Glen, who is 45 years old, begins to notice that his hands shake (tremors) when

Question

Glen, who is 45 years old, begins to notice that his hands shake (tremors) when he is performing everyday tasks such as signing his signature. His family members have noticed that he also has muffled speech and tends to shuffle when he walks. He is diagnosed with Early Onset Parkinson’s disease.

What is Early Onset Parkinson’s disease?

What specific cell type is affected in Parkinson’s disease?

What is dopamine? What effects does dopamine have on the body?

Explain the structure of a synapse and why Glen’s neurologist would prescribe him a dopamine agonist?

Glen has genetic testing performed and it is determined that he does carry an autosomal dominant mutation in the SNCA gene associated with Early Onset Parkinson’s disease. Glen has three children. Would you advise his children to have genetic testing performed to determine if they also carry the disease mutation? Why or why not?

Explanation / Answer

Parkinson's disease is a long term neuro-degenerative disorder, which majorly affects the motor system. People younger than 50 years of age when diagnosed with Parkinson's disease, it is referred to as early onset Parkinson's disease. Parkinson's disease majorly affects the dopaminergic neurons in the substantia niagra or the noradrenaline neurons in the locus coeruleus.

Dopamine is a catecholamine, it is a neurotransmitter, which helps regulate movement and emotional responses. In the central nervous system, dopamine plays a major role in reward-motivated behaviour.

A synapse is a structure that facilitates chemical and electrical signalling between two neurons. Synapses that facilitate chemical signalling consist of voltage gated Ca2+ channels in the pre-synaptic neruon which mediates the conversion of electrical signal to the controlled release of neurotransmitters. This may inhibit or excite the post-synaptic neuron by initiating an electrical response or signalling pathway. In an electrical synapse the pre-synaptic neurons are capable of inducing voltage fluctuations in the post-synaptic cell via special channels called gap junctions.
Since, the lack of motor co-ordination in patients affected by Parkinson's is attributed to lack of dopamine production by dopaminergic cells, treatment with dopamine agonist is usually prescribed (Dopamine agonist is a molecule that activate post-synaptic dopamine receptors).

Glen has been diagnosed with Early onset Parkinson's disease and further genetic studies have suggested the presence of an autosomal dominant mutation in SNCA gene. The SNCA gene provides for a protein alpha-synuclein which is known for its role in maintaining adequate amount of pre-synaptic vesicles and regulating the release of dopamine. Since, Glen has an autosomal dominant mutation in this gene, each of the children have a 50% chance of carrying this mutation. Therefore, genetic testing to determine the presence of this mutation is advisable.

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