Effects of sex chromosome dosage on corpus callosum morphology in supernumerary sex chromosome aneuploidies

Background

Supernumerary sex chromosome aneuploidies (sSCA) are characterized by the presence of one or more additional sex chromosomes in an individual’s karyotype; they affect around 1 in 400 individuals. Although there is high variability, each sSCA subtype has a characteristic set of cognitive and physical phenotypes. Here, we investigated the differences in the morphometry of the human corpus callosum (CC) between sex-matched controls 46,XY (N =99), 46,XX (N =93), and six unique sSCA karyotypes: 47,XYY (N =29), 47,XXY (N =58), 48,XXYY (N =20), 47,XXX (N =30), 48,XXXY (N =5), and 49,XXXXY (N =6).

Methods

We investigated CC morphometry using local and global area, local curvature of the CC boundary, and between-landmark distance analysis (BLDA). We hypothesized that CC morphometry would vary differentially along a proposed spectrum of Y:X chromosome ratio with supernumerary Y karyotypes having the largest CC areas and supernumerary X karyotypes having significantly smaller CC areas. To investigate this, we defined an sSCA spectrum based on a descending Y:X karyotype ratio: 47,XYY, 46,XY, 48,XXYY, 47,XXY, 48,XXXY, 49,XXXXY, 46,XX, 47,XXX. We similarly explored the effects of both X and Y chromosome numbers within sex. Results of shape-based metrics were analyzed using permutation tests consisting of 5,000 iterations.

Results

Several subregional areas, local curvature, and BLDs differed between groups.Moderate associations were found between area and curvature in relation to the spectrum and X and Y chromosome counts. BLD was strongly associated with X chromosome count in both male and female groups.

Conclusions

Our results suggest that X- and Y-linked genes have differential effects on CC morphometry. To our knowledge, this is the first study to compare CC morphometry across these extremely rare groups.

     

Exercise therapy for prevention of falls in people with Parkinson's disease: A protocol for a randomised controlled trial and economic evaluation

Background

People with Parkinson's disease are twice as likely to be recurrent fallers compared to other older people. As these falls have devastating consequences, there is an urgent need to identify and test innovative interventions with the potential to reduce falls in people with Parkinson's disease. The main objective of this randomised controlled trial is to determine whether fall rates can be reduced in people with Parkinson's disease using exercise targeting three potentially remediable risk factors for falls (reduced balance, reduced leg muscle strength and freezing of gait). In addition we will establish the cost effectiveness of the exercise program from the health provider's perspective.

Methods/Design

230 community-dwelling participants with idiopathic Parkinson's disease will be recruited. Eligible participants will also have a history of falls or be identified as being at risk of falls on assessment. Participants will be randomly allocated to a usual-care control group or an intervention group which will undertake weight-bearing balance and strengthening exercises and use cueing strategies to address freezing of gait. The intervention group will choose between the home-based or support group-based mode of the program. Participants in both groups will receive standardized falls prevention advice. The primary outcome measure will be fall rates. Participants will record falls and medical interventions in a diary for the duration of the 6-month intervention period. Secondary measures include the Parkinson's Disease Falls Risk Score, maximal leg muscle strength, standing balance, the Short Physical Performance Battery, freezing of gait, health and well being, habitual physical activity and positive and negative affect schedule.

Discussion

No adequately powered studies have investigated exercise interventions aimed at reducing falls in people with Parkinson's disease. This trial will determine the effectiveness of the exercise intervention in reducing falls and its cost effectiveness. This pragmatic program, if found to be effective, has the potential to be implemented within existing community services.

Trial registration

The protocol for this study is registered with the Australian New Zealand Clinical Trials Registry (ACTRN12608000303347).     

Affinity chromatography reveals RuBisCO as an ecdysteroid-binding protein

The aim of this work was to isolate plant ecdysteroid-binding proteins using affinity chromatography. Ecdysteroids as insect hormones have been investigated thoroughly but their function and the mechanism of action in plants and other organisms is still unknown although ecdysteroids occur in some plants in a relatively large amount. Therefore, 20-hydroxyecdysone was immobilized on a polymeric carrier as a ligand for affinity chromatography in order to isolate plant ecdysteroid-binding proteins from the cytosolic extract of New Zealand spinach (Tetragonia tetragonoides). Non-specifically bound proteins were eluted with a rising gradient of concentration of sodium chloride, and 3% (v/v) acetic acid was used for the elution of the specifically bound proteins. Using this method, ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) was isolated. The influence of ecdysteroids on RuBisCO was further studied. Our results show that ecdysteroids are able to increase the yield of RuBisCO-mediated reaction in which CO(2) is fixed into organic matter by more than 10%.     

beta -Arrestins regulate protease-activated receptor-1 desensitization but not internalization or Down-regulation.

The widely expressed beta-arrestin isoforms 1 and 2 bind phosphorylated G protein-coupled receptors (GPCRs) and mediate desensitization and internalization. Phosphorylation of protease-activated receptor-1 (PAR1), a GPCR for thrombin, is important for desensitization and internalization, however, the role of beta-arrestins in signaling and trafficking of PAR1 remains unknown. To assess beta-arrestin function we examined signaling and trafficking of PAR1 in mouse embryonic fibroblasts (MEFs) derived from beta-arrestin (betaarr) knockouts. Desensitization of PAR1 signaling was markedly impaired in MEFs lacking both betaarr1 and betaarr2 isoforms compared with wild-type cells. Strikingly, in cells lacking only betaarr1 PAR1 desensitization was also significantly impaired compared with betaarr2-lacking or wild-type cells. In wild-type MEFs, activated PAR1 was internalized through a dynamin- and clathrin-dependent pathway and degraded. Surprisingly, in cells lacking both betaarr1 and betaarr2 activated PAR1 was similarly internalized through a dynamin- and clathrin-dependent pathway and degraded, whereas the beta(2)-adrenergic receptor (beta(2)-AR) failed to internalize. A PAR1 cytoplasmic tail mutant defective in agonist-induced phosphorylation failed to internalize in both wild-type and beta-arrestin knockout cells. Thus, PAR1 appears to utilize a distinct phosphorylation-dependent but beta-arrestin-independent pathway for internalization through clathrin-coated pits. Together, these findings strongly suggest that the individual beta-arrestin isoforms can differentially regulate GPCR desensitization and further reveal a novel mechanism by which GPCRs can internalize through a dynamin- and clathrin-dependent pathway that is independent of arrestins.     

Genbank accession #: AF 124983

Plant Molecular Biology -     

Towards a unified paradigm for sequence‐based identification of fungi

The nuclear ribosomal internal transcribed spacer (ITS) region is the formal fungal barcode and in most cases the marker of choice for the exploration of fungal diversity in environmental samples. Two problems are particularly acute in the pursuit of satisfactory taxonomic assignment of newly generated ITS sequences: (i) the lack of an inclusive, reliable public reference data set and (ii) the lack of means to refer to fungal species, for which no Latin name is available in a standardized stable way. Here, we report on progress in these regards through further development of the UNITE database ( http://unite.ut.ee ) for molecular identification of fungi. All fungal species represented by at least two ITS sequences in the international nucleotide sequence databases are now given a unique, stable name of the accession number type (e.g. Hymenoscyphus pseudoalbidus|GU586904|SH133781.05FU), and their taxonomic and ecological annotations were corrected as far as possible through a distributed, third‐party annotation effort. We introduce the term ‘species hypothesis’ (SH) for the taxa discovered in clustering on different similarity thresholds (97–99%). An automatically or manually designated sequence is chosen to represent each such SH. These reference sequences are released ( http://unite.ut.ee/repository.php ) for use by the scientific community in, for example, local sequence similarity searches and in the QIIME pipeline. The system and the data will be updated automatically as the number of public fungal ITS sequences grows. We invite everybody in the position to improve the annotation or metadata associated with their particular fungal lineages of expertise to do so through the new Web‐based sequence management system in UNITE.     

Characterization of Functional Neuropeptide Y Receptors in a Human Neuroblastoma Cell Line

We identified receptors for neuropeptide Y (NPY) on an established human neuroblastoma cell line, SK-N-MC, which are functionally coupled to adenylate cyclase through the inhibitory guanine nucleotide-binding protein of adenylate cyclase, Gi. Intact SK-N-MC cells bound radiolabeled NPY with a KD of 2 nM and contained approximately 83,000 receptors/cell. Unlabeled porcine and human NPY and structurally related porcine peptide YY (PYY) competed with labeled NPY for binding to the receptors. NPY inhibited cyclic AMP accumulation in SK-N-MC cells stimulated by isoproterenol, dopamine, vasoactive intestinal peptide, cholera toxin, and forskolin. NPY inhibited isoproterenol-stimulated cyclic AMP production in a dose-dependent manner, with half-maximal inhibition at 0.5 nM NPY. Porcine and human NPY and porcine PYY gave similar dose-response curves. NPY also inhibited basal and isoproterenol-stimulated adenylate cyclase activity in disrupted cells. Pertussis toxin treatment of the cells completely blocked the ability of NPY to inhibit cyclic AMP production and adenylate cyclase activity. The toxin catalyzed the ADP-ribosylation of a 41-kDa protein in SK-N-MC cells that corresponds to Gi. The receptors on SK-N-MC cells appeared to be specific for NPY, as other neurotransmitter drugs, such as alpha-adrenergic, dopaminergic, muscarinic, and serotonergic antagonists, did not compete for either NPY binding or NPY inhibition of adenylate cyclase. Thus, SK-N-MC cells may be a useful model for investigating NPY receptors and NPY-mediated signal transduction.     

D1 Dopamine Receptors Can Interact with Both Stimulatory and Inhibitory Guanine Nucleotide Binding Proteins

Pretreatment of striatal membranes with N-ethylmaleimide in the presence of a D1-specific agonist inactivated endogenous guanine nucleotide binding proteins (G proteins), but not D1 dopamine receptors, resulting in a loss of high-affinity agonist binding sites. Such D1 receptors were solubilized, mixed with exogenous G proteins from cells not containing D1 receptors, and reconstituted into phospholipid vesicles. These reconstituted receptors were able to couple to the exogenous G proteins, and the proportion of agonist high-affinity sites of the receptor (40-57%) was similar to levels obtained with naive receptors coupling to endogenous G proteins (40%) upon solubilization and reconstitution. These hybrid high-affinity sites were fully modulated by guanine nucleotides. Pretreatment of cells with pertussis toxin prior to extraction of G proteins resulted in a 50% decrease in the proportion of high-affinity sites; these sites remained sensitive to guanine nucleotides. When D1 receptors were reconstituted with extracts of cyc- cells, which lack stimulatory G proteins, the proportion of high-affinity sites was reduced to 31% of the total. Pertussis toxin treatment of the cyc- cells completely abolished the formation of high-affinity sites. These results demonstrate that D1-dopaminergic receptors are able to couple to not only stimulatory G proteins (Gs), but also to inhibitory G proteins (Gi).