Constitutive ablation of caspase-6 reduces the inflammatory response and behavioural changes caused by peripheral pro-inflammatory stimuli

Traditionally, the family of caspases has been subcategorised according to their respective main roles in mediating apoptosis or inflammation. However, recent studies have revealed that caspases participate in diverse cellular functions beyond their canonical roles. Caspase-6 (C6) is one such protease known for its role as a pro-apoptotic executioner caspase and its aberrant activity in several neurodegenerative diseases. In addition to apoptosis, C6 has been shown to regulate B-cell activation and differentiation in plasma cells as well as macrophage activation. Furthermore, C6 has recently been postulated to play a role in mediating the inflammatory response through the production of TNF-α. In this study we further examine the role of C6 in mediating the inflammatory response and its contribution to the manifestation of behavioural abnormalities in mice. We find that C6 is a positive regulator of TNF-α transcription in macrophages and that ablation of C6 reduces lipopolysaccharide (LPS)-induced TNF-α levels in plasma. Furthermore, loss of C6 attenuates LPS-induced behavioural changes in mice and protects neurons from cytokine-mediated toxicity. These data further support the involvement of C6 in the inflammatory response and point to a previously unknown role for C6 in the pathophysiology of depression.

Preventing mutant huntingtin proteolysis and intermittent fasting promote autophagy in models of Huntington disease

Huntington disease (HD) is caused by the expression of mutant huntingtin (mHTT) bearing a polyglutamine expansion. In HD, mHTT accumulation is accompanied by a dysfunction in basal autophagy, which manifests as specific defects in cargo loading during selective autophagy. Here we show that the expression of mHTT resistant to proteolysis at the caspase cleavage site D586 (C6R mHTT) increases autophagy, which may be due to its increased binding to the autophagy adapter p62. This is accompanied by faster degradation of C6R mHTT in vitro and a lack of mHTT accumulation the C6R mouse model with age. These findings may explain the previously observed neuroprotective properties of C6R mHTT. As the C6R mutation cannot be easily translated into a therapeutic approach, we show that a scheduled feeding paradigm is sufficient to lower mHTT levels in YAC128 mice expressing cleavable mHTT. This is consistent with a previous model, where the presence of cleavable mHTT impairs basal autophagy, while fasting-induced autophagy remains functional. In HD, mHTT clearance and autophagy may become increasingly impaired as a function of age and disease stage, because of gradually increased activity of mHTT-processing enzymes. Our findings imply that mHTT clearance could be enhanced by a regulated dietary schedule that promotes autophagy.

Therapeutic modulation of the bile acid pool by Cyp8b1 knockdown protects against nonalcoholic fatty liver disease in mice

Bile acids (BAs) are surfactant molecules that regulate the intestinal absorption of lipids. Thus, the modulation of BAs represents a potential therapy for nonalcoholic fatty liver disease (NAFLD), which is characterized by hepatic accumulation of fat and is a major cause of liver disease worldwide. Cyp8b1 is a critical modulator of the hydrophobicity index of the BA pool. As a therapeutic proof of concept, we aimed to determine the impact of Cyp8b1 inhibition in vivo on BA pool composition and as protection against NAFLD. Inhibition of Cyp8b1 expression in mice led to a remodeling of the BA pool, which altered its signaling properties and decreased intestinal fat absorption. In a model of cholesterol-induced NAFLD, Cyp8b1 knockdown significantly decreased steatosis and hepatic lipid content, which has been associated with an increase in fecal lipid and BA excretion. Moreover, inhibition of Cyp8b1 not only decreased hepatic lipid accumulation, but also resulted in the clearance of previously accumulated hepatic cholesterol, which led to a regression in hepatic steatosis. Taken together, our data demonstrate that Cyp8b1 inhibition is a viable therapeutic target of crucial interest for metabolic diseases, such as NAFLD.-Chevre, R., Trigueros-Motos, L., Castaño, D., Chua, T., Corlianò, M., Patankar, J. V., Sng, L., Sim, L., Juin, T. L., Carissimo, G., Ng, L. F. P., Yi, C. N. J., Eliathamby, C. C., Groen, A. K., Hayden, M. R., Singaraja, R. R. Therapeutic modulation of the bile acid pool by Cyp8b1 knockdown protects against nonalcoholic fatty liver disease in mice.

Further Investigation of the Role of ACYP2 and WFS1 Pharmacogenomic Variants in the Development of Cisplatin-Induced Ototoxicity in Testicular Cancer Patients

Purpose: Adverse drug reactions such as ototoxicity, which occurs in approximately one-fifth of adult patients who receive cisplatin treatment, can incur large socioeconomic burdens on patients with testicular cancer who develop this cancer during early adulthood. Recent genome-wide association studies have identified genetic variants in ACYP2 and WFS1 that are associated with cisplatin-induced ototoxicity. We sought to explore the role of these genetic susceptibility factors to cisplatin-induced ototoxicity in patients with testicular cancer.Experimental Design: Extensive clinical and demographic data were collected for 229 patients with testicular cancer treated with cisplatin. Patients were genotyped for two variants, ACYP2 rs1872328 and WFS1 rs62283056, that have previously been associated with hearing loss in cisplatin-treated patients. Analyses were performed to investigate the association of these variants with ototoxicity in this cohort of adult patients with testicular cancer.Results: Pharmacogenomic analyses revealed that ACYP2 rs1872328 was significantly associated with cisplatin-induced ototoxicity [P = 2.83 × 10^-3, OR (95% CI):14.7 (2.6-84.2)]. WFS1 rs62283056 was not significantly associated with ototoxicity caused by cisplatin (P = 0.39); however, this variant was associated with hearing loss attributable to any cause [P = 5.67 × 10^-3, OR (95% CI): 3.2 (1.4-7.7)].Conclusions: This study has provided the first evidence for the role of ACYP2 rs1872328 in cisplatin-induced ototoxicity in patients with testicular cancer. These results support the use of this information to guide the development of strategies to prevent cisplatin-induced ototoxicity across cancers. Further, this study has highlighted the importance of phenotypic differences in replication studies and has provided further evidence for the role of WFS1 rs62283056 in susceptibility to hearing loss, which may be worsened by cisplatin treatment. Clin Cancer Res; 24(8); 1866-71. ©2018 AACR.

HACE1 is essential for astrocyte mitochondrial function and influences Huntington disease phenotypes in vivo

Oxidative stress is a prominent feature of Huntington disease (HD), and we have shown previously that reduced levels of hace1 (HECT domain and Ankyrin repeat containing E3 ubiquitin protein ligase 1) in patient striatum may contribute to the pathogenesis of HD. Hace1 promotes the stability of Nrf2 and thus plays an important role in antioxidant response mechanisms, which are dysfunctional in HD. Moreover, hace1 overexpression mitigates mutant huntingtin (mHTT)-induced oxidative stress in vitro through promotion of the Nrf2 antioxidant response. Here, we show that the genetic ablation of hace1 in the YAC128 mouse model of HD accelerates motor deficits and exacerbates cognitive and psychiatric phenotypes in vivo. We find that both the expression of mHTT and the ablation of hace1 alone are sufficient to cause deficits in astrocytic mitochondrial respiration. We confirm the crucial role of hace1 in astrocytes in vivo, since its ablation is sufficient to cause dramatic astrogliosis in wild-type FVB/N mice. Astrogliosis is not observed in the presence of mHTT but a strong dysregulation in the expression of astrocytic markers in HACE1-/- x YAC128 striatum suggests an additive effect of mHTT expression and hace1 loss on this cell type. HACE1-/- x YAC128 mice and primary cells derived from these animals therefore provide model systems that will allow for the further dissection of Nrf2 pathways and astrocyte dysfunction in the context of HD.

The global spectrum of protein-coding pharmacogenomic diversity

Differences in response to medications have a strong genetic component. By leveraging publically available data, the spectrum of such genomic variation can be investigated extensively. Pharmacogenomic variation was extracted from the 1000 Genomes Project Phase 3 data (2504 individuals, 26 global populations). A total of 12 084 genetic variants were found in 120 pharmacogenes, with the majority (90.0%) classified as rare variants (global minor allele frequency <0.5%), with 52.9% being singletons. Common variation clustered individuals into continental super-populations and 23 pharmacogenes contained highly differentiated variants (FST>0.5) for one or more super-population comparison. A median of three clinical variants (PharmGKB level 1A/B) was found per individual, and 55.4% of individuals carried loss-of-function variants, varying by super-population (East Asian 60.9%>African 60.1%>South Asian 60.3%>European 49.3%>Admixed 39.2%). Genome sequencing can therefore identify clinical pharmacogenomic variation, and future studies need to consider rare variation to understand the spectrum of genetic diversity contributing to drug response.

Early pridopidine treatment improves behavioral and transcriptional deficits in YAC128 Huntington disease mice

Pridopidine is currently under clinical development for Huntington disease (HD), with on-going studies to better characterize its therapeutic benefit and mode of action. Pridopidine was administered either prior to the appearance of disease phenotypes or in advanced stages of disease in the YAC128 mouse model of HD. In the early treatment cohort, animals received 0, 10, or 30 mg/kg pridopidine for a period of 10.5 months. In the late treatment cohort, animals were treated for 8 weeks with 0 mg/kg or an escalating dose of pridopidine (10 to 30 mg/kg over 3 weeks). Early treatment improved motor coordination and reduced anxiety- and depressive-like phenotypes in YAC128 mice, but it did not rescue striatal and corpus callosum atrophy. Late treatment, conversely, only improved depressive-like symptoms. RNA-seq analysis revealed that early pridopidine treatment reversed striatal transcriptional deficits, upregulating disease-specific genes that are known to be downregulated during HD, a finding that is experimentally confirmed herein. This suggests that pridopidine exerts beneficial effects at the transcriptional level. Taken together, our findings support continued clinical development of pridopidine for HD, particularly in the early stages of disease, and provide valuable insight into the potential therapeutic mode of action of pridopidine.

Association Between SLC16A5 Genetic Variation and Cisplatin-Induced Ototoxic Effects in Adult Patients With Testicular Cancer

Importance

Cisplatin-induced ototoxic effects are an important complication that affects testicular cancer survivors as a consequence of treatment. The identification of genetic variants associated with this adverse drug reaction will further our mechanistic understanding of its development and potentially lead to strategies to prevent ototoxic effects.

Objective

To identify the genetic variants associated with cisplatin-induced ototoxic effects in adult testicular cancer patients.

Design, Setting, and Participants

This retrospective study was performed by the Canadian Pharmacogenomics Network for Drug Safety using patients recruited from 5 adult oncology treatment centers across Canada. Male patients who were 17 years or older, diagnosed with germ cell testicular cancer, and previously treated with cisplatin-based chemotherapy were recruited from July 2009 to April 2013 using active surveillance methodology. Cisplatin-induced ototoxic effects were independently diagnosed by 2 audiologists. Patients were genotyped for 7907 variants using a custom pharmacogenomic array. Logistic regression was used to identify genetic variants that were significantly associated with ototoxic effects. The validity of these findings was confirmed through independent replication and cell-based functional assays.

Exposures

Cisplatin-based chemotherapy.

Main Outcomes and Measures

Cisplatin-induced ototoxic effects.

Results

After exclusions, 188 patients (median [interquartile range] age, 31 [24-39] years) were enrolled in this study to form the discovery and replication cohorts. Association and fine-mapping analyses identified a protein-coding variant, rs4788863 in SLC16A5, that was associated with protection against cisplatin-induced ototoxic effects in 2 independent cohorts (combined cohort: odds ratio, 0.06; 95% CI, 0.02-0.22; P = 2.17 × 10-7). Functional validation of this transporter gene revealed that in vitro SLC16A5-silencing altered cellular responses to cisplatin treatment, supporting a role for SLC16A5 in the development of cisplatin-induced ototoxic effects. These results were further supported by the literature, which provided confirmatory evidence for the role that SLC16A5 plays in hearing.

Conclusions and Relevance

This study has identified a novel association between protein-coding variation in SLC16A5 and cisplatin-induced ototoxic effects. These findings have provided insight into the molecular mechanisms of this adverse drug reaction in adult patients with germ cell testicular cancer. Given that previous studies have shown that cimetidine, an SLC16A5-inhibitor, prevents murine cisplatin-induced ototoxic effects, the findings from this study have important implications for otoprotectant strategies in humans.

Compositional differences between Copaxone and Glatopa are reflected in altered immunomodulation ex vivo in a mouse model

Copaxone (glatiramer acetate, GA), a structurally and compositionally complex polypeptide nonbiological drug, is an effective treatment for multiple sclerosis, with a well-established favorable safety profile. The short antigenic polypeptide sequences comprising therapeutically active epitopes in GA cannot be deciphered with state-of-the-art methods; and GA has no measurable pharmacokinetic profile and no validated pharmacodynamic markers. The study reported herein describes the use of orthogonal standard and high-resolution physicochemical and biological tests to characterize GA and a U.S. Food and Drug Administration-approved generic version of GA, Glatopa (USA-FoGA). While similarities were observed with low-resolution or destructive tests, differences between GA and USA-FoGA were measured with high-resolution methods applied to an intact mixture, including variations in surface charge and a unique, high-molecular-weight, hydrophobic polypeptide population observed only in some USA-FoGA lots. Consistent with published reports that modifications in physicochemical attributes alter immune-related processes, genome-wide expression profiles of ex vivo activated splenocytes from mice immunized with either GA or USA-FoGA showed that 7-11% of modulated genes were differentially expressed and enriched for immune-related pathways. Thus, differences between USA-FoGA and GA may include variations in antigenic epitopes that differentially activate immune responses. We propose that the assays reported herein should be considered during the regulatory assessment process for nonbiological complex drugs such as GA.

ABCA8 Regulates Cholesterol Efflux and High-Density Lipoprotein Cholesterol Levels

Objective—

High-density lipoproteins (HDL) are considered to protect against atherosclerosis in part by facilitating the removal of cholesterol from peripheral tissues. However, factors regulating lipid efflux are incompletely understood. We previously identified a variant in adenosine triphosphate–binding cassette transporter A8 ( ABCA8 ) in an individual with low HDL cholesterol (HDLc). Here, we investigate the role of ABCA8 in cholesterol efflux and in regulating HDLc levels.

Approach and Results—

We sequenced ABCA8 in individuals with low and high HDLc and identified, exclusively in low HDLc probands, 3 predicted deleterious heterozygous ABCA8 mutations (p.Pro609Arg [P609R], IVS17-2 A>G and p.Thr741Stop [T741X]). HDLc levels were lower in heterozygous mutation carriers compared with first-degree family controls (0.86±0.34 versus 1.17±0.26 mmol/L; P =0.005). HDLc levels were significantly decreased by 29% ( P =0.01) in Abca8b −/− mice on a high-cholesterol diet compared with wild-type mice, whereas hepatic overexpression of human ABCA8 in mice resulted in significant increases in plasma HDLc and the first steps of macrophage-to-feces reverse cholesterol transport. Overexpression of wild-type but not mutant ABCA8 resulted in a significant increase (1.8-fold; P =0.01) of cholesterol efflux to apolipoprotein AI in vitro. ABCA8 colocalizes and interacts with adenosine triphosphate–binding cassette transporter A1 and further potentiates adenosine triphosphate–binding cassette transporter A1–mediated cholesterol efflux.

Conclusions—

ABCA8 facilitates cholesterol efflux and modulates HDLc levels in humans and mice.

Characterization of subventricular zone-derived progenitor cells from mild and late symptomatic YAC128 mouse model of Huntington's disease

Huntington's disease (HD) is caused by an expansion of CAG repeats in the HTT gene, leading to expression of mutant huntingtin (mHTT) and selective striatal neuronal loss, frequently associated with mitochondrial dysfunction and decreased support of brain-derived neurotrophic factor (BDNF). New neurons derived from the subventricular zone (SVZ) are apparently not able to rescue HD pathological features. Thus, we analyzed proliferation, migration and differentiation of adult SVZ-derived neural stem/progenitor cells (NSPC) from mild (6month-old (mo)) and late (10mo) symptomatic HD YAC128 mice expressing full-length (FL)-mHTT versus age-matched wild-type (WT) mice. SVZ cells derived from 6mo YAC128 mice exhibited higher migratory capacity and a higher number of MAP2+ and synaptophysin+cells, compared to WT cells; MAP2 labeling was enhanced after exposure to BDNF. However, BDNF-evoked neuronal differentiation was not observed in 10mo YAC128 SVZ-derived cells. Interestingly, 6mo YAC128 SVZ-derived cells showed increased intracellular Ca²⁺ levels in response to KCl, which was potentiated by BDNF, evidencing the presence of differentiated neurons. In contrast, KCl depolarization-induced intracellular Ca²⁺ increase in 10mo YAC128 SVZ-derived cells was shown to be increased only in BDNF-treated YAC128 SVZ-derived cells, suggestive of decreased differentiation capacity. In addition, BDNF-untreated NSPC from 10mo YAC128 mice exhibited lower mitochondrial membrane potential and increased mitochondrial Ca²⁺ accumulation, in relation with NSPC from 6mo YAC128 mice. Data evidence age-dependent reduced migration and decreased acquisition of a neuronal phenotype, accompanied by decreased mitochondrial membrane potential in SVZ-derived cells from YAC128 mice through HD symptomatic phases.

A pharmacogenetic signature of high response to Copaxone in late-phase clinical-trial cohorts of multiple sclerosis

Background

Copaxone is an efficacious and safe therapy that has demonstrated clinical benefit for over two decades in patients with relapsing forms of multiple sclerosis (MS). On an individual level, patients show variability in their response to Copaxone, with some achieving significantly higher response levels. The involvement of genes (e.g., HLA-DRB1*1501) with high inter-individual variability in Copaxone’s mechanism of action (MoA) suggests the potential contribution of genetics to treatment response. This study aimed to identify genetic variants associated with Copaxone response in patient cohorts from late-phase clinical trials.

Methods

Single nucleotide polymorphisms (SNPs) associated with high and low levels of response to Copaxone were identified using genome-wide SNP data in a discovery cohort of 580 patients from two phase III clinical trials of Copaxone. Multivariable Bayesian modeling on the resulting SNPs in an expanded discovery cohort with 1171 patients identified a multi-SNP signature of Copaxone response. This signature was examined in 941 Copaxone-treated MS patients from seven independent late-phase trials of Copaxone and assessed for specificity to Copaxone in 310 Avonex-treated and 311 placebo-treated patients, also from late-phase trials.

Results

A four-SNP signature consisting of rs80191572 (in UVRAG), rs28724893 (in HLA-DQB2), rs1789084 (in MBP), and rs139890339 (in ZAK(CDCA7)) was identified as significantly associated with Copaxone response. Copaxone-treated signature-positive patients had a greater reduction in annualized relapse rate (ARR) compared to signature-negative patients in both discovery and independent cohorts, an effect not observed in Avonex-treated patients. Additionally, signature-positive placebo-treated cohorts did not show a reduction in ARR, demonstrating the predictive as opposed to prognostic nature of the signature. A 10% subset of patients, delineated by the signature, showed marked improvements across multiple clinical parameters, including ARR, MRI measures, and higher proportion with no evidence of disease activity (NEDA).

Conclusions

This study is the largest pharmacogenetic study in MS reported to date. Gene regions underlying the four-SNP signature have been linked with pathways associated with either Copaxone’s MoA or the pathophysiology of MS. The pronounced association of the four-SNP signature with clinical improvements in a ~10% subset of the MS patient population demonstrates the complex interplay of immune mechanisms and the individualized nature of response to Copaxone.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-017-0436-y) contains supplementary material, which is available to authorized users.

A novel humanized mouse model of Huntington disease for preclinical development of therapeutics targeting mutant huntingtin alleles

Huntington disease (HD) is a neurodegenerative disease caused by a mutation in the huntingtin (HTT) gene. HTT is a large protein, interacts with many partners and is involved in many cellular pathways, which are perturbed in HD. Therapies targeting HTT directly are likely to provide the most global benefit. Thus there is a need for preclinical models of HD recapitulating human HTT genetics. We previously generated a humanized mouse model of HD, Hu97/18, by intercrossing BACHD and YAC18 mice with knockout of the endogenous mouse HD homolog (Hdh). Hu97/18 mice recapitulate the genetics of HD, having two full-length, genomic human HTT transgenes heterozygous for the HD mutation and polymorphisms associated with HD in populations of Caucasian descent. We have now generated a companion model, Hu128/21, by intercrossing YAC128 and BAC21 mice on the Hdh-/- background. Hu128/21 mice have two full-length, genomic human HTT transgenes heterozygous for the HD mutation and polymorphisms associated with HD in populations of East Asian descent and in a minority of patients from other ethnic groups. Hu128/21 mice display a wide variety of HD-like phenotypes that are similar to YAC128 mice. Additionally, both transgenes in Hu128/21 mice match the human HTT exon 1 reference sequence. Conversely, the BACHD transgene carries a floxed, synthetic exon 1 sequence. Hu128/21 mice will be useful for investigations of human HTT that cannot be addressed in Hu97/18 mice, for developing therapies targeted to exon 1, and for preclinical screening of personalized HTT lowering therapies in HD patients of East Asian descent.

Palmitoylation of caspase-6 by HIP14 regulates its activation

Caspase-6 (CASP6) has an important role in axonal degeneration during neuronal apoptosis and in the neurodegenerative diseases Alzheimer and Huntington disease. Decreasing CASP6 activity may help to restore neuronal function in these and other diseases such as stroke and ischemia, where increased CASP6 activity has been implicated. The key to finding approaches to decrease CASP6 activity is a deeper understanding of the mechanisms regulating CASP6 activation. We show that CASP6 is posttranslationally palmitoylated by the palmitoyl acyltransferase HIP14 and that the palmitoylation of CASP6 inhibits its activation. Palmitoylation of CASP6 is decreased both in Hip14-/- mice, where HIP14 is absent, and in YAC128 mice, a model of Huntington disease, where HIP14 is dysfunctional and where CASP6 activity is increased. Molecular modeling suggests that palmitoylation of CASP6 may inhibit its activation via steric blockage of the substrate-binding groove and inhibition of CASP6 dimerization, both essential for CASP6 function. Our studies identify palmitoylation as a novel CASP6 modification and as a key regulator of CASP6 activity.

eEF2K inhibition blocks Aβ42 neurotoxicity by promoting an NRF2 antioxidant response

Soluble oligomers of amyloid-β (Aβ) impair synaptic plasticity, perturb neuronal energy homeostasis, and are implicated in Alzheimer's disease (AD) pathogenesis. Therefore, significant efforts in AD drug discovery research aim to prevent the formation of Aβ oligomers or block their neurotoxicity. The eukaryotic elongation factor-2 kinase (eEF2K) plays a critical role in synaptic plasticity, and couples neurotransmission to local dendritic mRNA translation. Recent evidence indicates that Aβ oligomers activate neuronal eEF2K, suggesting a potential link to Aβ induced synaptic dysfunction. However, a detailed understanding of the role of eEF2K in AD pathogenesis, and therapeutic potential of eEF2K inhibition in AD, remain to be determined. Here, we show that eEF2K activity is increased in postmortem AD patient cortex and hippocampus, and in the hippocampus of aged transgenic AD mice. Furthermore, eEF2K inhibition using pharmacological or genetic approaches prevented the toxic effects of Aβ42 oligomers on neuronal viability and dendrite formation in vitro. We also report that eEF2K inhibition promotes the nuclear factor erythroid 2-related factor (NRF2) antioxidant response in neuronal cells, which was crucial for the beneficial effects of eEF2K inhibition in neurons exposed to Aβ42 oligomers. Accordingly, NRF2 knockdown or overexpression of the NRF2 inhibitor, Kelch-Like ECH-Associated Protein-1 (Keap1), significantly attenuated the neuroprotection associated with eEF2K inhibition. Finally, genetic deletion of the eEF2K ortholog efk-1 reduced oxidative stress, and improved chemotaxis and serotonin sensitivity in C. elegans expressing human Aβ42 in neurons. Taken together, these findings highlight the potential utility of eEF2K inhibition to reduce Aβ-mediated oxidative stress in AD.

The targetable A1 Huntington disease haplotype has distinct Amerindian and European origins in Latin America

Huntington disease (HD) is a dominant neurodegenerative disorder caused by a CAG repeat expansion in the Huntingtin (HTT) gene. HD occurs worldwide, but the causative mutation is found on different HTT haplotypes in distinct ethnic groups. In Latin America, HD is thought to have European origins, but indigenous Amerindian ancestry has not been investigated. Here, we report dense HTT haplotypes in 62 mestizo Peruvian HD families, 17 HD families from across Latin America, and 42 controls of defined Peruvian Amerindian ethnicity to determine the origin of HD in populations of admixed Amerindian and European descent. HD in Peru occurs most frequently on the A1 HTT haplotype (73%), as in Europe, but on an unexpected indigenous variant also found in Amerindian controls. This Amerindian A1 HTT haplotype predominates over the European A1 variant among geographically disparate Latin American controls and in HD families from across Latin America, supporting an indigenous origin of the HD mutation in mestizo American populations. We also show that a proportion of HD mutations in Peru occur on a C1 HTT haplotype of putative Amerindian origin (14%). The majority of HD mutations in Latin America may therefore occur on haplotypes of Amerindian ancestry rather than on haplotypes resulting from European admixture. Despite the distinct ethnic ancestry of Amerindian and European A1 HTT, alleles on the parent A1 HTT haplotype allow for development of identical antisense molecules to selectively silence the HD mutation in the greatest proportion of patients in both Latin American and European populations.

Sudden death due to paralysis and synaptic and behavioral deficits when Hip14/Zdhhc17 is deleted in adult mice

BACKGROUND

Palmitoylation, the addition of palmitate to proteins by palmitoyl acyltransferases (PATs), is an important regulator of synaptic protein localization and function. Many palmitoylated proteins and PATs have been implicated in neuropsychiatric diseases, including Huntington disease, schizophrenia, amyotrophic lateral sclerosis, Alzheimer disease, and X-linked intellectual disability. HIP14/DHHC17 is the most conserved PAT that palmitoylates many synaptic proteins. Hip14 hypomorphic mice have behavioral and synaptic deficits. However, the phenotype is developmental; thus, a model of post-developmental loss of Hip14 was generated to examine the role of HIP14 in synaptic function in the adult.

RESULTS

Ten weeks after Hip14 deletion (iHip14 Δ/Δ ), mice die suddenly from rapidly progressive paralysis. Prior to death the mice exhibit motor deficits, increased escape response during tests of anxiety, anhedonia, a symptom indicative of depressive-like behavior, and striatal synaptic deficits, including reduced probability of transmitter release and increased amplitude but decreased frequency of spontaneous post-synaptic currents. The mice also have increased brain weight due to microgliosis and astrogliosis in the cortex.

CONCLUSIONS

Behavioral changes and electrophysiological measures suggest striatal dysfunction in iHip14 Δ/Δ mice, and increased cortical volume due to astrogliosis and microgliosis suggests a novel role for HIP14 in glia. These data suggest that HIP14 is essential for maintenance of life and neuronal integrity in the adult mouse.

Mycophenolate mofetil and animal models

Mycophenolate mofetil (MMF), is the morpholinoethyl ester of mycophenolic acid (MPA). Though initially developed as an anti-rejection treatment, MMF is beginning to find application in more common immune-mediated diseases. MMF has been shown to be effective against transplant-associated vascular disease, lupus and other inflammatory diseases via multiple mechanisms in several animal models. MMF treatment blocks the proliferation of T cells and B cells, attenuates the production of autoreactive IgG and IgM, diminishes complement deposition, and reduces the production of multiple proinflammatory cytokines including TNF-α, IFN-γ, IL-2, IL-3, IL-4, IL-5, IL-6 and IL-12. It also increases production of the anti-inflammatory mediator IL-10. In addition, MMF reduces the infiltration of immune cells into sites of inflammation by interfering with the expression of cell-surface molecules critical for this process, including MHC class II, CD40, CD80, CD86, I-A, and ICAM-1. Additional mechanisms involving mannosylation and N-linked glycosylation of cell-surface molecules are only beginning to be investigated. This article will focus on the contribution of animal models of disease as investigational tools in the development of MMF as an immunomodulatory drug. The use of mice, rats, rabbits, monkeys, baboons and interspecific xenografts will be discussed.

Mycophenolate mofetil as an immunomodulatory silver bullet in atherogenesis?

Atherosclerotic vascular disease is a chronic disorder of the vasculature with a substantial impact on society. Although the availability of statins has represented an unparalleled improvement in the treatment of patients with such cardiovascular disease, even more effective measures are required to reverse this disorder with a continuously growing incidence. The classification of atherosclerosis as an inflammatory disorder has prompted the hypothesis that immunomodulation could comprise a novel anti-atherosclerotic strategy. Mycophenolate mofetil (MMF) has various anti-atherogenic effects on major components of the atherosclerotic plaque such as T-lymphocytes, monocytes/macrophages and the endothelium. MMF can inhibit leukocyte recruitment to the subendothelium and the subsequent reduced activation of leukocytes will translate into attenuation of subendothelial crosstalk between T-cells and macrophages. This cascade of events will interrupt the self-perpetuating pro-inflammatory environment within the arterial wall, the hallmark of atherosclerotic vascular disease.