5-HTTLPR polymorphism: analysis in South African autistic individuals

Area of Science:

• Genetics
• Neuroscience
• Psychiatry

Background:

• The serotonin transporter promoter length polymorphism (5-HTTLPR) is associated with autism spectrum disorder (ASD) and influences response to SSRIs.
• Individual responses to SSRIs vary due to 5-HTTLPR S or L alleles, impacting autism symptom treatment.
• Previous studies show diverse 5-HTTLPR allele frequencies across different autistic populations globally.

Purpose of the Study:

• To compare 5-HTTLPR allele and genotype frequencies in South African autistic populations (African, mixed, Caucasian) against control groups.
• To investigate the association between 5-HTTLPR genotypes and autism risk across different South African ethnic groups.
• To compare South African autistic population allele frequencies with international cohorts.

Main Methods:

• Genotyping of 5-HTTLPR alleles and genotypes in South African autistic individuals and ethnic-matched controls.
• Statistical analysis to determine the association between 5-HTTLPR genotypes and autism.
• Comparative analysis of allele frequencies with global autism population studies.

Main Results:

• The S/S genotype showed a highly significant association with autism across all South African ethnic groups studied.
• In the South African African population, the S/S genotype was found in 33% of autistic individuals but none of the controls.
• Increased odds of autism were observed for the S/S genotype compared to L/L in mixed (10.15-fold) and Caucasian (2.74-fold) South African groups.
• Significant differences in allele frequencies were found between South African autistic populations and Japanese, Korean, and Indian groups, but not French, German, Israeli, Portuguese, or American groups.

Conclusions:

• This study is the first in South Africa to demonstrate significant differences in 5-HTTLPR allele and genotype frequencies in autistic individuals from diverse ethnic backgrounds.
• The S/S genotype is a significant risk factor for autism in South African populations.
• Findings suggest a potential role for 5-HTTLPR in autism etiology and highlight the need for further research into allele transmission within South African families affected by autism.