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The large individual variation in meat quality seen both within and between animals is not fully understood. Consequently, our long-term goal is to identify reliable proteins which control or determine bovine meat quality. Using a proteomic approach, bovine skeletal muscle samples were analyzed by two-dimensional gel electrophoresis (2-DE) using an immobilized pH 4-7 gradient in the first dimension and mass spectrometry. We first tested the reproducibility of the method. These experiments showed slightly greater intersample than intrasample variability. In order to evaluate the type of visualized proteins in 2-DE, we initiated the construction of a protein reference map of bovine Semitendinosus muscle. In total, 129 protein spots corresponding to 75 different gene products were identified. Of these proteins, the largest portion is involved in metabolism (25.5%), cell structure (17%), cell defense (16%) and contractile apparatus (14.5%). One quarter of the identified proteins are represented by two or several protein spots and multiple isoforms of troponin T are present. Peptide mass fingerprint results indicate that these isoforms are partly generated by alternative splicing. The data presented here are an important step for further proteome analyses on bovine muscle. This may lead to progress in understanding the mechanisms controlling postmortem muscle metabolism and meat quality.

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Myostatin plays a major role in muscle growth and development and animals with disruption of this gene display marked increases in muscle mass. Little is known about muscle physiological adaptations in relation to this muscle hypertrophy. To provide a more comprehensive view, we analyzed bovine muscles from control, heterozygote and homozygote young Belgian blue bulls for myostatin deletion, which results in a normal level of inactive myostatin. Heterozygote and homozygote animals were characterized by a higher proportion of fast-twitch glycolytic fibers in Semitendinosus muscle. Differential proteomic analysis of this muscle was performed using two-dimensional gel electrophoresis followed by mass spectrometry. Thirteen proteins, corresponding to 28 protein spots, were significantly altered in response to the myostatin deletion. The observed changes in protein expression are consistent with an increased fast muscle phenotype, suggesting that myostatin negatively controls mainly fast-twitch glycolytic fiber number. Finally, we demonstrated that differential mRNA splicing of fast troponin T is altered by the loss of myostatin function. The structure of mutually exclusive exon 16 appears predominantly expressed in muscles from heterozygote and homozygote animals. This suggests a role for exon 16 of fast troponin T in the physiological adaptation of the fast muscle phenotype.

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