Disease-causing mutations in BEST1 gene are associated with altered sorting of bestrophin-1 protein

Doumanov, Jordan A. et al.Mutations in BEST1 gene, encoding the bestrophin-1 (Best1) protein are associated with macular dystrophies. Best1 is predominantly expressed in the retinal pigment epithelium (RPE), and is inserted in its basolateral membrane. We investigated the cellular localization in polarized MDCKII cells of disease-associated Best1 mutant proteins to study specific sorting motifs of Best1. Real-time PCR and western blots for endogenous expression of BEST1 in MDCK cells were performed. Best1 mutant constructs were generated using site-directed mutagenesis and transfected in MDCK cells. For protein sorting, confocal microscopy studies, biotinylation assays and statistical methods for quantification of mislocalization were used. Analysis of endogenous expression of BEST1 in MDCK cells revealed the presence of BEST1 transcript but no protein. Confocal microscopy and quantitative analyses indicate that transfected normal human Best1 displays a basolateral localization in MDCK cells, while cell sorting of several Best1 mutants (Y85H, Q96R, L100R, Y227N, Y227E) was altered. In contrast to constitutively active Y227E, constitutively inactive Y227F Best1 mutant localized basolaterally similar to the normal Best1 protein. Our data suggest that at least three basolateral sorting motifs might be implicated in proper Best1 basolateral localization. In addition, non-phosphorylated tyrosine 227 could play a role for basolateral delivery. © 2013 by the authors; licensee MDPI, Basel, Switzerland.This work was supported by Agence Nationale de la Recherche (Chaire d’Excellence to Shomi S. Bhattacharya), Fondation Voir et Entendre (Young Investigator Grants to Christina Zeitz and Emeline F. Nandrot), Centre National de la Recherche Scientifique (CNRS) and Fondation Bettencourt Schueller (to Emeline F. Nandrot), Université Pierre et Marie Curie-Paris6 (Bonus Qualité Recherche to Christina Zeitz), Foundation Fighting Blindness (grant number CD-CL-0808-0466-CHNO to Isabelle Audo), Centre d’Investigation Clinique 503 recognized as a Foundation Fighting Blindness Center (grant number C-CMM-0907-0428-INSERM04), Fundacion Progreso y Salud (to Shomi S. Bhattacharya, Maria Luz Bellido Diaz, Abhay Krishna and Paloma Dominguez Gimenez), Instituto de Salud Carlos III (grant number CM06/00183 to Maria Luz Bellido Diaz) and Bulgarian National Science Fund (grant number DDVU 02/10). Additionally, the Institut de la Vision is funded by Institut National de la Santé et de la Recherche Médicale, Université Pierre et Marie Curie-Paris 6, Centre National de la Recherche Scientifique and Départment de Paris.Peer Reviewe

Community occupational therapists’ clinical reasoning: Identifying tacit knowledge

Abstract : Background: Occupational therapy interventions in the community, a fast expanding practice setting, are central to an important social priority, the ability to live at home. These interventions generally involve only a small number of home visits, which aim at maximising the safety and autonomy of community-dwelling clients. Knowing how community occupational therapists determine their interventions, i.e. their clinical reasoning, can improve intervention efficacy. However, occupational therapists are often uninformed about and neglect the importance of clinical reasoning, which could underoptimise their interventions. Aim: To synthesise current knowledge about community occupational therapists’ clinical reasoning. Method: A scoping study of the literature on community occupational therapists’ clinical reasoning was undertaken. Results: Fifteen textbooks and 25 articles, including six focussing on community occupational therapists’ clinical reasoning, were reviewed. Community occupational therapists’ clinical reasoning is influenced by internal and external factors. Internal factors include past experiences, expertise and perceived complexity of a problem. One of the external factors, practice context (e.g. organisational or cultural imperatives, physical location of intervention), particularly shapes community occupational therapists’ clinical reasoning, which is interactive, complex and multidimensional. However, the exact influence of many factors (personal context, organisational and legal aspects of health care, lack of resources and increased number of referrals) remains unclear. Conclusion: Further studies are needed to understand better the influence of internal and external factors. The extent to which these factors mould the way community occupational therapists think and act could have a direct influence on the services they provide to their clients

Mislocalisation of BEST1 in iPSC-derived retinal pigment epithelial cells from a family with autosomal dominant vitreoretinochoroidopathy (ADVIRC)

Autosomal dominant vitreoretinochoroidopathy (ADVIRC) is a rare, early-onset retinal dystrophy characterised by distinct bands of circumferential pigmentary degeneration in the peripheral retina and developmental eye defects. ADVIRC is caused by mutations in the Bestrophin1 (BEST1) gene, which encodes a transmembrane protein thought to function as an ion channel in the basolateral membrane of retinal pigment epithelial (RPE) cells. Previous studies suggest that the distinct ADVIRC phenotype results from alternative splicing of BEST1 pre-mRNA. Here, we have used induced pluripotent stem cell (iPSC) technology to investigate the effects of an ADVIRC associated BEST1 mutation (c.704T > C, p.V235A) in patient-derived iPSC-RPE. We found no evidence of alternate splicing of the BEST1 transcript in ADVIRC iPSC-RPE, however in patient-derived iPSC-RPE, BEST1 was expressed at the basolateral membrane and the apical membrane. During human eye development we show that BEST1 is expressed more abundantly in peripheral RPE compared to central RPE and is also expressed in cells of the developing retina. These results suggest that higher levels of mislocalised BEST1 expression in the periphery, from an early developmental stage, could provide a mechanism that leads to the distinct clinical phenotype observed in ADVIRC patients

Effects of Ca2+ ions on bestrophin-1 surface films

Mladenova, Kirika et al.Human bestrophin-1 (hBest1) is a transmembrane calcium-activated chloride channel protein – member of the bestrophin family of anion channels, predominantly expressed in the membrane of retinal pigment epithelium (RPE) cells. Mutations in the protein cause ocular diseases, named Bestrophinopathies. Here, we present the first Fourier transform infrared (FTIR) study of the secondary structure elements of hBest1, π/A isotherms and hysteresis, Brewster angle microscopy (BAM) and atomic force microscopy (AFM) visualization of the aggregation state of protein molecules dispersed as Langmuir and Langmuir-Blodgett films. The secondary structure of hBest1 consists predominantly of 3-helices (27.2%), α-helixes (16.3%), β-turns and loops (32.2%). AFM images of hBest1 suggest approximate lateral dimensions of 100 × 160 Å and 75 Å height. Binding of calcium ions (Ca) induces conformational changes in the protein secondary structure leading to assembly of protein molecules and changes in molecular and macro-organization of hBest1 in monolayers. These data provide basic information needed in pursuit of molecular mechanisms underlying retinal and other pathologies linked to this protein.This work was supported by grants from Sofia University “St. Kliment Ohridski” (No. 93/12.04.2016) and Bulgarian Science Fund (DFNI-T02/7, 12.12.2014).Peer Reviewe

Solvent-Free Synthesis of Multifunctional Block Copolymer and Formation of DNA and Drug Nanocarriers

The synthesis of well-defined multifunctional polymers is of great importance for the development of complex materials for biomedical applications. In the current work, novel and multi-amino-functional diblock copolymer for potential gene and drug delivery applications was successfully synthesized. A highly efficient one-step and quantitative modification of an alkyne-functional polycarbonate-based precursor was performed, yielding double hydrophilic block copolymer with densely grafted primary amine side groups. The obtained positively charged block copolymer co-associated with DNA, forming stable and biocompatible nanosized polyplexes. Furthermore, polyion complex (PIC) micelles with tunable surface charge and decorated with cell targeting moieties were obtained as a result of direct mixing in aqueous media of the multi-amino-functional block copolymer and a previously synthesized oppositely charged block copolymer bearing disaccharide end-group. The obtained well-defined nanosized PIC–micelles were loaded with the hydrophobic drug curcumin. Both types of nanoaggregates (polyplexes and PIC–micelles) were physico-chemically characterized. Moreover, initial in vitro evaluations were performed to assess the nanocarriers’ potential for biomedical applications

Nanoarchitectonics of Spherical Nucleic Acids with Biodegradable Polymer Cores: Synthesis and Evaluation

Spherical nucleic acids (SNAs) have gained significant attention due to their unique properties allowing them to overcome the challenges that face current nanocarriers used for gene therapies. The aim of this study is to synthesize and characterize polymer–oligonucleotide conjugates of different architecture and to evaluate the possibility of forming SNAs with biodegradable cores. Initially, two types of azide (multi)functional polyester-based (co)polymers were successfully synthesized and characterized. In the next step, short oligonucleotide strands were attached to the polymer chains applying the highly efficient and metal-free “click” reaction, thus forming conjugates with block or graft architecture. Both conjugates spontaneously self-assembled in aqueous media forming nanosized SNAs with a biodegradable polyester core and a surface of oligonucleotide chains as evidenced from dynamic and electrophoretic light scattering measurements. The nano-assemblies were in vitro evaluated for potential cytotoxicity. Furthermore, the interactions of the newly synthesized SNAs with membrane lipids were studied. The preliminary results indicate that both types of polymer-based SNAs are good candidates for potential application in gene therapy and that it is worth to be further evaluated

Self-organization and surface properties of hBest1 in models of biological membranes

The transmembrane Ca2+ − activated Cl− channel - human bestrophin-1 (hBest1) is expressed in retinal pigment epithelium and mutations of BEST1 gene cause ocular degenerative diseases colectivelly referred to as “bestrophinopathies”. A large number of genetical, biochemical, biophysical and molecular biological studies have been performed to understand the relationship between structure and function of the hBest1 protein and its pathophysiological significance. Here, we review the current understanding of hBest1 surface organization, interactions with membrane lipids in model membranes, and its association with microdomains of cellular membranes. These highlights are significant for modulation of channel activity in cells

Cholesterol alters the phase separation in model membranes containing hBest1

Human retinal pigment epithelial (RPE) cells express the transmembrane Ca2+-dependent Cl− channel bestrophin-1 (hBest1) of the plasma membrane. Mutations in the hBest1 protein are associated with the development of distinct pathological conditions known as bestrophinopathies. The interactions between hBest1 and plasma membrane lipids (cholesterol (Chol), 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and sphingomyelin (SM)) determine its lateral organization and surface dynamics, i.e., their miscibility or phase separation. Using the surface pressure/mean molecular area (π/A) isotherms, hysteresis and compressibility moduli (Cs−1) of hBest1/POPC/Chol and hBest1/SM/Chol composite Langmuir monolayers, we established that the films are in an LE (liquid-expanded) or LE-LC (liquid-condensed) state, the components are well-mixed and the Ca2+ ions have a condensing effect on the surface molecular organization. Cholesterol causes a decrease in the elasticity of both films and a decrease in the ΔGmixπ values (reduction of phase separation) of hBest1/POPC/Chol films. For the hBest1/SM/Chol monolayers, the negative values of ΔGmixπ are retained and equalized with the values of ΔGmixπ in the hBest1/POPC/Chol films. Shifts in phase separation/miscibility by cholesterol can lead to changes in the structure and localization of hBest1 in the lipid rafts and its channel functions

Original Synthesis of a Nucleolipid for Preparation of Vesicular Spherical Nucleic Acids

Spherical nucleic acids (SNAs)—nanostructures, consisting of a nanoparticle core densely functionalized with a shell of short oligonucleotide strands—are a rapidly emerging class of nanoparticle-based therapeutics with unique properties and specific applications as drug and nucleic acid delivery and gene regulation materials. In this contribution, we report on the preparation of hollow SNA nanoconstructs by co-assembly of an originally synthesized nucleolipid—a hybrid biomacromolecule, composed of a lipidic residue, covalently linked to a DNA oligonucleotide strand—with other lipids. The nucleolipid was synthesized via a click chemistry approach employing initiator-free, UV light-induced thiol-ene coupling of appropriately functionalized intermediates, performed in mild conditions using a custom-made UV light-emitting device. The SNA nanoconstructs were of a vesicular structure consisting of a self-closed bilayer membrane in which the nucleolipid was intercalated via its lipid–mimetic residue. They were in the lower nanometer size range, moderately negatively charged, and were found to carry thousands of oligonucleotide strands per particle, corresponding to a grafting density comparable to that of other SNA structures. The surface density of the strands on the bilayer implied that they adopted an unextended conformation. We demonstrated that preformed vesicular structures could be successfully loaded with either hydrophilic or hydrophobic dyes