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Lecture

Limb embryology I

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Department
Biology
Course
BIOL 2P95
Professor
Dirk De Clercq
Semester
Fall

Description
Outline of Lecture 04 Limb embryology I. Timeline of limbthevelopment th - Starts in 4 week, finished by 8 week - Upper limb initiated 3-4 days before lower limb and stays ahead II. Development of the three limb axes A. Limb initiation - Limb bud is mesenchyme covered by ectoderm - Bones originate from somatic mesoderm, muscles from somitic mesoderm - FGF8 from Intermediate mesoderm initiates AER - Then, FGF8 from AER stimulates growth in progress zone B. Proximal/Distal Axis - Pattern of HOX genes (more distally) controls P/D differentiation - Defects (early teratogen) lead to limb truncations C. Anterior/Posterior Axis - SHH from the mesenchymal ZPA (posterior) controls A/P patterning - Defects lead to ectrodactyly (too few digits) or polydactyly (too many digits) - Webbing of finger and toes removed by apoptosis - Defects (e.g. MSX2, BMP4) lead to syndactyly (fused digital soft tissue) D. Dorsal/Ventral Axis - Not well understo
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