Identification of genetic variants associated with Huntington's disease progression: a genome-wide association study

Background Huntington's disease is caused by a CAG repeat expansion in the huntingtin gene, HTT. Age at onset has been used as a quantitative phenotype in genetic analysis looking for Huntington's disease modifiers, but is hard to define and not always available. Therefore, we aimed to generate a novel measure of disease progression and to identify genetic markers associated with this progression measure. Methods We generated a progression score on the basis of principal component analysis of prospectively acquired longitudinal changes in motor, cognitive, and imaging measures in the 218 indivduals in the TRACK-HD cohort of Huntington's disease gene mutation carriers (data collected 2008–11). We generated a parallel progression score using data from 1773 previously genotyped participants from the European Huntington's Disease Network REGISTRY study of Huntington's disease mutation carriers (data collected 2003–13). We did a genome-wide association analyses in terms of progression for 216 TRACK-HD participants and 1773 REGISTRY participants, then a meta-analysis of these results was undertaken. Findings Longitudinal motor, cognitive, and imaging scores were correlated with each other in TRACK-HD participants, justifying use of a single, cross-domain measure of disease progression in both studies. The TRACK-HD and REGISTRY progression measures were correlated with each other (r=0·674), and with age at onset (TRACK-HD, r=0·315; REGISTRY, r=0·234). The meta-analysis of progression in TRACK-HD and REGISTRY gave a genome-wide significant signal (p=1·12 × 10−10) on chromosome 5 spanning three genes: MSH3, DHFR, and MTRNR2L2. The genes in this locus were associated with progression in TRACK-HD (MSH3 p=2·94 × 10−8 DHFR p=8·37 × 10−7 MTRNR2L2 p=2·15 × 10−9) and to a lesser extent in REGISTRY (MSH3 p=9·36 × 10−4 DHFR p=8·45 × 10−4 MTRNR2L2 p=1·20 × 10−3). The lead single nucleotide polymorphism (SNP) in TRACK-HD (rs557874766) was genome-wide significant in the meta-analysis (p=1·58 × 10−8), and encodes an aminoacid change (Pro67Ala) in MSH3. In TRACK-HD, each copy of the minor allele at this SNP was associated with a 0·4 units per year (95% CI 0·16–0·66) reduction in the rate of change of the Unified Huntington's Disease Rating Scale (UHDRS) Total Motor Score, and a reduction of 0·12 units per year (95% CI 0·06–0·18) in the rate of change of UHDRS Total Functional Capacity score. These associations remained significant after adjusting for age of onset. Interpretation The multidomain progression measure in TRACK-HD was associated with a functional variant that was genome-wide significant in our meta-analysis. The association in only 216 participants implies that the progression measure is a sensitive reflection of disease burden, that the effect size at this locus is large, or both. Knockout of Msh3 reduces somatic expansion in Huntington's disease mouse models, suggesting this mechanism as an area for future therapeutic investigation

Synthesis, structural studies and applications of beta-phenylproline and (phenylazo)phenylalanine derivatives

Se ha llevado a cabo la síntesis y el estudio, en diferentes tipos de aplicaciones, de diversos aminoácidos no proteicos que presentan funcionalidad adicional en la cadena lateral. Concretamente, el trabajo se ha centrado en el análogo de prolina que incorpora un sustituyente fenilo en posición beta del anillo de pirrolidina y en varios análogos de fenilalanina con uno o dos grupos azobenceno en la cadena lateral. Se han desarrollado métodos sintéticos para la preparación de todos ellos en forma enantiopura. Estos aminoácidos no proteicos han mostrado su capacidad para estabilizar determinados tipos de conformaciones peptidicas así como para generar nanoestructuras de morfología esférica o fibrilar por procesos de autoensamblaje. La presencia de grupos azobenzeno confiere fotosensibilidad a estas nanoestructuras.Peer Reviewe

Effect of a β-phenyl substituent on the puckering modes of proline

Trabajo presentado a la Small Molecule NMR Conference celebrada en Santiago de Compostela (España) del 22 al 25 de septiembre de 2013.The high significance of proline in peptide conformation and biology stimulates the development of proline analogues with tailored properties. The attachment of substituents to the five-membered ring is particularly atractive in this regard. Such substituents may serve to incorporate additional functionality as well as to modulate the conformational properties of proline. In this context, we have explored the effect produced by a phenyl substituent attached to the β-carbon atom of proline on the puckering modes adopted by the pyrrolidine ring. Both the cis and trans configurations of the β-phenyl group relative to the carbonyl moiety have been considered. The puckering modes of such proline analogues, cis- and trans-β-phenylproline, have been examined by NMR when incorporated into model dipeptides. We observed that the pyrrolidine conformation is significantly affected by the presence of the β-phenyl group. Those conformations that alleviate most the steric hindrance introduced by the bulky phenyl substituent are preferred. The orientation adopted by the aromatic moiety is much more restricted in the cis isomer. Thus, cis-β-phenylproline shows a highly marked propensity to adopt a Cγ-endo arrangement. In contrast, the trans derivative exhibits a higher flexibility, with Cγ-endo and Cγ-exo pyrrolidine shapes being accessible, as for proline itself.Peer reviewe

β-Phenylproline: the high β-turn forming propensity of proline combined with an aromatic side chain

The conformational propensities of the proline analogue bearing a phenyl substituent attached to the β carbon, in either a cis or a trans configuration relative to the carbonyl group, have been investigated. The behaviour of cis- and trans(βPh)Pro has been compared with that of proline in homochiral and heterochiral dipeptide sequences. NMR and IR studies as well as X-ray diffraction analysis provide evidence that the β-phenyl substituent does not disrupt the tendency of proline to occupy the i+1 position of a β-turn. The puckering of the pyrrolidine ring is significantly affected by the presence of the aromatic substituent, which tends to occupy positions that minimize steric repulsions. As a consequence, this substituent adopts specific well-defined orientations, which are more restricted for the cis derivative. Interactions between this aromatic group and that in the adjacent phenylalanine residue may be responsible for some of the conformational differences observed among the different peptides studied.The authors thank the Ministerio de Ciencia e Innovación FEDER (project CTQ2010-17436; FPU fellowship to P.F.) and Gobierno de Aragón (research group E40) for financial support.Peer Reviewe

Bis(azobenzene)-Based Photoswitchable, Prochiral, Cα-Tetrasubstituted α-Amino Acids for Nanomaterials Applications

Light-driven chirality: Sequential light-driven isomerization of prochiral, bis(azobenzene)-containing amino acids results in the formation of chiral entities that have been characterized by different techniques. Metal nanoparticles conjugated with these amino acids retain the photoswitching properties and show conformation-dependent magnetic susceptibility that can be reversibly controlled by irradiation (see figure).Financial support from the Ministerio de Ciencia e Innovación (grant CTQ2010-17436, FPU fellowship to P. F.), the University of Padova (“Progetto Strategico” HELIOS 2008, prot. STPD08RCX).Peer Reviewe

Access to enantiomerically pure cis- and trans-β-phenylproline by high-performance liquid chromatography resolution

El pdf del artículo es la versión pre-print.The preparation of all four stereoisomers of the proline analog that bears a phenyl group attached to the β carbon either cis or trans to the carboxylic acid (cis- and trans-β-phenylproline, respectively) has been addressed. The methodology developed allows access to multigram quantities of the target amino acids in enantiomerically pure form and suitably protected for use in peptide synthesis. Racemic precursors of cis-β-phenylproline and trans-β-phenylproline were prepared from easily available starting materials and subjected to high-performance liquid chromatography enantioseparation. Semipreparative columns (250 × 20 mm) containing chiral stationary phases based on amylose (Chiralpak IA) (Daicel-Chiral Technologies Europe, Illkirch, France) or cellulose (Chiralpak IC) were used respectively for the resolution of the cis- and trans-β-phenylproline precursors.P. F. is grateful to the Ministerio de Ciencia e Innovación for an FPU grant.Peer Reviewe

Access to enantiomerically pure cis- and trans-β-phenylproline by high-performance liquid chromatography resolution

El pdf del artículo es la versión pre-print.The preparation of all four stereoisomers of the proline analog that bears a phenyl group attached to the β carbon either cis or trans to the carboxylic acid (cis- and trans-β-phenylproline, respectively) has been addressed. The methodology developed allows access to multigram quantities of the target amino acids in enantiomerically pure form and suitably protected for use in peptide synthesis. Racemic precursors of cis-β-phenylproline and trans-β-phenylproline were prepared from easily available starting materials and subjected to high-performance liquid chromatography enantioseparation. Semipreparative columns (250 × 20 mm) containing chiral stationary phases based on amylose (Chiralpak IA) (Daicel-Chiral Technologies Europe, Illkirch, France) or cellulose (Chiralpak IC) were used respectively for the resolution of the cis- and trans-β-phenylproline precursors.P. F. is grateful to the Ministerio de Ciencia e Innovación for an FPU grant.Peer Reviewe

Multistimuli-responsive supramolecular organogels formed by low-molecular-weight peptides bearing side-chain azobenzene moieties

This work demonstrates that the incorporation of azobenzene residues into the side chain of low-molecular-weight peptides can modulate their self-assembly process in organic solvents leading to the formation of stimuli responsive physical organogels. The major driving forces for the gelation process are hydrogen bonding and π-π interactions, which can be triggered either by thermal or ultrasound external stimuli, affording materials having virtually the same properties. In addition, a predictive model for gelation of polar protic solvent was developed by using Kamlet-Taft solvent parameters and experimental data. The obtained viscoelastic materials exhibited interconnected multistimuli responsive behaviors including thermal-, photo-, chemo- and mechanical responses. All of them displayed thermoreversability with gel-to-sol transition temperatures established between 33-80 °C and gelation times from minutes to several hours. Structure-property relationship studies of a designed peptide library have demonstrated that the presence and position of the azobenzene residue can be operated as a versatile regulator to reduce the critical gelation concentration and enhance both the thermal stability and mechanical strength of the gels, as demonstrated by comparative dynamic rheology. The presence of N-Boc protecting group in the peptides showed also a remarkable effect on the formation and properties of the gels. Despite numerous examples of peptide-based gelators known in the literature, this is the first time in which low-molecular-weight peptides bearing side chain azobenzene units are used for the synthesis of >intelligent> supramolecular organogels. Compared with other approaches, this strategy is advantageous in terms of structural flexibility since it is compatible with a free, unprotected amino terminus and allows placement of the chromophore at any position of the peptide sequence.The authors thank the Ministerio de Ciencia e Innovación–FEDER (project CTQ2010-17436, FPU fellowship to P.F.), Gobierno de Aragón–FSE (research group E40), CSIC (project PIE 200980I059), Alexander von Humboldt Foundation (fellowship for Experienced Researchers to D.D.D) and the University of Regensburg (Anschubfinanzierung von Wissenschaftlichen Projekten-2011) for financial support.Peer Reviewe

Photocontrolled self-assembly of a bis-azobenzene-containing α-amino acid

Light-responsive vesicles: Derivatives of an α-amino acid with two azobenzene side chains self-assemble into vesicular structures that undergo morphological transitions upon light irradiation (see scheme). This is the first example of photoresponsive vesicle-like supramolecular structures formed exclusively by peptides or derivatized amino acids. The entrapment and subsequent light-induced release of functionalized gold nanoparticles are also shown. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Financial support from the Ministerio de Ciencia e Innovación-FEDER (grant CTQ2010-17436, FPU fellowship to P.F.), Gobierno de Aragón-FSE (research group E40), and the University of Padova (PRAT A. M. C91 J11003560001 and M. M. CPDA119117) are gratefully acknowledged.Peer Reviewe