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First frameshift mutation in the active protein S gene associated with a quantitative hereditary deficiency.

The authors used a strategy combining the amplification-refractory mutations system (ARMS) and denaturing gradient gel electrophoresis (DGGE) to screen the active protein S (PS) gene in a family with PS deficiency, and found a frameshift mutation in exon V. The protein, if expressed, would have an aberrant amino acid sequence from positions 82 to 90 and a premature stop codon in position 91. The mutation co-segregated with the deficient phenotype and was not found in 120 normal chromosomes. It is proposed that the deletion of a T in the codon corresponding to Pro 82 described here is responsible for the deficient phenotype.

Adult↗

A frameshift mutation in the HuP2 paired domain of the probable human homolog of murine Pax-3 is responsible for Waardenburg syndrome type 1 in an Indonesian family.

Waardenburg syndrome type 1 (WS1) is an autosomal dominant disorder characterized by deafness, dystopia canthorum, heterochromia iridis, white forelock, and premature greying. A similar phenotype is caused in the mouse by mutations in the Pax-3 gene. This observation, together with comparisons of conserved syntenies in the murine and human genetic maps, suggested that at least some WS1 mutations should occur in HuP2, the probable human homolog of Pax-3. Two mutations in the HuP2 sequence of individuals with WS1 have been reported recently. Both of them occur in the highly conserved paired box region of the gene, which encodes a DNA binding domain. The functional consequences of these mutations are at present speculative. We report here a 14 bp deletion in the paired domain encoded by exon 2 of HuP2 in an Indonesian family segregating for WS1. This frameshift mutation results in a premature termination codon in exon 3. The HuP2 product is a truncated protein lacking most of the paired domain and all of the predicted homeo domain. We propose that the WS1 phenotype in this family is due to loss of function of HuP2 and discuss two mechanisms for the dominant effect of this mutation.

Amino Acid Sequence↗

A frameshift mutation in exon 2 of the phenylalanine hydroxylase gene linked to RFLP haplotype 1.

A deletion of a single base in codon 55 (exon 2) of the phenylalanine hydroxylase (PAH) gene has been identified by direct DNA sequencing of 94 phenylketonuria (PKU) chromosomes. This mutation alters the reading frame so that a stop signal (TAA) is generated in codon 60 of the PAH gene. Haplotype analysis revealed that all PKU alleles showing the codon 55 frameshift mutation exhibited haplotype 1. In our panel of DNA probes 13% of all mutant haplotype 1 alleles carry this particular mutation. Patients who were compound heterozygotes for this deletion and R408W in exon 12, or the splice mutation in intron 12, were affected by severe PKU. Thus, the clinical data provide additional evidence that haplotype 1 PKU alleles carry molecular defects which confer a null phenotype. In addition, we were able to show that the newly detected mutation occurs on alleles of different ethnic background.

Amino Acid Sequence↗

Frameshift mutations at two hotspots in vasopressin transcripts in post-mitotic neurons.

Mutations in DNA underlie carcinogenesis, inherited pathology, and aging and are generally thought to be introduced during meiosis and mitosis. Here we report that in post-mitotic neurons specific frameshift mutations occur at high frequency. These mutations were identified in vasopressin transcripts in magnocellular neurons of the homozygous Brattleboro rat and predominantly consist of a GA deletion in GAGAG motifs. Immunocytochemistry provides evidence for similar events in wild-type rats. However, the diseased state of the Brattleboro rat, resulting in a permanent activation of vasopressin neurons, enhanced the mutational rate. These data reveal hitherto unrecognized somatic mutations in nondividing neurons.

Amino Acid Sequence↗

Carnitine uptake defect: frameshift mutations in the human plasmalemmal carnitine transporter gene.

The genetic defect associated with carnitine uptake is characterized by progressive infantile-onset carnitine responsive cardiomyopathy, weakness, recurrent hypoglycemic hypoketotic encephalopathy, and failure to thrive. The cDNA encoding the sodium ion-dependent, high-affinity human carnitine transporter (557 amino acids) has been recently cloned and mapped to human chromosome 5q31. We herein report the first molecular characterization of the mutations responsible for the carnitine uptake defect in two unrelated patients. RT-PCR analysis of patient lymphoblasts and fibroblasts followed by sequencing of PCR products and their subclones revealed frameshift mutations in the plasmalemmal carnitine transporter. In both patients, the abnormal transcripts showed a partial cDNA deletion of nucleotides 255-1649 resulting in a predicted truncated protein of 92 amino acids. Both patients are compound heterozygotes; in one patient the second mutant allele revealed a 19-bp insertion between nucleotides 874 and 875 resulting in a frameshift yielding a predicted truncated protein of 284 amino acids, while in the second patient the second mutant allele had a deletion of nucleotides 875-1046 resulting in a predicted truncated protein of 237 amino acids.

Amino Acid Sequence↗

Model for the participation of quasi-palindromic DNA sequences in frameshift mutation.

A model is described for the templated production of frameshift and base-substitution mutations mediated through aberrant DNA structures arising as a consequence of quasi-palindromic DNA sequences. Two general mechanisms are considered. One evokes the formation and processing of imperfect DNA secondary structures (hairpins) for the production of mutations. The other evokes a "strand switch" during DNA synthesis which, in a manner unique to quasi-palindromic sequences, may be resolved to produce frameshift or base-substitution mutations, or both. It is the unique combination of symmetrical and asymmetrical elements of the quasi-palindromic sequence itself that provides the basis for both models. Through the mechanisms described, the symmetrical elements permit unusually paired DNA substrates, and the asymmetrical elements permit templated insertions, deletions, and base substitutions. The model predicts a class of mutations--simultaneously frameshifts and base substitutions--whose sequences can be predicted from a local quasi-palindromic sequence. This prediction appears to be met by a significant fraction (more than 15%) of frameshift mutations in the iso-1-cytochrome c gene of Saccharomyces cerevisiae.

Base Sequence↗

A heterozygous frameshift mutation in the V1 domain of keratin 5 in a family with Dowling-Degos disease.

Dowling-Degos disease (DDD) is an autosomal-dominant genodermatosis characterized by reticulate pigmentation of the flexures. By direct DNA sequencing, we have identified a frameshift mutation in exon 1 of KRT5 in the proband from an extended Spanish DDD kindred. Cloning of PCR products confirmed that this was a 2-bp deletion mutation, designated c.442delAG, leading to a premature termination codon in the V1 domain of the K5 polypeptide, designated p.S148fsX30. These data confirm that haploinsufficiency for K5 causes DDD and points to a prominent role for the keratin intermediate filament cytoskeleton within basal keratinocytes in epidermal pigment biology.

Adult↗

Ionizing and ultraviolet radiation-induced reversion of sequenced frameshift mutations in Escherichia coli: a new role for umuDC suggested by delayed photoreactivation.

The ultraviolet (UV) and gamma radiation-induced reversion of the trpA21, trpA9813, and trpE9777 sequenced-frameshift mutations were studied in Escherichia coli K-12 with or without the plasmid pKM101. Radiation induced the reversion of all 3 frameshifts, and pKM101 enhanced this reversion 10-50-fold. Factors influencing the differential radiation revertability of frameshifts are discussed. The two most revertable frameshifts, trpE9777 and trpA9813, were used as probes to understand the role of the umuDC genes in radiation-induced frameshift reversion. Unlike the UV radiation-induced reversion of base-substitution mutations, the reversion of these frameshifts was not enhanced in a uvrA umuC strain by photoreactivation after a post-UV-irradiation incubation. The UmuDC proteins are suggested to have functions in the radiation induction of frameshifts that are more complex than are their functions in the induction of base substitutions.

Bacterial Proteins↗

Sensorineural hearing impairment in patients with Pmp22 duplication, deletion, and frameshift mutations.

OBJECTIVE: To characterize and distinguish the types of sensorineural hearing impairment (SNHI) that occur in hereditary motor and sensory neuropathy Type 1a (HMSN-1a) and hereditary neuropathy with liability to pressure palsies (HNPP), which are caused by deletion or frameshift mutation. STUDY DESIGN: Prospective study. SETTING: Ambulatory patients in a university hospital. PATIENTS: Twelve patients with HMSN-1a due to a duplication of the PMP22 gene on chromosome 17p11.2, 16 patients with HNPP due to the common PMP22 deletion (HNPP del), and 11 HNPP patients with a frame shift mutation (heterozygous PMP22 G-insertion) (HNPP mut), all confirmed by molecular genetic analysis. INTERVENTIONS: Pure-tone audiograms and speech audiograms were obtained. MAIN OUTCOME MEASURES: Results of cross-sectional analysis comprising linear regression of hearing threshold on age. RESULTS: Pure-tone audiograms showed mild to moderate SNHI, predominant at the low and the high frequencies. SNHI showed significant progression by approximately 0.4 dB per year at 0.25 to 4 kHz and up to 1 to 2 dB per year at 4 to 8 kHz. Patients with HMSN-1a had substantial, presumably congenital, SNHI but did not show significant progression beyond presbyacusis. Patients with HNPP showed postnatal onset at age 11 years with progression of SNHI in excess of presbyacusis by 0.4 dB per year. All three types of neuropathy showed normal speech recognition. CONCLUSIONS: All three types of neuropathy showed SNHI with normal speech recognition. HMSN-1a showed stable SNHI without progression beyond presbyacusis. HNPP showed progression beyond presbyacusis with postnatal onset. The differences in SNHI may be explained by the differences in PMP22 expression. The progressive SNHI in HNPP might be explained by the liability for exogenous factors associated with this disorder.

Adult↗

Frameshift mutations in exons 9 and 10 of the porphobilinogen deaminase gene produce a crossreacting immunological material (CRIM)-negative form of acute intermittent porphyria.

Single-strand conformation polymorphism analysis was used to screen all 15 exons of the porphobilinogen deaminase gene from 13 patients with acute intermittent porphyria. Unique banding patterns in two amplified gene fragments, one containing exon 9 and another containing exon 10, were further investigated. Sequence analysis of cloned genomic DNA revealed a single base pair insertion in the middle of exon 9 in one patient and a single base pair deletion near the 3' end of exon 10 in two related patients. Both mutations change the reading frame of the mRNA transcript and predict proteins that are normal at their NH2-terminal ends but contain novel, unrelated sequences at their COOH-terminal ends and are prematurely terminated. Frameshift mutations in the porphobilinogen deaminase gene are uncommon; this is the first report of an insertion mutation causing acute intermittent porphyria.

Base Sequence↗

A case of Japanese cleidocranial dysplasia with a CBFA1 frameshift mutation.

Cleidocranial dysplasia (CCD), which is caused by mutations of the core binding factor alpha 1 (CBFA1)/runt-related gene 2 (Runx2), is an autosomal, dominantly inherited disorder of high penetrance affecting skeletal ossification and tooth development. Recently, we found a novel frameshift mutation 383-T-insertion (S128F) in exon 3 in the CBFA1 gene of a Japanese classic CCD patient. We describe our detailed investigation of the patient with CCD associated with the CBFA1 mutation. The patient showed the characteristic expression of CCD, such as dysplasia of the clavicles, patent fontanelles, short stature, impacted supernumerary teeth, and delayed eruption of the permanent teeth. In addition to these characteristics, orthopantomography delayed ossification of the mandibular symphysis and a three-dimensional computed tomograph (3D-CT) analysis showed hypoplasia of the zygomatic arch. Furthermore, the acellular cementum of an impacted supernumerary tooth was absent in this patient. Thus, the CBFA1 mutation was critical for the pathogenesis of CCD in this patient.

Amino Acid Sequence↗

A complete deficiency of coagulation factor XIII A-subunit due to a novel compound heterozygote of Ser 413 Leu missense and an nt 389 (ins G) frameshift mutation.

Coagulation factor XIII consists of two A- and two B-subunits, and either gene mutation can cause a complete deficiency. In a newborn patient with persistent bleeding from the umbilical cord stump, the plasma A-subunit protein was not detectable. Direct PCR sequencing revealed an nt 389 (ins G) frameshift mutation in exon 4 resulting in a new stop codon and a Ser 413 Leu missense mutation in exon 10 in either allele. His mother and father were heterozygous for the nt 389 (ins G) and the Ser 413 Leu, respectively, with about 50% reduction of the plasma A-subunit proteins. In all family members examined only those with either mutation showed the reduced subunit A protein levels. Thus, this complete deficiency of factor XIII was due to a novel compound heterozygous mutation in the A-subunit gene.

DNA Transposable Elements↗

A new frameshift mutation encoding a truncated amelogenin leads to X-linked amelogenesis imperfecta.

The amelogenin proteins are the most abundant organic components of developing dental enamel. Their importance for the proper mineralization of enamel is evident from the association between previously identified mutations in the X-chromosomal gene that encodes them and the enamel defect amelogenesis imperfecta. In this investigation, an adult male presenting with a severe hypoplastic enamel phenotype was found to have a single base deletion at the codon for amino acid 110 of the X-chromosomal 175-amino acid amelogenin protein. The proband's mother, who also has affected enamel, carries the identical deletion on one of her X-chromosomes, while the father has both normal enamel and DNA sequence. This frameshift mutation deletes part of the coding region for the repetitive portion of amelogenin as well as the hydrophilic tail, replacing them with a 47-amino acid segment containing nine cysteine residues. While greater than 60% of the protein is predicted to be intact, the severity of this phenotype illustrates the importance of the C-terminal region of the amelogenin protein for the formation of enamel with normal thickness.

Adult↗

Fibrillin-1 (FBN1) gene frameshift mutations in Marfan patients: genotype-phenotype correlation.

Marfan syndrome (MFS) is a multisystemic disease associated with mutations in the fibrillin-1 gene. Most of the reported mutations are missense substitutions mainly affecting the epidermal growth factor (EGF)-like protein domain structure and the calcium-binding (cb) site. The aim of our study was to investigate the correlation between fibrillin-1 frameshift mutations and the clinical phenotype in patients affected by MFS. In 48 out of 66 Marfan patients a pathogenetic mutation was found. We detected novel mutations causing premature termination codon in exons 19, 37, 40 and 41 of four Italian patients. The first mutation in exon 19 (cbEGF #8 domain) results in a clinical phenotype involving mainly the skeletal and cardiovascular systems. Interestingly, we noticed that, while mutations in exons 37 and 41 (eight cysteine domains #4 and #5) are milder, the mutation in exon 40 (cbEGF #24 domain) is more severe and causes major cardiovascular involvement with thoracic and abdominal aortic aneurysms. It is noteworthy that the degree of the severity in the phenotype of one of our patients and another from the literature carrying a mutation in exon 41 could be explained with alterations in mRNA expression.

Adult↗

CARD15 frameshift mutation in patients with CROHN disease is associated with immune dysregulation.

BACKGROUND: Mutations in the caspase-activating recruitment domain 15 (CARD15) gene are associated with Crohn disease (CD). CARD15 is an intracellular receptor for bacterial lipopolysaccharides (LPS). LPS-induced activation of transfectants containing the frameshift mutation (1007fs) of CARD15 is impaired. The aim of this study was to investigate whether the presence of CARD15 1007fs affects activation of CD patients' own cells. Patients (4 homozygotes, 6 heterozygotes, and 6 wild-type) were matched according to clinical picture and medication. METHODS: Immune inflammatory status was evaluated by measuring monocyte HLA-DR and CD11b densities and the proportion of CD14dimCD16+ monocytes, and was found to be comparable in the three groups. Blood mononuclear cells were cultured overnight in serum-free medium alone, or the medium supplemented with LPS (0.1-10.0 ng/mL), a combination of IFN-gamma (100 IU/mL) and granulocyte-macrophage colony stimulating factor (GM-CSF) (5 ng/mL), or both. TNF and IL-10 levels in the culture supernatant were determined. RESULTS: LPS 0.1 or 1.0 ng/mL alone did not increase TNF levels. IFN-gamma/GM-CSF induced TNF release, and co-culture with LPS 1.0 or 10.0 ng/mL was strongly synergistic. CARD15 1007fs mutation was linked in a gene-dose-dependent manner to low TNF release induced by IFN-gamma/GM-CSF (P value for linear trend = 0.001). The degree of synergism in co-culture was normal or high, suggesting that 1007fs did not depress responses to LPS. IL-10 levels were not related to CARD15 1007fs. CONCLUSIONS: In CD patients, CARD15 1007fs is associated in a gene-dose-dependent manner to low mononuclear cell TNF release by IFN-gamma/GM-CSF but does not impair TNF release by LPS. This type of immune dysregulation may influence susceptibility to and/or phenotype of CD.

Adult↗

Human alpha2-globin nonsense-mediated mRNA decay induced by a novel alpha-thalassaemia frameshift mutation at codon 22.

We describe a novel alpha-thalassaemia determinant in a 3-year-old girl presenting a mild microcytic and hypochromic anaemia, and normal haemoglobin A2 level. Molecular studies revealed heterozygosity for a novel microdeletion (-C) at codon 22 of the alpha2-globin gene. As the frameshift mutation generates a premature translation termination codon at position 48/49, we investigated the effect of the nonsense codon on the alpha2-globin gene expression. Although it does not affect RNA splicing, the premature nonsense codon induces accelerated mRNA degradation. To our knowledge, this is the first time the nonsense-mediated mRNA decay has been reported to occur in human alpha-globin mRNA.

Codon, Nonsense↗

Moderation of phenotypic severity in dystrophic and junctional forms of epidermolysis bullosa through in-frame skipping of exons containing non-sense or frameshift mutations.

Non-sense mutations on both alleles of either the type VII collagen gene (COL7A1) or the genes encoding laminin 5 (LAMA3, LAMB3, or LAMC2) usually result in clinically severe forms of recessive dystrophic or junctional epidermolysis bullosa, respectively. In this study we assessed two unrelated families whose mutations in genomic DNA predicted severe recessive dystrophic epidermolysis bullosa or junctional epidermolysis bullosa phenotypes but in whom the manifestations were milder than expected. The recessive dystrophic epidermolysis bullosa patients had a homozygous single base-pair frameshift mutation in exon 19 of COL7A1 (2470insG). Clinically, there was generalized blistering but only mild scarring. Skin biopsy revealed positive type VII collagen immunoreactivity and recognizable anchoring fibrils. The junctional epidermolysis bullosa patients were compound heterozygotes for a frameshift/non-sense combination of mutations in exons 3 and 17 of LAMB3 (29insC/Q834X). These patients did not have the lethal form of junctional epidermolysis bullosa but, as adults, displayed the milder generalized atrophic benign epidermolysis bullosa variant. There was undetectable laminin 5 staining at the dermal-epidermal junction using an antibody to the beta3 chain, but faintly positive alpha3 and gamma2 chain labeling, and there was variable hypoplasia of hemidesmosomes. To explain the milder recessive dystrophic epidermolysis bullosa and junctional epidermolysis bullosa phenotypes in these families, reverse transcription-polymerase chain reaction, using RNA extracted from frozen skin, was able to provide evidence for some rescue of mutant mRNA transcripts with restoration of the open- reading frame. In the recessive dystrophic epidermolysis bullosa patients, transcripts containing in-frame skipping of exon 19 of COL7A1 in the cDNA were detected, and in the junctional epidermolysis bullosa patients transcripts with in-frame skipping of exon 17 of LAMB3 were identified. The truncated proteins encoded by these transcripts are expected to lack certain critical domains involved in cell-matrix attachment, but may still be able to contribute to adhesion thereby moderating the severity of the skin blistering. This study shows the limitations in predicting phenotype in epidermolysis bullosa solely based on mutation analysis of genomic DNA and emphasizes the importance of immunohistochemistry, electron microscopy, and mRNA assessment as parallel investigations.

Adolescent↗

A novel beta-thalassemia frameshift mutation (codon 14/15), detectable by direct visualization of abnormal restriction fragment in amplified genomic DNA.

A new frameshift mutation due to an insertion of G between codon 14/15 of the beta-globin gene was found in two unrelated Chinese patients with Cooley's anemia. The first patient (W.S.) was homozygous for haplotype 5 (Chinese) and carried a codon 41/42 (four base pair deletion) mutant, while the second patient (C.K.) was homozygous for haplotype 2 (Chinese), and also had a codon 17 (A----T) nonsense mutation. Molecular cloning and M13 sequencing of the beta gene in patient W.S. revealed that the new mutant was found in a beta-globin gene framework type 3 (Asian). Direct sequencing was performed on polymerase chain reaction-amplified genomic DNA from patient C.K. With the new mutation, an additional BstNI or EcoRII recognition site is generated and the abnormal restriction fragment (134 basepair) can be directly visualized on polyacrylamide gel electrophoresis of the amplified genomic DNA.

Base Sequence↗