Hussein I R, El-Beshlawy A, Salem A, Mosaad R, Zaghloul N, Ragab L, Fayek H, Gaber K, El-Ekiabi M
Department of Molecular Genetics and Enzymology, National Research Centre, Cairo, Egypt.
Haemophilia. 2008 Sep;14(5):1082-7. doi: 10.1111/j.1365-2516.2008.01779.x. Epub 2008 Jun 28.
Haemophilia A is the most common inherited X-linked recessive bleeding disorder. The aim was to investigate the usefulness of two DNA markers in linkage analysis, one intragenic BCL1 affecting restriction site in intron 18, and is detected as restriction fragment length polymorphism (RFLP), and one extragenic variable number of tandem repeat (VNTR) locus DXS52 (St14) to formulate an informative and accurate carrier detection and prenatal diagnosis. The study included 46 families with at least one child affected with haemophilia A, and 30 unrelated normal females as control group. Polymerase chain reaction (PCR) and restriction enzyme analysis were used to study the polymorphism in BCL1, and long-distance PCR for detection of VNTR (ST14) alleles. The incidence of BCL1 (+) allele was 74%, 72% and 60% in patients, mothers and control group, respectively. Expected heterozygosity for BCL1 was 40% in mothers of affected cases compared with 48% in the female control group. However, observed heterozygosity was found to be 48% in the mothers of affected cases, compared with 60% in the control group. Thus, 48% of the studied families are informative for this marker alone. Nine different alleles of VNTR (St14) were observed in mothers and six alleles in affected cases and six in the control group. The most prevalent alleles were 1300 bp (45.5% and 34%) and 700 bp (13.6% and 20%) in patients and their mothers, respectively. Observed heterozygosity in mothers was 41% compared with 43.3% in controls. The combined use of both BCL1 and St14 markers raised the informative rate to 63.6%. Carrier detection and prenatal diagnosis is possible in haemophilia A families using both DNA markers. We suggest screening haemophilic families first for BCL1 polymorphism followed by analysis of St14 locus.
甲型血友病是最常见的遗传性X连锁隐性出血性疾病。目的是研究两种DNA标记在连锁分析中的实用性，一种是影响内含子18中限制性位点的基因内BCL1，可检测为限制性片段长度多态性（RFLP），另一种是基因外串联重复可变数目（VNTR）位点DXS52（St14），以制定信息丰富且准确的携带者检测和产前诊断方法。该研究纳入了46个至少有一名患甲型血友病儿童的家庭，以及30名无关的正常女性作为对照组。采用聚合酶链反应（PCR）和限制性酶切分析来研究BCL1的多态性，并采用长距离PCR检测VNTR（ST14）等位基因。BCL1（+）等位基因在患者、母亲和对照组中的发生率分别为74%、72%和60%。与女性对照组的48%相比，患病例母亲中BCL1的预期杂合度为40%。然而，在患病例母亲中观察到的杂合度为48%，而对照组为60%。因此，仅该标记就使48%的研究家庭具有信息价值。在母亲中观察到VNTR（St14）的9种不同等位基因，在患病例中观察到6种，在对照组中观察到6种。患者及其母亲中最常见的等位基因分别为1300 bp（45.5%和34%）和700 bp（13.6%和20%）。母亲中观察到的杂合度为41%，而对照组为43.3%。同时使用BCL1和St14标记可将信息率提高到63.6%。使用这两种DNA标记对甲型血友病家庭进行携带者检测和产前诊断是可行的。我们建议首先对血友病家庭进行BCL1多态性筛查，然后分析St14位点。
