The actin containing tropomyosin and troponin decorated thin filaments form one of
the crucial components of the contractile apparatus in muscles. The thin filaments
are organized into densely packed lattices interdigitated with myosin-based thick
filaments. The crossbridge interactions between these myofilaments drive muscle contraction,
and the degree of myofilament overlap is a key factor of contractile force determination.
As such, the optimal length of the thin filaments is critical for efficient activity,
therefore, this parameter is precisely controlled according to the workload of a given
muscle. Thin filament length is thought to be regulated by two major, but only partially
understood mechanisms: it is set by (i) factors that mediate the assembly of filaments
from monomers and catalyze their elongation, and (ii) by factors that specify their
length and uniformity. Mutations affecting these factors can alter the length of thin
filaments, and in human cases, many of them are linked to debilitating diseases such
as nemaline myopathy and dilated cardiomyopathy.
