The actin cytoskeleton is crucial for many functions including cell motility, cytokinesis, and vesicle formation. Tropomyosins (Tm) are actin associated proteins which regulate the functional capacity of actin filaments. At least 40 Tm isoforms are produced from four genes (αTm, βTm, γTm, and δTm), with differential expression and localisation in tissues, cells and subcellular compartments. As some Tms are potential targets for anti-cancer therapies, one aim of this project was to measure how eliminating one subset of isoforms affected expression of other Tms in brain. Using a knockout (KO) mouse model lacking the γTm-gene 9d exon, regional distributions of Tms were investigated by Western blotting in wild type and 9d KO adult mouse Whole Brain, Cerebellum, Amygdala, Hypothalamus, Cerebral Cortex, Hippocampus, and Olfactory Bulb. KO of γTm-gene isoforms Tm5NM1 and Tm5NM2 was shown to induce upregulation of other γTm-gene products. Regional expression patterns of other Tms, including the δTm-gene product Tm4, were established in brain. A previously unidentified product immunoreactive with the Tm4 antibody was observed and characterised as having similar biochemical properties to Tm4; 2D gel electrophoresis indicated Tm4 and this associated product were both post translationally modified. To investigate Tm4 function in neural cells, rat neuroblastoma cells (B35) were stably transfected with a mammalian vector containing the Tm4 gene. These cells were compared with previously developed B35 clones overexpressing the neuronal isoforms: TmBr1, TmBr2, or TmBr3. Using light microscopy it was shown that while overexpression of these isoforms each induced neurite outgrowth, each had highly specific effects on neurite morphology. Analyses of TmBr2 and Tm4 overexpressing B35 cells by fluorescence activated cell sorting indicated these isoforms could significantly affect cell cycle exit. Quantitative proteomics approaches (LC-MS/MS and iTRAQ) identified proteins affected by overexpression of Tm5NM1, TmBr2, TmBr3, or Tm4 isoforms in B35 cells. These data show for the first time that Tms differentially induce changes in the levels of many other proteins, and Tm expression results in isoform specific profiles of other actin binding proteins (ABP). The actin cytoskeleton underpins neurite outgrowth and branching, and these Tms have been identified as regulators of these events and ABP expression.