SLC6A4 Repeat and Single-Nucleotide Polymorphisms Are Associated With Depression and Rest Tremor in Parkinson's Disease: An Exploratory Study

Conclusion: The current study reveals two PD symptoms associated with SLC6A4 polymorphisms, and provides new insight into how serotonergic system genetically participates in the symptomatic progression of PD. Further study is warranted in additional populations. Introduction Parkinson's disease (PD) is a common neurodegenerative disease with bradykinesia, rigidity, and rest tremor as its cardinal motor manifestations (1). Non-motor symptoms such as depression, cognitive problems, sleep disorders, and gastrointestinal disturbance have a great impact on life quality in PD patients (2, 3), and are usually present in PD before the onset of motor signs (4). A hallmark of PD pathology is degeneration of dopaminergic neurons in the substantia nigra, leading to reduction of dopamine output to the striatum (5). In addition to dopamine, dysregulation of serotonin, which is a neurotransmitter linked with cognition and emotional states, also plays an important role in PD progression (6). The serotonin level is mainly regulated by the serotonin reuptake transporter (5-HTT) encoded by the gene SLC6A4. There are two polymorphisms in its promoter region, including a repeat polymorphism 5-HTTLPR and a single nucleotide polymorphism rs25531 located within 5-HTTLPR. 5-HTTLPR consists of 14-repeat and 16-repeat variants, as well as several rare variants such as 15-, 19-, 20-, or 22- repeat. The 14-repeat and 16-repeat elements are denoted as the long (L) allele and the short (S)...
Source: Frontiers in Neurology - Category: Neurology Source Type: research