The cross-striated musculature consists of highly organised structures with the sarcomere as the basic contractile unit. To allow efficient muscle function, exact formation of these structures is essential. The cellular processes, which are necessary to enable precise sarcomere organisation and their regulatory sequence of events, are not completely understood. In order to elucidate such complex processes in detail, all involved factors ought to be known. Aiming at the determination of previously unknown factors, a highly organised screening procedure has been developed to identify novel genes with still uncharacterised function in the striated muscle development. These genes were evolutionary conserved and foreseen to be expressed in the striated musculature, which suggested an important role for muscle function. One interesting candidate among them is the leucine-rich repeat containing protein 39 (LRRC39). This study is aimed to characterise this gene and analyses its impact on muscle functions. The data presented in this dissertation confirmed the expression patterns of LRRC39 in the heart and the skeletal muscle in model organisms. To address potential functions of this gene, loss-experiments in zebrafish were conducted. As result, deformations in the heart structure and skeletal muscle tissue were observed to indicate the importance of Lrrc39 for the muscle development of zebrafish. By electron microscopy, the disturbed sarcomere organisation of the zebrafish skeletal muscle was revealed to firmly confirm the functional role of Lrrc39. To elucidate the mechanisms behind the observed phenotypes upon the reduction of Lrrc39, transcriptomics and proteomics techniques were employed. A careful profiling by mass spectrometry was conducted, which showed drastic changes of essential proteins for the sarcomere assembly. Furthermore, subcellular localisation studies and protein-protein interaction analysis were conducted to identify the a-helical tail region of the well-known structure proteins myosin heavy chain (MHC) as interaction partners of LRRC39. Over the years of researches in the field of muscle development and function revealed the importance of the head domain of MHC proteins in regards to their motor activity for muscle contraction. However, the properties of the a-helical tail region are less well-understood. To address this point, a set of experiments were performed to suggest the possible involvement of LRRC39 to the regulation of MHC proteins through altered phosphorylation patterns of MHC. This suggests a link between the sarcomere assembly and muscle contraction in the context of LRRC39 and MHC proteins. In sum, this study presented a novel protein of the sarcomere with its vital function for the sarcomere organisation.
Verknüpfung zu Publikationen oder weiteren Datensätzen
