b2815 Tissue Engineering and Nanotheranostics “9.61x6.69”214 Tissue Engineering and Nanotheranostics
turn begins with the development of microtubules on the centriole
sides at the base, or proximal, ends of the centriole. This occurs dur
ing the “Sphase” of the mitotic cycle. See Fig. 8.
While details of the development process are still being discov
ered, in general, it occurs as described in the following paragraphs:
The centriole is immersed in a sea of proteins, probably num
bering more than 110, known as the centrosome. Tubulins form an
abundance of these proteins. The centrosome aside from the cen
trioles, is known as the microtubule organizing center (MTOC).
During the Sphase of the mitotic cycle, a protein known as
“asterless”, or “Asl”, deposits itself on the outside of a C microtubule,
near the base of the proximal end of each centriole. The Asl in turn
then recruits another protein: Plk4 (proteinlike kinase four) which
forms an extended patch over the Asl deposit. Plk4 plays a prominent
role in the entire centriole development process both as an enabler
and as a regulator.
Fig. 8. The mitotic cycle.