Semaphorin 3A Binds to the Perineuronal Nets via Chondroitin Sulfate Type E Motifs in Rodent Brains

Chondroitin sulfate (CS) and the CS-rich extracellular matrix structures called perineuronal nets (PNNs) restrict plasticity and regeneration in the CNS. Plasticity is enhanced by chondroitinase ABC treatment that removes CS from its core protein in the chondroitin sulfate proteoglycans or by preventing the formation of PNNs, suggesting that chondroitin sulfate proteoglycans in the PNNs control plasticity. Recently, we have shown that semaphorin3A (Sema3A), a repulsive axon guidance molecule, localizes to the PNNs and is removed by chondroitinase ABC treatment (Vo, T., Carulli, D., Ehlert, E. M., Kwok, J. C., Dick, G., Mecollari, V., Moloney, E. B., Neufeld, G., de Winter, F., Fawcett, J. W., and Verhaagen, J. (2013) Mol. Cell. Neurosci. 56C, 186–200). Sema3A is therefore a candidate for a PNN effector in controlling plasticity. Here, we characterize the interaction of Sema3A with CS of the PNNs. Recombinant Sema3A interacts with CS type E (CS-E), and this interaction is involved in the binding of Sema3A to rat brain-derived PNN glycosaminoglycans, as demonstrated by the use of CS-E blocking antibody GD3G7. In addition, we investigate the release of endogenous Sema3A from rat brain by biochemical and enzymatic extractions. Our results confirm the interaction of Sema3A with CS-E containing glycosaminoglycans in the dense extracellular matrix of rat brain. We also demonstrate that the combination of Sema3A and PNN GAGs is a potent inhibitor of axon growth, and this inhibition is reduced by the CS-E blocking antibody. In conclusion, Sema3A binding to CS-E in the PNNs may be a mechanism whereby PNNs restrict growth and plasticity and may represent a possible point of intervention to facilitate neuronal plasticity.     

Population structure,biometrics and moult of migrant Purple Sandpipers Calidris maritima in southwest Iceland in spring

Capsule Iceland is a stop‐over site for a population of Purple Sandpipers that winter in Britain. Here, they accumulate fuel loads for onward migration along with birds that have wintered in Iceland.

Aims To establish whether Purple Sandpipers from Britain stop‐over in Iceland during spring migration and, if so, to describe their population structure, changes in mass and moult.

Methods Purple Sandpipers were cannon‐netted on the coast of the Reykjanes Peninsula in southwest Iceland during May 2003 and 2005. Birds were aged, sexed (some by DNA) and standard biometric measurements made. Active body moult was scored.

Results Bill and wing lengths showed that the Purple Sandpipers we caught were similar to one of the populations that winter in Britain rather than Icelandic breeding birds. There were more males than females throughout the migration period (63% males for first‐year‐birds and 67% for adult birds). Accounting for a bias due to a higher percentage of males in a less usual habitat (muddy/sandy bays), the values for rocky sites were 52% males for first‐year birds and 62% for adults. The percentage of first‐year birds was 19% in 2003 and 32% in 2005, though the latter figure was biased by catches in muddy/sandy bays where there was a higher percentage of young birds. The percentage of first‐year birds was 25% on just the rocky shores in 2005. Many birds were in latter stages of body moult, and males were slightly in advance of females. Increasing mass showed that they were preparing for onward migration. The average increase of 0.58 g per day was similar to the rate measured in Orkney at an earlier point on the migration route. However, a high turnover of birds could be the reason for these low values. By late May, and close to the assumed departure date, the Purple Sandpipers of the different age/sex classes had fuel indices of 24–29% (33–42% of the lean mass). This was lower than that for the high Arctic sandpipers (Knots and Sanderlings) leaving southwest Iceland for Greenland and Canada.

Conclusions Our study confirmed that Purple Sandpipers do stop‐over in Iceland, and the possible lower rate of fuel accumulation and smaller amount stored, compared with Knots and Sanderlings, suggests a different migration pattern.     

Inferring Admixture Histories of Human Populations Using Linkage Disequilibrium

Long-range migrations and the resulting admixtures between populations have been important forces shaping human genetic diversity. Most existing methods for detecting and reconstructing historical admixture events are based on allele frequency divergences or patterns of ancestry segments in chromosomes of admixed individuals. An emerging new approach harnesses the exponential decay of admixture-induced linkage disequilibrium (LD) as a function of genetic distance. Here, we comprehensively develop LD-based inference into a versatile tool for investigating admixture. We present a new weighted LD statistic that can be used to infer mixture proportions as well as dates with fewer constraints on reference populations than previous methods. We define an LD-based three-population test for admixture and identify scenarios in which it can detect admixture events that previous formal tests cannot. We further show that we can uncover phylogenetic relationships among populations by comparing weighted LD curves obtained using a suite of references. Finally, we describe several improvements to the computation and fitting of weighted LD curves that greatly increase the robustness and speed of the calculations. We implement all of these advances in a software package, ALDER, which we validate in simulations and apply to test for admixture among all populations from the Human Genome Diversity Project (HGDP), highlighting insights into the admixture history of Central African Pygmies, Sardinians, and Japanese.     

Syntheses,biological evaluation and SAR of ingenol mebutate analogues for treatment of actinic keratosis and non-melanoma skin cancer

Ingenol mebutate is the active ingredient in Picato® a new drug for the treatment of actinic keratosis. A number of derivatives related to ingenol mebutate were prepared by chemical synthesis from ingenol with the purpose of investigating the SAR and potency in assays relating to pro-inflammatory effects (induction of PMN oxidative burst and keratinocyte cytokine release), the potential of cell death induction, as well as the chemical stability. By modifications of the ingenol scaffold several prerequisites for activity were identified. The chemical stability of the compounds could be linked to an acyl migration mechanism. We were able to find analogues of ingenol mebutate with comparable in vitro properties. Some key features for potent and more stable ingenol derivatives have been identified.     

Drosophila ref(2)P is required for the parkin-mediated suppression of mitochondrial dysfunction in pink1 mutants

Autophagy is a critical regulator of organellar homeostasis, particularly of mitochondria. Upon the loss of membrane potential, dysfunctional mitochondria are selectively removed by autophagy through recruitment of the E3 ligase Parkin by the PTEN-induced kinase 1 (PINK1) and subsequent ubiquitination of mitochondrial membrane proteins. Mammalian sequestrome-1 (p62/SQSTM1) is an autophagy adaptor, which has been proposed to shuttle ubiquitinated cargo for autophagic degradation downstream of Parkin. Here, we show that loss of ref(2)P, the Drosophila orthologue of mammalian P62, results in abnormalities, including mitochondrial defects and an accumulation of mitochondrial DNA with heteroplasmic mutations, correlated with locomotor defects. Furthermore, we show that expression of Ref(2)P is able to ameliorate the defects caused by loss of Pink1 and that this depends on the presence of functional Parkin. Finally, we show that both the PB1 and UBA domains of Ref(2)P are crucial for mitochondrial clustering. We conclude that Ref(2)P is a crucial downstream effector of a pathway involving Pink1 and Parkin and is responsible for the maintenance of a viable pool of cellular mitochondria by promoting their aggregation and autophagic clearance.     

Blocking Apoptotic Signaling Rescues Axon Guidance in Netrin Mutants

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Accumulation of Intraneuronal β-Amyloid 42 Peptides Is Associated with Early Changes in Microtubule-Associated Protein 2 in Neurites and Synapses

Pathologic aggregation of β-amyloid (Aβ) peptide and the axonal microtubule-associated protein tau protein are hallmarks of Alzheimer''s disease (AD). Evidence supports that Aβ peptide accumulation precedes microtubule-related pathology, although the link between Aβ and tau remains unclear. We previously provided evidence for early co-localization of Aβ42 peptides and hyperphosphorylated tau within postsynaptic terminals of CA1 dendrites in the hippocampus of AD transgenic mice. Here, we explore the relation between Aβ peptide accumulation and the dendritic, microtubule-associated protein 2 (MAP2) in the well-characterized amyloid precursor protein Swedish mutant transgenic mouse (Tg2576). We provide evidence that localized intraneuronal accumulation of Aβ42 peptides is spatially associated with reductions of MAP2 in dendrites and postsynaptic compartments of Tg2576 mice at early ages. Our data support that reduction in MAP2 begins at sites of Aβ42 monomer and low molecular weight oligomer (M/LMW) peptide accumulation. Cumulative evidence suggests that accumulation of M/LMW Aβ42 peptides occurs early, before high molecular weight oligomerization and plaque formation. Since synaptic alteration is the best pathologic correlate of cognitive dysfunction in AD, the spatial association of M/LMW Aβ peptide accumulation with pathology of MAP2 within neuronal processes and synaptic compartments early in the disease process reinforces the importance of intraneuronal Aβ accumulation in AD pathogenesis.     

Reconstructing Roma History from Genome-Wide Data

The Roma people, living throughout Europe and West Asia, are a diverse population linked by the Romani language and culture. Previous linguistic and genetic studies have suggested that the Roma migrated into Europe from South Asia about 1,000–1,500 years ago. Genetic inferences about Roma history have mostly focused on the Y chromosome and mitochondrial DNA. To explore what additional information can be learned from genome-wide data, we analyzed data from six Roma groups that we genotyped at hundreds of thousands of single nucleotide polymorphisms (SNPs). We estimate that the Roma harbor about 80% West Eurasian ancestry–derived from a combination of European and South Asian sources–and that the date of admixture of South Asian and European ancestry was about 850 years before present. We provide evidence for Eastern Europe being a major source of European ancestry, and North-west India being a major source of the South Asian ancestry in the Roma. By computing allele sharing as a measure of linkage disequilibrium, we estimate that the migration of Roma out of the Indian subcontinent was accompanied by a severe founder event, which appears to have been followed by a major demographic expansion after the arrival in Europe.