Neurofibromatosis type I (NF1) is a multi-system disease caused by mutations in the NF1 gene. NF1 encodes a RAS-GAP protein, Neurofibromin, which negatively regulates RAS signaling. Besides neuroectodermal malformations and tumours, the skeletal system is often affected in NF1 patients, scoliosis and long bone dysplasias being a main cause of considerable morbidity. Interestingly, a reduction of muscle strength and size has been reported in NF1 patients. However it remained unclear whether the observed muscle weakness was a consequence of the skeletal ramifications developing during puberty and early adulthood or if there was a muscular phenotype before the onset of a bone phenotype.
We recently demonstrated a primary defect of embryonic muscle development in a mouse model for NF1 (Kossler et al. 2011).
This defect resulted in a continuous myopathy in Nf1Prx1 mice displaying dystrophic features such as muscle mass reduction, muscle strength reduction and connective tissue overgrowth.
At the moment, the tissue-specific contribution of Nf1 in connective tissue versus the muscle lineage is unclear. This subject is a matter of current research, where Nf1 is inactivated in a tissue-specific fashion using appropriate Cre driver lines.