标题：Different missense mutations at the tissue-nonspecific alkaline phosphatase gene locus in autosomal recessively inherited forms of mild and severe hypophosphatasia.
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1992
卷号：89
期号：20
页码：9924-9928
DOI：10.1073/pnas.89.20.9924
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Hypophosphatasia is a heritable form of rickets/osteomalacia with extremely variable clinical expression. Severe forms are inherited in an autosomal recessive fashion; the mode of transmission of mild forms is uncertain. The biochemical hallmark of hypophosphatasia is deficient activity of the tissue-nonspecific isozyme of alkaline phosphatase (TNSALP). Previously, we demonstrated in one inbred infant that an identical missense mutation in both alleles of the gene encoding TNSALP caused lethal disease. We have now examined TNSALP cDNAs from four unrelated patients with the severe perinatal or infantile forms of hypophosphatasia. Each of the eight TNSALP alleles from these four individuals contains a different point mutation that causes an amino acid substitution. These base changes were not detected in at least 63 normal individuals and, thus, appear to be causes of hypophosphatasia in the four patients. (Two additional base substitutions, found in one allele from each of the four patients, are linked polymorphisms.) Twenty-three unrelated patients (of 50 screened), who reflect the entire clinical spectrum of hypophosphatasia, possess one of our of the above eight mutations. In two of these additional patients, mild forms of the disease are also inherited in an autosomal recessive fashion. Our findings indicate that hypophosphatasia can be caused by a number of different missense mutations and that the specific interactions of different TNSALP mutant alleles are probably important for determining clinical expression. Severe forms, perinatal and infantile disease, are largely the result of compound heterozygosity for different hypophosphatasia alleles. At least some cases of childhood and adult hypophosphatasia are inherited as autosomal recessive traits.
