Molecular characterization of two deletion events involving Alu-sequences, one novel base substitution and two tentative hotspot mutations in the hypoxanthine phosphoribosyltransferase (HPRT) gene in five patients with Lesch-Nyhan syndrome

Mutations identified in the hypoxanthine phosphoribosyltransferase (HPRT) gene of patients with Lesch-Nyhan (LN) syndrome are dominated by simple base substitutions. Few hotspot positions have been identified, and only three large genomic rearrangements have been characterized at the molecular level. We have identified one novel mutation, two tentative hot spot mutations, and two deletions by direct sequencing of HPRT cDNA or genomic DNA from fibroblasts or T-lymphocytes from LN patients in five unrelated families. One is a missense mutation caused by a 610C→T transition of the first base of HPRT exon 9. This mutation has not been described previously in an LN patient. A nonsense mutation caused by a 508C→T transition at a CpG site in HPRT exon 7 in the second patient and his younger brother is the fifth mutation of this kind among LN patients. Another tentative hotspot mutation in the third patient, a frame shift caused by a G nucleotide insertion in a monotonous repeat of six Gs in HPRT exon 3, has been reported previously in three other LN patients. The fourth patient had a tandem deletion: a 57-bp deletion in an internally repeated Alu-sequence of intron 1 was separated by 14 bp from a 627-bp deletion that included HPRT exon 2 and was flanked by a 4-bp repeat. This complex mutation is probably caused by a combination of homologous recombination and replication slippage. Another large genomic deletion of 2969 bp in the fifth patient extended from one Alu-sequence in the promoter region to another Alu-sequence of intron 1, deleting the whole of HPRT exon 1. The breakpoints were located within two 39-bp homologous sequences, one of which overlapped with a well-conserved 26-bp Alu-core sequence previously suggested as promoting recombination. These results contribute to the establishment of a molecular spectrum of LN mutations, support previous data indicating possible mutational hotspots, and provide evidence for the involvement of Alu-mediated recombination in HPRT deletion mutagenesis. Received: 21 April 1998 / Accepted: 16 July 1998     

Drug Susceptibility Patterns in MDR-TB Patients: Challenges for Future Regimen Design. A Cross-Sectional Study

Globally, there is substantial concern regarding the challenges of treating complex drug resistance patterns in multidrug resistant tuberculosis cases. Utilising data from three different settings (Estonia, Latvia, Romania) we sought to contrast drug susceptibility profiles for multidrug resistant tuberculosis cases, highlight the difficulties in designing universal regimen, and inform future regimen selection. Demographic and microbiological surveillance data for multidrug resistant tuberculosis cases from 2004–13 were analysed. High levels of additional resistance to currently recommended second line drugs were seen in all settings, with extensive variability between countries. Accurate drug susceptibility testing and drug susceptibility testing data are vital to inform the development of comprehensive, flexible, multidrug resistant tuberculosis guidance.     

MicroRNAs take part in pathophysiology and pathogenesis of Male Pattern Baldness

Male Pattern Baldness (MPB) or androgenetic alopecia is a common form of hair loss with androgens and genetics having etiological significance. Androgens are thought to pathophysiologically power on cascades of chronically dramatic alterations in genetically susceptible scalp dermal papillas, specialized cells in hair follicles in which androgens react, and finally resulting in a patterned alopecia. However, the exact mechanisms through which androgens, positive regulators of growth and anabolism in most body sites, paradoxically exert their effects on balding hair follicles, are not yet known. The role of microRNAs, a recently discovered class of non-coding RNAs, with a wide range of regulatory functions, has been documented in hair follicle formation and their deregulation in cancer of prostate, a target organ of androgens has also been delineated. Yet, there is a lack of knowledge in agreement with microRNAs’ contribution in pathophysiology of MPB. To investigate the role of microRNAs in pathogenesis of MPB, we selected seven microRNAs, predicted bioinformatically on a reverse engineering basis, from previously published microarray gene expression data and analyzed their expression in balding relative to non-balding dermal papillas. We found for the first time upregulation of four microRNAs (miR-221, miR-125b, miR-106b and miR-410) that could participate in pathogenesis of MPB. Regarding microRNAs’ therapeutic potential and accessibility of hair follicles for gene therapy, these microRNAs can be considered as good candidates for a new revolutionized generation of treatments.     

Regulation of DAPK1 by Natural Products: An Important Target in Treatment of Stroke

Neurochemical Research - Stroke is a sudden neurological disorder that occurs due to impaired blood flow to an area of the brain. Stroke can be caused by the blockage or rupture of a blood vessel...     

The impact of the glial spatial buffering on the K+ Nernst potential

Astrocytes play a critical role in CNS metabolism, regulation of volume and ion homeostasis of the interstitial space. Of special relevance is their clearance of K⁺ that is released by active neurons into the extracellular space. Mathematical analysis of a modified Nernst equation for the electrochemical equilibrium of neuronal plasma membranes, suggests that K⁺ uptake by glial cells is not only relevant during neuronal activity but also has a non-neglectable impact on the basic electrical membrane properties, specifically the resting membrane potential, of neurons and might be clinically valuable as a factor in the genetics and epigenetics of the epilepsy and tuberous sclerosis complex.     

Higher climate warming sensitivity of Siberian larch in small than large forest islands in the fragmented Mongolian forest steppe

Forest fragmentation has been found to affect biodiversity and ecosystem functioning in multiple ways. We asked whether forest size and isolation in fragmented woodlands influences the climate warming sensitivity of tree growth in the southern boreal forest of the Mongolian Larix sibirica forest steppe, a naturally fragmented woodland embedded in grassland, which is highly affected by warming, drought, and increasing anthropogenic forest destruction in recent time. We examined the influence of stand size and stand isolation on the growth performance of larch in forests of four different size classes located in a woodland‐dominated forest‐steppe area and small forest patches in a grassland‐dominated area. We found increasing climate sensitivity and decreasing first‐order autocorrelation of annual stemwood increment with decreasing stand size. Stemwood increment increased with previous year's June and August precipitation in the three smallest forest size classes, but not in the largest forests. In the grassland‐dominated area, the tree growth dependence on summer rainfall was highest. Missing ring frequency has strongly increased since the 1970s in small, but not in large forests. In the grassland‐dominated area, the increase was much greater than in the forest‐dominated landscape. Forest regeneration decreased with decreasing stand size and was scarce or absent in the smallest forests. Our results suggest that the larch trees in small and isolated forest patches are far more susceptible to climate warming than in large continuous forests pointing to a grim future for the forests in this strongly warming region of the boreal forest that is also under high land use pressure.     

Multi-scale modeling of complex neuronal networks: a view towards striatal cholinergic pattern formations

The phenomena related to brain function occur as the interplay of various modules at different spatial and temporal scales. Particularly, the integration of the dynamical behavior of cells within the complex brain topology reveals a heterogeneous multi-scale problem, which has, to date, mainly been addressed by methods of statistical physics such as mean-field approximations. In contrast, the present study introduces an abstract mathematical model of a deterministic nature that provides a robust integral transformation of the microscopic activities into macroscopic spatiotemporal patterns. The existence of the transformation operator is guaranteed by the convergence of a repetitive patching of the network domain with its fundamental domains that express the local topologies of the tissue. Depending on the choice of the local connectivity function, this framework represents a computationally efficient generalization of the classical Kirchhoff’s, Hebbian, and Hopfield’s approaches. The capabilities of this multi-scale method have been evaluated within the structure of the dorsal striatum of rats, a brain region with major involvement in motor and cognitive information processing. Numerical simulations suggest the formation of characteristic spatiotemporal patterns due to the activation of cholinergic interneurons.     

Phylogeography and population genetics of the riparian relict tree Pterocarya fraxinifolia (Juglandaceae) in the South Caucasus

We aimed to (i) assess the extant genetic diversity of the riparian relict tree Pterocarya fraxinifolia across its current distribution range in the South Caucasus, including the past refugial areas Colchis and Hyrcan, and (ii) test if a separation of these areas is reflected in its phylogeographic history. Genetic diversity of natural populations was examined using nuclear microsatellite and plastid DNA markers. Spatial genetic structure was evaluated using Bayesian clustering methods and the reconstruction of plastid DNA networks. Divergence times of Colchic and Hyrcanian populations were estimated via divergence dating using a relaxed molecular clock. Allelic richness, private allelic richness, and expected heterozygosity were significantly higher in Hyrcan than in Colchis and the Greater Caucasus, and significant genetic differentiation was revealed between the two groups. Whereas only two plastid haplotypes were detected for the Colchic and Caucasian populations, the Hyrcanian populations displayed 11 different haplotypes. Significant isolation by distance was detected in Hyrcan. The most recent common ancestor of all P. fraxinifolia haplotypes was dated to a time well before a suggested glaciation period in the Caucasus during the late Pliocene (5.98 Ma [11.3–2.48 Ma HPD]). The widespread Colchic haplotype that also occurs along the southern slope of the Greater Caucasus and reaches south-eastern Azerbaijan has appeared more recently (0.24 Ma [1.41–0 Ma HPD]). This diversification pattern of Colchic haplotypes from ancient Hyrcanian haplotypes suggests a colonization of the region from south-east to north-west that predates the last glacial maximum (LGM). Natural populations of P. fraxinifolia show low-to-intermediate levels of genetic diversity and a significant decrease of diversity from Hyrcan to Colchis. However, the genetic differentiation between Colchic-Caucasian and Hyrcanian populations for nuclear markers suggests that independent gene pools existed in both areas at least since the LGM. Particular attention to conservation seems justified for the more diverse Hyrcanian populations.     

Different amyloid aggregation of smooth muscles titin in vitro

A comparative study of amyloid properties of the aggregates of smooth muscle titin (SMT) from chicken gizzard was carried out. These aggregates were formed in two solutions: 0.15 M glycine-KOH, pH 7.2–7.4 (SMT(Gly)) and 0.2 M KCl, 10 mM imidazole, pH 7.0 (SMT(KCl)). Electron microscopy data showed that SMT aggregates has an amorphous structure in both cases. The results of atomic-force microscopy demonstrated slight differences in morphology in two types of aggregates. The SMT(Gly) aggregates were represented as branching chains, composed of spherical aggregates approximately 300–500 nm in diameter and up to 35 nm in height. The SMT(KCl) aggregates formed sponge-like structures with strands of 8–10 nm in height. Structural analysis of SMT aggregates by X-ray diffraction revealed the presence of cross-β-sheet structure in the samples under study. In the presence of SMT(Gly) aggregates, thioflavine T fluorescence intensity was higher (~3-fold times) compared with that in the presence of SMT(KCl) aggregates. Congo red-stained SMT(Gly) aggregates had yellow to apple-green birefringence under polarized light, which was not observed for SMT(KCl) aggregates. Dynamic light scattering data showed the similar rate of aggregation for both types of aggregates, though SMT(KCl) aggregates were able to partially disaggregate under increased ionic strength of the solution. The ability of SMT to aggregation followed by disaggregation may be functionally significant in the cell.