Vainzof Mariz, Richard Pascale, Herrmann Ralf, Jimenez-Mallebrera Cecilia, Talim Beril, Yamamoto Lydia U, Ledeuil Céline, Mein Rachael, Abbs Stephen, Brockington Martin, Romero Norma B, Zatz Mayana, Topaloglu Haluk, Voit Thomas, Sewry Caroline, Muntoni Francesco, Guicheney Pascale, Tomé Fernando M S
Department of Genetics Biology, Human Genome Research Center, IB-USP, R. Matão, 106, Cidade Universitária, São Paulo, SP-CEP 05508-900, Brazil.
Neuromuscul Disord. 2005 Oct;15(9-10):588-94. doi: 10.1016/j.nmd.2005.04.009.
The congenital muscular dystrophies (CMD) are clinically and genetically heterogeneous. The merosin (laminin alpha2 chain) deficient form (MDC1A), is characterized clinically by neonatal hypotonia, delayed motor milestones and associated contractures. It is caused by deficiency in the basal lamina of muscle fibers of the alpha2 chain of laminins 2 and 4 (LAMA2 gene at 6q22-23). Laminin alpha2 chain is also expressed in fetal trophoblast, which provides a suitable tissue for prenatal diagnosis in families where the index case has total deficiency of the protein. This article reports the collective experience of five centers over the past 10 years in 114 prenatal diagnostic studies using either protein analysis of the chorionic villus (CV) of the trophoblast plus DNA molecular studies with markers flanking the 6q22-23 region and intragenic polymorphisms (n=58), or using only DNA (n=44) or only protein (n=12) approaches. Of the 102 fetuses studied by molecular genetics, 27 (26%) were predicted to be affected while 75 (74%) were considered as unaffected, with 52 (51%) being heterozygous, thus conforming closely to an autosomal recessive inheritance. In 18 of the 27 affected fetuses, the trophoblast was studied by immunocytochemistry and there was a total or only traces deficiency of the protein in CV basement membrane in all. In 10 cases material from the presumably affected fetus was available for analysis after termination of the pregnancy and immunohistochemical study confirmed the diagnosis in all of them. Prenatal studies of 'at risk' pregnancies in the five centers produced neither false negative (merosin-deficiency in CVs in a normal fetus), nor false positive (normal merosin expression in CVs and affected child), indicating the reliability of the technique, when all the necessary controls are done. Our experience suggests that protein and DNA analysis can be used either independently or combined, according to the facilities of each center, to provide accurate prenatal diagnosis of the MDC1A, and have an essential role in genetic counseling.
先天性肌营养不良症（CMD）在临床和遗传方面具有异质性。缺乏层黏连蛋白α2链（merosin）的类型（MDC1A），临床特征为新生儿肌张力低下、运动发育迟缓及相关挛缩。它是由层黏连蛋白2和4的α2链（位于6q22 - 23的LAMA2基因）在肌纤维基底层中缺乏所致。层黏连蛋白α2链也在胎儿滋养层细胞中表达，这为索引病例蛋白完全缺乏的家庭提供了合适的产前诊断组织。本文报道了五个中心在过去10年中对114例产前诊断研究的总体经验，这些研究采用了两种方法：一是对滋养层绒毛膜（CV）进行蛋白分析，同时结合6q22 - 23区域侧翼标记和基因内多态性的DNA分子研究（n = 58）；二是仅使用DNA（n = 44）或仅使用蛋白（n = 12）方法。在通过分子遗传学研究的102例胎儿中，预计27例（26%）受影响，75例（74%）被认为未受影响，其中52例（51%）为杂合子，因此与常染色体隐性遗传非常相符。在27例受影响胎儿中的18例中，通过免疫细胞化学对滋养层进行了研究，所有病例的CV基底膜中均存在蛋白完全缺乏或仅微量缺乏的情况。在10例病例中，终止妊娠后可获得疑似受影响胎儿的材料进行分析，免疫组织化学研究在所有病例中均证实了诊断。五个中心对“高危”妊娠的产前研究既未出现假阴性（正常胎儿的CV中层黏连蛋白缺乏），也未出现假阳性（CV中层黏连蛋白表达正常但孩子受影响），这表明当进行所有必要对照时，该技术具有可靠性。我们的经验表明，根据每个中心的设备情况，蛋白和DNA分析可单独或联合使用，以提供准确的MDC1A产前诊断，并在遗传咨询中发挥重要作用。
