Breathing new life into the rational design of Alzheimer's therapeutics.

γ-secretase is a promising therapeutic target for Alzheimer's disease, but all inhibitors and modulators have failed due to toxicity or low efficacy. In this issue of Cell, Yang et al. provide cryo-EM structures of γ-secretase bound to three inhibitors and a modulator, giving new promise to targeting γ-secretase therapeutically.

APOE gene and neuropsychiatric disorders and endophenotypes: A comprehensive review.

The Apolipoprotein E (APOE) gene is one of the main candidates in neuropsychiatric genetics, with hundreds of studies carried out in order to explore the possible role of polymorphisms in the APOE gene in a large number of neurological diseases, psychiatric disorders, and related endophenotypes. In the current article, we provide a comprehensive review of the structural and functional aspects of the APOE gene and its relationship with brain disorders. Evidence from genome-wide association studies and meta-analyses shows that the APOE gene has been significantly associated with several neurodegenerative disorders. Cellular and animal models show growing evidence of the key role of APOE in mechanisms of brain plasticity and behavior. Future analyses of the APOE gene might find a possible role in other neurological diseases and psychiatric disorders and related endophenotypes. © 2016 Wiley Periodicals, Inc.

Loss of Nicastrin from Oligodendrocytes Results in Hypomyelination and Schizophrenia with Compulsive Behavior.

The biological underpinnings and the pathological lesions of psychiatric disorders are centuries-old questions that have yet to be understood. Recent studies suggest that schizophrenia and related disorders likely have their origins in perturbed neurodevelopment and can result from a large number of common genetic variants or multiple, individually rare genetic alterations. It is thus conceivable that key neurodevelopmental pathways underline the various genetic changes and the still unknown pathological lesions in schizophrenia. Here, we report that mice defective of the nicastrin subunit of γ-secretase in oligodendrocytes have hypomyelination in the central nervous system. These mice have altered dopamine signaling and display profound abnormal phenotypes reminiscent of schizophrenia. In addition, we identify an association of the nicastrin gene with a human schizophrenia cohort. These observations implicate γ-secretase and its mediated neurodevelopmental pathways in schizophrenia and provide support for the "myelination hypothesis" of the disease. Moreover, by showing that schizophrenia and obsessive-compulsive symptoms could be modeled in animals wherein a single genetic factor is altered, our work provides a biological basis that schizophrenia with obsessive-compulsive disorder is a distinct subtype of schizophrenia.

High-sensitivity troponin T and N-terminal pro-B-type natriuretic peptide (NT-proBNP) and risk of incident heart failure in patients with CKD: the Chronic Renal Insufficiency Cohort (CRIC) Study.

High-sensitivity troponin T (hsTnT) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) strongly predict heart failure (HF) in the general population. However, the interpretation of levels of these biomarkers as predictors of HF is uncertain among patients with CKD. Here, we investigated whether hsTnT and NT-proBNP are associated with incident HF among patients with CKD. In a prospective cohort analysis, we studied 3483 people with CKD in the Chronic Renal Insufficiency Cohort (CRIC) Study recruited from June of 2003 to August of 2008 who were free of HF at baseline. We used Cox regression to examine the association of baseline levels of hsTnT and NT-proBNP with incident HF after adjustment for demographic factors, traditional cardiovascular risk factors, markers of kidney disease, pertinent medication use, and mineral metabolism markers. At baseline, hsTnT levels ranged from ≤5.0 to 738.7 pg/ml, and NT-proBNP levels ranged from ≤5 to 35,000 pg/ml. Compared with those who had undetectable hsTnT, participants in the highest quartile (>26.5 pg/ml) had a significantly higher rate of HF (hazard ratio, 4.77; 95% confidence interval, 2.49 to 9.14). Similarly, compared with those in the lowest NT-proBNP quintile (<47.6 pg/ml), participants in the highest quintile (>433.0 pg/ml) experienced a substantially higher rate of HF (hazard ratio, 9.57; 95% confidence interval, 4.40 to 20.83) [corrected]. In conclusion, hsTnT and NT-proBNP were strongly associated with incident HF among a diverse cohort of individuals with mild to severe CKD. Elevations in these biomarkers may indicate subclinical changes in volume and myocardial stress that subsequently contribute to clinical HF.

Heart Failure in Non-Caucasians, Women, and Older Adults: A White Paper on Special Populations From the Heart Failure Society of America Guideline Committee.

The presentation, natural history, clinical outcomes, and response to therapy in patients with heart failure differ in some ways across populations. Women, older adults, and non-Caucasian racial or ethnic groups compose a substantial proportion of the overall heart failure population, but they have typically been underrepresented in clinical trials. As a result, uncertainty exists about the efficacy of some guideline-directed medical therapies and devices in specific populations, which may result in the under- or overtreatment of these patients. Even when guideline-based treatments are prescribed, socioeconomic, physical, or psychologic factors may affect non-Caucasian and older adult patient groups to a different extent and affect the application, effectiveness, and tolerability of these therapies. Individualized therapy based on tailored biology (genetics, proteomics, metabolomics), socioeconomic and cultural considerations, and individual goals and preferences may be the optimal approach for managing diverse patients. This comprehensive approach to personalized medicine is evolving, but in the interim, the scientific community should continue efforts focused on intensifying research in special populations, prescribing guideline-directed medical therapy unless contraindicated, and implementing evidence-based strategies including patient and family education and multidisciplinary team care in the management of patients.

Advanced (stage D) heart failure: a statement from the Heart Failure Society of America Guidelines Committee.

We propose that stage D advanced heart failure be defined as the presence of progressive and/or persistent severe signs and symptoms of heart failure despite optimized medical, surgical, and device therapy. Importantly, the progressive decline should be primarily driven by the heart failure syndrome. Formally defining advanced heart failure and specifying when medical and device therapies have failed is challenging, but signs and symptoms, hemodynamics, exercise testing, biomarkers, and risk prediction models are useful in this process. Identification of patients in stage D is a clinically important task because treatments are inherently limited, morbidity is typically progressive, and survival is often short. Age, frailty, and psychosocial issues affect both outcomes and selection of therapy for stage D patients. Heart transplant and mechanical circulatory support devices are potential treatment options in select patients. In addition to considering indications, contraindications, clinical status, and comorbidities, treatment selection for stage D patients involves incorporating the patient's wishes for survival versus quality of life, and palliative and hospice care should be integrated into care plans. More research is needed to determine optimal strategies for patient selection and medical decision making, with the ultimate goal of improving clinical and patient centered outcomes in patients with stage D heart failure.

Evolution of a self-renewing, participant-centered workshop series in BMB assessment.

We present as a case study the evolution of a series of participant-centered workshops designed to meet a need in the life sciences education community-the incorporation of best practices in the assessment of student learning. Initially, the ICABL (Inclusive Community for the Assessment of Biochemistry and Molecular Biology/BMB Learning) project arose from a grass-roots effort to develop material for a national exam in biochemistry and molecular biology. ICABL has since evolved into a community of practice in which participants themselves-through extensive peer review and reflection-become integral stakeholders in the workshops. To examine this evolution, this case study begins with a pilot workshop supported by seed funding and thoughtful programmatic assessment, the results of which informed evidence-based changes that, in turn, led to an improved experience for the community. Using participant response data, the case study also reveals critical features for successful workshops, including participant-centered activities and the value of frequent peer review of participants' products. Furthermore, we outline a train-the-trainer model for creating a self-renewing community by bringing new perspectives and voices into an existing core leadership team. This case study, then, offers a blueprint for building a thriving, evolving community of practice that not only serves the needs of individual scientist-educators as they seek to enhance student learning, but also provides a pathway for elevating members to positions of leadership.

Combined admixture mapping and association analysis identifies a novel blood pressure genetic locus on 5p13: contributions from the CARe consortium.

Admixture mapping based on recently admixed populations is a powerful method to detect disease variants with substantial allele frequency differences in ancestral populations. We performed admixture mapping analysis for systolic blood pressure (SBP) and diastolic blood pressure (DBP), followed by trait-marker association analysis, in 6303 unrelated African-American participants of the Candidate Gene Association Resource (CARe) consortium. We identified five genomic regions (P< 0.001) harboring genetic variants contributing to inter-individual BP variation. In follow-up association analyses, correcting for all tests performed in this study, three loci were significantly associated with SBP and one significantly associated with DBP (P< 10(-5)). Further analyses suggested that six independent single-nucleotide polymorphisms (SNPs) contributed to the phenotypic variation observed in the admixture mapping analysis. These six SNPs were examined for replication in multiple, large, independent studies of African-Americans [Women's Health Initiative (WHI), Maywood, Genetic Epidemiology Network of Arteriopathy (GENOA) and Howard University Family Study (HUFS)] as well as one native African sample (Nigerian study), with a total replication sample size of 11 882. Meta-analysis of the replication set identified a novel variant (rs7726475) on chromosome 5 between the SUB1 and NPR3 genes, as being associated with SBP and DBP (P< 0.0015 for both); in meta-analyses combining the CARe samples with the replication data, we observed P-values of 4.45 × 10(-7) for SBP and 7.52 × 10(-7) for DBP for rs7726475 that were significant after accounting for all the tests performed. Our study highlights that admixture mapping analysis can help identify genetic variants missed by genome-wide association studies because of drastically reduced number of tests in the whole genome.

Association of genetic variation with systolic and diastolic blood pressure among African Americans: the Candidate Gene Association Resource study.

The prevalence of hypertension in African Americans (AAs) is higher than in other US groups; yet, few have performed genome-wide association studies (GWASs) in AA. Among people of European descent, GWASs have identified genetic variants at 13 loci that are associated with blood pressure. It is unknown if these variants confer susceptibility in people of African ancestry. Here, we examined genome-wide and candidate gene associations with systolic blood pressure (SBP) and diastolic blood pressure (DBP) using the Candidate Gene Association Resource (CARe) consortium consisting of 8591 AAs. Genotypes included genome-wide single-nucleotide polymorphism (SNP) data utilizing the Affymetrix 6.0 array with imputation to 2.5 million HapMap SNPs and candidate gene SNP data utilizing a 50K cardiovascular gene-centric array (ITMAT-Broad-CARe [IBC] array). For Affymetrix data, the strongest signal for DBP was rs10474346 (P= 3.6 × 10(-8)) located near GPR98 and ARRDC3. For SBP, the strongest signal was rs2258119 in C21orf91 (P= 4.7 × 10(-8)). The top IBC association for SBP was rs2012318 (P= 6.4 × 10(-6)) near SLC25A42 and for DBP was rs2523586 (P= 1.3 × 10(-6)) near HLA-B. None of the top variants replicated in additional AA (n = 11 882) or European-American (n = 69 899) cohorts. We replicated previously reported European-American blood pressure SNPs in our AA samples (SH2B3, P= 0.009; TBX3-TBX5, P= 0.03; and CSK-ULK3, P= 0.0004). These genetic loci represent the best evidence of genetic influences on SBP and DBP in AAs to date. More broadly, this work supports that notion that blood pressure among AAs is a trait with genetic underpinnings but also with significant complexity.

Associations between kidney function and subclinical cardiac abnormalities in CKD.

Heart failure is a common consequence of CKD, and it portends high risk for mortality. However, among patients without known heart failure, the associations of different stages of estimated GFR (eGFR) with changes in cardiac structure and function are not well described. Here, we performed a cross-sectional analysis to study these associations among 3487 participants of the Chronic Renal Insufficiency Cohort Study. We estimated GFR using cystatin C. The prevalence of left ventricular hypertrophy (LVH) assessed by echocardiography was 32%, 48%, 57%, and 75% for eGFR categories ≥60, 45-59, 30-44, and <30 ml/min per 1.73 m(2), respectively. In fully adjusted multivariable analyses, subjects with eGFR levels of <30 ml/min per 1.73 m(2) had twofold higher odds of LVH (OR=2.20, 95% CI=1.40-3.40; P<0.001) relative to subjects with eGFR≥60 ml/min per 1.73 m(2). This reduction in kidney function also significantly associated with abnormal LV geometry but not diastolic or systolic dysfunction. An eGFR of 30-44 ml/min per 1.73 m(2) also significantly associated with LVH and abnormal LV geometry compared with eGFR≥60 ml/min per 1.73 m(2). In summary, in this large CKD cohort, reduced kidney function associated with abnormal cardiac structure. We did not detect significant associations between kidney function and systolic or diastolic function after adjusting for potential confounding variables.

Guanylyl cyclase (GC)-A and GC-B activities in ventricles and cardiomyocytes from failed and non-failed human hearts: GC-A is inactive in the failed cardiomyocyte.

Cardiomyocytes release atrial natriuretic peptide (ANP) and B-type natriuretic peptide to stimulate processes that compensate for the failing heart by activating guanylyl cyclase (GC)-A. C-type natriuretic peptide is also elevated in the failing heart and inhibits cardiac remodeling by activating the homologous receptor, GC-B. We previously reported that GC-A is the most active membrane GC in normal mouse ventricles while GC-B is the most active membrane GC in failing ventricles due to increased GC-B and decreased GC-A activities. Here, we examined ANP and CNP-specific GC activity in membranes obtained from non-failing and failing human left ventricles and in membranes from matched cardiomyocyte-enriched pellet preparations. Similar to our findings in the murine study, we found that CNP-dependent GC activity was about half of the ANP-dependent GC activity in the non-failing ventricular and was increased in the failing ventricle. ANP and CNP increased GC activity 9- and 5-fold in non-failing ventricles, respectively. In contrast to the mouse study, in failing human ventricles, ANP-dependent activity was unchanged compared to non-failing values whereas CNP-dependent activity increased 35% (p=0.005). Compared with ventricular membranes, basal GC activity was reduced an order of magnitude in membranes derived from myocyte-enriched pellets from non-failing ventricles. ANP increased GC activity 2.4-fold but CNP only increased GC activity 1.3-fold. In contrast, neither ANP nor CNP increased GC activity in equivalent preparations from failing ventricles. We conclude that: 1) GC-B activity is increased in non-myocytes from failing human ventricles, possibly as a result of increased fibrosis, 2) human ventricular cardiomyocytes express low levels of GC-A and much lower levels or possibly no GC-B, and 3) GC-A in cardiomyocytes from failing human hearts is refractory to ANP stimulation.

Gamma-secretase-regulated proteolysis of the Notch receptor by mitochondrial intermediate peptidase.

Notch is a transmembrane receptor that controls a diverse array of cellular processes including cell proliferation, differentiation, survival, and migration. The cellular outcome of Notch signaling is dependent on extracellular and intracellular signals, but the complexities of its regulation are not well understood. Canonical Notch signaling involves ligand association that triggers sequential and regulated proteolysis of Notch at several sites. Ligand-dependent proteolysis at the S2 site removes the bulk of the extracellular domain of Notch. Subsequent γ-secretase-mediated intramembrane proteolysis of the remaining membrane-tethered Notch fragment at the S3 site produces a nuclear-destined Notch intracellular domain (NICD). Here we show that following γ-secretase cleavage, Notch is proteolyzed at a novel S5 site. We have identified this S5 site to be eight amino acids downstream of the S3 site. Biochemical fractionation and purification resulted in the identification of the S5 site protease as the mitochondrial intermediate peptidase (MIPEP). Expression of the MIPEP-cleaved NICD (ΔNICD) results in a decrease in cell viability and mitochondria membrane potential. The sequential and regulated proteolysis by γ-secretase and MIPEP suggests a new means by which Notch function can be modulated.

Suberoylanilide hydroxamic acid (vorinostat) up-regulates progranulin transcription: rational therapeutic approach to frontotemporal dementia.

Progranulin (GRN) haploinsufficiency is a frequent cause of familial frontotemporal dementia, a currently untreatable progressive neurodegenerative disease. By chemical library screening, we identified suberoylanilide hydroxamic acid (SAHA), a Food and Drug Administration-approved histone deacetylase inhibitor, as an enhancer of GRN expression. SAHA dose-dependently increased GRN mRNA and protein levels in cultured cells and restored near-normal GRN expression in haploinsufficient cells from human subjects. Although elevation of secreted progranulin levels through a post-transcriptional mechanism has recently been reported, this is, to the best of our knowledge, the first report of a small molecule enhancer of progranulin transcription. SAHA has demonstrated therapeutic potential in other neurodegenerative diseases and thus holds promise as a first generation drug for the prevention and treatment of frontotemporal dementia.

Expression, localization, and biochemical characterization of nicotinamide mononucleotide adenylyltransferase 2.

Nicotinamide mononucleotide (NMN) adenylyltransferase 2 (Nmnat2) catalyzes the synthesis of NAD from NMN and ATP. The Nmnat2 transcript is expressed predominately in the brain; we report here that Nmnat2 is a low abundance protein expressed in neurons. Previous studies indicate that Nmnat2 localizes to Golgi. As Nmnat2 is not predicted to contain a signal sequence, lipid-binding domain, or transmembrane domain, we investigated the nature of this interaction. These experiments reveal that Nmnat2 is palmitoylated in vitro, and this modification is required for membrane association. Surprisingly, exogenous Nmnat2 is toxic to neurons, indicating that protein levels must be tightly regulated. To analyze Nmnat2 localization in neurons (previous experiments relied on exogenous expression in HeLa cells), mouse brains were fractionated, showing that Nmnat2 is enriched in numerous membrane compartments including synaptic terminals. In HeLa cells, in addition to Golgi, Nmnat2 localizes to Rab7-containing late endosomes. These studies show that Nmnat2 is a neuronal protein peripherally attached to membranes via palmitoylation and suggest that Nmnat2 is transported to synaptic terminals via an endosomal pathway.

Development of a Certification Exam to Assess Undergraduate Students' Proficiency in Biochemistry and Molecular Biology Core Concepts.

With support from the American Society for Biochemistry and Molecular Biology (ASBMB), a community of biochemistry and molecular biology (BMB) scientist-educators has developed and administered an assessment instrument designed to evaluate student competence across four core concept and skill areas fundamental to BMB. The four areas encompass energy and metabolism; information storage and transfer; macromolecular structure, function, and assembly; and skills including analytical and quantitative reasoning. First offered in 2014, the exam has now been administered to nearly 4000 students in ASBMB-accredited programs at more than 70 colleges and universities. Here, we describe the development and continued maturation of the exam program, including the organic role of faculty volunteers as drivers and stewards of all facets: content and format selection, question development, and scoring.

Meeting report: BioMolViz workshops for developing assessments of biomolecular visual literacy.

While molecular visualization has been recognized as a threshold concept in biology education, the explicit assessment of students' visual literacy skills is rare. To facilitate the evaluation of this fundamental ability, a series of NSF-IUSE-sponsored workshops brought together a community of faculty engaged in creating instruments to assess students' biomolecular visualization skills. These efforts expanded our earlier work in which we created a rubric describing overarching themes, learning goals, and learning objectives that address student progress toward biomolecular visual literacy. Here, the BioMolViz Steering Committee (BioMolViz.org) documents the results of those workshops and uses social network analysis to examine the growth of a community of practice. We also share many of the lessons we learned as our workshops evolved, as they may be instructive to other members of the scientific community as they organize workshops of their own.

Glu-333 of nicastrin directly participates in gamma-secretase activity.

gamma-Secretase is a proteolytic membrane complex that processes a variety of substrates including the amyloid precursor protein and the Notch receptor. Earlier we showed that one of the components of this complex, nicastrin (NCT), functions as a receptor for gamma-secretase substrates. A recent report challenged this, arguing instead that the Glu-333 residue of NCT predicted to participate in substrate recognition only participates in gamma-secretase complex maturation and not in activity per se. Here, we present evidence that Glu-333 directly participates in gamma-secretase activity. By normalizing to the active pool of gamma-secretase with two separate methods, we establish that gamma-secretase complexes containing NCT-E333A are indeed deficient in intrinsic activity. We also demonstrate that the NCT-E333A mutant is deficient in its binding to substrates. Moreover, we find that the cleavage of substrates by gamma-secretase activity requires a free N-terminal amine but no minimal length of the extracellular N-terminal stub. Taken together, these studies provide further evidence supporting the role of NCT in substrate recognition. Finally, because gamma-secretase cleaves itself during its maturation and because NCT-E333A also shows defects in gamma-secretase complex maturation, we present a model whereby Glu-333 can serve a dual role via similar mechanisms in the recruitment of both Type 1 membrane proteins for activity and the presenilin intracellular loop during complex maturation.

Chronic kidney disease and prevalent atrial fibrillation: the Chronic Renal Insufficiency Cohort (CRIC).

BACKGROUND: The epidemiology of atrial fibrillation (AF) has been mainly investigated in patients with end-stage renal disease, with limited data on less advanced chronic kidney disease (CKD) stages. METHODS: A total of 3,267 adult participants (50% non-Hispanic blacks, 46% women) with CKD from the Chronic Renal Insufficiency Cohort were included in this study. None of the study participants had been on dialysis. Those with self-identified race/ethnicity other than non-Hispanic black or white (n = 323) or those without electrocardiographic data (n = 22) were excluded. Atrial fibrillation was ascertained by a 12-lead electrocardiogram and self-report. Age-, sex-, and race/ethnicity-specific prevalence rates of AF were estimated and compared between subgroups. Cross-sectional associations and correlates with prevalent AF were examined using unadjusted and multivariable-adjusted logistic regression analysis. RESULTS: The mean estimated glomerular filtration rate was 43.6 (+/-13.0) mL/(min 1.73 m(2)). Atrial fibrillation was present in 18% of the study population and in >25% of those > or =70 years old. In multivariable-adjusted models, 1-SD increase in age (11 years) (odds ratio 1.27, CI 95% 1.13-1.43, P < .0001), male [corrected] sex (0.80, 0.65-0.98, P = .0303), smoking (former vs never) (1.34, 1.08-1.66, P = .0081), history of heart failure (3.28, 2.47-4.36, P < .001), and history of cardiovascular disease (1.94, 1.56-2.43, P < .0001) were significantly associated with AF. Race/ethnicity, hypertension, diabetes, body mass index, physical activity, education, high-sensitivity C-reactive protein, total cholesterol, and alcohol intake were not significantly associated with AF. An estimated glomerular filtration rate <45 mL/(min 1.73 m(2)) was associated with AF in an unadjusted model (1.35, 1.13-1.62, P = .0010), but not after multivariable adjustment (1.12, 0.92-1.35, P = .2710). CONCLUSIONS: Nearly 1 in 5 participants in Chronic Renal Insufficiency Cohort, a national study of CKD, had evidence of AF at study entry, a prevalence similar to that reported among patients with end-stage renal disease and 2 to 3 times of that reported in the general population. Risk factors for AF in this CKD population do not mirror those reported in the general population.

Corin variant associated with hypertension and cardiac hypertrophy exhibits impaired zymogen activation and natriuretic peptide processing activity.

Corin is a cardiac serine protease that acts as the pro-atrial natriuretic peptide (ANP) convertase. Recently, 2 single-nucleotide polymorphisms (SNPs) (T555I and Q568P) in the human corin gene have been identified in genetic epidemiological studies. The minor I555/P568 allele, which is more common in African Americans, is associated with hypertension and cardiac hypertrophy. In this study, we examined the effect of T555I and Q568P amino acid substitutions on corin function. We found that corin frizzled-like domain 2, where T555I/Q568P substitutions occur, was required for efficient pro-ANP processing in functional assays. Mutant corin lacking this domain had 30+/-5% (P<0.01) activity compared to that of wild type. Similarly, corin variant T555I/Q568P had a reduced (38+/-7%, P<0.01) pro-ANP processing activity compared to that of wild type. The variant also exhibited a low activity (44+/-15%, P<0.05) in processing pro-brain natriuretic peptide (BNP). We next examined the biochemical basis for the loss of activity in T555I/Q568P variant and found that the zymogen activation of the corin variant was impaired significantly, as indicated by the absence of the activated protease domain fragment. This finding was confirmed in human embryonic kidney (HEK)293 cells and murine HL-1 cardiomyocytes. Thus, our results show that the corin gene SNPs associated with hypertension and cardiac hypertrophy impair corin zymogen activation and natriuretic peptide processing activity. Our data suggest that corin deficiency may be an important mechanism in hypertensive and heart diseases.