Hackel Christine, Oliveira Luiz Eduardo Chimello, Ferraz Lucio Fabio Caldas, Tonini Maria Manuela Oliveira, Silva Daniela Nunes, Toralles Maria Betania, Stuchi-Perez Eliana Gabas, Guerra-Junior Gil
Centro de Biologia Molecular e Engenharia Genetica, Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brazil.
J Mol Med (Berl). 2005 Jul;83(7):569-76. doi: 10.1007/s00109-005-0651-7. Epub 2005 Mar 16.
Mutations of the steroid 5alpha-reductase type 2 (SRD5A2) gene in 46,XY subjects cause masculinization defects of varying degrees, due to reduced or impaired enzymatic activity. In this study, sequence abnormalities of the SRD5A2 gene were assessed by polymerase chain reaction with specific primers and automated sequencing analysis in DNA samples from 20 patients with suspected steroid 5alpha-reductase type 2 deficiency from 18 Brazilian families. Eleven subjects presented SRD5A2 homozygous single-base mutations (two first cousins and four unrelated patients with G183S, two with R246W, one with del642T, one with G196S, and one with 217_218insC plus the A49T variant in heterozygosis), whereas four were compound heterozygotes (one with Q126R/IVS3+1G>A, one with Q126R/del418T, and two brothers with Q126R/G158R). Three patients were heterozygous for A207D, G196S, and R266W substitutions. The V89L polymorphism was found in heterozygosis in one of them (with A207D) and in one case with an otherwise normal gene sequence. The A49T variant was also detected in heterozygosis in the second case without other sequencing abnormalities. Four patients harbor yet non-described SRD5A2 gene mutations: a single nucleotide deletion (del642T), a G158R amino acid substitution, a splice junction mutation (IVS3+1G>A), and the insertion of a cytosine (217_218insC) occurring at a CCCC motif. This is the first report of a single-nucleotide insertion in the coding sequence of the SRD5A2 gene. In addition to these new mutations, this investigation reveals the prevalence of G183S substitution among a subset of African-Brazilian patients and presents evidences of the recurrence of already known mutations.
46,XY个体中，2型类固醇5α-还原酶（SRD5A2）基因突变会导致不同程度的男性化缺陷，这是由于酶活性降低或受损所致。在本研究中，采用聚合酶链反应和特异性引物以及自动测序分析，对来自18个巴西家庭的20例疑似2型类固醇5α-还原酶缺乏症患者的DNA样本进行了SRD5A2基因序列异常评估。11名受试者出现SRD5A2纯合单碱基突变（两名一级表亲以及四名无关患者为G183S，两名患者为R246W，一名患者为del642T，一名患者为G196S以及一名杂合状态下携带217_218insC加A49T变异的患者），而四名患者为复合杂合子（一名患者为Q126R/IVS3 + 1G>A，一名患者为Q126R/del418T，以及两名兄弟为Q126R/G158R）。三名患者为A207D、G196S和R266W替代的杂合子。其中一名患者（携带A207D）以及一名基因序列正常的患者中发现了杂合状态的V89L多态性。第二例患者中也检测到杂合状态的A49T变异，且无其他测序异常。四名患者携带尚未描述的SRD5A2基因突变：一个单核苷酸缺失（del642T）、一个G158R氨基酸替代、一个剪接连接点突变（IVS3 + 1G>A）以及在CCCC基序处发生的一个胞嘧啶插入（217_218insC）。这是SRD5A2基因编码序列中单核苷酸插入的首次报道。除了这些新突变外，本研究还揭示了非洲裔巴西患者亚组中G183S替代的患病率，并提供了已知突变复发的证据。
