Originally isolated from human erythrocytes, the tropomodulin (TMOD) family of proteins cap the pointed end of actin filaments (1,2). A component of the membrane skeleton, TMOD binds to the amino terminus of tropomyosin, which coats the surface of actin, and thus blocks the elongation and depolymerization of actin filaments (3,4). Four TMOD isoforms, TMOD1 - TMOD4, have been characterized in humans (2). TMOD expression is isoform-specific; TMOD3 is expressed ubiquitously, whereas TMOD2 and TMOD4 are expressed in neuronal tissue and muscle, respectively (5). TMOD4, which has a similar organization to TMOD2, is intergenically spliced by the putative transformation suppressor gene product YL-1 (1). The human TMOD4 gene maps to the telomeric end of chromosome 1q12, and encodes a 351 amino acid protein (1,5). The expression and chromosomal location of the TMOD4 gene make it a candidate for limb girdle musclular dystrophy 1B (5).