Altered dynein axonemal assembly factor 1 expression in C-Boutons in bulbar and spinal cord motor-neurons in sporadic amyotrophic lateral sclerosis

Abstract

Dyneins are major components of microtubules. Dynein assembly is modulated by a heterogeneous group of dynein axonemal assembly factors (DNAAFs). The present study analyzes dynein axonemal assembly factor 1 (DNAAF1) and leucine-rich repeat-containing protein 50 (LRRC50), the corresponding encoded protein, in lower motor neurons in spinal cord of sALS postmortem samples and hSOD1-G93A transgenic mice compared with controls. DNAAF1 mRNA is significantly reduced in the anterior horn in sALS, and LRRC50 immunoreactivity is significantly reduced in C-boutons of the remaining motor neurons of the anterior horn, dorsal nucleus of the vagus nerve, and hypoglossal nuclei at terminal stages of ALS. LRRC50 immunoreactivity has a perinuclear distribution in motor neurons in sALS thus suggesting a disorder of transport. The number of LRRC50-/S1R-immunoreactive structures is also significantly decreased in hSOD1-G93A transgenic mice at the age of 90days (preclinical stages), and the number of motor neurons with LRRC50immunoreactive structures is significantly reduced in animals aged 150days (clinical stages). These observations suggest cholinergic denervation of motor neurons as a pathogenic factor in motor neuron disease. LRRC50 protein levels were not detected in human CSF.