Morphological and functional alterations in the substantia nigra pars compacta of the Mecp2-null mouse

N Panayotis, M Pratte, A Borges-Correia, A Ghata… - Neurobiology of …, 2011 - Elsevier
N Panayotis, M Pratte, A Borges-Correia, A Ghata, L Villard, JC Roux
Neurobiology of disease, 2011Elsevier
Rett syndrome (RTT) is a severe neurological disorder caused by mutations in the MECP2
gene, in which older patients often develop parkinsonian features. Although Mecp2 has
been shown to modulate the catecholaminergic metabolism of the RTT mouse model, little is
known about the central dopaminergic neurons. Here we found that the progression of the
motor dysfunction in the Mecp2-deficient mouse becomes more severe between 4 and
9weeks of age. We then studied the phenotype of the dopaminergic neurons of the …
Rett syndrome (RTT) is a severe neurological disorder caused by mutations in the MECP2 gene, in which older patients often develop parkinsonian features. Although Mecp2 has been shown to modulate the catecholaminergic metabolism of the RTT mouse model, little is known about the central dopaminergic neurons. Here we found that the progression of the motor dysfunction in the Mecp2-deficient mouse becomes more severe between 4 and 9weeks of age. We then studied the phenotype of the dopaminergic neurons of the substantia nigra pars compacta (SNpc). We found a major reduction in the number of tyrosine hydroxylase (Th)-expressing neurons, as well as a reduction in their soma size, by 5weeks of age. We showed that this deficit is not due to apoptosis and that the remaining neurons express a mature dopaminergic phenotype. A reduction in the Th-staining intensity was also found in the caudate–putamen (CPu), the main dopaminergic target for SNpc. We found that the amount of activated-Th (pSer40-Th) is slightly reduced at 5weeks of age in the Mecp2-deficient mouse, but that this amount is affected more importantly by 9weeks of age. Neurochemical measurements revealed a significant reduction of dopamine content at 5 and 9weeks of age in the CPu whereas SNpc contents were preserved. Finally, we found that chronic L-Dopa treatment improved the motor deficits previously identified. Altogether, our findings demonstrate that Mecp2-deficiency induces nigrostriatal deficits, and they offer a new perspective to better understand the origin of motor dysfunction in RTT.
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