Final answer:
Rho protein family members do not affect the organization of actin in the formation of cilia (Option E).
Step-by-step explanation:
The Rho protein family members do not affect actin organization in the formation of cilia. While Rho proteins are crucial for actin dynamics in forming lamellipodia, filopodia, and actin stress fibers, and are involved in the formation of ruffles on the cell surface, they do not play a direct role in the formation of cilia. Cilia are primarily composed of microtubules, which are made of alpha- and beta-tubulin protein monomers, and their assembly and maintenance are regulated by other proteins, not the Rho family.
Actin organization plays a significant role in cell motility and shape, involved in the formation of various structures such as stress fibers, which are important for the exertion of forces on the substrate. Stress fibers consist of actin filaments, myosin II, and associated proteins and contribute to the tension and contractile forces necessary for cell movement and adhesion.
It is intriguing to consider the evolutionary relationship between non-muscle actin stress fibers and muscle sarcomeres. Although non-muscle cells do not have the highly organized sarcomere structure, their actin and myosin proteins interact to create contractile forces that resemble the basic function of muscle sarcomeres, suggesting an evolutionary link.
Different isoforms of actin, such as beta-actin and gamma-actin, may provide subtle functional advantages for different cells. However, while some actin isoforms are essential for survival, as indicated by the lethality of loss of the beta-actin gene in mice, others are not as critical, evidenced by some humans living with mutated actin genes without lethal consequences.
Thus, the correct option is E.