RTN1 and Parkinson disease: Furthermore, the same perturbation of expression, being the downregulation of HDAC4-regulated genes TSPAN7, ATP1A3, RTN1, and PRKCB and the upregulation of ER stress genes ERO1A, PDIA6, and FKBP9, was seen in the same two idiopathic PD cases exhibiting HDAC4 mislocalization.