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PubMed1996

Genetic variation in the morphology of the septo-hippocampal cholinergic and GABAergic system in mice. I. Cholinergic and GABAergic markers.

In the present study, variations of cholinergic and GABAergic markers in the medial septum/vertical limb of the diagonal band of Broca (MS/vDB) and the hippocampus of eight different inbred mouse strains were investigated. By means of immunocytochemistry against the acetylcholine-synthesizing enzyme choline acetyltransferase (ChAT), the cholinergic neurons were visualized and the number of ChAT-positive neuronal profiles in the MS/vDB was counted. Cholinergic and GABAergic septo-hippocampal projection neurons were detected with a combined retrograde tracing and immunocytochemical approach. In order to quantify the cholinergic innervation of various hippocampal sub-regions, we estimated the density of acetylcholinesterase (AChE)-containing fibers as visualized by AChE histochemistry. Additionally, the densities of muscarinic receptors (mainly the subtypes M1 and M2) in different hippocampal areas of seven inbred strains were measured by means of quantitative receptor autoradiography. We found significant strain differences for the number of ChAT-positive neurons in the MS/vDB; in the numbers of cholinergic septo-hippocampal projection neurons; in the density of cholinergic fibers in hippocampal subfields CA3c, CA1, and in the dentate gyrus; and in the density of muscarinic receptors in the hippocampus. In contrast the GABAergic component of the septo-hippocampal projection did not differ between the strains investigated. The number of ChAT-reactive neurons in the MS/vDB was not correlated with either hippocampal cholinergic markers. This might be attributed to different collateralization of cholinergic neurons or to different projections of these neurons to other brain regions. These results show a strong hereditary variability within the septo-hippocampal cholinergic system in mice. In view of the role of the cholinergic system in learning and memory processes, strain differences in cholinergic markers might be helpful in explaining behavioral variation.

Animals↗
PubMed1979

Genetic variation and relative catalytic efficiencies: lactate dehydrogenase B allozymes of Fundulus heteroclitus.

In order to evaluate whether functional differences exist between allelic variants of a B type lactate dehydrogenase (LDH; L-lactate:NAD+ oxidoreductase, EC 1.1.1.27) in the teleost fish Fundulus heteroclitus (Linnaeus), the kinetic properties of pyruvate reduction were examined. While the pH dependence and the temperature dependence for maximal catalysis were indistinguishable among the allozymes, reaction velocities at low pyruvate concentrations were significantly different. At pH values below 8.00, the LDH-BbBb allozyme showed a greater reaction rate at lower temperatures (e.g., 10 degrees C) than LDH-BaBa. The phenomenon was reversed at higher temperatures (e.g., greater than 25 degrees C) for pH values between 6.50 and 7.00. The rates for the heterozygous phenotype, LDH-BaBb, were not the arithmetic average of the two homotetrameric allozymes. When reaction rates were compared at constant relative alkalinity, that is, a constant [OH-]/[H+] ratio, the findings were similar. The differences in the temperature dependence and the pH dependence for pyruvate reduction found between the LDH-B allozymes may reflect a selective adaptation and help explain the geographical variation in the Ldh-B gene frequencies of F. heteroclitus.

Animals↗
PubMed1998

Climate-dependent genetic variation of alpha-2HS-glycoprotein.

We studied the possible effects of climatic factors on the world distribution of alleles determining alpha 2-HS-glycoprotein (AHSG) phenotypes in human populations. New data on AHSG polymorphism in certain ethnic groups of Russia are presented. All available data on the distribution of AHSG gene frequencies in the world (number of populations n = 51) were used to analyze possible correlations between AHSG*2 allele frequencies and seven climatic-geographic parameters. A strong positive correlation was found between AHSG*2 allele frequency and geographic latitude of territories inhabited by the study populations (r = 0.814). The dependence of the AHSG*2 allele distribution in the world on the intensity of ultraviolet radiation (400-315 nm) was estimated at r = -0.826. Such climatic characteristics as the total amount of insolation and the average annual temperature proved to make equal contributions to variation in AHSG*2 allele frequency (r = -0.683 and -0.658, respectively). A computer cartographic model of the AHSG*2 allele distribution in the Old World populations of the Northern Hemisphere was constructed.

Alleles↗
PubMed2000

Genetic variation among four Mexican populations (Huichol, Purepecha, Tarahumara, and Mestizo) revealed by two VNTRs and four STRs.

Allele distributions of two polymorphisms with variable number of tandem repeats (VNTR), D1S80 and APOB, and four polymorphisms with short tandem repeats (STR), VWA, TH01, CSF1PO, and HPRTB, were analyzed in three Mexican ethnic groups: Huichol, Purepecha, and Tarahumara. Genotype distribution was in agreement with Hardy-Weinberg expectations for each locus and ethnic group. Heterozygosity (H), power of discrimination, and probability of exclusion were estimated. The three groups presented some distinctive genetic features: (1) a diminished genetic diversity (H = 66.8% to 73.4%) and mean number of alleles by locus (5.8 to 6.3) in comparison with Mexican mestizos (H = 78.3%, 10.5 alleles/locus), and (2) uneven allele distributions as evidenced by "distinctive alleles" with high frequencies, especially in the Tarahumara and the Huichol. Genetic relatedness analysis included data from a previously typed mestizo population, the largest and most widely distributed population in Mexico. Allele distribution differentiation was observed among all four groups, except between mestizo and Purepecha (p > 0.05), which was interpreted as indicating a larger Spanish component in the Purepecha as a result of gene flow effects. Although intrapopulation inbreeding (FIS) was not significant, heterozygote deficiency in the total population (FIT) and divergence among populations (FST) were significant (p < 0.05). Genetic distances displayed a closer relationship among mestizos, Purepechas, and Huichols in relation to Tarahumaras. Correlation between the observed genetic features and the geographic isolation level points to genetic drift as the main cause of differentiation among these Mexican populations.

Consanguinity↗
PubMed2001

Genetic variation in the MHC II promoter: lessons for regulation and for comparative genomics.

Sequence data have been accumulating that reveal variation in gene promoters of the immune system, notably in MHC class II, cytokines and chemokines. The variation is non-random: it occurs most often in proximity to and within certain regulatory elements such as CRE and NFY (in MHC class II these are respectively the X2 and Y boxes). These are elements that are widely used elsewhere in the genome, and appear to act as rheostats (modulators of expression) in contrast to the type of on-off switch operated by the RFX element that is unique to a single family of promoters such as MHC class II. It is proposed that a complex mouse phenotype described in Prague and elsewhere may reflect this pattern of variation in/around CRE. Such rheostats are expected to operate in other promoters. Their identification will be facilitated by short-range comparisons (e.g. human-chimp), and indeed this is a motive for extending comparative genomics.

Animals↗
PubMed2006

Genetic variations of the Plasmodium vivax dihydropteroate synthase gene.

Dihydropteroate synthase gene of Plasmodium vivax was recently identified. In the present study, the sequences of the dyhydropteroate synthase gene of 68 P. vivax isolates from various geographic areas were compared. Sequencing revealed limited polymorphism at codons 383 and 553 in all analyzed samples. Interstrain analysis showed several genotypic variations in the tandem repeats domain which produce length polymorphism between different parasite isolates.

Amino Acid Sequence↗
PubMed1999

Genetic variation within and among populations of the threatened lichen Lobaria pulmonaria in Switzerland and implications for its conservation.

The foliose epiphytic lichen Lobaria pulmonaria has suffered a significant decline in European lowlands during the last decades and therefore is considered as endangered throughout Europe. An assessment of the genetic variability is necessary to formulate biologically sound conservation recommendations for this species. We investigated the genetic diversity of the fungal symbiont of L. pulmonaria using 143 specimens sampled from six populations (two small, one medium, three large) in the lowland, the Jura Mountains, the pre-Alps and the Alps of Switzerland. Among all nuclear and mitochondrial regions sequenced for this study, variability was found only in the internal transcribed spacer (ITS I), with three polymorphic sites, and in the nuclear ribosomal large subunit (nrLSU), with four polymorphic sites. The variable sites in the nrLSU are all located within a putative spliceosomal intron. We sequenced these two regions for 81 specimens and detected six genotypes. Two genotypes were common, two were found only in the more diverse populations and two were found only in one population each. There was no correlation between population size and genetic diversity. The highest genetic diversity was found in populations where the fungal symbiont is reproducing sexually. Populations with low genetic diversity included only the two same common genotypes. Our study provides evidence suggesting that L. pulmonaria is self-incompatible and heterothallic. Based on our results we give populations with sexually reproducing individuals a higher rank in terms of conservation priority than strictly asexual populations. The remaining lowland populations are so small, that one single catastrophic event such as a windthrow might destroy the entire population. Hence we suggest augmenting such populations in size and genetic diversity using small thallus fragments or vegetative diaspores collected in other populations. As we did not detect any locally adapted genotypes, these transplants can be taken from any other genetically diverse population in Switzerland.

Base Sequence↗
PubMed1999

Ethnic differences in cancer risk resulting from genetic variation.

Ethnic differences in cancer incidence and mortality exist and are probably the result of genetic and epidemiological risk factors. Genetic differences caused by founder mutations are reviewed, with special emphasis on mutations in BRCA1 and BRCA2. Germline mutations in cancer susceptibility genes have been identified in individuals of all races and ethnic groups. Differences among ethnic groups for cancer risks have been recognized, and a proportion of the differences may be the result of founder mutations within these genes. The BRCA2 999del5 mutation in Iceland and the three BRCA1 and BRCA2 mutations in Ashkenazic Jews have been well characterized and were easy to study because the patient population and anonymous samples were readily available and ethnicity was known. Mutations in BRCA1 and BRCA2 probably account for approximately 3 to 10% of breast cancer in the general population and a much higher proportion in those with a strong family history of breast and ovarian cancers and in those of Ashkenazic Jewish descent. However, no overall increased risk of breast or ovarian cancers exists among Ashkenazic Jewish women compared with non-Jewish Caucasians. Some ethnic variation in cancer risk may be explained by founder mutations identified in cancer-predisposing genes. Knowledge acquired by studying the effect of a single mutation in a well defined population may be applied to larger, more heterogeneous populations. Individuals from all racial and ethnic groups carry deleterious mutations. Mutations are simply easier to find and characterize when identified in a specific ethnic group.

BRCA1 Protein↗
PubMed2002

The historical biogeography of two Caribbean butterflies (Lepidoptera: Heliconiidae) as inferred from genetic variation at multiple loci.

Mitochondrial DNA and allozyme variation was examined in populations of two Neotropical butterflies, Heliconius charithonia and Dryas iulia. On the mainland, both species showed evidence of considerable gene flow over huge distances. The island populations, however, revealed significant genetic divergence across some, but not all, ocean passages. Despite the phylogenetic relatedness and broadly similar ecologies of these two butterflies, their intraspecific biogeography clearly differed. Phylogenetic analyses of mitochondrial DNA sequences revealed that populations of D. iulia north of St. Vincent are monophyletic and were probably derived from South America. By contrast, the Jamaican subspecies of H. charithonia rendered West Indian H. charithonia polyphyletic with respect to the mainland populations; thus, H. charithonia seems to have colonized the Greater Antilles on at least two separate occasions from Central America. Colonization velocity does not correlate with subsequent levels of gene flow in either species. Even where range expansion seems to have been instantaneous on a geological timescale, significant allele frequency differences at allozyme loci demonstrate that gene flow is severely curtailed across narrow ocean passages. Stochastic extinction, rapid (re)colonization, but low gene flow probably explain why, in the same species, some islands support genetically distinct and nonexpanding populations, while nearby a single lineage is distributed across several islands. Despite the differences, some common biogeographic patterns were evident between these butterflies and other West Indian taxa; such congruence suggests that intraspecific evolution in the West Indies has been somewhat constrained by earth history events, such as changes in sea level.

Animals↗
PubMed1984

Environmental and genetic variation in milk yield of native cattle and crosses with Brown Swiss in India.

Effects of year, season, parity, age, their two-way interactions, lactation length and calving interval on milk yield were investigated utilizing 9,086 lactation records collected from 1930 to 1975 from six breed groups kept in one herd at Karnal, India. The breed groups involved three native breeds (Sahiwal, Red Sindhi and Tharpakar) and three crossbreds with Brown Swiss (F1 crosses between Brown Swiss and three native breeds, inter se crosses, and 3/4 Brown Swiss). Breed, year, season, parity, age and all of the two-way interactions with the exception of breed X season and parity X season were important. Tharpakar produced more milk than Sahiwal and Red Sindhi by 232 and 204 kg. The milk production difference between Sahiwal and Red Sindhi was only 28 kg. The three crossbreds outproduced the purebreds by an average of 766 kg; however, differences in management could have favored crossbreds. Among the crossbreds, F1 crosses were superior. The linear and quadratic regressions on lactation length accounted for 28% of the variation in milk yield after year, season, parity, age and their interactions were absorbed. Calving interval and lactation length together accounted for 29%. Estimates of heritability, from paternal half-sib analyses, and repeatability of milk yield for Red Sindhi, Sahiwal and Tharpakar ranged from .10 to .30. Differences among heritability estimates from different parities were small when more than 500 records were involved.

Age Factors↗
PubMed2004

The nature of genetic variation in sex and reproduction-related genes among sibling species of the Drosophila melanogaster complex.

Much is known about the biology of Drosophila melanogaster. As a model organism, a comprehensive understanding of its development, physiology and reproduction has been acquired. As a result, a broad variety of transferable genetic tools and information has allowed sibling species of the D. melanogaster complex to emerge as an important speciation model system. By comparing D. melanogaster with its close relative, Drosophila simulans, as well as its other sibling species, we are beginning to understand the nature of genetic changes during the early stages of speciation. In general, we find that genes and traits involved in sex and reproduction are more variable. A large assortment of genes and traits that are involved in various aspects of mating and fertility reveal diagnostic differences between these sibling species. Sex and reproduction-related (SRR) genes are, on average, more diverged than genes with no apparent reproductive function. Furthermore, SRR genes appear more permissive at opting in novel function. These results follow a general trend observed in other taxa and demonstrate the preferential involvement of SRR genes in reproductive isolation and species formation.

Animals↗