Expression of the avian gene cNOC2 encoding nucleolar complex associated protein 2 during embryonic development.

Genetic information that directs a cell during different phases of embryogenesis is locked up in the genome. Therein is contained the road map for growth, proliferation, differentiation and morphogenesis. The cellular transportation machinery plays a major role to ensure that all the components for transcription and translation are available at the right place at the right time. Nucleolar complex associated protein2 (NOC2) has a highly conserved UPF0120 domain, and is an element involved in ribosome transportation from the nucleoplasm to the cytoplasm. However, its gene expression pattern is still unknown. We chose the developing chick embryo to investigate the possible involvement of avian NOC2 (cNOC2) in developmental processes, particularly neurogenesis and myogenesis. For this purpose, we constructed a fragment of chicken cNOC2, which contains the UPF0120 domain coding sequence, into pDrive vector, and performed in situ hybridization on chicken embryos of different stages with this gene probe. A dynamic expression pattern of cNOC2 transcripts can be seen beginning as early as from stage HH7 until stage HH32. Using in situ hybridization we could detect that cNOC2 transcripts were expressed ubiquitously, but prominent expression could be found in the neural tissue, the somites and in the developing limbs. Comparison of cNOC2 gene expression with the proliferation marker gene cPCNA, muscle specific marker genes cMyf5 and cMyoD in single or double in situ hybridisation show that cNOC2 is expressed in the myotome, similar to cMyf5 and cMyoD, but not like cPCNA, which is hardly detectable in the myotome. Our results suggest that cNOC2 is involved in the development of neural tissue, somites and limbs.

Myogenin (Myf4) upregulation in trans-differentiating fibroblasts from a congenital myopathy with arrest of myogenesis and defects of myotube formation.

Congenital myopathies often have an unclear aetiology. Here, we studied a novel case of a severe congenital myopathy with a failure of myotube formation. Polymerase chain reaction-based analysis was performed to characterize the expression patterns of the Desmin, p21, p57, and muscle regulatory factors (MRFs) MyoD, Myf4, Myf5 and Myf6 in differentiating skeletal muscle cells (SkMCs), normal human fibroblasts and patient-derived fibroblasts during trans-differentiation. The temporal and spatial pattern of MRFs was further characterized by immunocyto- and immunohistochemical stainings. In differentiating SkMCs, each MRF showed a characteristic expression pattern. Normal trans-differentiating fibroblasts formed myotubes and expressed all of the MRFs, which were detected. Interestingly, the patient's fibroblasts also showed some fusion events during trans-differentiation with a comparable expression profile for the MRFs, particularly, with increased expression of Myf4 and p21. Immunohistochemical analysis of normal and patient-derived skeletal musculature revealed that Myf4, which is downregulated during normal fetal development, was still present in patient-derived skeletal head muscle, which was also positive for Desmin and sarcomeric actin. The abnormal upregulation of Myf4 and p21 in the patient who suffered from a severe congenital myopathy suggests that the regulation of Myf4 and p21 gene expression during myogenesis might be of interest for further studies.