LRRK2 and Parkinson disease: For example, overexpression of human SNCA gene in mice does not alter thermal thresholds,81 while mice transgenic for leucine-rich repeat kinase 2 (LRRK2;R1441G PARK8 mutants) display no reduction in mechanical or chemical thresholds.82,83 These findings argue against any face validity of these particular transgenic models and suggest that neither of these gene abnormalities is linked to development of pain in PD.