Further data on a 9.1-kb insertion-deletion polymorphism: survey of Mediterranean populations

We report the distribution of a previously described 9.1-kb insertion-deletion polymorphism located on chromosome 22. We analyzed 1,844 individuals sampled from 26 Mediterranean populations in mainland Italy, Sicily, Sardinia, Tunisia, Libya, Morocco, Egypt, Greece, and Albania. The 9.1 kb - allele is the prevalent allele in the North African (range, 0.53-0.56), Greek (0.51), and Albanian (0.66) populations, whereas the 9.1 kb + allele is most frequent in a mainland Italian town (0.55) and in all Sicilian and Sardinian towns and villages thus far tested, with marked fluctuation ranges of 0.53-0.78 and 0.56-0.80, respectively. In tests for Hardy-Weinberg equilibrium the genotype frequencies observed in Athens and in four of the nine towns in Sicily (but in none of the towns in Sardinia) departed highly significantly from the expected values. Identical results were found in the same towns for a second insertion-deletion polymorphism located on chromosome 22ql13 at a distance compatible with a low incidence of recombination. The data, which are in good agreement with the different histories of the two islands (Sardinia and Sicily), are consistent with a west-east differentiation in Sicily and support the evidence for ancient gene flow from the Iberian peninsula to Sardinia.     

Protein polymorphism in native goats from central Argentina

Under the name of Creole goats, individuals of various origins, morphological and productivity characters are grouped. To characterize the genetic pool of goats from different sources in central Argentina, protein polymorphism revealed by electrophoresis was analyzed. A total of 109 adult animals from Santa Marı́a, Colón and Ischilı́n Districts, Córdoba Province, were studied. The red cells lysates were subjected to starch gel electrophoresis and specific staining procedures to reveal the activity of different enzymes and hemoglobin. Separation of plasmatic proteins was carried out by electrophoresis in polyacrylamide gel and stained with Coomassie Blue. From a total of 14 loci analyzed, eight were polymorphic in at least one flock. Four codominant alleles were detected in the locus βHemoglobin (βHb); three alleles in malic enzyme (Me), glucose 6 phosphate dehydrogenase (G6pdh) and lactate dehydrogenase (Ldh) and two alleles in catalase (Cat), transferrin (Tf), esterase-2 (Es-2) and phosphoglucomutase (Pgm). In all the cases, the observed genotype frequencies were not significantly different from those expected from Hardy–Weinberg equilibrium. The proportion of polymorphic loci (P%) varied between 21.4% and 42.9% and mean heterozygosity (H), between 0.061 and 0.117. Alleles at loci Cat, Me and Es-2 showed significantly different frequencies according to the sample origin. The flock from Colón District presented the highest levels of polymorphism. This is the only stock which includes hybrids of varying grade between Creole stocks and male specimens from Saanen and Nubian breeds.     

A 9.1-kb insertion/deletion polymorphism suggests a common pattern of genetic diversity in Island Melanesia

Earlier reports suggest a distinct pattern of genetic variation linked to both language and geographic distance in Island Melanesia. Inland Papuan-speaking populations from different islands tend to share one allelic profile, while shore-based or more cosmopolitan populations share another, related to Southeast Asian influence over the past 3000 years. In the present paper, we report the genotypes and allele frequencies of an informative 9.1-thousand-base-pairs (kb) insertion/deletion polymorphism in 19 populations living in Island Melanesia. The populations studied inhabit the islands of New Britain, New Ireland, New Hanover, and Mussau in the Bismarck Archipelago, and speak either Austronesian or Papuan languages. We also include for reference a collection from New Guinea and Bougainville. The data show a marked fluctuation in the allele frequency among the different isolates, with the 9.1-kb(-) allele frequency ranging from 0.67 to 0.98. The deletion allele reaches fixation in some Papuan-speaking interior populations of New Britain, as well as in the interiors of New Guinea and Bougainville. However, certain inland Austronesian-speaking populations also share a similar high frequency of the deletion. Our data suggest that language distinctions are generally, but not invariably, indicative of diverse allelic patterns in this complex region, where inland groups on large islands tend to be often distinctive from shore-based populations.     

Genetic relationship among Mongolian native goat populations estimated by blood protein polymorphism

Several local strains and populations of goats distinguished by morphogenetic and performance characteristics are kept by goat breeders in different natural climatic regions of Mongolia, namely Bayandelger, Ulgii Red, Erchim Black, Dorgon and Zavkhan Buural. The genetic relationships among eight native goat populations in Mongolia at 33 biochemical genetic loci was assessed. A total of 440 animals in eight regional zones were studied. Twelve loci, i.e. the serum transferrin, serum amylase, serum alkaline phosphatase, serum prealbumin-3, cell esterase-D, hemoglobin (Hb) β, hemoglobin (Hb) α-II, cell peptidase-B, cell tetrazolium oxidase, cell esterase-1, cell esterase-2 and cell catalase loci, were found to be polymorphic. The data indicated that Mongolian native goats are not highly differentiated (D=0.0002–0.0038) genetically. To set Mongolian native goats in a larger context, the present data were compared with those on other goat breeds and populations in east and southeast Asia that were previously reported. The average heterozygosity in the Mongolian native goats did not significantly differ from those in other Asian goat populations and breeds. A phylogenetic tree of the gene constitution of the Mongolian native goats and other Asian goat breeds and populations was constructed and revealed that genetically the Mongolian native goats had diverged slightly from the group consisting of Chinese, Japanese, Korean and Indonesian native goats, but markedly from the Indian goat group.     

A study of the insertion-deletion polymorphism of the serotonin transporter gene in populations from the Volga-Ural region

The insertion-deletion polymorphism of the serotonin transporter gene (SLC6A4) was studied using the polymerase chain reaction (PCR) in eight populations from the Volga-Ural region (the Bashkir, Chuvash, Tatar, Udmurt, Mari, Mordovian, and Komi populations and the population of Russians living in the Arkhangel's skii raion of Bashkortostan). For this polymorphic system, the pattern of distribution of main population parameters was established in the region studied. Depending on population ethnicity, specific trends were revealed in the pattern of frequencies of alleles and genotypes of gene SLC6A4.     

Chromosome polymorphism in populations of the grasshopper Trimerotropis pallidipennis from southern Argentina

Three populations of the grasshopper Trimerotropis pallidipennis from southern Argentina have been studied cytologically. A very characteristic B-chromosome was found in all three. They also showed geographical variability in respect of the presence of pericentric inversions, and the inversion system was found to influence chiasma frequency. The Laguna Blanca population, which is on the hypothetical pathway the species is believed to have followed during its migration from northern to southern latitudes, has the same karyotype composition as the N. American form, with fixed inversions in the 3 largest autosomes and the X-chromosome. Its members have a high total chiasma frequency and a great number of interstitial chiasmata. The Sierra de la Ventana population, situated at the absolute eastern border of the species distribution is highly polymorphic with respect to the presence of inversions in the medium chromosomes. Its members have the lowest total chiasma frequency and a greatly reduced number of interstitial chiasmata. Situated geographically between the other two, the Choele-Choel population has the highest frequency of inversions and many of them are homozygous. Its members have a higher total chiasma frequency than that observed in specimens from Sierra de la Ventana, and a greatly reduced number of interstitial chiasmata, similar to that observed in individuals from the latter population.     

A 9.1-kb gap in the genome reference map is shown to be a stable deletion/insertion polymorphism of ancestral origin

We show a mute 9.1-kb gap in the human genome reference map, unraveled by RDA studies, to be a worldwide deletion/insertion polymorphism of stable type. The molecular and population data presented suggest its origin from a unique ancestral transposition event in chromosomal region 22q11.2, overlapping the IglambdaV genes at about 450 kb from the cluster of the IglambdaJ-C genes. These findings are not meant to be just another report of a polymorphic marker suitable for population studies. Rather, we wish to stress that a large number of inborn mute gaps may be spread all over the genome and that the many RDA-detected microdeletions already available are efficient tools for the discovery of this otherwise hidden category of genetic variation. Apart from their possible impact on expression of structural genes, mute gaps must be filled for the reference map of our genome to be truly completed.     

Haptoglobin polymorphism among fourteen populations of India

Haptoglobin (HP) is a serum protein that has the capability of binding the extracorpuscular haemoglobin released during haemolysis. It plays an important role in protection of haemolytic disease by reducing the oxidative and peroxidative potential at free haemoglobin. The present study was aimed to determine the prevalence of HP polymorphism among different Indian populations, anthropologically belonging to diverse ethnicity. The polymorphism was screened among 642 unrelated individuals belonging to 14 population groups of India including both tribal and non-tribal caste groups from different geographical regions of India with distinct linguistic affiliations. An attempt is also made to understand the distribution of HP polymorphism among the studied populations. The result reveals the HP gene to be polymorphic in all the studied populations. Except the two tribal populations (Thotis of Andhra Pradesh and Patelias of Rajasthan) and one caste population (Rajput of Himachal Pradesh), all the studied populations are found to obey the Hardy-Weinberg equilibrium. The significance of the present study is elucidated with the prevalence of high mutant HP*2 allele frequency in India. Selection could be one of the most plausible explanations for this high HP frequency because of its uniformly high occurrence among all the studied populations.     

Mathematical properties of Fst between admixed populations and their parental source populations

We consider the properties of the F(st) measure of genetic divergence between an admixed population and its parental source populations. Among all possible populations admixed among an arbitrary set of parental populations, we show that the value of F(st) between an admixed population and a specific source population is maximized when the admixed population is simply the most distant of the other source populations. For the case with only two parental populations, as a function of the admixture fraction, we further demonstrate that this F(st) value is monotonic and convex, so that F(st) is informative about the admixture fraction. We illustrate our results using example human population-genetic data, showing how they provide a framework in which to interpret the features of F(st) in admixed populations.     

Linkage analysis of a complex disease through use of admixed populations

Linkage disequilibrium arising from the recent admixture of genetically distinct populations can be potentially useful in mapping genes for complex diseases. McKeigue has proposed a method that conditions on parental admixture to detect linkage. We show that this method tests for linkage only under specific assumptions, such as equal admixture in the parental generation and admixture that occurs in a single generation. In practice, these assumptions are unlikely to hold for natural populations, resulting in an inflation of the type I error rate when testing for linkage by this method. In this article, we generalize McKeigue's approach of testing for linkage to allow two different admixture models: (1) intermixture admixture and (2) continuous gene flow. We calculate the sample size required for a genomewide search by this method under different disease models: multiplicative, additive, recessive, and dominant. Our results show that the sample size required to obtain 90% power to detect a putative mutant allele at a genomewide significance level of 5% can usually be achieved in practice if informative markers are available at a density of 2 cM.     

Individuals from non-native populations are stronger and bigger than individuals from native populations of a widespread seaweed

Biological Invasions - Many species introduced to non-native regions undergo profound phenotypic change, but conflicting evidence remains on the frequency of such trait differentiation. Here, we...     

Distribution and pathogenicity of Trypanosoma cruzi isolated from peridomestic populations of Triatoma infestans and Triatoma guasayana from rural Western Argentina

We assessed the distribution of Trypanosoma cruzi infection in peridomestic triatomines collected manually at a district-wide scale in rural villages around Olta, Western Argentina, and typed the isolated strains according to their pathogenicity to laboratory mice. Of 1623 triatomines examined, only 14 (0.9%) were infected with T. cruzi based on microscopical examination of feces. The prevalence of T. cruzi infection was 0.8% in Triatoma infestans, 2.3% in T. guasayana, and nil in T. garciabesi, T. platensis, and T. eratyrusiformis. Local transmission occurred in kitchens, store-rooms and goat corrals or nearby, though at very low levels. T. cruzi was detected by at least one parasitological method in 11 (79%) of 14 microscope-positive bugs. Hemoculture was the most sensitive method (67%) followed by culture of organ homogenates, histopathology or xenodiagnosis of inoculated suckling mice (55-58%), and culture of microscope-positive bug feces (46%). The evidence suggests that most of the isolated T. cruzi strains would be myotropic type III. Our study establishes for the first time that peridomestic, microscope-positive T. guasayana nymphs were actually infected with T. cruzi, and may be implicated as a putative secondary vector of T. cruzi in domestic or peridomestic sites.     

Genetic relationships among populations of Aedes aegypti from Uruguay and northeastern Argentina inferred from ISSR‐PCR data

Aedes aegypti (L.) (Diptera: Culicidae), the main vector of yellow fever and dengue viruses, was eradicated from Argentina between 1955 and 1963, but reinvaded the country in 1986. In Uruguay, the species was reintroduced in 1997. In this study we used highly polymorphic inter‐simple sequence repeats (ISSR) markers to analyse the genetic structure of Ae. aegypti populations from Uruguay and northeastern Argentina to identify possible colonization patterns of the vector. Overall genetic differentiation among populations was high (F_ST = 0.106) and showed no correlation with geographic distance, which is consistent with the short time since the reintroduction of the species in the area. Differentiation between pairs of Argentine populations (F_ST 0.072 to 0.221) was on average higher than between Uruguayan populations (F_ST?0.044 to 0.116). Bayesian estimation of population structure defined four genetic clusters and most populations were admixtures of two of them: Mercedes and Treinta y Tres (Uruguay) were mixtures of clusters 1 and 3; Salto (Uruguay) and Paraná (Argentina) of clusters 1 and 4; Fray Bentos (Uruguay) of clusters 2 and 3, and Gualeguaychú (Argentina) of clusters 2 and 3. Posadas and Buenos Aires in Argentina were fairly genetically homogeneous. Our results suggest that Ae. aegypti recolonized Uruguay from bordering cities in Argentina via bridges over the Uruguay River and also from Brazil.     

Oligoryzomys flavescens (Rodentia, Muridae): gene flow among populations from central-eastern Argentina

In species acting as hosts of infectious agents, the extent of gene flow between populations is of particular interest because the expansion of different infectious diseases is usually related to the dispersal of the host. We have estimated levels of gene flow among populations of the sigmodontine rodent Oligoryzomys flavescens, in which high titers of antibodies have been detected for a Hantavirus in Argentina that produces a severe pulmonary syndrome. Enzyme polymorphism was studied by means of starch gel electrophoresis in 10 populations from the area where human cases of Hantavirus have occurred. Genetic differentiation between populations was calculated from F_ST values with the equation Nm = [(1/F_ST−1]/4. To assess the relative importance of current gene flow and historical associations between populations, the relationship of population pairwise log Nm and log geographic distance was examined. Low F_ST (mean = 0.038) and high Nm (15.27) values suggest high levels of gene flow among populations. The lack of an isolation by distance pattern would indicate that this species has recently colonized the area. The northernmost population, located on the margin of a great river, shows very high levels of gene flow with the downstream populations despite the large geographic distances. Passive transport of animals down the river by floating plants would promote unidirectional gene flow. This fact and the highest mean heterozygosity of that northernmost population suggest it is a center of dispersal within the species' range. This revised version was published online in July 2006 with corrections to the Cover Date.     

Distribution of a novel enzyme of sialidase family among native filamentous fungi

Sialidases (neuraminidases, EC 3.2.1.18) are widely distributed in biological systems but there are only scarce data on its production by filamentous fungi. The aim of this study was to obtain information about sialidase distribution in filamentous fungi from non-clinical isolates, to determine availability of sialidase gene, and to select a perspective producer. A total of 113 fungal strains belonging to Ascomycota and Zygomycota compassing 21 genera and 51 species were screened. Among them, 77 strains (11 orders, 14 families and 16 genera) were able to synthesize sialidase. Present data showed a habitat-dependent variation of sialidase activity between species and within species, depending on location. Sialidase gene was identified in sialidase-positive and sialidase-negative strains. .Among three perspective strains, the best producer was chosen based on their sialidase production depending on type of cultivation, medium composition, and growth temperature. The selected P. griseofulvum Р29 was cultivated in 3L bioreactor at 20 °C on medium supplemented with 0.5% milk whey. The results demonstrated better growth and 2.3-fold higher maximum enzyme activity compared to the shaken flask cultures. Moreover, the early occurring maximum (48 h) is an important prerequisite for future up scaling of the process.     

Characterization of experimental cattle populations from Argentina with a low-density SNP genotyping panel

The objectives of the present experiment were to evaluate a low-density SNP array designed for the molecular characterisation of gene banks and to assess the genetic diversity and population structure of beef cattle herds from an Argentinean research station. Forty-nine animals from three breeds (Angus, Hereford, and Argentinean Creole) were genotyped using the multi-species IMAGE001 60-K SNP array (10 K for cattle). Genotypes of other 19 cattle populations from Argentina, other American countries, and Europe were included in the study. Of special interest was the characterization of the Argentinean Creole, the only autochthonous cattle breed in the country. Due to the merging of different datasets, approximately 5 K SNPs were effectively used. Genetic differentiation (F_ST), principal component analysis, neighbour-joining tree of Reynolds distances and ancestry analysis showed that autochthonous American breeds are clearly differentiated, but all have genetic influences of Iberian cattle. The analysed herds of Argentinean Creole showed no evidence of recent admixture and represent a unique genetic pool within local American breeds. An experimental herd and the local commercial Hereford population have also diverged, probably due to the influence of current selection objectives in the breed. Our results illustrate the utility of using low-cost, low density SNP arrays in the evaluation of animal genetic resources. This type of panels could become a very useful resource in developing countries, where most endangered cattle breeds are located. The results also reinforce the importance of experimental herds as reservoir of genetic diversity, particularly in the case of local breeds under-represented in traditional production systems.     

Chromosomal polymorphism of populations of Anopheles arabiensis (Diptera: Culicidae) from Reunion island and cross-fertility among continental African populations

Cytological examination of a sample of Anopheles gambiae complex mosquitoes from Reunion island revealed the presence of An. arabiensis only. Chromosomal polymorphisms were observed only for inversion 3Ra, the standard homozygote form being predominant. Cross-mating experiments with laboratory specimens originating from continental Africa produced viable and fertile offspring with no chromosomal asynapsis observed in the F1 female progeny. There was no evidence for speciation of the Reunion island populations. The results are discussed with regard to the behaviour of the vector and its influence on the vectorial capacity of this species, and the history of malaria and malaria control in the South-West islands of the Indian Ocean and on Reunion island in particular.