrain (L/R sides)
mutation causes holoprosencephaly (“whole” forebrain, no midline) —> single-lobed brain, facial abnormalities (cleft lip/palate, cyclopia)
What is the key role of fibroblast growth factor in embryonic development?
FGF transcription factor is necessary for proximal to distal limb growth (patterning)
expressed in the apical ectodermal ridge, which communicates with underlying mesoderm to induce limb growth
______ is the key transcription factor expressed in the apical ectodermal ridge to cause embryonic limb growth in the proximal to distal direction
FGF (fibroblast growth factor)
expressed in the apical ectodermal ridge, which communicates with underlying mesoderm to induce limb growth
What would be the effect of a LOF mutation in fibroblast growth factor on embryological development?
FGF transcription factor is necessary for proximal to distal limb growth (patterning)
expressed in the apical ectodermal ridge (AER), which communicates with underlying mesoderm to induce limb growth
mutation = lack of limb growth
what is the role of Wnt-7a in embryological development? how does it exert this function?
Wnt-7a is required for dorsal patterning
expressed in apical ectodermal ridge (AER), where it activates LMX-1 gene in underlying mesoderm
signaling is repressed on ventral side
_____ is a key transcription factor expressed in the apical ectodermal ridge, where it activates LMX-1 gene in underlying mesoderm to induce dorsal development
Wnt-7a
repressed on the ventral side
what is the consequence of a LOF Wnt-7a mutation on embryological development?
Wnt-7a is required for dorsal patterning - expressed in apical ectodermal ridge (AER), where it activates LMX-1 gene in underlying mesoderm
signaling is repressed on ventral side by Engrailed1
mutation = lack of dorsal side patterning (ex, mouse paw with sole on both sides)
embryological patterning in the anterior-posterior plane depends on the zone of polarizing activity which influences the apical ectodermal ridge via _____ signaling
SHH signaling - required for anterior-posterior patterning
what do the homeobox genes regulate in embryonic development?
HOX genes code for transcription factors that regulate AP axis development (anterior-posterior)
homeosis = transforming one structure into another; homeotic genes lead to formation of body segments
all homeotic genes contain a shared homeobox base sequence
what results from a mutation in HOX genes?
HOX genes code for transcription factors that regulate AP axis development (anterior-posterior)
mutation —> abnormal limb formations (polydactyly, syndactyly, etc)
what is the key role of each of the following in embryological development?
a. SHH
b. FGF
c. Wnt-7a
d. Hox
a. SHH: brain hemispheres + limb AP axis
b. FGF: limb proximal-distal axis
c. Wnt-7a: limb dorsal-ventral axis (“dorsalization”)
d. Hox: limb AP axis
a mutation in which key embryological transcription factor will cause each of the following developmental defects?
a. holoprosencephaly
b. loss of limb development
c. lack of dorsalization (soles on both sides of a paw)
d. polydactyly
a. SHH: brain hemispheres + limb AP axis
b. FGF: limb proximal-distal axis
c. Wnt-7a: limb dorsal-ventral axis (“dorsalization”)
d. Hox: limb AP axis
what 2 key embryological genes are necessary for proper limb AP axis (anterior-posterior) development?
- SHH genes (Sonic hedgehog)
- Hox genes (homeotic)
