[
1984]
Current knowledge concerning the protein components of muscle is based largely on biochemical analysis of myofibrillar preparations. Such in vitro studies are limited because direct evidence for the in vivo function of isolated proteins is difficult to obtain. In vitro techniques, futhermore, are restricted often to the study of abundant proteins. Very little is known about minor sarcomeric components or how the sarcomere is assembled overall. Certainly, the assembly and function of a structure as complex as the sarcomere require many more than the dozen or so proteins commonly studied. Genetic techniques provide an alternative approach to the study of muscle. Mutations that cause muscle disfunction define genes required to construct a normal muscle. cell. The nature of mutant defects provides insights into the functions of the wild-type gene products. Genetic analysis is not restricted to the study of abundant proteins. The genes for even low-abundance proteins are subject to mutation, and if a gene product is required for muscle assembly or function, such mutants will be muscle-defective. Macromolecular complexes provide special opportunities for genetic intervention, because gene products that directly interact in the structure can often be identified. Mutational defects that affect one member of an interacting pair of proteins can be compensated by mutations affecting its interacting partner. Not all genes, hwoever, are directly accessible to genetic analysis. For example, genes whose products are essential for cell or organism viability and genes having more than one functional copy present special problems.....