Dynamical Systems Approach to Higher-level Heritability

To explain higher-level heritability, we propose a dynamical systems approach, based on simulations of the high-dimensional replicator equation with mutation dynamics. We assume that all variants are generated from within the groups of variants through mutations. Simulating the equation with a random interaction matrix and possible variants, we report that this system tends to have many attractors, of fixed point, chaotic and quasiperiodic type. In a chaotic attractor, special gene-like variants appear to control the heritability ofthe system, in the sense that removal of the variants would easily enable the system to depart from the attractor. Those variants do not predominate in thepopulation size, but have the lowest net reproduction and mutation rates on average. Because their rate of growth is small, they are named neutral phenotypes. Additionally, combinatorial effects of these neutral variants to the entire system are reported.     

Metabolic Enzyme Alterations and Astrocyte Dysfunction in a Murine Model of Alexander Disease With Severe Reactive Gliosis

Alexander disease (AxD) is a rare and fatal neurodegenerative disorder caused by mutations in the gene encoding glial fibrillary acidic protein (GFAP). In this report, a mouse model of AxD (GFAP^Tg;Gfap^+/R236H) was analyzed that contains a heterozygous R236H point mutation in murine Gfap as well as a transgene with a GFAP promoter to overexpress human GFAP. Using label-free quantitative proteomic comparisons of brain tissue from GFAP^Tg;Gfap^+/R236H versus wild-type mice confirmed upregulation of the glutathione metabolism pathway and indicated proteins were elevated in the peroxisome proliferator-activated receptor (PPAR) signaling pathway, which had not been reported previously in AxD. Relative protein-level differences were confirmed by a targeted proteomics assay, including proteins related to astrocytes and oligodendrocytes. Of particular interest was the decreased level of the oligodendrocyte protein, 2-hydroxyacylsphingosine 1-beta-galactosyltransferase (Ugt8), since Ugt8-deficient mice exhibit a phenotype similar to GFAP^Tg;Gfap^+/R236H mice (e.g., tremors, ataxia, hind-limb paralysis). In addition, decreased levels of myelin-associated proteins were found in the GFAP^Tg;Gfap^+/R236H mice, consistent with the role of Ugt8 in myelin synthesis. Fabp7 upregulation in GFAP^Tg;Gfap^+/R236H mice was also selected for further investigation due to its uncharacterized association to AxD, critical function in astrocyte proliferation, and functional ability to inhibit the anti-inflammatory PPAR signaling pathway in models of amyotrophic lateral sclerosis (ALS). Within Gfap⁺ astrocytes, Fabp7 was markedly increased in the hippocampus, a brain region subjected to extensive pathology and chronic reactive gliosis in GFAP^Tg;Gfap^+/R236H mice. Last, to determine whether the findings in GFAP^Tg;Gfap^+/R236H mice are present in the human condition, AxD patient and control samples were analyzed by Western blot, which indicated that Type I AxD patients have a significant fourfold upregulation of FABP7. However, immunohistochemistry analysis showed that UGT8 accumulates in AxD patient subpial brain regions where abundant amounts of Rosenthal fibers are located, which was not observed in the GFAP^Tg;Gfap^+/R236H mice.     

Coordination polymers of Ln(III): Synthesis, characterization, catalytic and antimicrobial aspects

Coordination polymers of HEAP-ED with La(III), Pr(III), Nd(III), Sm(III), Gd(III), Tb(III) and Dy(III) metal ions have been synthesized and characterized by elemental analyses, electronic spectra, magnetic susceptibilities, FTIR, NMR, scanning electronic microscopy (SEM) and thermogravimetric analyses. Catalytic activity of selected coordination polymers was examined for pharmaceutical important organic synthesis. Antimicrobial activity of isolated Ln(III) coordination polymers against Escherichia coli, Bacillus subtilis, Staphylococcus aureus (bacteria) and Saccharomyces cerevisiae (yeast) were measured. It was observed from the study that the Ln(III) coordination polymers acted as an efficient and effective catalysts and antimicrobial agents.     

Alternative biofacies model for dysaerobic communities

An abundant calcareous fauna has been discovered in the oxygen minimum zone (OMZ; < 0.5 ml/l O₂) off central California at oxygen concentrations considerably less than those predicted by previous ecological models. Analysis of box core samples and bottom photographs has revealed a distinct depth zonation of echinoderms. Asteroids and ophiuroids are most abundant along the upper and lower edges of the OMZ, respectively, whereas echinoids are found near the core of this zone where oxygen levels are as low as 0.3 ml/l O₂. As these heart urchins are very abundant (14/m²), they represent a potentially significant component of the fossil record of OMZ's. Locally these urchins are capable of disturbing over 90% of near surface sediment. The core of the OMZ is inhabited by hermit crabs that actively transport and recycle gastropod shells. This 'biotransport' results in an accumulation of potentially preservable, non-endemic. hard-bodied organisms which may lead to misinterpretation of paleo-oxygenation conditions. We propose an alternative to the Rhoads & Morse (1971, Lethaia 4 ) biofacies model for open-ocean, dysaerobic environments which consists of: (1) a zone devoid of maeroinvertebrates. characterized by laminated sediments (<0.1 ml/l O₂); (2) a zone dominated by small (1–2 mm) soft-bodied infauca which exhibits moderate disturbance of laminae due to bioturbation (0.1–0.3 ml/l O₂); and (3) a zone inhabited by an abundant calcareous fauna characterized by highly bioturbated sediments (>0.3 ml/l O₂).     

Thermal Diapirism and the Habitability of the Icy Shellof Europa

Europa’s chaos and lenticulae features may have originated by thermal diapirs related to convective plumes. Warm ice plumes could be habitable, since their temperature is close to the ice melting temperature. Moreover, thermal plumes intruding into the lower stagnant lid warm several kilometers of country ice above 230 K for periods of 10⁵ years, and hundreds of meters above 240 K for periods of 10⁴ years. Diapir coalescence generating chaos areas should provide a large zone with temperature above ∼240 K for thousands of years. A temperature above ∼230 K is potentially interesting for astrobiology, since it corresponds to the lowest temperature at which microbial metabolic activity in Antarctic ice has been reported. So, the warming by thermal plumes could cause an aureole of biological activation/reactivation in the country ice. Adaptation of life to either high salinity or low temperature is similar: it requires the synthesis of compatible solutes, like trehalose or glycerol, which are efficient cryoprotectants. We therefore propose that the future astrobiological exploration of Europa should include the search for compatible solutes in chaos and lenticulae features.     

THE GENETIC STRUCTURE OF A HYBRID ZONE BETWEEN TWO CHROMOSOME RACES OF THE SCELOPORUS GRAMMICUS COMPLEX (SAURIA,PHRYNOSOMATIDAE) IN CENTRAL MEXICO

The F5 (2n = 34) and FM2 (2n = 44–46) chromosome races of the Sceloporus grammicus complex form a parapatric hybrid zone in the Mexican state of Hidalgo, characterized by steep concordant clines among three diagnostic chromosome markers across a straight-line distance of about 2 km. Here, we show that this zone is actually structured into local patches in which hybridization extends over an extremely irregular front. The distribution of hybrid-index (HI) scores across the transect reveals some hybridization at almost all localities mapped in a central 7 km × 3 km area. Pooling the central samples produces both a strong heterozygote deficit for all diagnostic markers and strong linkage disequilibria between all pairwise combinations of these (unlinked) markers. Moreover, a highly significant association exists between the habitat on which each individual was caught and its karyotype (F5 chromosomes are more likely to be found on oak). Analysis of genotype frequencies over a range of spatial scales shows that there is no significant heterozygote deficit or habitat association within local areas of less than about 200 m; however, there is significant linkage disequilibrium over the smallest scales (R = D (pquv)^1/2 = 0.29, support limits, 0.18–0.36) over 100 m. These patterns suggest that lizards mate and choose habitats randomly within local patches. This conclusion is supported by mark-recapture estimates of dispersal (≈ 80 m in a generation) and by inference of matings from embryo and maternal karyotypes. Closer examination of the two-dimensional pattern reveals a convoluted cline for all three markers, with a width of 830 m (support limits 770 m–930 m). This cline width, combined with the strength of local linkage disequilibrium, implies a dispersal rate of σ = 160 m in a generation and an effective selection pressure of 30% on each chromosome marker. The proportion of inviable embryos is greater in females from the center of the hybrid zone; this is caused by effects associated with both karyotype and location. The hybrid zone is likely to be maintained by selection against chromosomal heterozygotes, by other kinds of selection against hybrids, and by selection adapting the chromosome races to different habitats. The structure of the contact may be caused by both random drift and by selection in relation to habitat.     

EVIDENCE FOR A MOSAIC HYBRID ZONE IN THE GRASS SHRIMP PALAEMONETES KADIAKENSIS (PALAEMONIDAE) AS REVEALED BY MULTIPLE GENETIC MARKERS

Molecular techniques provide powerful tools for studying the geographic structure of hybrid zones and the dynamics of gene exchange between incipient species. We examined allozyme variation at five loci (PGM, GPI, MDH-1, MDH-2, and LDH) for 27 populations of Palaemonetes kadiakensis from the central, coastal, and eastern regions of Texas. Central Texas populations of P. kadiakensis exhibited highly significant linkage disequilibrium and departures from Hardy-Weinberg genotype proportions. In populations with linkage disequilibrium, allelic differences at GPI defined two types of P. kadiakensis, designated A and B. Both types existed in central Texas with little or no evidence of interbreeding, whereas the populations from all other localities showed complete introgression of type B alleles into the type A gene pool. We also examined ribosomal DNA (rDNA) and mitochondrial DNA (mtDNA) variation in a subset of populations, chosen to cover a range of geographic locations and levels of linkage disequilibrium. Two groups of mtDNA haplotypes and two restriction fragment patterns for the rDNA corresponded to allozyme type A and B individuals in populations exhibiting linkage disequilibrium. In populations with ongoing hybridization, all hybrid animals (N= 15) exhibited type A mtDNA. Exhibition of type A mtDNA indicated that type A females had mated successfully with type B males, but type B females had not mated successfully with type A males. Genotype distributions suggest reduced reproduction by hybrid offspring in central Texas populations. These patterns are consistent with a mosaic model of hybrid zone dynamics.     

Strong genetic structuring without assortative mating or reduced hybrid survival in an onychophoran in the Tallaganda State Forest region,Australia

Genetic studies have revealed a large degree of previously unappreciated diversity in morphologically conserved taxa. To understand the implications of this phenomenon, studies investigating the processes responsible for generating and maintaining functional and neutral diversity within such taxa are needed. With this aim, patterns of differentiation across a contact zone between two catchment‐specific, and genetically and subtly morphologically distinguishable, races of the onychophoran Euperipatoides rowelli Reid, 1996 at the Tallaganda State Forest study system, Australia, were quantified using diagnostic body‐pattern differences, microsatellite markers, and the cytochrome c oxidase subunit I (COI) mitochondrial gene. These data were used to test whether hybridization occurred, and whether the reduced survival of hybrids compared with non‐hybrids and/or assortative mating were potentially important factors in retaining the divergence between these races, which probably arose during isolation in Pleistocene glacial refuges. It was found that hybrids at the focal contact zone do not have reduced embryo‐to‐adult survival compared with non‐hybrids, and that races apparently freely interbreed without substantial assortative mating, consistent with little or no cost to hybridization. Nonetheless, at their respective transect ends the races remain distinct. This phenomenon was attributed to the elevated location of the contact zone, which is likely to make it poor habitat for E. rowelli, and thus may restrict dispersal and gene flow. There was also tentative evidence for a relaxed selection against hybridization in the hybrid zone, and the relative importance of these two explanations will require separate investigation. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 589–602.