Browsing by Subject "YBX3"

The group has identified two rare, previously uncharacterized missense variants in the YBX3 gene in a Finnish patient presenting with an unusual form of nemaline myopathy. The patient also inherited two biallelic TPM3 variants, one RYR1 variant from the father and one SRPK3 variant from the mother. TPM3 and RYR1 are known nemaline myopathy causing genes and the other variants identified in the patients, including the YBX3 variants, are thought to have a modifying effect on the phenotype. YBX3 encodes Y-box binding protein 3 (YB-3) and, YB-3 is a member of the Y-box binding (YB) protein family, that in addition to YB-3 consists of YB-1 and YB-2. The YB-proteins have mainly been studied in the context of cancer, with most studies focusing on YB-1. Studies indicate the ability of YB-proteins to compensate for the loss of one homolog suggesting functional redundancy between YB-3 and YB-1, and YB-3 and YB-2. Compared to its homologs, YB-3 is highly expressed in skeletal muscle. The aim of this thesis was to try out a new cell culturing method when investigating the role of YB-3 in the differentiation of myoblasts into myotubes. MSY-3 is the murine orthologue of YB-3. MSY3-knockdown mouse C2C12 myoblast lines were established using GIPZ lentiviral short hairpin constructs and by selection with puromycin. The success of transfection was determined using qPCR. The myoblasts were differentiated for 20 days on a gelatin hydrogel surface to support long-term culture and to provide phenotypes of higher physiological relevance with improved contractile maturity. Myoblasts cultured on coverslips were immunofluorescently stained for MSY-3. HeLa cells were transfected with a construct encoding N-terminally FLAG-tagged human YB-3 in a pcDNA-vector. YB-3-FLAG was purified using anti-FLAG magnetic beads. The eluated immunoprecipitation sample was sent to N-terminal sequencing to obtain information on post-translational modifications, to support further experiments regarding the post-translational cleavage of YB-3. N-terminal sequencing revealed an enrichment of YB-3 and YB-1 in the immunoprecipitation sample but not of YB-2, and previously undescribed post-translational modifications were identified. The MSY3-knockdown myotubes exhibited no spontaneous twitching on the hydrogel, while the control C2C12 myotubes twitched frequently. Misalignment of the MSY3-knockdown myotubes and changes in morphology was also observed in one of the MSY3-knockdown cell lines. This suggests that differentiating myoblasts on gelatin hydrogel is a potential strategy for studying the functions of YB-3 in myoblast differentiation and to elucidate its role in skeletal muscle.