Myocyte enhancer factor-2D expression in ALS lymphomonocytes

Introduction: Myocyte enhancer factor-2 (MEF2) is a family of transcription factors promoting muscle differentiation and development. However, MEF2 is also critical for adult muscle function, regulating both fibre-type specification and sarcomere integrity. MEF2 regulation in mature skeletal muscle is not completely understood, albeit one important factor is represented by neural input, with the involvement of the protein phosphatase calcineurin. Besides muscle specific roles, MEF2 genes are also involved in neuronal differentiation and survival, and display some important functions even in other cell types, such as T-lymphocytes. Amyotrophic lateral sclerosis (ALS) is a fatal disorder characterized by motor neuron degeneration and muscle wasting, mutual interacting phenomena in which the dysregulation of intracellular calcium and calcineurin activity plays a contributory role. Interestingly, the activity of calcineurin is inhibited in lymphocytes obtained from ALS patients, suggesting the possibility of investigating MEF2 role in this accessible peripheral model. In fact, peripheral blood mononuclear cells (PBMC) express MEF2 proteins and, in particular, MEF2D has been recently shown to be regulated and to regulate gene transcription through modulation of the epigenetic machinery in human monocytes and in subsequently differentiated macrophages. Aim: of this preliminary work consisted in assessing a putative dysregulation of MEF2D expression in ALS PBMC. Methods: MEF2D expression was assessed by western blotting in an incident cohort of 10 definite ALS patients with respect to 10 matched healthy controls. Moreover, nuclear compartmentalization of MEF2D was samples in a subgroup of subjects by immunohistochemistry, followed by DAPI staining. Results: MEF2D expression did not show overt differences between ALS patients and controls. Discussion: Albeit exploratory, our results argue against a dysregulation of MEF2-associated functions in blood mononuclear cells obtained from ALS patients. However, we can not discard a selective dysregulation of this transcription factor either in the CNS or in muscles in ALS patients. This might not be the case in other neurodegenerative disorders, such as Parkinson’s disease where altered autophagy, the main catabolic pathway of MEF2D, has been found altered.