Correct option is A
Explanation-
During tetrapod limb development, the digits (fingers/toes) are initially formed connected by interdigital tissue. This tissue must undergo programmed cell death (apoptosis) to separate the digits properly.
The signaling pathway responsible for this:
BMP (Bone Morphogenetic Protein) signaling triggers apoptosis in the interdigital mesenchyme, allowing for the proper separation of digits.
Incorrect options -
Option B – FGF (Fibroblast Growth Factor):
FGFs promote cell proliferation and limb outgrowth, especially from the apical ectodermal ridge (AER). FGF maintains survival of limb cells and prevents apoptosis—opposite of what is needed for digit separation.
Option C – Wnt
Wnt signaling is involved in patterning and axis formation of the limb. It is important for dorsal-ventral patterning, but not directly responsible for apoptosis in interdigital tissue.
Option D – Shh (Sonic Hedgehog)
Shh is critical for anterior-posterior patterning of the limb (e.g., thumb to little finger). It indirectly influences digit identity and number, but not directly linked to apoptosis of interdigital cells.
So, the correct answer is option A - BMP
