This connection is involved in the tight modulation of motor strategies computed by a cortico-basal ganglia- thalamo-cortical loop.Indeed, based on the canonical anatomofunctional model of basal ganglia, nigrostriatal dopamine is able to modulate the motor loop by acting on dopaminergic receptors located on striatal GABAergic medium spiny neurons.Dysregulation of the nigrostriatal pathway is causative from Parkinson disease (PD) in humans. Toxic and/or genetic ablation of SNpc neurons produces experimental parkinsonism in mice and primates. The common features of PD and PD animal models are motor impairments (hypotonia, bradykinesia, hypokinesia). RTT pathology, in some aspects, overlaps the motor phenotype observed in PD patients. Several neuropathological studies on postmortem brain samples argued for an SNpc alteration evidenced by neuromelanin hypopigmentation, reduction in the structure area, and even controversial, signs of apoptosis. In parallel, an hypometabolism was underlined by a reduction of several catecholamines (dopamine, noradrenaline, adrenaline) and their principal metabolic by-products. Mouse models of RTT are available and the most studied are constitutively deleted Mecp2 mice developed by Adrian Bird or Katelyn McCormick laboratories.In accordance with the motor spectrum of the RTT phenotype, Mecp2-null mice show motor abnormalities from postnatal day 30 that worsen until death. These models offer a crucial substrate to elucidate the molecular and neuroanatomical correlates of an MeCP2-deficiency.
Rett syndrome (RTT) is a genetic disorder that typically becomes apparent after 6–18 months of age in females. Symptoms include impairments in language, coordination, and repetitive movements. Those affected often have slower growth, difficulty walking, and a smaller head size. Complications of Rett syndrome can include seizures, scoliosis, and sleeping problems. The severity of the condition is variable.Rett syndrome is due to a genetic mutation in the MECP2 gene, on the X chromosome. It almost always occurs as a new mutation, with less than one percent of cases being inherited from a persons parents. It occurs almost exclusively in girls; boys who have a similar mutation typically die shortly after birth. Diagnosis is based on the symptoms and can be confirmed with genetic testing.There is no known cure for Rett syndrome. Treatment is directed at improving symptoms. Anticonvulsants may be used to help with seizures. Special education, physiotherapy, and braces may also be useful. Many of those with the condition live into middle age.The condition affects about 1 in 8,500 females. In 1999, Lebanese-American physician Huda Zoghbi discovered the mutation that causes the condition. Signs and symptoms
Stage I
Stage I, called early-onset, typically begins between 6 and 18 months of age. This stage is often overlooked because symptoms of the disorder may be somewhat vague, and parents and doctors may not notice the subtle slowing of development at first. The infant may begin to show less eye contact and have reduced interest in toys.