Ashton-Prolla P, Tong B, Shabbeer J, Astrin K H, Eng C M, Desnick R J
Department of Human Genetics, Mount Sinai School of Medicine, New York, NY 10029, USA.
J Investig Med. 2000 Jul;48(4):227-35.
Fabry disease, an inborn error of glycosphingolipid catabolism, results from mutations in the X-chromosomal gene encoding the lysosomal exoglycosidase, alpha-galactosidase A (alpha-Gal A; EC 3.2.1.22). The nature of the molecular lesions in the alpha-Gal A gene in 36 unrelated families was determined in order to provide precise heterozygote detection, prenatal diagnosis, and to define genotype/phenotype correlations.
Genomic DNA was isolated from affected males and/or carrier females from 36 unrelated families with Fabry disease. The entire alpha-Gal A coding region and flanking intronic sequences were analyzed by PCR amplification and solid-phase or cycle sequencing. Markers closely linked to the alpha-Gal A gene were analyzed to determine if probands with the same mutations were related.
Twenty-two novel mutations were identified including 10 missense (P40L, W95S, S148N, C172R, M187V, N224S, W226R, A230T, D266H, N320Y), three nonsense (Y134X, C142X, W204X in two families), three splice-site defects (IVS2(+1), IVS3(+1), IVS4(+1)) and six small deletions or insertions (26delA in two families, 672ins37, 774delAC, 833insA, 1139delC, 1188insT). Of the remaining 12 families (33.3%), each had a previously identified mutation, eight of which occurred at CpG dinucleotides including R112C (two families), R112H, R227Q, R227X (three families), and R301Q. Haplotype analysis of the mutant alleles that occurred in two or three presumably unrelated families revealed that the families with the rare novel alleles (W204X and 26delA) were probably related, whereas those with mutations involving CpG dinucleotides (R112C and R227X) were not, the latter being consistent with their origins as independent mutational events. Genotype/phenotype correlations revealed that certain mutations previously found in mild variant patients also were found in classic patients. In addition, the genotypes and spectrum of phenotypic severity were determined in five heterozygotes with no family history.
These results illustrate the molecular heterogeneity of the lesions causing Fabry disease and emphasize the fact that CpG dinucleotides constitute important hot spots for mutation in the alpha-Gal A gene. These studies also permit precise heterozygote detection and prenatal diagnosis in these families, and delineate phenotype-genotype correlations in this disease.
法布里病是一种鞘糖脂分解代谢的先天性疾病，由编码溶酶体外切糖苷酶α - 半乳糖苷酶A（α - Gal A；EC 3.2.1.22）的X染色体基因突变引起。为了实现精确的杂合子检测、产前诊断并确定基因型/表型相关性，我们对36个无亲缘关系的家族中α - Gal A基因的分子病变性质进行了研究。
从36个患有法布里病的无亲缘关系家族的患病男性和/或携带者女性中分离基因组DNA。通过PCR扩增以及固相或循环测序对整个α - Gal A编码区和侧翼内含子序列进行分析。对与α - Gal A基因紧密连锁的标记进行分析，以确定具有相同突变的先证者是否有亲缘关系。
共鉴定出22种新突变，包括10种错义突变（P40L、W95S、S148N、C172R、M187V、N224S、W226R、A230T、D266H、N320Y）、3种无义突变（两个家族中的Y134X、C142X、W204X）、3种剪接位点缺陷（IVS2(+1)、IVS3(+1)、IVS4(+1)）以及6种小缺失或插入（两个家族中的26delA、672ins37、774delAC、833insA、1139delC、1188insT）。在其余12个家族（33.3%）中，每个家族都有一个先前已鉴定的突变，其中8个发生在CpG二核苷酸处，包括R112C（两个家族）、R112H、R227Q、R227X（三个家族）和R301Q。对两个或三个可能无亲缘关系的家族中出现的突变等位基因进行单倍型分析发现，携带罕见新等位基因（W204X和26delA）的家族可能有亲缘关系，而涉及CpG二核苷酸突变（R112C和R227X）的家族则无亲缘关系，后者与其作为独立突变事件的起源一致。基因型/表型相关性研究表明，先前在症状较轻的患者中发现的某些突变在典型患者中也存在。此外，还确定了5名无家族病史的杂合子的基因型和表型严重程度范围。
这些结果说明了导致法布里病的病变在分子水平上的异质性，并强调了CpG二核苷酸是α - Gal A基因中重要的突变热点这一事实。这些研究还使得在这些家族中能够进行精确的杂合子检测和产前诊断，并明确了该疾病的表型 - 基因型相关性。
