LHX6 and Leigh syndrome: Here, using mouse models of Leigh syndrome that lack mitochondrial complex I subunit NDUFS4 in a constitutive or conditional manner, we demonstrated that mitochondrial dysfunction leads to a reduction of GABAergic neurons in the rostral external globus pallidus (GPe) and identified a specific affectation of pallidal Lhx6–expressing inhibitory neurons contributing to altered GPe excitability.