RET-like immunostaining of spinal motoneurons in amyotrophic lateral sclerosis.

The receptor tyrosine kinase RET is part of a functional receptor for glial cell derived neurotrophic factor (GDNF) and neurturin (NTN) which are potent neurotrophic factors for motoneurons. Here, we have studied RET-like immunoreactivity of motoneurons in post-mortem spinal cords of patients with amyotrophic lateral sclerosis (ALS) and in controls. We report that the intensity of RET-like immunostaining of motoneurons in ALS is decreased significantly to 81% of control values. Despite this change, the proportion of all large (>40 micron diameter) motoneurons showing RET-like immunoreactivity in ALS remains high (82-85%) and is not significantly different to controls. The persistence of RET-like immunoreactivity in the majority of large motoneurons in ALS could be important in the design of clinical trials of GDNF and NTN.