The Human Gene Mutation Database (HGMD) constitutes a comprehensive core collection of data on germ‐line mutations in nuclear genes underlying or associated with human inherited disease (http://www.hgmd.org). Data cataloged include single base‐pair substitutions in coding, regulatory, and splicing‐relevant regions, microdeletions and microinsertions, indels, and triplet repeat expansions, as well as gross gene deletions, insertions, duplications, and complex rearrangements. Each mutation is entered into HGMD only once, in order to avoid confusion between recurrent and identical‐by‐descent lesions. By June 2005, the database contained in excess of 53,000 different lesions detected in 2029 different nuclear genes, with new entries currently accumulating at a rate in excess of 5000 per annum. HGMD includes cDNA reference sequences, now provided for more than 90% of the listed genes, splice junction data, disease‐associated and functional polymorphisms, and links to data present in publicly available online locus‐specific mutation databases.
Mutations in the serine protease inhibitor Kazal type 1 gene (SPINK1) encoding pancreatic secretory trypsin inhibitor (PSTI) have recently been found to be associated with chronic pancreatitis. Nevertheless, knowledge of severe mutations is particularly scarce, both in terms of number and in the extent of clinical information. The aim of this study was to expand the known spectrum of such mutations. 46 unrelated families, each including at least two pancreatitis patients and carrying neither cationic trypsinogen (PRSS1) mutations nor the frequent SPINK1 N34S mutation, participated in this study. The four exons and their flanking sequences of the SPINK1 gene were screened by denaturing high performance liquid chromatography analysis (DHPLC); and mutations were identified by direct sequencing. A heterozygous microdeletion mutation (c.27delC), which occurs within a symmetric element, was identified in two families. In one family, c.27delC showed segregation with the disease across two generations, with a penetrance of up to 75%. But in the other family, however, the same mutation manifested as a low-penetrance susceptibility factor. In addition, a novel heterozygous splicing mutation, c.87+1G>A (G>A substitution at nucleotide +1 of intron 2) was found in one family with familial pancreatitis. Our results also helped to resolve the sharply differing views about PSTI's role in pancreatitis.
No general rules have been proposed to account for the functional consequences of gene regulatory mutations. In a first attempt to establish the nature of such rules, an analysis was performed of the DNA sequence context of 153 different single base-pair substitutions in the regulatory regions of 65 different human genes underlying inherited disease. Use of a recently proposed measure of DNA sequence complexity (taking into account the level of structural repetitiveness of a DNA sequence, rather than simply the oligonucleotide composition) has served to demonstrate that the concomitant change in local DNA sequence complexity surrounding a substituted nucleotide is related to the likelihood of a regulatory mutation coming to clinical attention. Mutations that led to an increase in complexity exhibited higher odds ratios in favour of pathological consequences than mutations that led to a decrease or left complexity unchanged. This relationship, however, was discernible only for pyrimidine-to-purine transversions. Odds ratios for other types of substitution were not found to be significantly associated with local changes in sequence complexity, even though a trend similar to that observed for Y-->R transversions was also apparent for transitions. These findings suggest that the maintenance of a defined level of DNA sequence complexity, or at least the avoidance of an increase in sequence complexity, is a critical prerequisite for the function of gene regulatory regions.
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