how frequently does the letter "l" appear in:
growth factor of the tgf-beta superfamily that plays essential roles in many developmental processes including cartilage and bone formation. plays also an important role in the regulation of iron metabolism by acting as a ligand for hemojuvelin/hjv. initiates the canonical bmp signaling cascade by associating with type i receptor acvr1 and type ii receptor acvr2b. in turn, acvr1 propagates signal by phosphorylating smad1/5/8 that travel to the nucleus and act as activators and repressors of transcription of target. can also signal through non-canonical pathway such as taz-hippo signaling cascade to modulate vegf signaling by regulating vegfr2 expression.
tissue specificity expressed in the lung. low levels seen in the kidney.
user
I found thirty-two "l"s in the provided passage.
assistant