Influence of the 5-HTTLPR polymorphism and environmental risk factors in a Brazilian sample of patients with autism spectrum disorders

Graduate Program in Genetics and Molecular Biology, Universidade Federal do Rio Grande do Sul, Brazil.
Brain research (Impact Factor: 2.84). 04/2009; 1267:9-17. DOI: 10.1016/j.brainres.2009.02.072
Source: PubMed


The 5-HTTLPR polymorphism of serotonin transporter gene is widely investigated in association studies in autism spectrum disorders (ASD). The results of such studies, however, remain controversial possibly due to the great genetic heterogeneity related to ASD and the lack of evaluation of the triallelic functional structure of 5-HTTLPR. This study tested for association between the 5-HTTLPR and ASD in a Brazilian sample by case-control and family-based association test (FBAT) methods, considering the biallelic and triallelic structures of this polymorphism. In addition, we performed an exploratory analysis of associations between specific clinical outcomes of ASD patients and 5-HTTLPR as well as several prenatal environmental factors. Genotyping was achieved in 151 ASD patients, 179 unrelated controls and 105 complete trios. There was no evidence of association between the 5-HTTLPR with ASD in both case-control and FBAT tests, but the LaLa 5-HTTLPR genotype was associated with mood instability in patients (P=0.006). The prenatal exposure to potential neuroteratogenic drugs was associated with epilepsy (P<0.001). Our findings suggest that the 5-HTTLPR is not associated with ASD in the Brazilian population, even considering the triallelic structure. Additionally, this study suggested a role of the 5-HTTLPR and environmental factors in the clinical expression of ASD.

1 Follower
8 Reads
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: OBJETIVOS: O presente estudo refere-se a uma revisão sistemática, cujo objetivo foi conduzir uma análise da produção científica de autores brasileiros sobre Transtornos do espectro autista (TEA), no período de 2002 a 2009. MÉTODOS: A busca bibliográfica foi realizada nas bases de dados: PUBMED, SciELO, LILACS e portal CAPES, incluindo diversos descritores, tais como autismo e transtorno invasivo do desenvolvimento. RESULTADOS: Um total de 93 artigos foi identificado, tendo sido publicados, sobretudo por autores da região Sudeste e de universidades públicas. Aproximadamente um terço dos artigos foi publicado em revistas com algum fator de impacto variando entre 0,441 e 3,211; sendo a maioria dos artigos baseada em amostras pequenas. Foram identificadas 140 dissertações e teses; 82,1% eram dissertações de mestrado. O principal tema de pesquisa abordado neste material relacionou-se a programas de intervenção para TEA. CONCLUSÃO: Esta revisão mostra o interesse de pesquisadores brasileiros na temática dos TEA, entretanto, uma parte considerável dessa produção científica se concentra em dissertações/teses e a minoria em artigos científicos publicados em revistas com elevado fator de impacto. Os resultados desta revisão sistemática mostram a necessidade de novos estudos com amostras maiores que levariam a um maior impacto e visibilidade da produção científica brasileira relativa aos TEA.
    Revista da Associação Médica Brasileira 12/2009; 56(5):607-614. DOI:10.1590/S0104-42302010000500026 · 0.93 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This systematic review sought to conduct a general analysis of the Brazilian scientific output on autism spectrum disorders (ASD) published between 2002 and 2009. A literature search was conducted in the scientific databases PubMed, SciELO, and LILACS and in the CAPES portal, using keywords such as "autism" and "pervasive developmental disorders". A total of 93 articles were identified, most of which were authored by researchers from Southeast Brazil and affiliated with public universities. Approximately one-third of all articles were published in journals with an impact factor ranging from 0.441 to 3.211; most were based on small sample sizes. Furthermore, 140 theses and dissertations were identified, 82.1% of which were master's theses. Interventions for ASD were the predominant research topic. Brazilian researchers are clearly interested in the topic of ASD; however, a substantial portion of their scientific output is limited to doctoral dissertations or master's theses. A minority of articles was published in journals with a high impact factor. These findings suggest the need for studies with larger sample sizes, which could produce higher-impact findings and thus increase visibility of the Brazilian scientific output in the field of ASD research.
    Revista da Associação Médica Brasileira 01/2010; 56(5):607-14. · 0.93 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A promoter-linked insertion/deletion polymorphism of the serotonin transporter gene (SLC6A4) has been implicated in autism spectrum disorders (ASDs) in numerous family based association studies. However, the results of these investigations have been inconsistent in that both the long and short alleles have been shown to be over-transmitted to affected offspring. In order to further elucidate the relationship between the 5-HTTLPR variant and autism risk, we undertook a thorough study of parent-of-origin effects, maternal genotype effects, and offspring genotype effects in a sample of affected offspring from the Autism Genetic Resource Exchange (AGRE). Both the overall autism phenotype and measures of autism behaviors from the Autism Diagnostic Interview-Revised [Lord et al. (1994); J Autism Dev Disord 24(5): 659–685] were considered. We found evidence of over-transmission (risk allele short, P = 0.012), maternal effects (risk allele long, P = 0.035), and parent-of-origin effects (risk allele short from mother, P = 0.018) of the 5-HTTLPR variant in the AGRE sample. Population- and gender-specific effects were also explored as associations may be heterogeneous across populations and sexes. Parent-of-origin effects of the variant were associated with maternally inherited copies of the short allele that resulted in more impaired overall level of language (P = 0.04). Our study was conducted to further investigate the 5-HTTLPR risk variants by identifying allelic associations that may be population-specific, phenotype-specific, or conferred by maternal or parent-of-origin effects. In light of conflicting observations from previous studies, these are just a few of the possible explanations that deserve attention.
    American Journal of Medical Genetics Part B Neuropsychiatric Genetics 03/2011; 156(2):139-44. DOI:10.1002/ajmg.b.31146 · 3.42 Impact Factor
Show more