Exam 19: Development of the Limbs

Nail-patella syndrome is caused by mutations in which gene?

Aristaless-like 4 (Alx4) is a homeobox gene involved in the establishment of the limb pattern. What is the phenotype of the Alx4 mouse mutant (Strong's Luxoid)?

Which region of the developing limb specifies the cranial-caudal axis of the developing limb bud?

Dispatched 1 is essential for diffusion of Shh.In the Dispatched mouse mutant,which digit does not develop?

Shh signaling is essential for normal patterning of the digits.Fate labeling studies have shown that the digits are patterned by a combination of the dose,diffusion,and length of exposure to Shh signaling.Which digit is dependent solely on diffusion of Shh for its development?

The term arachnodactyly specifically refers to which defect?

Mutations in the transcription factor p63 (also known as TP73L) in humans can affect the development of the limbs.What is the phenotype of the limbs when this gene is mutated?

The AER,the thickened ectoderm at the distal tip of the limb bud,controls limb outgrowth.Genetic inactivation experiments in mice and manipulation studies in chicks have identified the key factors expressed in the AER that control outgrowth once the limb bud has formed.What family of growth factors in the AER promotes outgrowth?

Researchers have shown that the HoxA and D complex of transcription factors,which are expressed in nested domains within the limb bud,are essential for outgrowth and normal patterning of the limb bud.This is clearly shown by the genetic inactivation of Hoxa11 and Hoxd11.In the forelimb,which structure(s) is/are affected?

Which gene is mutated in hand-foot-genital syndrome?

Which signaling factor is essential for patterning of the limb across the cranial-caudal axis?

What term describes the typical limb phenotype of children who have been exposed to thalidomide during prenatal development?

Shh signaling is essential for normal patterning of the digits.When Shh signaling is genetically inactivated in mice,which digit forms?

When Lmx1b is genetically inactivated in mice,how do the LMCl and LMCm motor neurons migrate?

Gli3 is essential for normal limb development.In mice,mutation of Gli3 results in which limb defect?

Which growth factor is expressed by the dorsal limb ectoderm and is essential for patterning the dorsal-ventral axis?