Old and new genetics help ordering loci at the telomere of the human X-chromosome long arm

Summary A Sardinian pedigree described in 1964 for having been found to segregate at the X-linked loci for the Xg^a antigen, G6PD deficiency, Protan and Deutan color blindness, with an instance of recombination between the last two loci, was re-examined with respect to four common X-linked DNA polymorphisms detected by molecular probes homologous to critical subregions of the human X chromosome. Two branches of this pedigree-including the one with the Protan-Deutan recombinant-were found to segregate also for the common BamHI polymorphism identified with the cDNA probe pHPT-2 of the HPRT gene (Xq26). The analysis of the chromosome haplotypes in the male offspring of the phase known penta-heterozygous mother suggests that the probable order of the relevant loci is HPRT, Deutan, G6PD, Protan, Xq telomere. Though we are fully aware of the risks of generalizing the significance of observations made on a single exceptional pedigree, we believe that this report outlines the potential of families of the type described as reasearch tools to resolve the linear order of tightly X-linked loci and to investigate the biology of genetic recombination in humans.     

Linkage Disequilibrium for Two X-Linked Genes in Sardinia and Its Bearing on the Statistical Mapping of the Human X Chromosome

The distribution of four X-linked mutants (G6PD, Deutan, Protan and Xg) among lowland and once highly malarial populations of Sardinia discloses a clear-cut example of linkage disequiligrium between two of them (G6PD and Protan). In the same populations the distribution of G6PD-deficiency versus colorblindness of the Deutan type and the Xg blood-group is not significantly different from that expected at equilibrium. These data suggest indirectly that the loci for G6PD and Protan may be nearer to one another than those for G6PD and Deutan.     

Decomposition processes interacting with microtopography maintain ecosystem heterogeneity in a subalpine grassland

Plant and Soil - Grasslands are among the largest ecosystems in the world and store up to 30% of the global reserves of carbon. Decomposition processes have a crucial role in maintaining carbon...     

Elevation-induced variations of pollen assemblages in the North-western Alps: An analysis of their value as temperature indicators

Seventy-seven modern pollen samples from various elevations (350-2680 m a.s.l.) in two different areas of the north-western Alps (the Aosta Valley, Italy and the Taillefer Massif, France) were statistically analyzed to derive correlations between pollen assemblages, elevation and temperature at the sampled points. Numerical classifications were performed on pollen data to judge similarities between the two areas. The results show that a strong relationship exists between altitude and variations in pollen taxa percentages despite some floristic differences between the two areas. As a test, transfer functions from pollen percentages to elevation and temperature were calculated from pollen data. The reconstruction appears to be reliable, with a higher reliability at sites located over 1000m. This analysis aims to serve as a basis for further quantitative reconstruction of temperature changes during the Holocene based on fossil pollen data from sensitive regions that encompass a significant altitudinal gradient.     

Nicking activity on pBR322 DNA of ribosome inactivating proteins from Phytolacca dioica L. leaves

Ribosome-inactivating proteins isolated from Phytolacca dioica L. leaves are rRNA-N-glycosidases, as well as adenine polynucleotide glycosylases. Here we report that some of them cleave supercoiled pBR322 dsDNA, generating relaxed and linear molecules. PD-L1, the glycosylated major form isolated from the winter leaves of adult P . dioica plants, produces both free 3'-OH and 5'-P termini randomly distributed along the DNA molecule, as suggested by labelling experiments with [alpha- 32P]dCTP and [gamma- 32 P]dATP. Moreover, when the reaction is carried out under low-salt conditions, cleavage is observed mainly at a specific site, located downstream of the ampicillin resistance gene (close to position 3200), ending with the deletion of a fragment of approximately 70 nucleotides. This cleavage pattern is similar to that obtained under the same conditions with mung bean nuclease, a single-strand endonuclease. Furthermore, pBR322 DNA treated with PD-L1 shows reduced transforming activity with E . coli HB101 competent cells in comparison to untreated control plasmid DNA.     

A novel approach to search for identity by descent in small samples of patients and controls from the same mendelian breeding unit: a pilot study on myopia.

Autosomal dominant high myopia, a genetic disorder already mapped to region 18p11.31, is common in Carloforte (Sardinia, Italy), an isolated village of 8,000 inhabitants descending from a founder group of 300 in the early 1700s. Fifteen myopic propositi and 36 normal controls were selected for not having ancestors in common at least up to the grandparental generation, although still descendants of the original founders. All subjects were genotyped for 14 markers located on autosome 18 at a resolution of about 10 cM. Allelic distributions were found to be similar at all tested loci in propositi and controls, except for the candidate marker D18S63 known to segregate in close linkage association with high myopia. In particular, the frequency of allele 85 among the propositi was almost double that of the controls (Fisher's exact test, p = 0.037). The association is more striking when the frequency of the genotype 85/85 in the two groups is compared (Fisher's exact test, p = 0.005). This conclusion was further evaluated through a bootstrap analysis by computing the overall probability of the observed data under the null hypothesis (i.e. no difference between the two groups in frequency distributions for the chromosome 18 markers). Again, marker D18S63 was found to have a sample probability lower than 0.004, which is significant at the 0.05 level after correcting for simultaneous testing of multiple loci. The study demonstrates the efficiency of our novel strategy to detect identity by descent (IBD) in small numbers of patients and controls when they are both part of well-defined Mendelian breeding units (MBUs). The iterative application of our strategy in separate MBUs is expected to become the method of choice to evaluate the ever-growing number of reported associations between candidate genes and multifactorial traits and diseases.     

Plant and lichen colonization in an asbestos mine: Spontaneous bioattenuation limits air dispersion of fibres

Abstract

Plant and lichen phytosociological studies describe the different dynamic stages of colonization. This approach has been applied to the Balangero asbestos mine, the most important of Western Europe up to 1990, which is a potential source for the air-dispersion of carcinogenic fibres. Vegetation relevés and maps have shown that plants and lichens develop spontaneously on the asbestos-rich substrates. Early colonization stages with low-covering hyperaccumulators, such as Thlaspi sylvium and Minuartia laricifolia, and with Thymus alpestris and T. cfr. humifusus, are followed, some decades later, by mature plant communities, which completely cover the asbestos-rich debris, thereby limiting the dispersion of fibres. Lichen colonization, even when limited to low covering early stages with pioneer crustose species, such as Scoliciosporum umbrinum and Candelariella vitellina, and young foliose thalli of Xanthoparmelia tinctina, is important whenever asbestos veins are exposed on serpentinite blocks and walls. Plants and lichens can be considered as bioattenuation (spontaneous bioremediation) agents in ecological recovery.     

A PHYLOGENETIC ANALYSIS OF DIOON (ZAMIACEAE)

A phylogenetic analysis of all the intrageneric taxa of the genus Dioon Lindley (Zamiaceae) was undertaken by using chloroplast DNA restriction fragment length polymorphism analysis. Wagner parsimony analysis on a 187 character matrix yielded two equally parsimonious trees, differing only for the position of D. caputoi. The consensus tree has two well-defined major clades. The first is composed of D. mejiae, D. rzedowskii, and D. spinulosum; the second is composed of D. califanoi, D. caputoi, D. edule var. angustifolium, D. edule var. edule, D. holmgrenii, D. merolae, D. purpusii, D. tomasellii var. sonorense, and D. tomasellii var. tomasellii. A phenetic analysis of the same data showed results broadly congruent with the cladistic analysis. This resulting phylogeny is partially congruent with morphological data and is also compatible with the biogeography of the genus. Modem species of Dioon may have evolved as a consequence of a very fast succession of vicariance events that mainly occurred during the early Cenozoic. The short time between each of these events may not have allowed the accumulation of a large number of morphological synapomorphies for the groups of species.