Balancing the intermolecular forces in peptide amphiphiles for controlling self-assembly transitions.

While the influence of alkyl chain length and headgroup size on self-assembly behaviour has been well-established for simple surfactants, the rational control over the pH- and concentration-dependent self-assembly behaviour in stimuli responsive peptides remains an elusive goal. Here, we show that different amphiphilic peptides can have similar self-assembly phase diagrams, providing the relative strengths of the attractive and repulsive forces are balanced. Using palmitoyl-YYAAEEEEK(DO3A:Gd)-NH2 and palmitoyl-YAAEEEEK(DO3A:Gd)-NH2 as controls, we show that reducing hydrophobic attractive forces through fewer methylene groups in the alkyl chain will lead to a similar self-assembly phase diagram as increasing the electrostatic repulsive forces via the addition of a glutamic acid residue. These changes allow creation of self-assembled MRI vehicles with slightly different micelle and nanofiber diameters but with minimal changes in the spin-lattice T1 relaxivity. These findings reveal a powerful strategy to design self-assembled vehicles with different sizes but with similar self-assembly profiles.

Comprehensive RNA Analysis of the NF1 Gene in Classically Affected NF1 Affected Individuals Meeting NIH Criteria has High Sensitivity and Mutation Negative Testing is Reassuring in Isolated Cases With Pigmentary Features Only.

BACKGROUND: The detection rate for identifying the underlying mutation in neurocutaneous syndromes is affected by the sensitivity of the mutation test and the heterogeneity of the disease based on the diagnostic criteria. Neurofibromatosis type (NF1) has been defined for 29years by the National Institutes for Health (NIH) criteria which include ≥6 Café au Lait macules (CAL) as a defining criterion. The discovery of SPRED1 as a cause of Legius syndrome which is manifested by CAL, freckling and learning difficulties has introduced substantial heterogeneity to the NIH criteria. METHODS: We have defined the sensitivity of comprehensive RNA analysis on blood of presumed NF1 patients meeting NIH criteria with at least one nonpigmentary criterion and determined the proportion of children with ≥6 CAL and no family history that has an NF1 or SPRED1 genetic variant. RNA analysis was carried out from 04/2009-12/2015 on 361 NF1 patients. FINDINGS: A presumed causative NF1 mutation was found in 166/171 (97.08%-95% CI 94.56-99.6%) of familial cases and 182/190 (95.8%-95% CI 92.93-98.65%) sporadic de novo cases. Two of thirteen (15%) mutation negative individuals had dysembryoplastic neuroepithelial tumour (DNET) compared to 2/348 (0.6%) with an NF1 variant (p=0.007). No SPRED1 variants were found in the thirteen individuals with no NF1 variant. Of seventy-one individuals with ≥6 CAL and no non-pigmentary criterion aged 0-20years, 47 (66.2%) had an NF1 variant six (8.5%) a SPRED1 variant and 18 (25.3%) no disease causing variant. Using the 95.8% detection rate the likelihood of a child with ≥6 CAL having constitutional NF1 drops from 2/3 to 1/9 after negative RNA analysis. INTERPRETATION: RNA analysis in individuals with presumed NF1 has high sensitivity and includes a small subset with DNET without an NF1 variant. Furthermore negative analysis for NF1/SPRED1 provides strong reassurance to children with ≥6 CAL that they are unlikely to have NF1.

The BRCA2 polymorphic stop codon: stuff or nonsense?

BACKGROUND: Despite classification of the BRCA2c.9976A>T, p.(Lys3326Ter) variant as a polymorphism, it has been associated with increased risks of pancreatic, lung, oesophageal and breast cancer. METHODS: We have noticed multiple co-occurrences of the BRCA2 c.9976A>T variant with the pathogenic BRCA2c.6275_6276delTT frameshift mutation p.(Leu2092ProfsTer7) and using a cohort study have assessed if this might account for these tumour risk associations. RESULTS: We identified 52 families with BRCA2c.6275_6276delTT, all of which occur in cis with the BRCA2c.9976A>T variant allele as demonstrated by co-segregation in all family members tested. Of 3245 breast/ovarian cancer samples sequenced for BRCA2, only 43/3245 (1.3%) carried BRCA2 c.9976A>T alone, after excluding individuals with BRCA2c.6275_6276delTT (n=22) or other BRCA1 (n=3) or BRCA2 (n=2) pathogenic mutations. The resultant frequency (1.3%) after removal of co-occurring mutations is lower than the 1.7% and 1.67% frequencies from two control populations for BRCA2 c.9976A>T, but similar to the 1.39% seen in the Exome Aggregation Consortium database. We did not identify increased frequencies of oesophageal, pancreatic or lung cancer in families with just BRCA2 c.9976A>T using person-years at risk analysis. CONCLUSIONS: It is likely that the previous associations of increased cancer risks due to BRCA2c.9976A>T represent reporting bias and are contributed to because the variant is in LD with BRCA2c.6275_6276delTT.

Tumour MLH1 promoter region methylation testing is an effective prescreen for Lynch Syndrome (HNPCC).

BACKGROUND AND AIMS: Lynch syndrome (LS) patients have DNA mismatch repair deficiency and up to 80% lifetime risk of colorectal cancer (CRC). Screening of mutation carriers reduces CRC incidence and mortality. Selection for constitutional mutation testing relies on family history (Amsterdam and Bethesda Guidelines) and tumour-derived biomarkers. Initial biomarker analysis uses mismatch repair protein immunohistochemistry and microsatellite instability. Abnormalities in either identify mismatch repair deficiency but do not differentiate sporadic epigenetic defects, due to MLH1 promoter region methylation (13% of CRCs) from LS (4% of CRCs). A diagnostic biomarker capable of making this distinction would be valuable. This study compared two biomarkers in tumours with mismatch repair deficiency; quantification of methylation of the MLH1 promoter region using a novel assay and BRAF c.1799T>A, p.(Val600Glu) mutation status in the identification of constitutional mutations. METHODS: Tumour DNA was extracted (formalin fixed, paraffin embedded, FFPE tissue) and pyrosequencing used to test for MLH1 promoter methylation and presence of the BRAF c.1799T>A, p.(Val600Glu) mutation 71 CRCs from individuals with pathogenic MLH1 mutations and 73 CRCs with sporadic MLH1 loss. Specificity and sensitivity was compared. FINDINGSS: Unmethylated MLH1 promoter: sensitivity 94.4% (95% CI 86.2% to 98.4%), specificity 87.7% (95% CI 77.9% to 94.2%), Wild-type BRAF (codon 600): sensitivity 65.8% (95% CI 53.7% to 76.5%), specificity 98.6% (95% CI 92.4% to 100.0%) for the identification of those with pathogenic MLH1 mutations. CONCLUSIONS: Quantitative MLH1 promoter region methylation using pyrosequencing is superior to BRAF codon 600 mutation status in identifying constitutional mutations in mismatch repair deficient tumours.

Multivariate analysis of MLH1 c.1664T>C (p.Leu555Pro) mismatch repair gene variant demonstrates its pathogenicity.

Genetic testing of an Irish kindred identified an exonic nucleotide substitution c.1664T>C (p.Leu555Pro) in the MLH1 mismatch repair (MMR) gene. This previously unreported variant is classified as a "variant of uncertain significance" (VUS). Immunohistochemical (IHC) analysis and microsatellite instability (MSI) studies, genetic testing, a literature and online MMR mutation database review, in silico phenotype prediction tools, and an in vitro MMR activity assay were used to study the clinical significance of this variant. The MLH1 c.1664T>C (p.Leu555Pro) VUS co-segregated with three cases of classic Lynch syndrome-associated malignancies over two generations, with consistent loss of MLH1 and PMS2 protein expression on IHC, and evidence of the MSI-High mutator phenotype. The leucine at position 555 is well conserved across a number of species, and this novel variant has not been reported as a normal polymorphism in the general population. In silico and in vitro analyses suggest that this variant may have a deleterious effect on the MLH1 protein and abrogate MMR activity. Evidence from clinical, histological, immunohistochemical, and molecular genetic data suggests that MLH1 c.1664T>C (p.Leu555Pro) is likely to be the pathogenic cause of Lynch syndrome in this family.

Rates of loss of heterozygosity and mitotic recombination in NF2 schwannomas, sporadic vestibular schwannomas and schwannomatosis schwannomas.

Biallelic inactivation of the NF2 gene occurs in the majority of schwannomas. This usually involves a combination of a point mutation or multiexon deletion, in conjunction with either a second point mutation or loss of heterozygosity (LOH). We have performed DNA sequence and dosage analysis of the NF2 gene in a panel of 239 schwannoma tumours: 97 neurofibromatosis type 2 (NF2)-related schwannomas, 104 sporadic vestibular schwannomas (VS) and 38 schwannomatosis-related schwannomas. In total, we identified germline NF2 mutations in 86 out of 97 (89%) NF2 patients and a second mutational event in 77 out of 97 (79%). LOH was by far the most common form of second hit. A combination of microsatellite analysis with either conventional comparative genomic hybridization (CGH) or multiplex ligation-dependent probe amplification (MLPA) identified mitotic recombination (MR) as the cause of LOH in 14 out of 72 (19%) total evaluable tumours. Among sporadic VS, at least one NF2 mutation was identified by sequence analysis or MLPA in 65 out of 98 (66%) tumours. LOH occurred in 54 out of 96 (56%) evaluable tumours, but MR only accounted for 5 out of 77 (6%) tested. LOH was present in 28 out of 34 (82%) schwannomatosis-related schwannomas. In all eight patients who had previously tested positive for a germline SMARCB1 mutation, this involved loss of the whole, or part of the long arm, of chromosome 22. In contrast, 5 out of 22 (23%) tumours from patients with no germline SMARCB1 mutation exhibited MR. High-resolution Affymetrix SNP6 genotyping and copy number (CN) analysis (Affymetrix, Santa Clara, CA, USA) were used to determine the chromosomal breakpoint locations in tumours with MR. A range of unique recombination sites, spanning approximately 11.4 Mb, were identified. This study shows that MR is a mechanism of LOH in NF2 and SMARCB1-negative schwannomatosis-related schwannomas, occurring less frequently in sporadic VS. We found no evidence of MR in SMARCB1-positive schwannomatosis, suggesting that susceptibility to MR varies according to the disease context.

Further genotype--phenotype correlations in neurofibromatosis 2.

Neurofibromatosis 2 (NF2) is caused by mutations in the NF2 gene predisposing carriers to develop nervous system tumours. Different NF2 mutations result in either loss/reduced protein function or gain of protein function (abnormally behaving mutant allele i.e. truncated protein potentially causing dominant negative effect). We present a comparison between the clinical presentations of patients with mutations that are predicted to produce truncated protein (nonsense/frameshift mutations) to those that results in loss of protein expression (large deletions) to elucidate further genotype-phenotype correlations in NF2. Patients with nonsense/frameshift mutations have a younger age of diagnosis and a higher prevalence/proportion of meningiomas (p = 0.002, p = 0.014), spinal tumours (p = 0.004, p = 0.004) and non-VIII cranial nerve tumours (p = 0.006, p = 0.003). We also found younger age of diagnosis of vestibular schwannomas (p = 0.007), higher mean numbers of cutaneous lesions (p = 0.003) and spinal tumours (p = 0.006) in these patients. With respect to NF2 symptoms, we found younger age of onset of hearing loss (p = 0.010), tinnitus (p = 0.002), paraesthesiae (p = 0.073), wasting and weakness (p = 0.001) and headaches (p = 0.049) in patients with nonsense/frameshift mutations. Our comparison shows, additional, new correlations between mutations in the NF2 gene and the NF2 disease phenotype, and this further confirms that nonsense/frameshift mutations are associated with more severe NF2 symptoms. Therefore patients with this class of NF2 mutation should be followed up closely.

Detection of a deletion of exons 8-16 of the UBE3A gene in familial Angelman syndrome using a semi-quantitative dosage PCR based assay.

Angelman syndrome (AS) is a neurodevelopmental disorder caused by failure of expression of the maternal copy of the imprinted UBE3A gene through a variety of mechanisms detected by methylation studies, mutation analysis of UBE3A and FISH. In 10-15% of suspected cases of AS these investigations do not reveal a genetic abnormality. We report here the development of a semi-quantitative dosage PCR technique used to identify sub-microscopic deletions involving UBE3A. Using this method we analysed a panel of 26 patients from 24 families, all fulfilling the clinical criteria for AS. We identified a deletion of UBE3A exons 8-16 in a sibling pair. Analysis of parental samples revealed the same deletion in their phenotypically normal mother. This is an inexpensive and valuable method for detecting UBE3A deletions in a small but important proportion of AS cases of unidentifiable cause.

Neurofibromatosis 2 (NF2) and malignant mesothelioma in a man with a constitutional NF2 missense mutation.

Neurofibromatosis 2 (NF2) is caused by inactivating mutations of the NF2 tumor suppressor gene. Somatic NF2 mutations also occur in a high proportion of human primary malignant mesotheliomas. We report an elderly man with NF2, malignant mesothelioma, and a constitutional NF2 missense mutation. The long latent period for mesothelioma in this patient (61 years) raises the possibility that the type of mutant NF2 allele could affect mesothelioma tumorigenesis or progression.

The location of constitutional neurofibromatosis 2 (NF2) splice site mutations is associated with the severity of NF2.

Neurofibromatosis 2 (NF2) patients with constitutional splice site NF2 mutations have greater variability in disease severity than NF2 patients with other types of mutations; the cause of this variability is unknown. We evaluated genotype-phenotype correlations, with particular focus on the location of splice site mutations, using mutation and clinical information on 831 patients from 528 NF2 families with identified constitutional NF2 mutations. The clinical characteristics examined were age at onset of symptoms of NF2 and number of intracranial meningiomas, which are the primary indices of the severity of NF2. Two regression models were used to analyse genotype-phenotype correlations. People with splice site mutations in exons 1-5 had more severe disease than those with splice site mutations in exons 11-15. This result is compatible with studies showing that exons 2 and 3 are required for self-association of the amino terminal of the NF2 protein in vitro, and that deletions of exons 2 and 3 in transgenic and knockout mouse models of NF2 cause a high prevalence of Schwann cell derived tumours.

Multiple meningiomas: differential involvement of the NF2 gene in children and adults.

OBJECTIVE: To screen for NF2 mutations in people with meningiomas. METHODS: Lymphocyte or tumour DNA was analysed from 46 individuals from 36 families who presented with a meningioma at age < or =15 years without vestibular schwannoma (VS), or who had multiple meningiomas in adulthood before the diagnosis of VS. RESULTS: Eight of 13 people with meningioma and other features of neurofibromatosis 2 (NF2) had an identified constitutional NF2 mutation in blood DNA, but none of the other subjects had identified constitutional NF2 mutations. CONCLUSIONS: Constitutional NF2 mutations are the most likely cause of meningioma in children and in people with a meningioma plus other non-VS features of NF2. Mosaic NF2 may be the cause of about 8% of multiple meningiomas in sporadic adult cases, but there are other causes in the majority of other such patients and in multiple meningioma in families.

Mutation scanning of the NF2 gene: an improved service based on meta-PCR/sequencing, dosage analysis, and loss of heterozygosity analysis.

We describe the development and implementation of a neurofibromatosis type 2 (NF2) mutation scanning service based on novel techniques. All 17 exons of the NF2 gene are amplified in four polymerase chain reaction (PCR) reactions, using the meta-PCR technique to link the NF2 exons into chimeric concatamers. The meta-PCR products are then scanned for point mutations by direct sequencing. A four-exon dosage assay is used to test for large deletion/duplication mutations. In certain cases when tumour studies are necessary, these techniques are also combined with loss of heterozygosity analysis with three highly polymorphic microsatellite markers located within or close to the NF2 gene. Over a period of 2 years, we have applied these techniques in a service setting to the analysis of 271 patient samples (245 lymphocyte DNA; 26 schwannoma DNA). Meta-PCR and sequencing identified 90 point mutations in the 271 blood and tumor samples, 48 of which have not been reported previously. Dosage analysis identified large deletions in 12 of the lymphocyte DNA samples. In addition, over 84% of mutations were identified in 23 schwannoma DNA samples in which complete analysis was possible. Adoption of this novel strategy has increased the overall mutation detection rate in familial NF2 cases to 88% and sporadic NF2 cases to 59%. It has also allowed us to decrease our reporting turnaround times, and because of a low overall failure rate, permitted the running of an efficient and cost-effective service.

Evaluation of clinical diagnostic criteria for neurofibromatosis 2.

BACKGROUND: Four sets of clinical diagnostic criteria for neurofibromatosis 2 (NF2) have been developed by groups of expert clinicians, but sensitivity has never been formally assessed. The sets of criteria differ for people without bilateral vestibular schwannomas, which are pathognomonic for NF2. OBJECTIVE: To empirically evaluate the four existing sets of clinical diagnostic criteria for NF2. METHODS: The study was based on 163 of 403 people in the United Kingdom NF2 registry (41%) who presented without bilateral vestibular schwannomas. The authors applied the sets of criteria to each person at initial assessment and at the most recent clinical evaluation (mean +/- SE length of follow-up, 13 +/- 1 years). RESULTS: In people with "definite NF2" and a negative family history of NF2, the 1987 US NIH and 1991 NIH criteria each identify 78% of people at the most recent clinical evaluation but 0% at initial assessment. The National Neurofibromatosis Foundation (NNFF) criteria and the Manchester criteria each identify higher proportions at both time points (NNFF criteria, 91% and 10%; Manchester criteria, 93% and 14%), but the proportions at initial assessment are still low. CONCLUSIONS: None of the existing sets of criteria are adequate at initial assessment for diagnosing people who present without bilateral vestibular schwannomas as having NF2, particularly people with a negative family history of NF2. The authors recommend that a single, revised set of diagnostic criteria be devised to replace all of the existing sets of criteria.

The effect of meals rich in thermally stressed olive and safflower oils on postprandial serum paraoxonase activity in patients with diabetes.

OBJECTIVE: To determine the effects of meals rich in thermally stressed safflower (TSAF) and olive (TSOL) oils on postprandial serum paraoxonase (PON1) arylesterase activity and low density lipoprotein (LDL) oxidation in patients with type 2 diabetes. DESIGN: A randomised cross-over study. SETTING: Diabetes clinic and general practice. SUBJECTS: Fourteen patients (six men and eight women) with type 2 diabetes, aged 48-67 y, glycated haemoglobin <10% and fasting blood glucose <11 mmol/l were recruited. INTERVENTIONS: Patients received a milkshake rich in TSAF or TSOL and at least a week later they received the alternate milkshake. These fats contained high levels of lipid oxidation and degradation products. Blood samples were taken fasted and 4 h after consumption of the milkshake. MAIN OUTCOME MEASURES: Serum PON1 activity and lag time in LDL oxidation. RESULTS: After the meal rich in TSOL, serum PON1 activity increased significantly in women (12 (2.22) micromol/ml/min, mean (95% confidence interval), P=0.03) and not in men (0 (-4.4) micromol/ml/min) during the postprandial period. The increase in PON1 activity after the TSOL meal was significantly (P=0.03) greater in women compared with men. In women, the increase in serum PON1 activity after the TSOL meal was significantly different (13 (1.25) micromol/ml/min, P=0.04) compared with the corresponding change (-1 micromol/ml/min) after the TSAF meal. The lag time in LDL oxidation and indices of oxidative stress and antioxidant capacity did not vary significantly during the meals. CONCLUSIONS: Meals rich in TSOL may increase postprandial serum PON1 activity in middle-aged and older diabetic women. This change is potentially anti-atherogenic and may favour the use of olive oil over polyunsaturated fats in the diet of patients with type 2 diabetes. SPONSORSHIP: The study was supported by a grant from the National Heart Foundation of New Zealand.

A study of the structure-activity relationship for diazaborine inhibition of Escherichia coli enoyl-ACP reductase.

Enoyl acyl carrier protein (ACP) reductase catalyses the last reductive step of fatty acid biosynthesis, reducing the enoyl group of a growing fatty acid chain attached to ACP to its acyl product using NAD(P)H as the cofactor. This enzyme is the target for the diazaborine class of antibacterial agents, the biocide triclosan, and one of the targets for the front-line anti-tuberculosis drug isoniazid. The structures of complexes of Escherichia coli enoyl-ACP reductase (ENR) from crystals grown in the presence of NAD+ and a family of diazaborine compounds have been determined. Analysis of the structures has revealed that a mobile loop in the structure of the binary complex with NAD+ becomes ordered on binding diazaborine/NAD+ but displays a different conformation in the two subunits of the asymmetric unit. The work presented here reveals how, for one of the ordered conformations adopted by the mobile loop, the mode of diazaborine binding correlates well with the activity profiles of the diazaborine family. Additionally, diazaborine binding provides insights into the pocket on the enzyme surface occupied by the growing fatty acid chain.

High resolution deletion analysis of constitutional DNA from neurofibromatosis type 2 (NF2) patients using microarray-CGH.

Neurofibromatosis type 2 (NF2) is an autosomal dominant disorder whose hallmark is bilateral vestibular schwannoma. It displays a pronounced clinical heterogeneity with mild to severe forms. The NF2 tumor suppressor (merlin/schwannomin) has been cloned and extensively analyzed for mutations in patients with different clinical variants of the disease. Correlation between the type of the NF2 gene mutation and the patient phenotype has been suggested to exist. However, several independent studies have shown that a fraction of NF2 patients with various phenotypes have constitutional deletions that partly or entirely remove one copy of the NF2 gene. The purpose of this study was to examine a 7 Mb interval in the vicinity of the NF2 gene in a large series of NF2 patients in order to determine the frequency and extent of deletions. A total of 116 NF2 patients were analyzed using high-resolution array-comparative genomic hybridization (CGH) on an array covering at least 90% of this region of 22q around the NF2 locus. Deletions, which remove one copy of the entire gene or are predicted to truncate the schwannomin protein, were detected in 8 severe, 10 moderate and 6 mild patients. This result does not support the correlation between the type of mutation affecting the NF2 gene and the disease phenotype. This work also demonstrates the general usefulness of the array-CGH methodology for rapid and comprehensive detection of small (down to 40 kb) heterozygous and/or homozygous deletions occurring in constitutional or tumor-derived DNA.