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Recurrence of a nonsense mutation in the conserved domain of SRY in a Brazilian patient with 46,XY gonadal dysgenesis.

We tested a female patient with 46,XY karyotype and pure gonadal dysgenesis for the presence of the SRY gene and for mutations within the SRY conserved domain. A point mutation was identified at nucleotide position 209 with respect to the first ATG. The base substitution is a G-->A transition in the first nucleotide of codon 70 which changes a tryptophan (TGG) to a stop codon (TAG). Even though the father was not available for investigation we assumed that it is a de novo mutation, since it probably generates a nonfunctional truncated protein.

Adolescent↗

Recurrent LDL-receptor mutation causes familial hypercholesterolaemia in South African coloureds and Afrikaners.

Three low-density lipoprotein receptor (LDLR) gene mutations were previously shown to cause familial hypercholesterolaemia (FH) in up to 90% of affected Afrikaners. Association of each mutation with a single chromosomal background provided molecular genetic evidence that the proposed 'founder gene effect' was responsible for the high prevalence of FH among white Afrikaners. In this study we report the identification of the FH Afrikaner-2 (FH2) mutation, Val408 to Met, in the so-called coloured population of South Africa, a people of mixed ancestry, with rapid non-radioactive methods for mutation detection. Haplotype analysis with polymorphisms on both sides of the FH2 mutation indicated that the identical LDLR gene mutations found in two different South African population groups were caused by independent events at a potential CpG mutational 'hot spot'. The allelic variation giving rise to the different chromosomal backgrounds of the FH2 mutation does not affect the properties of the abnormal LDLR protein product which causes FH in these subjects. This mutation is thus expected to cause the same severe form of FH in affected coloureds as was previously demonstrated in Afrikaners. Detection of mutant LDLR gene alleles in polymerase chain reaction products, directly after gel electrophoresis, now allows accurate presymptomatic diagnosis of the FH2 mutation in FH patients from two different South African population groups.

Base Sequence↗

The human homologue (PEG3) of the mouse paternally expressed gene 3 (Peg3) is maternally imprinted but not mutated in women with familial recurrent hydatidiform molar pregnancies.

OBJECTIVES: We mapped a locus for autosomal recessive molar pregnancies with biparental genomic contribution to chromosome 19q13.4 between D19S924 and D19S890. This 5-Mb region is homologous to proximal mouse chromosome 7 and contains a cluster of Krüppel-type zinc finger genes, including the human homologue of the mouse imprinted genes: the paternally expressed gene 3 (PEG3) and the maternally expressed Zim1 genes. We analyzed the PEG3 gene for mutations in women with familial recurrent hydatidiform moles and to determine its imprinting status in humans. METHODS: We used database searches and screened cDNA libraries to find the complete genomic structure of PEG3. Polymerase chain reaction (PCR) amplification and direct sequencing of coding exons and flanking introns were performed on genomic DNA from the affected women. Allele-specific methylation and expression were studied by methylation-sensitive Southern analysis of a 5' located CpG island and by reverse-transcription PCR of total lymphoblast-derived RNA of normal individuals who were informative for two expressed polymorphisms. RESULTS: We did not detect any mutations in the coding region of PEG3 in the affected women. We observed allele-specific methylation of the CpG island and expression from the paternal allele in two independent informative pedigrees. CONCLUSION: Consistent with the findings in the mouse, the human PEG3 gene is expressed from the paternal allele. Our data support that PEG3 is not mutated in women with familial recurrent hydatidiform moles, although mutations in the regulatory regions that might affect imprinting or transcriptional level of the gene could not be evaluated.

Animals↗

Prospective study of FGFR3 mutations as a prognostic factor in nonmuscle invasive urothelial bladder carcinomas.

PURPOSE: To determine the frequency and the prognostic value of fibroblast growth factor receptor 3 (FGFR3) mutations in patients with nonmuscle invasive bladder tumors according to tumor stage and grade. PATIENTS AND METHODS: Seven hundred seventy-two patients with newly diagnosed bladder tumors were recruited. Tumors were reviewed by expert pathologists. Patients were prospectively followed-up (median, 62.6 months for disease-free patients) through review of hospital records and telephone interviews. The sequence of exons 7 and 10 of FGFR3 was analyzed by polymerase chain reaction and direct sequencing. We assessed the association of mutations with stage and grade. The predictive value of mutations for recurrence, progression, and mortality were assessed using Kaplan-Meier and Cox multivariable models. RESULTS: Mutations were more common among low malignant potential neoplasms (LMPN; 77%) and TaG1/TaG2 tumors (61%/58%) than among TaG3 tumors (34%) and T1G3 tumors (17%). The S249C, Y375C, S248C, and G372C mutations accounted for 91.5% of all sequence changes. The A393E substitution was associated with LMPN (P < .001). The F386L polymorphism was more frequent among patients with low-grade tumors (odds ratio, 6.97; 95%CI, 1.40 to 47.06; P = .009). In the multivariable analysis of all superficial tumors, mutations were associated with increased risk of recurrence. However, in the stratified analyses only patients with TaG1 tumors had a significantly higher risk of recurrence (hazard ratio, 2.12; 95%CI, 1.28 to 3.53; P = .004). CONCLUSION: The findings of this large study strongly support the notion that FGFR3 mutations characterize a subgroup of bladder cancers with good prognosis; patients with mutant TaG1 tumors have a higher risk of recurrence; and the F386L variant is selectively associated with low-grade tumors.

Adult↗

Is p53 gene mutation an indicatior of the biological behaviors of recurrence of hepatocellular carcinoma?

AIM: To evaluate mutant p53 gene in primary hepatocellular carcinoma and to investigate the correlation between it and the recurrence of hepatocellular carcinoma. METHODS: Mutations of p53 gene were examined using anti-human p53 monoclonal antibody and immunohistochemical staining in 79 resected hepatocellular carcinomas. The correlations among variables of p53 positivity and invasiveness, disease free interval and survival were studied. In addition, in those who developed recurrence, the correlation among p53 positivity, clinical features and post-recurrence survival were also studied. RESULTS: Of these 79 cases, 64 (81 %) had p53 mutation. Those patients with mutant p53 positivity had significantly more tumor recurrence (76.6 % vs 40.0 %, P=0.0107). However, the COX proportional hazards model showed that p53 overexpression had only weak correlations with recurrence free interval and survival time (P=0.088 and 0.081), which was probably related to the short duration of follow-up. The invasiveness variables may be predictors of HCC recurrence. On univariate analysis, more patients with mutant p53 positivity had vascular permeation (78.1 vs 40.0 %, P=0.0088, O.R. (odds ratio) =5.3), grade II-IV differentiation (98.4 vs 80.0 %, P=0.0203, O.R. =15.7), no complete capsule (82.8 vs 53.3 %, P=0.0346, O.R. =4.2) and daughter nodules (60.9 vs. 33.3 %, P=0.0527, O.R. =3.1) than patients with negative p53 staining. On multivariate analysis, only vascular permeation and grade of differentiation remained significant (P=0.042 and 0.012). There was no statistically significant correlation between the status of p53 in the primary lesion and the clinical features of recurrent hepatocellular carcinomas examined, including extrahepatic metastasis (P=0.1103) and the number of recurrent tumors (P=1.000) except for disease over more than one segment in the extent of recurrent tumors (P=0.0043). The post-recurrence median survival was lower in patients in whom p53 mutation had been detected in the primary lesion with a weak significance (3.42 months vs 11.0 months, P=0.051). CONCLUSION: Our findings suggest that p53 mutation correlates significantly with invasiveness including vascular permeation, grade of cellular differentiation, incomplete capsule and multinodular lesions. Hepatocellular carcinomas with p53 mutations had more tumor recurrence and p53 mutation may also influence disease recurrence interval and survival time. Hepatocellular carcinomas with p53 mutations recur more extensively with a shorter survival. Therefore, p53 mutation in the primary lesion is useful as an indicator of the biological behavior of recurrent hepatocellular carcinomas.

Adult↗

Thirty-four novel mutations detected in factor VIII gene by multiplex CSGE: modeling of 13 novel amino acid substitutions.

Detection of causal mutations is required for genetic counseling. Molecular modeling combined with patients' phenotype provides significant insight into structure-function relationship of factor (F)VIII molecule. Our objective was to identify defects in the gene of FVIII by a sensitive and simple scanning technique with high throughput in order to study molecular mechanisms by which novel amino acid substitutions may lead to hemophilia A. A cohort of 81 families with mild, moderate and severe hemophilia A negative in intron 22 inversion was studied. For detection of mutations in the FVIII gene a conformation sensitive gel electrophoresis (CSGE) was modified by multiplexing. Thirteen novel amino acid substitutions were studied by molecular modeling and a correlation with the cross-reactive material (CRM) phenotype was performed. In 74 families, 59 different mutations were detected. Six different mutations were recurrent in 21 unrelated families. Thirty-four novel mutations included 19 point mutations, four small insertions, nine small deletions and two complex mutations. Thirteen novel amino acid substitutions occurred at residues conserved in FVIII orthologs. Five of them were associated with a discrepancy between FVIII activity and antigen; another five with CRM reduced phenotype and one with undetectable FVIII antigen. Multiplexing of the CSGE significantly increased its throughput without substantial loss of sensitivity. Molecular modeling suggested mechanisms by which substitutions at residues 382 and 569, located outside the proposed FIXa-binding region, may influence FVIII/FIXa interaction. His2155 was predicted to participate in FVIII/VFW binding.

Amino Acid Substitution↗

The effect of deleterious alleles on adaptation in asexual populations.

We calculate the fixation probability of a beneficial allele that arises as the result of a unique mutation in an asexual population that is subject to recurrent deleterious mutation at rate U. Our analysis is an extension of previous works, which make a biologically restrictive assumption that selection against deleterious alleles is stronger than that on the beneficial allele of interest. We show that when selection against deleterious alleles is weak, beneficial alleles that confer a selective advantage that is small relative to U have greatly reduced probabilities of fixation. We discuss the consequences of this effect for the distribution of effects of alleles fixed during adaptation. We show that a selective sweep will increase the fixation probabilities of other beneficial mutations arising during some short interval afterward. We use the calculated fixation probabilities to estimate the expected rate of fitness improvement in an asexual population when beneficial alleles arise continually at some low rate proportional to U. We estimate the rate of mutation that is optimal in the sense that it maximizes this rate of fitness improvement. Again, this analysis relaxes the assumption made previously that selection against deleterious alleles is stronger than on beneficial alleles.

Adaptation, Physiological↗

Recurrence of the T666M calcium channel CACNA1A gene mutation in familial hemiplegic migraine with progressive cerebellar ataxia.

Familial hemiplegic migraine (HM) is an autosomal dominant migraine with aura. In 20% of HM families, HM is associated with a mild permanent cerebellar ataxia (PCA). The CACNA1A gene encoding the alpha1A subunit of P/Q-type voltage-gated calcium channels is involved in 50% of unselected HM families and in all families with HM/PCA. Four CACNA1A missense mutations have been identified in HM: two in pure HM and two in HM/PCA. Different CACNA1A mutations have been identified in other autosomal dominant conditions: mutations leading to a truncated protein in episodic ataxia type 2 (EA2), small expansions of a CAG trinucleotide in spinocerebellar ataxia type 6 and also in three families with EA2 features, and, finally, a missense mutation in a single family suffering from episodic ataxia and severe progressive PCA. We screened 16 families and 3 nonfamilial case patients affected by HM/PCA for specific CACNA1A mutations and found nine families and one nonfamilial case with the same T666M mutation, one new mutation (D715E) in one family, and no CAG repeat expansion. Both T666M and D715E substitutions were absent in 12 probands belonging to pure HM families whose disease appears to be linked to CACNA1A. Finally, haplotyping with neighboring markers suggested that T666M arose through recurrent mutational events. These data could indicate that the PCA observed in 20% of HM families results from specific pathophysiologic mechanisms.

Calcium Channels↗

Fibroblast growth factor receptor 3 mutation in nonsyndromic coronal synostosis: clinical spectrum, prevalence, and surgical outcome.

OBJECT: A recurrent point mutation in the fibroblast growth factor receptor 3 gene that converts proline 250 into arginine has been reported recently in cases of apparently nonsyndromic coronal craniosynostosis. The goal of the present study was to examine the phenotype of patients in whom this mutation was present, to determine the prevalence of the condition, and to assess the functional and the morphological outcome of the surgically treated patients. METHODS: A DNA analysis was performed in 103 children suffering from apparently isolated coronal synostosis, 41 of whom had bilateral and 62 of whom had unilateral disease. There were 31 boys and 72 girls in the study group. Sixty cases were sporadic and 43 were familial; the 43 familial cases arose in 33 unrelated families. The mutation was found in seven (12%) of 60 sporadic cases and in 24 (73%) of the 33 families. The functional and morphological results were assessed in all surgically treated patients who had at least 1 year of follow up and who were at least 3 years of age at the time of assessment. A comparison was made between patients with the mutation and those without. CONCLUSIONS: The most typical presentation was seen in girls and consisted of a bicoronal synostosis resulting in a severe brachycephaly associated with mild hypertelorism and marked bulging of the temporal fossae, which resulted in a huge enlargement of the upper part of the face. The most frequently associated extracranial anomaly was brachydactyly, identified either clinically or radiologically. Based on the proportion of bilateral and unilateral coronal synostoses, the present data indicate that the mutation is associated with more severe cases and that girls with the mutation are more severely affected than boys. The functional and morphological results were worse in patients in whom the mutation was present as compared with those in whom it was not.

Arginine↗

High frequency of the 425A-->G splice-site mutation and novel mutations of the COL7A1 gene in central Europe: significance for future mutation detection strategies in dystrophic epidermolysis bullosa.

BACKGROUND: Mutations in the type VII collagen gene (COL7A1) are responsible for dominant and recessive forms of dystrophic epidermolysis bullosa (DEB). These mutations are usually specific for individual families; only a few cases of recurring mutations have been identified. OBJECTIVES: Forty-three unrelated Hungarian and German patients with different DEB phenotypes were screened for novel and recurrent COL7A1 mutations. METHODS: All patients were classified based on clinical and genetic findings, skin immunofluorescent antigen mapping, and electron microscopic studies. Mutation analysis was performed by amplification of genomic DNA with polymerase chain reaction using COL7A1-specific primers, heteroduplex analysis, and direct nucleotide sequencing. Restriction endonuclease digestion was used for family screening and mutation verification. Results In this group of patients, the splice-site mutation 425A-->G was observed frequently, in 11 of 86 alleles (12.8%), once in homozygous form and in nine cases in heterozygous form. One of 100 control alleles from clinically unaffected individuals also carried the mutation. We also identified three novel mutations: the 976-3C-->A splice-site mutation, and the 4929delT and 8441-15del20 deletions. CONCLUSIONS: High recurrence of the splice-site mutation 425A-->G in central European patients with DEB should be taken into account when designing COL7A1 mutation detection strategies. Reporting of three novel COL7A1 mutations in this study further emphasizes the molecular heterogeneity of DEB and provides more information for studies on genotype-phenotype correlations in different DEB subtypes.

Adolescent↗

The significance of p53 mutations as an indicator of the biological behavior of recurrent hepatocellular carcinomas.

The significance of p53 mutations in the primary lesion for recurrent hepatocellular carcinoma (HCC) was evaluated. Mutations of p53 were examined using nonradioisotopic (nonRI)-polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) in 98 resected HCCs. Of the 98 cases, 25 (26%) had a p53 mutation. In 83 patients who survived surgery, the presence of a p53 mutation was associated with a shortened overall survival (P < 0.001) and a shortened cancer-free survival (P < 0.05). In 43 patients who developed recurrence, there was no statistically significant correlation between the status of p53 in the primary lesion and the clinical features of recurrent HCCs examined, i.e., extrahepatic metastasis, the number of recurrent tumors, extent of recurrent tumors, and treatment for recurrent tumors. However, postrecurrence survival was significantly lower in patients in whom a p53 mutation had been detected in the primary lesion (P < 0.01). A multivariate analysis for prognostic value after recurrence revealed that the p53 mutation was a useful independent prognostic factor affecting survival after recurrence (P < 0.01). In conclusion, our findings suggest that HCCs with p53 mutations have a high malignant potential based on their poor prognosis. Therefore, a p53 mutation in the primary lesion is useful as an indicator of the biological behavior of recurrent HCCs.

Carcinoma, Hepatocellular↗

Common mutations in the fibroblast growth factor receptor 3 (FGFR 3) gene account for achondroplasia, hypochondroplasia, and thanatophoric dwarfism.

The mapping of the achondroplasia locus to the short arm of chromosome 4 and the subsequent identification of a recurrent missense mutation (G380R) in the fibroblast growth factor receptor 3 (FGFR-3) gene has been followed by the detection of common FGFR-3 mutations in two clinically related disorders: thanatophoric dwarfism (types I and II) and hypochondroplasia. The relative clinical homogeneity of achondroplasia was substantiated by demonstration of its genetic homogeneity as more than 98% of all patients hitherto reported exhibit mutations in the transmembrane receptor domain. Although most hypochondroplasia cases were accounted for by a recurrent missense substitution (N540K) in the first tyrosine kinase (TK 1) domain of the receptor, a significant proportion (40%) of our patients did not harbor the N540K mutation and three hypochondroplasia families were not linked to the FGFR-3 locus, thus supporting clinical heterogeneity of this condition. In thanatophoric dwarfism (TD), a recurrent FGFR-3 mutation located in the second tyrosine kinase (TK 2) domain of the receptor was originally detected in 100% of TD II cases, our series seven distinct mutations in three different protein domains were identified in 25 of 26 TD I patients, suggesting that TD, like achondroplasia, is a genetically homogenous skeletal disorder.

Achondroplasia↗

Different epitope structures select distinct mutant forms of an antibody variable region for expression during the immune response.

Antibody variable (V) regions that initially differ from one another by only single amino acid residues at VH-D and D-JH segment junctions (termed canonical V regions) can be elicited in strain A/J mice by three different haptens. Among such V regions an amino acid substitution due to somatic mutation is recurrently observed at VH CDR2 position 58, regardless of which of these haptens is used for immunization. This substitution confers upon a canonical V region a generic increase in affinity for all the haptens. Conversely, the type of amino acid substitution at VH position 59 resulting from somatic mutation that is recurrently observed among such V regions changes with the eliciting hapten, in a manner that correlates directly with the cognate affinity increases (or decreases) for hapten conferred by the observed substitutions. This small subregion of VH CDR2 therefore plays a major role in determining both affinity and specificity for antigen. The data confirm that affinity for antigen is of pivotal importance in determining the degree of selection of different mutant forms of a V region. Moreover, during an immune response a sufficiently diverse mutant repertoire can be generated from a single canonical V region to allow adaptation to increase affinity for three different epitopes.

Amino Acid Sequence↗

An unusual patient with hypercalciuria, recurrent nephrolithiasis, hypomagnesemia and G227R mutation of Paracellin-1. An unusual patient with hypercalciuria and hypomagnesemia unresponsive to thiazide diuretics.

A 19-year-old female patient with hypercalciuria and recurrent nephrolithiasis/urinary tract infection unresponsive to thiazide type diuretics is presented. The patient first experienced nephrolithiasis at the age of 4 years. Afterwards, recurrent passages of stones and urinary tract infection occurred. On diagnostic evaluation at the age of 19 years, she also had hypocitraturia and hypomagnesemia. Her serum calcium concentrations were near the lower limit of normal (8.5-8.8 mg/dl; normal range: 8.5-10.5), her serum magnesium concentrations were 1.15-1.24 mg/dl (normal range: 1.4-2.5) and urinary calcium excretion was 900 mg/24 h. PTH concentrations were increased (110-156 pg/ml; normal range: 10-65). We tried to treat the patient with hydrochlorothiazide at a dose of 50 mg/day. During treatment with thiazide diuretics, PTH concentration remained high and the patient had recurrent urinary tract infections and passages of stones. Serum magnesium concentration did not normalize even under the parenteral magnesium infusion. Her mother had a history of nephrolithiasis 20 years ago. Severe hypomagnesemia in association with hypercalciuria/urinary stones is reported as a rare autosomal recessive disorder caused by impaired reabsorption of magnesium and calcium in the thick assending limp of Henle's loop. Recent studies showed that mutations in the CLDN16 gene encoding paracellin-1 cause the disorder. In exon 4, a homozygous nucleotide exchange (G679C) was identified for the patient. This results in a point mutation at position Glycine227, which is replaced by an Arginine residue (G227R). The mother was heterozygous for this mutation. G227 is located in the fourth transmembrane domain and is highly conserved in the claudin gene family. This case indicates the pathogenetic role of paracellin-1 mutation in familial hypomagnesemia with hypercalciuria and nephrocalcinosis and further underlines the risk of stone formation in heterozygous mutation carriers.

Adult↗

Sporadic multiple primary melanoma cases: CDKN2A germline mutations with a founder effect.

Multiple primary cancers are one of the hallmarks of inherited predisposition. Outside the familial context, multiple primary tumors could be related either to germline de novo mutations or to low-penetrance mutations, in predisposing genes. We selected 100 patients who displayed multiple primary melanoma (MPM) without any known melanoma cases recorded within their families and looked for germline mutations in the two melanoma-predisposing genes identified to date, CDKN2A and CDK4 exon 2. Nine patients (9%) had germline mutations in CDKN2A, whereas none carried germline mutations in exon 2 of CDK4. Seven cases displayed a recurrent missense mutation, G101W, already described in more than 20 melanoma-prone families; one case carried a missense mutation never reported to date (P114S), and the last case was a carrier of a 6 bp insertion at nucleotide 57 resulting in a duplication of codons 18 and 19. To ascertain whether the G101W was a mutational hot spot for de novo mutations or a common founder mutation, we genotyped eight microsatellite markers flanking the CDKN2A gene. After allowing for recombination over time, haplotype sharing provided evidence for an original G101W mutation common to 6 out of 7 sporadic MPM cases. Therefore, it can be concluded that de novo germline CDKN2A mutations associated with MPM are rare.

Adult↗

Genetic heterogeneity of Saethre-Chotzen syndrome, due to TWIST and FGFR mutations.

Thirty-two unrelated patients with features of Saethre-Chotzen syndrome, a common autosomal dominant condition of craniosynostosis and limb anomalies, were screened for mutations in TWIST, FGFR2, and FGFR3. Nine novel and three recurrent TWIST mutations were found in 12 families. Seven families were found to have the FGFR3 P250R mutation, and one individual was found to have an FGFR2 VV269-270 deletion. To date, our detection rate for TWIST or FGFR mutations is 68% in our Saethre-Chotzen syndrome patients, including our five patients elsewhere reported with TWIST mutations. More than 35 different TWIST mutations are now known in the literature. The most common phenotypic features, present in more than a third of our patients with TWIST mutations, are coronal synostosis, brachycephaly, low frontal hairline, facial asymmetry, ptosis, hypertelorism, broad great toes, and clinodactyly. Significant intra- and interfamilial phenotypic variability is present for either TWIST mutations or FGFR mutations. The overlap in clinical features and the presence, in the same genes, of mutations for more than one craniosynostotic condition-such as Saethre-Chotzen, Crouzon, and Pfeiffer syndromes-support the hypothesis that TWIST and FGFRs are components of the same molecular pathway involved in the modulation of craniofacial and limb development in humans.

Acrocephalosyndactylia↗

Duration of anticoagulant treatment for venous thrombosis.

Patients with deep-vein thrombosis require long-term anticoagulant treatment to prevent recurrent venous thromboembolism. Anticoagulant treatment should be continued for at least 3 months in patients with a first-episode of proximal deep-vein thrombosis. In patients with a second-episode of venous thromboembolism, treatment should probably be continued for at least 1 year, because stopping treatment at 3 to 6 months is associated with a high rate of recurrent venous thromboembolism. Indefinite treatment may be indicated in patients with a second-episode of venous thromboembolism, but further clinical trials are required to clarify the risk and benefit of indefinite treatment. Further clinical trials are also required to determine if a longer course of treatment is indicated for subgroups of patients based on clinical characteristics and laboratory features (such as those with idiopathic thrombosis versus postoperative thrombosis, and those with or without identifiable molecular markers of a high risk of recurrent venous thromboembolism such as the factor V Leiden gene mutation).

Anticoagulants↗