Dominant factor XI deficiency caused by mutations in the factor XI catalytic domain

The bleeding diathesis associated with hereditary factor XI (fXI) deficiency is prevalent in Ashkenazi Jews, in whom the disorder appears to be an autosomal recessive condition. The homodimeric structure of fXI implies that the product of a single mutant allele could confer disease in a dominant manner through formation of heterodimers with wild-type polypeptide. We studied 2 unrelated patients with fXI levels less than 20% of normal and family histories indicating dominant disease transmission. Both are heterozygous for single amino acid substitutions in the fXI catalytic domain (Gly400Val and Trp569Ser). Neither mutant is secreted by transfected fibroblasts. In cotransfection experiments with a wild-type fXI construct, constructs with mutations common in Ashkenazi Jews (Glu117Stop and Phe283Leu) and a variant with a severe defect in dimer formation (fXI-Gly350Glu) have little effect on wild-type fXI secretion. In contrast, cotransfection with fXI-Gly400Val or fXI-Trp569Ser reduces wild-type secretion about 50%, consistent with a dominant negative effect. Immunoprecipitation of cell lysates confirmed that fXI-Gly400Val forms intracellular dimers. The data support a model in which nonsecretable mutant fXI polypeptides trap wild-type polypeptides within cells through heterodimer formation, resulting in lower plasma fXI levels than in heterozygotes for mutations that cause autosomal recessive fXI deficiency.     

Association of impaired phosphatidylinositol 3-kinase activity in GLUT1-containing vesicles with malinsertion of glucose transporters into the plasma membrane of fibroblasts from a patient with severe insulin resistance and clinical features of Werner syndrome

The purpose of this study was to examine the molecular mechanism responsible for the defective insulin-stimulated glucose transport in cultured fibroblasts from a patient (VH) with clinical features of Werner syndrome and severe insulin resistance. Thus, in cells derived from VH, the subcellular distribution, structure, functional activity, as well as plasma membrane insertion of GLUT1 glucose transporters were analyzed. Furthermore, the insulin signal transduction pathway leading to activation of phosphatidylinositol (PI) 3-kinase as well as components of GLUT1-containing membrane vesicles were characterized. In fibroblasts derived from VH, GLUT1 glucose transporters were overexpressed by 8-fold in plasma membranes (PM) and by 5-fold in high density microsomes, respectively. Exofacial photolabeling revealed that only 14% of the overexpressed PM-GLUT1 transporters were properly inserted into the plasma membrane. The complementary DNA structure of the patient's insulin receptor and the GLUT1 glucose transporter, the intrinsic activity of plasma membrane glucose transporters, the tyrosine phosphorylation, as well as the protein expression of insulin receptor substrate-1/2 and p85 alpha/beta- and p110 alpha/beta-subunits of PI 3-kinase were normal. However, insulin-stimulated association of the p85 subunit of PI 3-kinase was defective in fibroblasts derived from VH compared to those from controls, and this defect was associated with a reduced IRS-1-dependent activation of PI 3-kinase by 50.2% and 63.6% after incubation for 5 and 10 min with 100 nmol/L insulin, respectively. Furthermore, immunodetection of small GTP-binding Rab proteins in subcellular membrane fractions indicated a decreased expression of Rab4 in total cellular homogenates as well as in high density microsomes by 70% and 58%, respectively. After preparation of GLUT1-containing vesicles, Rab4 was not detected to be a component of these vesicles. Analysis of the PI 3-kinase in GLUT1-containing membrane vesicles revealed insulin-dependent targeting of the p85 subunit to the vesicles immunoadsorbed from VH and control fibroblasts. Importantly, the association of the p85 subunit as well as the p85-immunoprecipitable PI 3-kinase activity were markedly reduced in GLUT1-vesicles derived from the patient. In conclusion, impaired PI 3-kinase activity in GLUT1-containing membrane vesicles derived from fibroblasts of VH is associated with a defective docking and/or fusion process of glucose transporters with the plasma membrane and thus might contribute to the molecular defect causing insulin resistance in this patient.     

Angular malalignment as cause of limitation of forearm rotation: An analysis of prospectively collected data of both-bone forearm fractures in children

Introduction

Although limitation of pronation/supination following both-bone forearm fractures in children is often attributed to an angular malunion, no clinical study has compared pronation/supination and angular malalignment of the same child by analysis of prospectively collected clinical data.

Aim

The purpose of this trial is to explore whether limitation of pronation/supination can be predicted by the degree of angular malalignment in children who sustained a both-bone forearm fracture.

Methods

In four Dutch hospitals, children aged ≤16 years with a both-bone forearm fracture were prospectively followed up consecutive children for 6–9 months. At the final follow-up, pronation/supination and angular malunion on radiographs were determined.

Results

Between January 2006 and August 2010, a total of 410 children were prospectively followed up, of which 393 children were included for analysis in this study. The mean age of the children was 8.0 (±3.5) years, of which 63% were male and 40% fractured their dominant arm. The mean time to final examination was 219 (±51) days. Children with a metaphyseal both-bone fracture of the distal forearm with an angular malalignment of ≤15° had a 9–13% chance of developing a clinically relevant limitation (i.e., <50° of pronation and/or supination), while children with an angular malalignment of ≥16° had a 60% chance. Children with diaphyseal both-bone forearm fractures with ≤5° of angular malalignment had a 13% chance of developing a clinically relevant limitation, which showed no significant increase with a further increase of angular malalignment.

Conclusions

Children who sustained a both-bone forearm fracture localised in the distal metaphysis have a higher chance of developing a clinically relevant limitation of forearm rotation in case of a more severe angular malalignment, while children with a diaphyseal both-bone forearm fracture had a moderate chance of limitation, irrespective of the severity of the angular malalignment.     

BRAFV600E immunopositive Melanomas Show Low Frequency of Heterogeneity and Association With Epithelioid Tumor Cells: A STROBE-Compliant article

Treatment of BRAF^V600E-mutant melanoma by small molecule inhibitors that target BRAF or MEK kinases is increasingly used in clinical practice and significantly improve patient outcome. However, patients eventually become resistant and therapeutic improvement is required. Molecular diversity within individual tumors (intratumor heterogeneity) and between tumors within a single patient (intrapatient heterogeneity) poses a significant challenge to precision medicine.Using immunohistochemistry, we determined the extent of BRAF^V600E intratumor and intrapatient heterogeneity and the influence of morphological heterogeneity in a large series of 171 melanomas of 81 patients.The BRAF^V600E mutation rate found in our melanoma series is 44%, with none of 22 (0%) melanoma in situ, 23 of 56 (41%) primary tumors, 28 of 59 (48%) regional metastases, and 24 of 34 (71%) distant metastases harboring the mutation. In general, a diffuse homogeneous immunostaining was seen, even in tumors consisting of more than one cell type, that is, epithelioid, spindle, and/or small cell types. Nevertheless, BRAF^V600E-mutant melanomas more often had a purely epithelioid cell population (P = 0.063), that is more evident among distant metastases (P = 0.014). Only two of 75 (3%) mutated specimens (one primary and one metastasis) displayed heterogeneous BRAF^V600E expression. The primary tumor was also morphologically heterogeneous and exclusively displayed BRAF^V600E in the epithelioid component, confirming an association between BRAF^V600E and epithelioid cells. Twenty-eight of 30 patients (93%) had concordant BRAF mutation status between their tumors.Taken together, BRAF^V600E intratumor and intrapatient heterogeneity in melanoma is diminutive, nevertheless, the identified exceptions will have important implications for the clinical management of this disease.     

Post‐mortem multiple sclerosis lesion pathology is influenced by single nucleotide polymorphisms

Over the last few decades, several common single nucleotide polymorphisms (SNPs) have been identified that correlate with clinical outcome in multiple sclerosis (MS), but the pathogenic mechanisms underlying the clinical effects of these SNPs are unknown. This is in part because of the difficulty in the functional translation of genotype into disease‐relevant mechanisms. Building on our recent work showing the association of clinical disease course with post‐mortem MS lesion characteristics, we hypothesized that SNPs that correlate with clinical disease course would also correlate with specific MS lesion characteristics in autopsy tissue. To test this hypothesis, 179 MS brain donors from the Netherlands Brain Bank MS autopsy cohort were genotyped for 102 SNPs, selected based on their reported associations with clinical outcome or their associations with genes that show differential gene expression in MS lesions. Three SNPs linked to MS clinical severity showed a significant association between the genotype and either the proportion of active lesions (rs2234978/FAS and rs11957313/KCNIP1) or the proportion of mixed active/inactive lesions (rs8056098/CLEC16A). Three SNPs linked to MS pathology‐associated genes showed a significant association with either proportion of active lesions (rs3130253/MOG), incidence of cortical gray matter lesions (rs1064395/NCAN) or the proportion of remyelinated lesions (rs5742909/CTLA4). In addition, rs2234978/FAS T‐allele carriers showed increased FAS gene expression levels in perivascular T cells and perilesional oligodendrocytes, cell types that have been implicated in MS lesion formation. Thus, by combining pathological characterization of MS brain autopsy tissue with genetics, we now start to translate genotypes linked to clinical outcomes in MS into mechanisms involved in MS lesion pathogenesis.     

Diabetes Patients' Experiences With the Implementation of Insulin Therapy and Their Perceptions of Computer-Assisted Self-Management Systems for Insulin Therapy

Background

Computer-assisted decision support is an emerging modality to assist patients with type 2 diabetes mellitus (T2DM) in insulin self-titration (ie, self-adjusting insulin dose according to daily blood glucose levels). Computer-assisted insulin self-titration systems mainly focus on helping patients overcome barriers related to the cognitive components of insulin titration. Yet other (eg, psychological or physical) barriers could still impede effective use of such systems.

Objective

Our primary aim was to identify experiences with and barriers to self-monitoring of blood glucose, insulin injection, and insulin titration among patients with T2DM. Our research team developed a computer-assisted insulin self-titration system, called PANDIT. The secondary aim of this study was to evaluate patients’ perceptions of computer-assisted insulin self-titration. We included patients who used PANDIT in a 4-week pilot study as well as patients who had never used such a system.

Methods

In-depth, semi-structured interviews were conducted individually with patients on insulin therapy who were randomly recruited from a university hospital and surrounding general practices in the Netherlands. The interviews were transcribed verbatim and analyzed qualitatively. To classify the textual remarks, we created a codebook during the analysis, in a bottom-up and iterative fashion. To support examination of the final coded data, we used three theories from the field of health psychology and the integrated model of user satisfaction and technology acceptance by Wixom and Todd.

Results

When starting insulin therapy, some patients feared a lifelong commitment to insulin therapy and disease progression. Also, many barriers arose when implementing insulin therapy (eg, some patients were embarrassed to inject insulin in public). Furthermore, patients had difficulties increasing the insulin dose because they fear hypoglycemia, they associate higher insulin doses with disease progression, and some were ignorant of treatment targets. Patients who never used a computer-assisted insulin self-titration system felt they had enough knowledge to know when their insulin should be adjusted, but still believed that the system advice would be useful to confirm their reasoning. Furthermore, the time and effort saved with automated insulin advice was considered an advantage. Patients who had used PANDIT found the system useful if their glycemic regulation improved. Nevertheless, for some patients, the absence of personal contact with their caregiver was a drawback. While guidelines state that adjustment of basal insulin dose based on fasting plasma glucose values is sufficient, both patients who had and those who had not used PANDIT felt that such a system should take more patient data into consideration, such as lifestyle and diet factors.

Conclusions

Patients encounter multiple obstacles when implementing insulin therapy. Computer-assisted insulin self-titration can increase patient awareness of treatment targets and increase their confidence in self-adjusting the insulin dose. Nevertheless, some barriers may still exist when using computer-assisted titration systems and these systems could also introduce new barriers.     

Food Cue Reactivity in Fasting and Non-Fasting Subjects

In the present study, psychophysiological food cue reactivity was studied in fasting and non-fasting subjects. It was expected that food related stimuli would elicit stronger responses than control (soap) stimuli and that responses to food stimuli would be particularly strong in fasting subjects. The results show that although the subjects' craving was larger during presentation of food cues than during control stimuli, the larger craving was not reflected in increased psychophysiological responsivity (heart rate; frequency of skin conductance (SC) fluctuations) or salivation. Subjects in the fasting condition had a lower baseline frequency of SC-fluctuations, and a trend towards lower heart rate, indicating decreased sympathetic tonic level. In comparison with non-fasting subjects, no specifically enlarged food cue reactivity was found in fasting subjects. It is proposed that future research into food cue reactivity should focus on the role of learning rather than deprivation.