Naturally occurring mutations in cardiac Troponin T (cTnT) result in a clinical subset of Familial Hypertrophic Cardiomyopathy. To determine the mechanistic links between thin filament mutations and cardiovascular phenotypes we have generated and characterized several transgenic mouse models carrying cTnT mutations. We address two central questions regarding the previously observed changes in myocellular mechanics and Ca2+ homeostasis: (1) are they characteristic of all of severe cTnT mutations and (2) are they primary (early) or secondary (late) components of the myocellular response? Adult left ventricular myocytes were isolated from two- and six-month old transgenic mice carrying missense mutations at residue 92, flanking the TNT1 N-terminal tail domain. Results from R92L and R92W myocytes showed mutation-specific alterations in contraction and relaxation indices at 2-months with improvements by 6-months. Alterations in Ca2+ kinetics remained consistent with mechanical data in which R92L and R92W exhibited severe diastolic impairments at the early time point that improved with increasing age. Normal regulation of Ca2+ kinetics in the context of altered baseline cTnI phosphorylation suggested a pathogenic mechanism at the myofilament level taking precedence for R92L. Quantitation of Ca2+ handling proteins in R92W mice revealed a synergistic compensatory mechanism involving increased Ser-16 and Thr-17 phosphorylation of PLB contributing to the temporal onset of improved cellular mechanics and Ca2+ homeostasis. Therefore, independent cTnT mutations in the TNT1 domain result in primary mutation-specific effects and differential temporal onset of altered myocellular mechanics, Ca2+ kinetics, and Ca2+ homeostasis; complex mechanisms which may contribute to the clinical variability in cTnT-related FHC mutations.