Screening for Polymorphisms in the Aanat Gene and Their Association With Diurnal Preference

*Corresponding author e-mail: brunadvk@yahoo.com.br Introduction: Arylalkylamina N-Acetyltransferase (AANAT) is the rate-limiting enzyme of melatonin synthesis pathway. Polymorphisms in the AANAT gene are likely to alter melatonin rate of synthesis and causes shifting in circadian rhythm of individuals. Purpose: To perform a screening of the Aanat gene to identify which polymorphisms are present in Brazilian sample and seek associations with diurnal preference. Methods: Individuals with extreme diurnal preference were selected according Horne-Ostberg questionnaire scores. DNAs are amplified by Polymerase Chain Reaction and analyzed in Denaturing High Performance Liquid Chromatography (DHPLC). Segregated association tests for each SNP or haplotypes blocks were performed Results: A total of six polymorphisms were found. Two still not reported in data banks or in the literature. All polymorphisms in the Aanat gene found in this sample, except by one, presented very low frequencies, which maximum frequency 6%. The only one which is found more often, the C-263G is localized in the promoter region exactly at a putative biding site for the transcription factor SP1. This polymorphism is a Single Nucleotide Polymorphism (SNP), a C to G change in the position -263. A -263G allele is more present in evening preference volunteers. Conclusions: We observed that, except by one SNP in the promoter region, the frequency of variation of these SNPs in the AANAT gene are extremely low which indicate that it is very much conserved. There is a borderline association between SNP C-263G in the promoter region and extreme diurnal preference. This polymorphism is in the transcription factor SP1 biding site indicates that it can modulate the rate of transcription of AANAT gene with consequences in the temporality of the melatonin secretion curve. Publication History Article published online: 16 June 2026 © 2009. Brazilian Sleep Academy. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/) Thieme Revinter Publicações Ltda. Rua Rego Freitas, 175, loja 1, República, São Paulo, SP, CEP 01220-010, Brazil