Innocenti Federico, Liu Wanqing, Fackenthal Donna, Ramírez Jacqueline, Chen Peixian, Ye Xin, Wu Xiaolin, Zhang Wei, Mirkov Snezana, Das Soma, Cook Edwin, Ratain Mark J
Department of Medicine, The University of Chicago, Chicago, IL 60637, USA.
Pharmacogenet Genomics. 2008 Aug;18(8):683-97. doi: 10.1097/FPC.0b013e3283037fe4.
UDP-glucuronosyltransferase 2B7 (UGT2B7) plays a central role in the liver-mediated biotransformation of endogenous and exogenous compounds. The genetic basis of interindividual variability in UGT2B7 function is unknown. This study aimed to discover novel gene variants of functional significance.
Caucasian human livers (n=54) were used. UGT2B7 was resequenced in 12 samples [(six highest and six lowest for the formation of morphine-3-glucuronide (M3G)]. Haplotype-tagging single nucleotide polymorphisms were genotyped in the entire sample set. Samples were phenotyped for mRNA expression.
10 haplotype-tagging single nucleotide polymorphisms were identified and their haplotypes were inferred. Haplotype 4 (-45597G; -6682_-6683A; 372A; IVS1+9_IVS1+10A; IVS1+829T; IVS1+985G; IVS1+999C; IVS1+1250G; 801T; IVS4+185C) (frequency of 0.12) was associated with an increase in enzyme activity and gene expression. The 1/4 and 4/6 diplotypes had higher M3G formation compared with 1/1 (P<0.05) and 2/3 (P<0.01) diplotypes. Diplotypes containing haplotype 4 resulted in a significant 45% average increase in the formation of M3G compared with diplotypes without haplotype 4 (P=0.002). There was also an association between haplotype 4 and increased mRNA expression. IVS1+985A>G, 735A>G, and 1062C>T are the putative functional variants of haplotype 4. We also identified two mRNA splicing variants (UGT2B7_v2 and UGT2B7_v3) splicing out exon 1, 4, 5, and 6 but sharing exons 2 and 3 with the involvement of additional 5' exons. UGT2B7_v2 was detected in all livers tested, but UGT2B7_v3 was present at much lower levels compared with UGT2B7_v2. The UGT2B7 reference sequence mRNA is now named UGT2B7_v1.
UGT2B7 haplotype 4 is functional and its effects on the biotransformation of UGT2B7 substrates should be tested in controlled clinical trials. Biochemical studies should investigate the functional role of the newly discovered mRNA splicing variants.
尿苷二磷酸葡萄糖醛酸基转移酶2B7（UGT2B7）在肝脏介导的内源性和外源性化合物生物转化中起核心作用。UGT2B7功能个体间差异的遗传基础尚不清楚。本研究旨在发现具有功能意义的新基因变异。
使用白种人的肝脏（n = 54）。对12个样本（吗啡-3-葡萄糖醛酸苷（M3G）形成量最高的6个和最低的6个）中的UGT2B7进行重测序。在整个样本集中对单倍型标签单核苷酸多态性进行基因分型。对样本进行mRNA表达的表型分析。
鉴定出10个单倍型标签单核苷酸多态性，并推断出它们的单倍型。单倍型4（-45597G；-6682_-6683A；372A；IVS1 + 9_IVS1 + 10A；IVS1 + 829T；IVS1 + 985G；IVS1 + 999C；IVS1 + 1250G；801T；IVS4 + 185C）（频率为0.12）与酶活性和基因表达增加相关。与1/1（P < 0.05）和2/3（P < 0.01）双倍型相比，1/4和4/6双倍型的M3G形成量更高。与不含单倍型4的双倍型相比，含有单倍型4的双倍型导致M3G形成平均显著增加45%（P = 0.002）。单倍型4与mRNA表达增加之间也存在关联。IVS1 + 985A>G、735A>G和1062C>T是单倍型4的推定功能变异。我们还鉴定出两个mRNA剪接变异体（UGT2B7_v2和UGT2B7_v3），它们剪接掉外显子1、4、5和6，但与额外的5'外显子一起共享外显子2和3。在所有测试的肝脏中都检测到了UGT2B7_v2，但与UGT2B7_v2相比，UGT2B7_v3的水平要低得多。UGT2B7参考序列mRNA现在命名为UGT2B7_v1。
UGT2B7单倍型4具有功能，其对UGT2B7底物生物转化的影响应在对照临床试验中进行测试。生化研究应调查新发现的mRNA剪接变异体的功能作用。
