Novel EGR2 variant that associates with Charcot-Marie-Tooth disease when combined with lipopolysaccharide-induced TNF-α factor T49M polymorphism.

OBJECTIVE: To identify novel genetic mechanisms causing Charcot-Marie-Tooth (CMT) disease. METHODS: We performed a next-generation sequencing study of 34 genes associated with CMT in a patient with peripheral neuropathy. RESULTS: We found a non-previously described mutation in EGR2 (p.P397H). P397H mutation is located within the loop that connects zinc fingers 2 and 3, a pivotal domain for the activity of this transcription factor. Using promoter activity luciferase assays, we found that this mutation promotes decreased transcriptional activity of EGR2. In this patient, we also found a previously described nonpathogenic polymorphism in lipopolysaccharide-induced TNF-α factor (LITAF) (p.T49M). We show that the p.T49M mutation decreases the steady-state levels of the LITAF protein in Schwann cells. Loss of function of LITAF has been shown to produce deregulation in the NRG1-erbB signaling, a pivotal pathway for EGR2 expression by Schwann cells. Surprisingly, our segregation study demonstrates that p.P397H mutation in EGR2 is not sufficient to produce CMT disease. Most notably, only those patients expressing simultaneously the LITAF T49M polymorphism develop peripheral neuropathy. CONCLUSIONS: Our data support that the LITAF loss-of-function interferes with the expression of the transcriptional-deficient EGR2 P397H mutant hampering Schwann cell differentiation and suggest that in vivo both genes act in tandem to allow the proper development of myelin.

Diagnostic Validity Comparison Between Criteria Based on CSF Alzheimer's Disease Biomarkers.

AIM: To compare the diagnostic validity of NIA-AA criteria, for AD CSF biomarkers, with our own new criteria. MATERIALS AND METHODS: Between 2008 and 2011, 170 patients with Mild Cognitive Impairment (MCI) were included. CSF levels of Aß1-42, T-tau, P-tau181, and ratios of T-tau/Aß1-42 and P-tau181/Aß1-42 were analyzed. In our criteria, we considered 3 or more abnormal variables indicative of a high likelihood of MCI due to AD. RESULTS: After a clinical follow-up of 4.5 ± 1.2 years, 44 patients remained stable, 95 developed AD, 15 other forms of dementia, 7 died and 9 received other diagnoses. Using the NIA-AA criteria and our own criteria, the diagnostic validity of the CSF biomarkers was 58% versus 85%, specificity 84% versus 72%, PPV 82% versus 79% and NPV 61% versus 79%. CONCLUSION: The inclusion of the ratios in diagnostic criteria increases sensitivity and NPV for the diagnosis of MCI due to AD.

Comparison of two analytical platforms for CSF biomarkers of Alzheimer's disease.

Cerebrospinal fluid (CSF) biomarkers of Alzheimer's disease (AD) are currently being assessed with two different assays. Our objective was to study if there is a correlation between values obtained by both techniques, to compare their validity and search for conversion factor between values obtained for every protein. We compared the performances of two commonly used platforms, an enzyme-linked immunosorbent assay (ELISA) and a multiplex (xMAP) technology for measurement of CSF Aß 1-42, total tau (T-tau), and phosphorylated tau 181 (P-tau 181p) proteins, in 30 AD patients and 28 control subjects. The relations between the variables of both techniques were evaluated using the Spearman p correlation coefficient (α = 0.05). Receiver operating characteristic and area under the curve (AUC) analyses were calculated for the variables of both techniques. The two assays platforms yielded different absolute values for the various analytes, always higher in ELISA. We found some correction factor between values: 2,1- to 3-fold for Aß 1-42; 4,1- to 4,6-fold for T-tau; and 1,4- to 1,6-fold for P-tau 181p. In addition, those values were highly correlated (Aß 1-42: r = 0.70, P < 0.01; T-tau: r = 0.90, P < 0.01; P-tau 181p: r = 0.85, P < 0.01) and the AUC for the variables showed very similar values. In conclusion, the results obtained with ELISA and xMAP platforms were highly correlated and its validity is very similar. Differences in absolute values point to the need for a clear description of the technique used. Moreover, we found some conversion factor between values of every protein that may be useful for transformation between both techniques.