Tryptophan 2,3-Dioxygenase--Candidate Gene For Disorders

参与5-羟色胺代谢的酶的遗传变异可能会导致一系列神经精神疾病，从进食障碍、强迫症、酗酒到自闭症。仅从人类饮食中获得的色氨酸，通过色氨酸羟基酶转化为5-羟色胺，或通过色氨酸2，3-双加氧酶(TDO2)转化为犬尿氨酸。这两种酶在各自的途径中都是限速的。 这项研究的目的是筛选TD02基因的多态性，评估功能，并寻找疾病关联。最初的研究方法是单链构象多态性(SSCP)分析。大多数编码区(12个外显子中的11个)、内含子序列和启动子区域被成功地扩增并在酗酒、冲动、厌食或暴食症、强迫症、自闭症、严重抑郁和自杀的人群中进行了筛选，并参加了色氨酸耗竭研究。未发现内含子5、6或11的多态和外显子7的变异(A到C，749ASN到His)的关联。在启动子区域的SSCP筛选中，没有发现两个TATA盒区域的多态。在推测的启动子糖皮质激素反应元件中已经检测到两个变体。启动子、编码区和内含子已通过变性高效液相色谱(DHPLC)进行筛选，以寻找进一步的多态性并确认已发现的多态性。5？已建立了跨越该基因编码区的14个单核苷酸多态(SNPs)以及启动子区域的2个SNPs和1个GTT插入的核酸外切酶分析方法。这17个基因多态目前已经在4个人群中进行了基因分型：673名芬兰高加索人，220名美国高加索人，337名平原美洲印第安人和280名非裔美国人。单倍型区块已经确定，基于单倍型的酒精中毒关联研究正在进行中。

Genetic variations in the enzymes involved in serotonin metabolism may contribute to a wide range of neuropsychiatric diseases, from eating disorders, obsessive-compulsive disorder and alcoholism to autism. Tryptophan, obtained only from the diet in humans, is converted to serotonin by tryptophan hydroxylase, or to kynurenine by tryptophan 2,3-dioxygenase (TDO2). Both enzymes are rate limiting in their respective pathways. The purpose of this study is to screen the TD02 gene for polymorphisms, assess functionality, and search for disease associations. The original research method was single-strand conformational polymorphism (SSCP) analysis. Most of the coding region (11 of the 12 exons), the intronic sequence and the promoter region was successfully amplified and screened across populations with alcoholism, impulsivity, anorexia or bulimia nervosa, obsessive-compulsive disorder, autism, major depression and suicidality, and subjects enrolled in a tryptophan depletion study. No associations were found for polymorphisms in introns 5, 6 or 11 nor for a variant in exon 7 (A to C, 749 Asn to His). In the SSCP screening of the promoter region no polymorphisms were found in the regions of two TATA boxes. Two variants have been detected in the putative promoter glucocorticoid response elements. The promoter, coding region and introns have been screened by Denaturing High Performance Liquid Chromatography (DHPLC) to look for further polymorphisms and confirm those already found. 5? exonuclease assays have been developed for 14 single nucleotide polymorphisms (SNPs) spanning the coding region of the gene and for 2 SNPs and one GTT insertion in the promoter region. These 17 polymorphisms have now been genotyped in 4 populations; 673 Finnish Caucasians, 220 US Caucasians, 337 Plains American Indians and 280 African Americans. Haplotype blocks have been identified and haplotype-based association studies for alcoholism are underway.