Role of Heterochromatin Protein (HP) 1gamma during the process of myogenesis.

NANCY L. CHARÓ, NATALIA M. GALIGNIANA, SEBASTIAN SUSPERREGUY, JUDITH TONEATTO, GRACIELA PIWIEN PILIPUK.

Conferencia; 3 rd South American Workshop on new trends in advanced fluorescence microscopy techniques International Gregorio Weber Conference; 2011

Role of Heterochromatin Protein (HP) 1 gamma during the process of myogenesis. Abstract HP1γ is a non-histone nuclear protein that interacts with active RNA polymerase II regulating transcription(1). We found that, HP1γ is located in euchromatic and heterochromatic domains in the nucleus of C2C12 myoblasts, Using indirect immunofluorescence (IFI) and confocal microscopy as described (2). Remarkably, HP1γ, a protein so far described present only in the nucleus, is detected predominantly in the cytoplasm of the myotubes formed 4 days after induction of myogenesis. HP1γ partially co-localizes with actin fibers, and a fraction is detected in the sarcolemma. In contrast, HP1α, another member of the HP1 family localizes in the nucleus of myoblasts and myotubes showing no change in its subcellular distribution. Importantly, HP1γ localizes in the sarcomeric Z-disk and sarcolemma in myofibrils isolated from muscle of the limbs of the mouse. Western blot analysis of nuclear and cytoplasmic fractions also shows that HP1γ is present both in the nuclear and the cytoplasmic fractions of myotubes. To investigate the functional importance of HP1γ in the process of myogenesis, HP1γ was knocked–down using specific shRNA, and C2C12 myoblasts with HP1γ stably interfered were generated. C2C12HP1γ-/ - myoblasts are unable to differentiate or give rise to greatly enlarged “sac-like” myotubes, named myosacs, cells containing crowded clusters of nuclei and actin fibers not properly formed. In summary, HP1γ exhibits rapid changes in its subcellular distribution during the process of myogenesis and is an essential protein for the proper muscle development.