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PubMed1991

Discrimination between recurrent mutation and identity by descent: application to point mutations in exon 11 of the cystic fibrosis (CFTR) gene.

A total of 75 non-delta F508 chromosomes from 59 German cystic fibrosis patients was screened for mutations in exon 11 of the cystic fibrosis (CFTR) gene. These Caucasian patients were found to possess an identical haplotype background for two common mutations (G551D, R553X) consistent with their being identical by descent. However, a different R553X associated haplotype found in American black patients was suggestive of recurrent mutation, a postulate supported by the location of the R553X alteration in a hypermutable CpG dinucleotide. Likelihood estimates for recurrent mutation and identity by descent were compared and strongly supported the hypothesis of recurrent R553X mutation. The ability to distinguish between these two alternatives provides an indication of whether or not the search for mutations should be restricted to chromosomes with similar haplotypes.

Cystic Fibrosis↗
PubMed1999

Mutation analysis of the BRCA1 and BRCA2 genes results in the identification of novel and recurrent mutations in 6/16 flemish families with breast and/or ovarian cancer but not in 12 sporadic patients with early-onset disease. Mutations in brief no. 224. Online.

Since the identification of the BRCA1 and BRCA2 genes (MIM#s 113705 and 600185), more than hundred different mutations throughout both genes have been reported. Recurrent mutations are rare and mainly due to founder effects. We analyzed 12 sporadic female patients with breast cancer before age 35, as well as 16 unrelated families, presenting with either (i) at least 3 first degree relatives with breast and/or ovarian cancer diagnosed at any age, or (ii) at least 2 first and/or second degree relatives with breast and/or ovarian cancer before age 45 years. We performed a protein truncation test for BRCA1 exon 11 and BRCA2 exons 10 and 11 and heteroduplex analysis for all the remaining exons of BRCA1 and 2. Presence of genomic deletions encompassing exons 13 or 22 of BRCA1, known to be Dutch founder mutations, was investigated by PCR. In 6/16 (37.5%) unrelated families the causal mutation in either the BRCA1 or BRCA2 gene was identified. Four different mutations were found in the BRCA1 gene: IVS5+3A>G (intron 5), 1191delC (exon 11), R1443X (exon 13), IVS22+5G>A (intron 22) and two in the BRCA2 gene: 6503delTT (exon 11), 6831delTG (exon 11). 1191delC (BRCA1) and 6831delTG (BRCA2) are novel mutations. IVS5+3A>G in exon 5 of BRCA1 published by Peelen et al. (1997) as a novel Belgian mutation, was identified in one additional family, not fulfilling our inclusion criteria. In the group of 12 sporadic female patients no mutations were found.

Adult↗
PubMed2003

Mutational screening of the RB1 gene in Indian patients with retinoblastoma reveals eight novel and several recurrent mutations.

Retinoblastoma is the most common primary intraocular malignancy in children, caused by inactivation of the RB1 gene on chromosome 13. We carried out a mutational screen of the exons and promoter of the RB1 gene in Indian patients with retinoblastoma in order to determine the range of mutations giving rise to disease. Forty-seven patients were screened for mutations in all exons and promoter of the RB1 gene by single strand conformation polymorphism followed by sequencing. Tumors were available from 27 patients (12 bilateral and 15 unilateral retinoblastoma) while only peripheral blood was available from 20 patients, all with bilateral disease. Mutations were found in 22 patients, 9 from the analysis of tumors and 13 from peripheral blood. Eight novel mutations were identified, including 4 single base changes, 2 small deletions and 1 duplication. These are g.64365T>G (Tyr325Ter), g.78131G>A (Trp515Ter), g.150061G>T (Glu587Ter), g.170383C>G (S834X), g.41924A>C (IVS3-2A>C), g.150064ins4, g.160792del22, and g.76940del14 (IVS15 del +20-33). Almost all mutations produced nonsense codons or frameshifts. Recurrent mutations, especially at CpG sites were seen predominantly. Detectable mutations in exons were found in 46% of patients tested. Large deletions, epigenetic changes as well as mutations in non-coding regions may be the cause of disease in the remainder of patients. Knowledge of the full range of mutations can aid in the design of screening tests for individuals at risk.

Child↗
PubMed2004

Mutation hotspots in the human porphobilinogen deaminase gene: recurrent mutations G111R and R173Q occurring at CpG motifs.

Acute intermittent porphyria (AIP) is an inherited disorder in the haem biosynthetic pathway caused by a partial deficiency of porphobilinogen (PBG) deaminase. To date, more than 200 different mutations have been identified in the PBG deaminase gene (PBGD) in AIP patients from various countries and ethnic groups. While the majority of the PBGD gene mutations, including most of the mutations occurring at CpG dinucleotides, are family-specific, a few CpG mutations have been observed in a number of AIP patients of European origin. To study the origin of these common CpG mutations, eight intragenic single-nucleotide polymorphisms (SNPs) in the PBGD gene, as well as eight microsatellites flanking the gene in chromosome 11 were used to construct haplotypes in six AIP families of German, Polish and Swiss origins who carried either G111R (4707G>A) or R173Q (6391G>A) mutations. Among the three R173Q families, three distinct haplotypes were found to be cosegregated with the mutation. One Swiss and one German G111R family shared partially an intragenic and its extended microsatellite haplotype, whereas the Polish G111R family showed a unique haplotype. These results indicated that the recurrent CpG mutations that exist in the European AIP population can be either of ancestral origins or derived from de novo events.

Chromosome Mapping↗
PubMed1990

Recurrent mutation, gene conversion, or recombination at the human phenylalanine hydroxylase locus: evidence in French-Canadians and a catalog of mutations.

The codon 408 mutation (CGG----TGG, Arg----Trp) in exon 12 of the phenylalanine hydroxylase (PAH) gene occurs on haplotype 1 in French-Canadians; elsewhere this mutation (R408W) occurs on haplotype 2. A CpG dinucleotide is involved. The finding is compatible with a recurrent mutation, gene conversion, or a single recombination between haplotypes 2 and 1. A tabulation of 20 known mutations at the PAH locus reveals three instances of putative recurrent mutation.

Alleles↗
PubMed1998

A population study of mutations and LOH at breast cancer gene loci in tumours from sister pairs: two recurrent mutations seem to account for all BRCA1/BRCA2 linked breast cancer in Iceland.

The majority of breast cancer in high risk families is believed to result from a mutation in either of two genes named BRCA1 and BRCA2. A germline defect in either gene is usually followed by chromosomal deletion of the normal allele in the tumour. In Iceland two recurrent mutations have been identified, 999del5 BRCA2 and G5193A BRCA1. In this study, randomly selected pairs of sisters diagnosed with breast cancer at the age of 60 years or younger were analysed to evaluate the proportion of breast cancer resulting from BRCA1 and BRCA2. Genotypes and allele loss in tumour tissue from 42 sister pairs were compared using markers within and around the BRCA1 and BRCA2 genes. Eleven sister pairs were highly suggestive of BRCA2 linkage, and no obvious BRCA1 linkage was seen. Screening for the G5193A BRCA1 and 999del5 BRCA2 mutations showed the 999del5 mutation in the 11 BRCA2 suggestive pairs plus three pairs less indicative of linkage, and the G5193A BRCA1 mutation in one pair. When known mutation carriers are removed from the group, no indication of further linkage to BRCA1 or BRCA2 is seen. The results of our studies suggest that a large proportion of familial breast cancer in Iceland is the result of the 999del5 BRCA2 mutation, and it is unlikely that BRCA1 and BRCA2 germline mutations other than 999del5 and G5193A play a significant role in hereditary breast cancer in Iceland. Furthermore it can be concluded that most families with BRCA1 or BRCA2 linkage are easily identified by studying LOH around the defective gene in as few as two affected relatives.

Age Factors↗
PubMed1998

Molecular analysis of the six most recurrent mutations in the BRCA1 gene in 87 Spanish breast/ovarian cancer families.

BRCA1 accounts for nearly all families with multiple cases of both early onset breast and ovarian cancer and about 45% of families with breast cancer only. Although to date more than 200 distinct mutations have been described, several have been found to be recurrent in the gene. We have analyzed 87 Spanish breast/ovarian cancer families for the six most recurrent mutations in the BRCA1 gene. The analysis of the five exons where these mutations are located was made using the SSCP and sequenciation techniques. Four mutations were found in our families and only two carried one of the six mutations analyzed. In both cases the mutation identified was 185delAG. Our results suggest that these six mutations are not specially recurrent in the Spanish population and that differences in the geographical origin of the families can influence the type and proportion of mutations identified.

Adult↗
PubMed2004

Recurrent mutations in kindlin-1, a novel keratinocyte focal contact protein, in the autosomal recessive skin fragility and photosensitivity disorder, Kindler syndrome.

Kindler syndrome (OMIM 173650) is a rare autosomal recessive disorder characterized by trauma-induced blister formation (especially in childhood) and photosensitivity. Other features include mucocutaneous scarring and progressive poikiloderma. There is also an increased risk of skin and mucous membrane malignancy. The disorder was recently mapped to 20p12.3 and pathogenic mutations were identified in a new gene, KIND1. This gene encodes a 677 amino acid protein, kindlin-1, a component of focal contacts in keratinocytes. In this study, we identified four new recurrent mutations in KIND1 in 16 individuals with Kindler syndrome from 13 families of Pakistani (676insC), UK Caucasian (E304X), Omani (W616X), or Italian (958-1G > A) origins. Haplotype analysis demonstrated common ancestral mutant alleles for each mutation, apart from one of the six Pakistani families in which the mutation 676insC (which occurs in a repeat of seven cytosines) was present on a different genetic background. All mutations were homozygous, apart from the three UK Caucasian cases that were all compound heterozygotes (second allele mutations: L302X, 1161delA, 1909delA). All mutations were associated with markedly reduced or absent skin immunostaining with an antikindlin-1 antibody. These loss-of-function KIND1 mutations demonstrate the importance of kindlin-1 in maintaining epithelial integrity, although the mechanism linking this mutant protein to photosensitivity and poikiloderma remains to be determined. Delineation of these recurrent mutations is also relevant to optimizing mutation detection strategies in Kindler syndrome patients from particular ethnic backgrounds.

Adult↗
PubMed1997

Recurrent mutations in the type VII collagen gene (COL7A1) in patients with recessive dystrophic epidermolysis bullosa.

Mutations in the type VII collagen gene (COL7A1) are known to underlie different forms of the inherited blistering skin disease dystrophic epidermolysis bullosa (DEB). Most COL7A1 mutations are unique to individual families, and therefore it is usually necessary to screen all 118 exons of the gene to determine the molecular pathology in a patient with DEB. This study aimed to identify any recurrent mutations in COL7A1 that might be applicable to mutation-detection strategies in these patients. Mutational analysis was undertaken in 23 British patients with autosomal recessive DEB using PCR amplification of genomic DNA followed by heteroduplex analysis, nucleotide sequencing, and restriction site analysis. Two recurrent mutations were identified: R578X (6 of 46 alleles) and 7786delG (7 of 46 alleles). Haplotype analysis revealed that the mutations existed on similar allelic backgrounds in different patients, consistent with propagation of common British ancestral haplotypes, although R578X and 7786delG also have been described in DEB patients from other ethnic backgrounds. Given the high relative frequency of these two COL7A1 mutations, British patients with recessive DEB should be screened initially for these nucleotide changes by PCR amplification of genomic DNA and restriction analysis before more exhaustive screening of COL7A1.

Alleles↗
PubMed1979

Recurrent mutation and selection for increased penicillin titre in Aspergillus nidulans.

Recurrent mutation and selection has been used to increase penicillin titre in two closely related strains of Aspergillus nidulans. A selection programme was initiated from each of the two strains (programmes A and B) and continued through six cycles of mutation and selection. Near-ultraviolet light in conjuction with 8-methoxypsoralen was employed as the sole mutagen throughout programme A and ethyl methanesulphonate as the sole mutagen throughout programme B. Excluding the first cycle of A, where only 50 strains were assayed, the selection programmes were identical. In each programme, 100 survivors were assayed for penicillin titre after each mutagenic treatment and, on the basis of a single yield test, the best five strains were picked and carried forward to the next cycle. In both selection programmes, a near 300% increase in penicillin titre was achieved. This yield advance illustrates the effectiveness for strain development of experimental designs involving successive cycles of mutagenesis with a single-stage screen and the selection of the top few percent survivors in each cycle.

Aspergillus nidulans↗
PubMed2006

Soft sweeps III: the signature of positive selection from recurrent mutation.

Polymorphism data can be used to identify loci at which a beneficial allele has recently gone to fixation, given that an accurate description of the signature of selection is available. In the classical model that is used, a favored allele derives from a single mutational origin. This ignores the fact that beneficial alleles can enter a population recurrently by mutation during the selective phase. In this study, we present a combination of analytical and simulation results to demonstrate the effect of adaptation from recurrent mutation on summary statistics for polymorphism data from a linked neutral locus. We also analyze the power of standard neutrality tests based on the frequency spectrum or on linkage disequilibrium (LD) under this scenario. For recurrent beneficial mutation at biologically realistic rates, we find substantial deviations from the classical pattern of a selective sweep from a single new mutation. Deviations from neutrality in the level of polymorphism and in the frequency spectrum are much less pronounced than in the classical sweep pattern. In contrast, for levels of LD, the signature is even stronger if recurrent beneficial mutation plays a role. We suggest a variant of existing LD tests that increases their power to detect this signature.

Alleles↗
PubMed2004

Novel and recurrent mutations in the NF1 gene in Italian patients with neurofibromatosis type 1.

Neurofibromatosis type 1 (NF1) is one of the most common autosomal dominant disorders in humans, affecting 1 in 3500 individuals. NF1 is a fully penetrant exhibiting a mutation rate some 10-fold higher compared to most other disease genes. As a consequence, a high number of cases (up to 50%) are sporadic. Mutation detection is complex due to the large size of NF1 gene, the presence of pseudogenes and the great variety of lesions. In the present study we attempted to delineate the NF1 mutational spectrum in the Italian population reporting four-year experience with the direct analysis of the whole NF1 coding region in 110 unrelated subjects affected by NF1. For each patient, the whole coding sequence and all splice sites were studied for mutations, either by the protein truncation test (PTT), or, most often, by denaturing high performance liquid chromatography (DHPLC). Mutations were identified in 75 (68%) patients. Twenty-two mutations were found to be novel. The detection rate for the different methods was 7/18 (39%) for PTT, and 68/103 (66%) for DHPLC. The mutations were evenly distributed along the NF1 coding sequence. Thirty-two of the 75 unrelated NF1 patients in which germline mutations were identified (32/75, 43%) harbour 23 different recurrent mutations. Fifteen sequence variants likely to represent non-pathogenic polymorphisms were observed at the NF1 locus. Genotype-phenotype analysis was unable to detect any obvious correlation.

Chromatography, High Pressure Liquid↗
PubMed2002

Analysis of novel and recurrent mutations responsible for the tricho-rhino-phalangeal syndromes.

The tricho-rhino-phalangeal syndromes (TRPS type I, II, and III) are autosomal dominant disorders sharing the following characteristics: slowly growing and sparse scalp hair, medially thick and laterally thin eyebrows, bulbous tip of the nose, long flat philtrum, thin upper lip with vermilion border, and protruding ears. In addition, individuals with TRPS generally share skeletal and bone anomalies, including shortening of the phalanges and metacarpals (mild to severe brachydactyly), cone-shaped epiphyses, hip dysplasia, and short stature. The etiology of the different types of TRPS can result from either single base pair mutations, or the complete deletion of the TRPS1 gene, which encodes a zinc-finger transcription factor located on chromosomal band 8q24.1. We have identified nine heterozygous mutations, five novel and four recurrent, in unrelated families diagnosed with TRPS. The five novel mutations identified show 1- or 2-bp deletions and a single base substitution, whereas all of the recurrent mutations are single base substitutions. Seven of the nine mutations result in a premature stop codon, leading to a truncated, nonfunctional TRPS1 protein. The final two mutations are missense mutations in the GATA DNA binding zinc finger, which is believed to be important for the protein's normal function.

Amino Acid Substitution↗
PubMed1994

Evidence for origin, by recurrent mutation, of the phenylalanine hydroxylase R408W mutation on two haplotypes in European and Quebec populations.

The R408W mutation in the phenylalanine hydroxylase gene (PAH) of phenylketonuria patients occurs on haplotypes 2.3 and 1.8 in Europeans. The mutation involves a CpG dinucleotide; nonetheless, a single recombination event might also explain the two haplotype associations. By analysis of an STR in the PAH gene 5' to the 408 codon and of the VNTR system in the 3' UTR, we identified unique features of the haplotype 1.8 chromosome harbouring the R408W mutation which are not accounted for by recombination. We conclude that recurrent mutation is the origin of R408W on different PAH haplotypes in Europeans.

Alleles↗
PubMed1992

Protein C deficiency and thromboembolism: recurrent mutation at Arg 306 in the protein C gene.

A CGA----TGA transition in the protein C gene, resulting in an Arg306----Term substitution, was detected in a Swedish kindred with thrombotic disease whose members exhibit plasma protein C activity/antigen levels consistent with type I protein C deficiency. Although an identical lesion has been reported previously in several Dutch families, RFLP typing indicated that the Dutch and Swedish mutations were unlikely to be identical by descent and probably arose by recurrent mutation.

Amino Acid Sequence↗
PubMedDate not supplied

Recurrent mutation of the KIF21A gene in Japanese patients with congenital fibrosis of the extraocular muscles.

PURPOSE: To report recurrent mutation of the KIF21A gene in three Japanese families in which some members have congenital fibrosis of the extraocular muscles type 1 (CFEOM1), and to describe the clinical characteristics of the families. METHODS: Standard ocular examinations were performed on 18 normal and affected members of three unrelated families. To detect mutations, we determined the DNA sequence of exons 8, 20, and 21 and the splice sites of the KIF21A gene. RESULTS: All affected members had a heterozygous mutation of the KIF21A gene in exon 21 (R954W). Clinically, each patient had congenital bilateral ptosis, an infraducted primary position of each eye, and the inability to raise either eye above midline. CONCLUSIONS: The KIF21A gene mutation R954W was detected in the patients with CFEOM1 screened in this study, all of whom were Japanese, reflecting similar reports from Europe, America, the Middle East, and Japan. We suggest that mutations of the KIF21A gene contribute to the development of CFEOM1 regardless of ethnicity. We also found that the delimitation of the KIF21A gene mutation site enabled us to efficiently detect the KIF21A gene mutation despite the large number of KIF21A gene exons.

Adult↗
PubMed1995

Two further cases of mutation R1947X in the NF1 gene: screening for a relatively common recurrent mutation.

We present two further cases of mutation R1947X in the neurofibromatosis type 1 gene. To date, a total of nine cases of mutation R1947X have been reported giving a frequency of about 2% and confirming the recurrence of this mutation. R1947X occurs within a CpG dinucleotide and supports the hypothesis that the mutation rate for this dinucleotide is higher than that of other dinucleotides. As routine analysis for R1947X is advisable, we have developed an allele-specific oligonucleotide hybridization assay for the efficient screening of a large number of samples.

Alleles↗
PubMed2005

Novel and recurrent mutations in the C-terminal domain of COMP cluster in two distinct regions and result in a spectrum of phenotypes within the pseudoachondroplasia -- multiple epiphyseal dysplasia disease group.

Pseudoachondroplasia (PSACH) and some forms of multiple epiphyseal dysplasia (MED) result from mutations in the gene encoding cartilage oligomeric matrix protein (COMP). COMP is a large pentameric glycoprotein found predominantly in the extracellular matrix of cartilage, tendon, and ligament. As a modular protein, it is composed of a coiled-coil domain, four type II (T2) repeats, eight type III (T3) repeats, and a large globular C-terminal domain (CTD). The majority (>85%) of COMP mutations causing PSACH or MED are found in the exons encoding the T3 repeats, and the disease mechanism has been characterised in detail. Much less is known about disease-causing mutations in the CTD; in 10 years only seven mutations have been identified. In this study, we describe eight novel and two recurrent mutations that we have recently identified in patients with PSACH or MED. Interestingly, these mutations result in a spectrum of disease, ranging from mild MED to severe PSACH. Mapping of all known COMP CTD mutations on a three-dimensional model of the C-terminal domain shows that the CTD mutations cluster in two distinct regions. These regions are probably important in stabilising the T3-CTD structure and mediating intra- or intermolecular interactions.

Achondroplasia↗