Ibrahim Shahnaz, Maqbool Saadia, Azam Maleeha, Iqbal Mohammad Perwaiz, Qamar Raheel
Department of Pediatrics and Child Health, Aga Khan University, Karachi, Pakistan.
COMSATS Institute of Information Technology, Park Road, Tarlai Kalan, Islamabad, 45600, Pakistan.
Mol Biol Rep. 2018 Jun;45(3):353-360. doi: 10.1007/s11033-018-4169-9. Epub 2018 Mar 29.
Three index patients with hyperhomocysteinemia and ocular anomalies were screened for cystathionine beta synthase (CBS) and methylenetetrahydrofolate reductase (MTHFR) polymorphisms. Genotyping of hyperhomocysteinemia associated MTHFR polymorphisms C677T (rs1801133) and A1298C (rs1801131) was done by PCR-restriction fragment length polymorphism. Sanger sequencing was performed for CBS exonic sequences along with consensus splice sites. In the case of MTHFR polymorphisms, all the patients were heterozygous CT for the single nucleotide polymorphism (SNP) C677T and were therefore carriers of the risk allele (T), while the patients were homozygous CC for the risk genotype of the SNP A1298C. CBS sequencing resulted in the identification of two novel mutations, a missense change (c.467T>C; p.Leu156Pro) in exon 7 and an in-frame deletion (c.808_810del; p.Glu270del) in exon 10. In addition, a recurrent missense mutation (c.770C>T; p.Thr257Met) in exon 10 of the gene was also identified. The mutations were present homozygously in the patients and were inherited from the carrier parents. This is the first report from Pakistan where novel as well as recurrent CBS mutations causing hyperhomocysteinemia and lens dislocation in three patients from different families are being reported with the predicted effect of the risk allele of the MTHFR SNP in causing hyperhomocysteinemia.
对三名患有高同型半胱氨酸血症和眼部异常的索引患者进行了胱硫醚β合酶（CBS）和亚甲基四氢叶酸还原酶（MTHFR）基因多态性筛查。通过聚合酶链反应-限制性片段长度多态性对与高同型半胱氨酸血症相关的MTHFR基因多态性C677T（rs1801133）和A1298C（rs1801131）进行基因分型。对CBS外显子序列以及共有剪接位点进行了桑格测序。对于MTHFR基因多态性，所有患者在单核苷酸多态性（SNP）C677T方面均为杂合子CT，因此是风险等位基因（T）的携带者，而患者在SNP A1298C的风险基因型方面为纯合子CC。CBS测序结果鉴定出两个新突变，一个是外显子7中的错义变化（c.467T>C；p.Leu156Pro），另一个是外显子10中的框内缺失（c.808_810del；p.Glu270del）。此外，还在该基因的外显子10中鉴定出一个复发性错义突变（c.770C>T；p.Thr257Met）。这些突变在患者中呈纯合状态，并且是从携带者父母遗传而来。这是来自巴基斯坦的首份报告，报告了来自不同家庭的三名患者中导致高同型半胱氨酸血症和晶状体脱位的新的以及复发性CBS突变，以及MTHFR SNP风险等位基因在导致高同型半胱氨酸血症方面的预测作用。
