Novel and recurrent exon 13 mutations of COMP in pseudoachondroplasia.
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Achondroplasia↗
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A novel recurrent mitochondrial DNA mutation in ND3 gene is associated with isolated complex I deficiency causing Leigh syndrome and dystonia.
Defects in NADH:ubiquinone oxidoreductase (complex I), the largest complex of the mitochondrial respiratory chain, account for most cases of respiratory chain deficiency in human. Complex I contains at least 45 subunits, 7 of which are encoded by mitochondrial DNA (mtDNA). Here we report a novel 10197G>A mutation of the ND3 gene in three unrelated families with Leigh syndrome (LS) or dystonia. Variable degrees of heteroplasmy were found in all tissues tested and a high percentage of mutant mtDNA was observed in muscle. The 10197G>A mutation modifies a hydrophobic alanine residue into a hydrophilic threonine (A47T) in a highly conserved domain of ND3 subunit. Furthermore, this defect could be transferred along with the mutant mtDNAs to rho degrees lymphoblastoid cells in cybrid experiments. However, nuclear modifier genes may also play a role in the phenotypic expression and severity of the 10197G>A mutation. The association of the 10197G>A ND3 mutation with an isolated biochemical defect involving complex I and the discovery of the 10197G>A mutation with a similar phenotype in three unrelated families establish its pathogenicity and demonstrate that the amino acid position A47 is important for the function of complex I. These results show that the 10197G>A mutation in the mitochondrial ND3 gene should be considered as a common mtDNA mutation responsible for LS and dystonia.
Adult↗
Identification of recurrent and novel mutations in the LDL receptor gene in German patients with familial hypercholesterolemia.
In order to identify mutations in the low density lipoprotein receptor (LDLR) gene in primary hypercholesterolemia, we screened 100 unrelated German individuals with elevated plasma LDL-C (LDL-C > 4,7 mmol/l) for mutations in the 18 exons and their flanking intronic sequences including the promoter region of the LDL-R gene using a combination of polymerase chain reaction (PCR), denaturing gradient gel electrophoresis (DGGE) and direct sequencing. In addition we tested all patients for the presence of mutations in codons 3456 - 3553 of the gene encoding apolipoprotein B-100. In 56 individuals we detected 37 different mutations affecting the LDL-R gene, 16 of which, designated C122R, C127Y, C163W, F179L, R236W, E296X, R553C, V618D, T721I, V785D, G1358+2A, 257delTCTGGAGGT, 657delC, 676insACGGTATGGACTGCAdelGACG, C1205delTCT, 2420delTCCTTCT, have not yet been reported. One proband was a compound heterozygote showing two separate sequence variations (E207X and T705I). Seven patients were heterozygous for the mutation R3500Q within the apoB-100 gene. These results demonstrate that there is a broad spectrum of mutations in the LDL-R gene and that the R3500Q mutation is a frequent cause of hypercholesterolemia in the German population.
Adolescent↗
Use of the single-strand conformational polymorphism method to detect recurrent and novel mutations in the low-density lipoprotein receptor gene in patients with familial hypercholesterolaemia: detection of a novel mutation Asp200-->Gly.
The single-strand conformational polymorphism (SSCP) method was used to look for mutations in the 3' half of exon 4 of the low-density lipoprotein receptor gene in patients with familial hypercholesterolaemia (FH). One set of conditions were found which allowed the detection of four of the mutations that have previously been reported in this part of the gene and detected in patients in the United Kingdom: the 3-bp deletion (del Gly197) the 2-bp deletion (STOP 216), the Asp206-->Glu mutation and the Cys210-->STOP. The method was used to screen 50 patients with definite or probable FH from London. Two were identified who were carriers of the 3-bp deletion of Gly197, one who was a carrier of the Asp206-->Glu mutation and one who was a carrier of a novel mutation that alters Asp200-->Gly. This mutation creates a cutting site for the restriction enzyme MspI. In a further sample of 200 patients from London with FH one additional apparently unrelated individual was detected who was a carrier of this defect. Thus in the sample of 50 patients, four (8%) had a mutation in this part of exon 4 that could be readily detected using the SSCP method, suggesting that this approach will be useful for rapid screening for mutations in patients with FH.
Aspartic Acid↗
Comprehensive Clinicopathologic, Immunohistochemical, and Genomic Profiling of Sporadic Ampullary Somatostatin-producing D-cell Neuroendocrine Tumors Identifies Recurrent HRAS Hotspot Mutations.
Ampullary somatostatin-producing D-cell neuroendocrine tumors are rare neoplasms that may be associated with type 1 neurofibromatosis. The molecular features of sporadic ampullary somatostatin-producing D-cell neuroendocrine tumors (SAMSOM-NETs) remain poorly characterized. We performed an integrated morphological, immunohistochemical, and genomic analysis of a multicenter series of SAMSOM-NETs. Eleven cases were included (73% male; median age: 63 years). All six patients who underwent lymphadenectomy were staged as pN1, and liver metastases were found in three cases; however, no tumor-related deaths occurred (median follow-up: 104 months). Common histologic features that can pose diagnostic challenges in the differential diagnosis with adenocarcinoma included a tubulo-glandular architecture (100%), periodic Acid-Schiff (PAS)-positive intraluminal mucin (73%), MUC1 expression (100%), and carcinoembryonic antigen (45%) expression. All tumors exhibited dot-like cytoplasmic reactivity for cytokeratins (CK) CAM5.2 or CK AE1/AE3, and 82% were CK7-positive. ISL1 and PDX1 were diffusely expressed in all cases, while CDX2 was positive in 54% and ARX showed only focal expression in four tumors. Genomic profiling revealed microsatellite stability and low tumor mutational burden. Alterations in the RAS pathway, including HRAS mutations (4 cases, 36%), a KRAS mutation (1 case), and NF1 alterations (one case), were identified in 54% of cases and in all tumors with liver metastases. Additional molecular findings included a CDK12 splice-site alteration and an NTRK3::PRDM4 fusion. Potentially actionable alterations affecting kinase-related pathways were detected in 64% of tumors. Our findings support SAMSOM-NET as a peculiar neuroendocrine tumor subtype showing distinctive histologic and molecular characteristics with potential diagnostic and therapeutic implications.
Humans↗
The case of the unreliable SNP: recurrent back-mutation of Y-chromosomal marker P25 through gene conversion.
The Y-chromosomal binary marker P25 is a paralogous sequence variant, rather than a SNP: three copies of the P25 sequence lie within the giant palindromic repeats on Yq, and one copy has undergone a C to A transversion to define haplogroup R1b (designated C/C/A). Since gene conversion is known to be active in the palindromic repeats, we reasoned that P25 might be liable to back-mutation by gene conversion, yielding the ancestral state C/C/C. Through analysis of a set of binary markers in Y-chromosomes in two large samples from Great Britain and the Iberian Peninsula we show that such conversion events have occurred at least twice, and provide preliminary evidence that the reverse conversion event (yielding C/A/A) has also occurred. Because of its inherent instability, we suggest that P25 be used with caution in forensic studies, and perhaps replaced with the more reliable binary marker M269.
Chromosomes, Human, Y↗
BRCA1 and BRCA2 mutations among 233 unselected Finnish ovarian carcinoma patients.
Germline mutations of BRCA1 and BRCA2 predispose to hereditary breast-ovarian cancer syndrome. In Finland, 20 different BRCA1/2 mutations have been identified, and 13 of them are founder mutations that account for the vast majority of Finnish BRCA1/2 families. The purpose of our study was to determine the prevalence of BRCA1/2 mutations in unselected Finnish ovarian carcinoma patients and to evaluate the relationship between mutation carrier status and personal/family history of cancer. Two hundred and thirty-three patients were screened for all the 20 BRCA1/2 mutations known in the Finnish population. Additionally, a subgroup of patients with personal history of breast cancer and/or family history of breast and/or ovarian cancer was screened for novel BRCA1/2 mutations. Thirteen patients (5.6%) had mutations: eleven in BRCA1 and two in BRCA2. All the mutation-positive patients were carriers of the previously known Finnish BRCA1/2 mutations, and seven recurrent founder mutations accounted for 12 of the 13 mutations detected. A logistic regression analysis was used to determine the odds of mutation for ovarian carcinoma patients. The most significant predictor of a mutation was the presence of both breast and ovarian cancer in the same woman, but family history of breast cancer was also strongly related to mutation carrier status. Although BRCA1/2 mutation testing is not warranted in the general Finnish ovarian cancer patient population, patients who have also been diagnosed with breast cancer or have family history of breast or breast and ovarian cancer could benefit from referral to genetic counselling and mutation testing.
BRCA1 Protein↗
Spectrum of mutations in PTPN11 and genotype-phenotype correlation in 96 patients with Noonan syndrome and five patients with cardio-facio-cutaneous syndrome.
Noonan syndrome (NS) is a relatively common, but genetically heterogeneous autosomal dominant malformation syndrome. Characteristic features are proportionate short stature, dysmorphic face, and congenital heart defects. Only recently, a gene involved in NS could be identified. It encodes the non-receptor protein tyrosine phosphatase SHP-2, which is an important molecule in several intracellular signal transduction pathways that control diverse developmental processes, most importantly cardiac semilunar valvulogenesis. We have screened this gene for mutations in 96 familial and sporadic, well-characterised NS patients and identified 15 different missense mutations in a total of 32 patients (33%), including 23 index patients. Most changes clustered in one exon which encodes parts of the N-SH2 domain. Five of the mutations were recurrent. Interestingly, no mutations in the PTPN11 gene were detected in five additional patients with cardio-facio-cutaneous (CFC) syndrome, which shows clinical similarities to NS.
DNA Mutational Analysis↗
Assessment of a rapid-cycle PCR assay for the identification of the recurrent c.3421C>T mutation in the ABCC6 gene in pseudoxanthoma elasticum patients.
Pseudoxanthoma elasticum (PXE) is a heritable disorder of the connective tissue. Mutations in the ABCC6 gene could be linked to this disease and, just recently, the c.3421C>T mutation was also associated with a high risk of coronary artery disease. We have now developed new real-time PCR assays for the accurate and rapid determination of the c.3421C>T genotype. Using our new assay, we analyzed the presence of the c.3421C>T mutation in the largest collection of DNA samples from unrelated German PXE patients (n=64) and in a control cohort (n=910). For assay setup, two sets of samples with known genotype for the c.3421C>T mutation were analyzed over a period of 14 days. Results were confirmed by restriction endonuclease mapping, sequence-specific PCR and DNA sequencing. In order to ensure that no further mutations or deletions interfered with the c.3421C>T genotyping, we scanned the exon 24 of the ABCC6 gene by DHPLC and investigated the presence of the ABCC6del23-29 deletion in all patients. The assay has been set up on a group of patients with known genotype and validated on 64 PXE patients. In this group four PXE patients (6.3%) were found to be homozygous and 25 (39.0%) to be heterozygous carriers of the c.3421C>T mutation. The common ABCC6del23-29 deletion, possibly interfering with genotype determination, was searched and excluded. Furthermore, two novel mutations in the ABCC6 gene could be identified in two patients. The novel mutations c.3389C>T and c.3341G>A did not interfere with our new assay. Our new c.3421C>T genotyping assays can be used for the rapid identification of this frequent mutation in PXE patients and of the recently newly proposed cardiac risk factor in young patients with myocardial infarcts of unknown origin.
Adult↗
A recurrent keratin 14 mutation in Dowling-Meara epidermolysis bullosa simplex.
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Animals↗
A recurrent homozygous nonsense mutation within the LAMA3 gene as a cause of Herlitz junctional epidermolysis bullosa in patients of Pakistani ancestry: evidence for a founder effect.
The anchoring filament protein laminin 5 is abnormally expressed in the skin of patients with Herlitz junctional epidermolysis bullosa (H-JEB). In this study, we performed mutational analysis on genomic DNA from a H-JEB child of first-cousin Pakistani parents, and identified a homozygous C-to-T transition in the LAMA3 gene of laminin 5 resulting in a premature termination codon (CGA-TGA) on both alleles. This mutation, R650X, has been previously reported in two other seemingly unrelated H-JEB individuals of Pakistani ancestry. Although this mutation may represent a mutational hotspot within the LAMA3 gene, haplotype analysis based on a silent intragenic polymorphism (GCC/GCG, alanine 429; GenBank no. L34155), and on three flanking microsatellite polymorphism (D18S45, D18S478, and D18S480), suggests that a common ancestral allele may be present in all three cases.
Base Sequence↗
A recurrent intragenic deletion mutation in DSG4 gene in three Pakistani families with autosomal recessive hypotrichosis.
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Cadherins↗
A molecular and clinical study of Larsen syndrome caused by mutations in FLNB.
BACKGROUND: Larsen syndrome is an autosomal dominant osteochondrodysplasia characterised by large-joint dislocations and craniofacial anomalies. Recently, Larsen syndrome was shown to be caused by missense mutations or small inframe deletions in FLNB, encoding the cytoskeletal protein filamin B. To further delineate the molecular causes of Larsen syndrome, 20 probands with Larsen syndrome together with their affected relatives were evaluated for mutations in FLNB and their phenotypes studied. METHODS: Probands were screened for mutations in FLNB using a combination of denaturing high-performance liquid chromatography, direct sequencing and restriction endonuclease digestion. Clinical and radiographical features of the patients were evaluated. RESULTS AND DISCUSSION: The clinical signs most frequently associated with a FLNB mutation are the presence of supernumerary carpal and tarsal bones and short, broad, spatulate distal phalanges, particularly of the thumb. All individuals with Larsen syndrome-associated FLNB mutations are heterozygous for either missense or small inframe deletions. Three mutations are recurrent, with one mutation, 5071G-->A, observed in 6 of 20 subjects. The distribution of mutations within the FLNB gene is non-random, with clusters of mutations leading to substitutions in the actin-binding domain and filamin repeats 13-17 being the most common cause of Larsen syndrome. These findings collectively define autosomal dominant Larsen syndrome and demonstrate clustering of causative mutations in FLNB.
Abnormalities, Multiple↗
Identification of recurrent and novel mutations in exon 4 of the LDL receptor gene in patients with familial hypercholesterolemia in the United Kingdom.
A group of 200 patients with familial hypercholesterolemia (FH) who were attending lipid clinics in the London area have been screened for four known point mutations and a microdeletion in exon 4 of the low density lipoprotein receptor gene by polymerase chain reaction (PCR) amplification of genomic DNA and either enzyme digestion of the product or hybridization with allele-specific oligonucleotides. A point mutation of Ser156-->Leu that was initially described in a Puerto Rican family was found in one patient of Polish origin on a different haplotype from that described originally and thus is likely to have occurred independently. A 3-bp deletion that causes deletion of amino acid Gly197 was found in six of the patients, who were all of Jewish origin and who shared the same haplotype for the mutant allele. A mutation of Asp206-->Glu that has been described in the Afrikaner population was found in three patients, two of UK origin and one a recent immigrant from South Africa. In all cases the haplotype of the mutant allele was compatible with that described in the original patient. The mutations at Asp154 reported in South African patients and at Glu207 reported in French Canadian patients were not detected in this sample. However, two additional mutations have been identified in this sample: the first, a 2-bp deletion in codon 206 that was found in five patients, all of British ancestry, and the second, a point mutation in a single patient of Irish origin that creates a stop codon at residue Cys210.(ABSTRACT TRUNCATED AT 250 WORDS)
Alleles↗
A new and recurrent activating length mutation in exon 20 of the FLT3 gene in acute myeloid leukemia.
Activating length mutations in the juxtamembrane (JM) domain of the FLT3 gene (FLT3-LM) and mutations in the catalytic domain (FLT3D835/836) of this receptor tyrosine kinase represent the most frequent genetic alterations in acute myeloid leukemia (AML). Here, we describe a 6-bp insertion in the activation loop of FLT3 between codons 840 and 841 of FLT3 (FLT3-840GS) in 2 unrelated patients with AML. Screening for other activating mutations of FLT3, KIT, and NRAS showed no further genetic alterations in patients carrying the FLT3-840GS. In functional analyses we could show that this mutant is hyperphosphorylated on tyrosine and confers interleukin 3-independent growth to Ba/F3 cells, which can be inhibited by a specific FLT3 protein tyrosine kinase (PTK) inhibitor. Our results show for the first time that in addition to known mutations in the JM and the catalytic domain, further activating length mutations exist in the FLT3 gene.
Aged↗
Protein-tyrosine phosphatase, nonreceptor type 11 mutation analysis and clinical assessment in 45 patients with Noonan syndrome.
We report on PTPN11 (protein-tyrosine phosphatase, nonreceptor type 11) mutation analysis and clinical assessment in 45 patients with Noonan syndrome. Sequence analysis was performed for all of the coding exons 1-15 of PTPN11, revealing a novel 3-bp deletion mutation and 10 recurrent missense mutations in 18 patients. Clinical assessment showed that 1) the growth pattern was similar in mutation-positive and mutation-negative patients, with no significant difference in birth length [-0.6 +/- 2.2 sd (n = 10) vs. -0.6 +/- 1.4 sd (n = 21); P = 0.95], childhood height [-2.6 +/- 1.1 sd (n = 14) vs. -2.1 +/- 1.6 sd (n = 23); P = 0.28], or target height [-0.4 +/- 0.9 sd (n = 14) vs. -0.2 +/- 0.7 sd (n = 17); P = 0.52]; 2) pulmonary valve stenosis was more frequent in mutation-positive patients than in mutation-negative patients (10 of 18 vs. 6 of 27; P = 0.02), as was atrial septal defect (10 of 18 vs. 4 of 27; P = 0.005), whereas hypertrophic cardiomyopathy was present in five mutation-negative patients only; and 3) other features were grossly similar in the prevalence between mutation-positive and mutation-negative patients, but hematological abnormalities, such as bleeding diathesis and juvenile myelomonocytic leukemia, were exclusively present in mutation-positive patients (5 of 18 vs. 0 of 27; P = 0.007). The results suggest that PTPN11 mutations account for approximately 40% of Noonan syndrome patients, as has been reported previously. Furthermore, assessment of clinical features, in conjunction with data reported previously, implies that the type of cardiovascular lesions and the occurrence of hematological abnormalities are different in mutation-positive and mutation-negative patients, whereas the remaining findings are similar in the two groups of patients.
Adolescent↗
The SRY-1532 site of the human Y chromosome is subject to recurrent single nucleotide mutations.
Haplotype determination based on three Y-linked polymorphic sites, 92R7 (C/T), SRY-1532 (A/G), and YAP (-/+), in 127 males belonging to three caste Hindu populations of South India (Vizag Brahmins, Peruru Brahmins, and Kammas) and 13 males belonging to a migrant group (the Siddis) showed the existence of all four haplotypes (CA-, CG-, TG-, and TA-) under the YAP- background. This finding suggests that the reverse mutation (G-->A) at the SRY-1532 site, described earlier in the literature, is present in South Indian populations as well. The YAP+ mutation was seen in only five Siddi individuals. Four of these were of the CG+ haplotype structure, but a novel haplotype (CA+) was found in one male. To explain the occurrence of the six haplotypes found within these three sites, a haplotype tree is constructed that introduces a new reverse mutation at the SRY-1532 site (G-->A), occurring under the CG+ background after the migrant Siddi population arrived in India.
Gene Frequency↗
One novel and two recurrent missense DKC1 mutations in patients with dyskeratosis congenita (DKC).
X-linked dyskeratosis congenita (DKC) is a progressive multisystem disorder most severely affecting tissues with a high cellular turnover such as skin, mucous membranes, and blood. Most patients die of bone marrow failure, although the chances of succumbing to various types of cancer and pulmonary disease are also high. DKC is caused predominantly by missense mutations in the DKC1 gene linked to Xq28. Some of the clinical features are reminiscent of premature ageing and this agrees with recent indications that DKC could be a telomere maintenance disorder. There is considerable variability in the type, severity, and age at onset of the various anomalies. Recognition of this has increased with the finding that patients with Hoyeraal-Hreidarsson syndrome (HHS) who exhibit severe neurological problems in addition to early-onset pancytopenia, also bear mutations in the DKC1 gene. For these reasons, and compounded by the range of mutations, phenotype-genotype correlations and accurate assessments of prognosis have not been possible. To complement the present data, we here report on three new cases of DKC and their mutations. One is a novel mutation in the exon 3 (K43E). The other two represent a frequently recurring mutation in exon 11 (A353V) and a less frequently recurring mutation in the exon 3 (T49M).
Adolescent↗