Placental alkaline phosphatase polymorphism in some Italian populations

Summary Gene frequencies of Pl alleles for alkaline phosphatase of human placenta have been studied in the populations of Rome and L'Aquila. The latter represents a mixed sample of descendants from ancient Italic populations which in the last 20 centuries have been free from significant immigratory influx.The Pl gene frequencies in the two Italian populations are significantly different, the Pl ^s ₁ frequency being lower and Pl ^f ₁ frequency higher in the population of L'Aquila as compared to the population of Rome. The gene frequency of the 3 common Pl alleles in the population of Rome are quite similar to that found in some Northern-European populations. The frequency of the Pl ^s ₁ allele observed in the population of L'Aquila is the lowest (and correspondingly that for Pl ^f ₁ allele is the highest) amongst all populations studied so far.     

Is delayed childbearing changing gene frequencies in Western populations?

Experimental data and clinical observations suggest that delaying childbearing influences the biology of the mother-fetus relationship, with a negative effect on fetal development and predisposition to severe diseases such as type 1 diabetes. We reason that advanced maternal age may influence intrauterine selection, favoring genotypes that are more adapted to the intrauterine environment of less young women. In the present study we have investigated the relationship of maternal age to HP genotype and PGM1-Rh area (chromosome 1) that have been previously found to be associated with fertility and developmental parameters. HP phenotype was determined in 679 consecutive puerperae from the population of central Italy. PGM1 phenotype and Rh C phenotype were determined in 222 puerperae and 200 newborns. The HP 1,1 phenotype decreases and the HP 2,2 phenotype increases with maternal age. The proportion of phenotypes carrying both the Rh C and PGM1*1 alleles is much higher in puerperae older than 36 years than in puerperae of age 22 years. The frequency of the PGM1*1-Rh C haplotype increases and the frequency of the PGM1*2-Rh C haplotype decreases with maternal age. The changes in these genetic systems with advancing maternal age are similar in mothers and newborns. The delay of childbearing age, associated in Western countries with the fertility transition in addition to detrimental effects on intrauterine development and increased susceptibility to severe disorders, could bring about changes in the genetic composition of a population.     

High level of genetic differentiation for allelic richness among populations of the argan tree [Argania spinosa (L.) Skeels] endemic to Morocco

Genetic diversity at nine isozyme loci was surveyed in an endangered tree species, the argan tree, endemic to south-western Morocco. The species is highly diverse (3.6 alleles/locus) with populations strongly differentiated from each other (F _ST=0.25). This example is used to illustrate a method for standardizing measures of allelic richness in samples of unequal sample sizes, which was developed for the estimation of the number of species and relies on the technique of rarefaction. In addition, it is shown that the measure of subdivision, _ST, obtained when allelic richness is used in place ofh (Nei's index of diversity), is much larger than the F _ST [e.g. _ST(40)=0.52, where (40) indicates the specified sample used to estimate the allelic richness]. This suggests that rare alleles (which strongly influence measures of allelic richness) have a more scattered distribution than more frequent ones, a result which raises special conservation issues for the argan tree.     

Distribution of Blood Types of Four Systems and AB0 Incompatibility in Migrants of a Northern Town

The distribution of blood groups of the AB0, Rh, MN, and Kell systems were studied in migrants of a northern town of reproductive age and their newborn babies. Migrants of different ethnic groups exhibited significantly different frequencies of AB0 and Rh phenotypes. Maternal sera were tested for the presence of isoimmune antibodies to determine AB0 compatibility (or incompatibility) in mother–neonate pairs. Parents with blood group combinations resulting in mother–neonate pairs incompatible for erythrocyte antigens were less likely to have offspring with the paternal AB0 phenotype.     

Paradoxical effects of maternal stress on fetal steroids and postnatal reproductive traits in female mice from different intrauterine positions

We examined effects of maternal stress on prenatal serum concentrations of testosterone and estradiol and on postnatal reproductive traits in female mice from different intrauterine positions. On Day 18 of fetal life, control females positioned in utero between two male fetuses (2M females) had higher concentrations of testosterone and lower concentrations of estradiol in serum than control female fetuses located between two females (0M females). Control females positioned between a male and a female fetus (1M females) had intermediate levels of both hormones. Prior intrauterine position in control females accounted for differences in genital morphology (length of the anogenital separation) at birth and length of estrous cycles during adulthood. Maternal stress eliminated these postnatal differences due to prior intrauterine position: all 0M, 1M, and 2M female offspring of stressed mothers exhibited postnatal traits that were indistinguishable from those of control 2M females. Maternal stress resulted in an increase of over 1 ng/ml in serum testosterone in all female fetuses; the magnitude of the increase was similar for 0M, 1M, and 2M females. There was no effect of maternal stress on serum concentrations of estradiol in 0M and 2M female fetuses. Maternal stress resulted in a dramatic change in the postnatal traits of 0M females, whereas 2M females showed no change. Since the effect of maternal stress on sex steroids was similar among fetuses from different intrauterine positions but postnatal response to maternal stress varied by intrauterine position, other components of the endocrine system may mediate effects of maternal stress on these postnatal characteristics.     

The role of major histocompatibility complex diversity in vigour of fish males (Abramis brama L.) and parasite selection

The major histocompatibility complex (MHC) presents a group of genes with highly polymorphic loci involved in specific immune responses. The factors maintaining extensive MHC polymorphism have been questioned, considering three possible hypotheses of parasite‐mediated selection driving an extensive MHC diversity (i.e. heterozygote advantage, rare‐allele advantage, and favouring optimal MHC diversity). The patterns of MHC diversity of class IIB genes were investigated following two noncontradicting hypotheses, parasite‐driven selection and MHC‐based mating preferences, using males of common bream collected in the spawning period. Two allelic groups DAB1 and DAB3 were recognized from the phylogenetic analyses. Individuals expressed one or two alleles of the same or different allelic groups. Several individuals shared identical alleles; however, the presence of parasite species was not associated with the occurrence of a particular allele. The presence of different allelic groups (only DAB1, only DAB3, or both DAB1 and DAB3) in individuals was not associated with parasite presence or diversity. The expression of two DAB1 alleles was associated with higher endoparasite abundance. Moreover, nucleotide diversity in individuals expressing a single type of alleles (DAB1 or DAB3) increased with the abundance of ectoparasitic Dactylogyrus spp. (Monogenea) and Ergasilus sp. (Crustacea). This suggests that the expression of two alleles of a single allelic type is related to high metazoan parasite infection whereas no significant influence of parasitism on the combined allelic form (the presence of both DAB1 and DAB3 alleles) was found. Moreover, the expression of two alleles of a single allelic type was related to decreased immunocompetence measured by spleen size. The condition factor was higher in fish expressing the combined allelic type. Thus, the presence of alleles of different lineages in individuals appears to be advantageous for individual male fitness. The expression of a single allelic type was related to higher sexual ornamentation, which could support the role of MHC in the hypothesis of the sexual selection of ‘good genes’. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 90 , 525–538.     

Distribution of allozymic alleles and genetic diversity in the American Barley Core Collection

A survey of allozymic alleles and genetic diversity was made for 151 accessions of the American Barley Core Collection. A total of 25 alleles at ten loci were observed. Two loci were monomorphic. The average diversity index for individual loci ranged between 0.026 and 0.649. Most significant differences in allelic frequency and genetic diversity value were found between spring and winter barley. Spring barley showed a greatly higher average diversity than winter barley (t=2.124, P=0.071). The smallest differences in allelic frequencies and diversity values were observed between the two geographical regions, North and South America. Rare alleles were detected only in a few accessions. Seven rare alleles were associated with spring barley. The genetic similarities among the 151 accessions ranged from 0.20 to 1.00, which showed that a high level of genetic variability exists in this set of core accessions. Cluster analysis and principal coordinate analysis did not give clear-cut separation of different types of barley, but most of the winter barley accessions were closely associated. Received: 7 April 2000 / Accepted: 13 June 2000     

IGF2 DNA methylation is a modulator of newborn’s fetal growth and development

The insulin-like growth factor 2 (IGF2) gene, located within a cluster of imprinted genes on chromosome 11p15, encodes a fetal and placental growth factor affecting birth weight. DNA methylation variability at the IGF2 gene locus has been previously reported but its consequences on fetal growth and development are still mostly unknown in normal pediatric population. We collected one hundred placenta biopsies from 50 women with corresponding maternal and cord blood samples and measured anthropometric indices, blood pressure and metabolic phenotypes using standardized procedures. IGF2/H19 DNA methylation and IGF2 circulating levels were assessed using sodium bisulfite pyrosequencing and ELISA, respectively. Placental IGF2 (DMR0 and DMR2) DNA methylation levels were correlated with newborn’s fetal growth indices, such as weight, and with maternal IGF2 circulating concentration at the third trimester of pregnancy, whereas H19 (DMR) DNA methylation levels were correlated with IGF2 levels in cord blood. The maternal genotype of a known IGF2/H19 polymorphism (rs2107425) was associated with birth weight. Taken together, we showed that IGF2/H19 epigenotype and genotypes independently account for 31% of the newborn’s weight variance. No association was observed with maternal diabetic status, glucose concentrations or prenatal maternal body mass index. This is the first study showing that DNA methylation at the IGF2/H19 genes locus may act as a modulator of IGF2 newborn’s fetal growth and development within normal range. IGF2/H19 DNA methylation could represent a cornerstone in linking birth weight and fetal metabolic programming of late onset obesity.     

Association between Rh and plasma iron binding (transferrin)

Summary In order to establish the mechanism involved in the maintenance of the Rh polymorphism and fetomaternal compatibility relationships, we examined a sample of children from the North Area of Santiago (Chile), with respect to their growth and development patterns since 1973. This sample had shown large sib-sib segregation distortions for the Rh system. Metric variables, such as plasma protein fractions and iron, academic performance at the end of the last secondary grade and adult stature, were studied in relation to genetic markers, viz., sex, ABO, Xg, MN, Rh, haptoglobins, phosphoglucomutase, and esterase D, by means of unbalanced one way analyses of variance. Highly significant results were found for Rh phenotypes and total iron binding capacity (TIBC, transferrin). However, plasma iron did not differ significantly among Ph phenotypes. Children with the C (Rh) specificity had higher values of TIBC than non-C or c individuals (P < 0.00001). Evolutionary considerations regarding iron transport and erythroblastosis, relationships between Rh and the transferrin receptor at the plasma membrane, and the location of the Blym-I oncogene (that shares common sequences with transferrins) close to Rh in chromosome 1 are discussed. Less significant results were found between phosphoglucomutase and stature, gamma globulin level and sex, and academic performance (history) and sex.     

Maternally transmitted foetal <Emphasis Type="Italic">H19</Emphasis> variants and associations with birth weight

This study was designed to test the hypothesis that polymorphic variation in maternally transmitted foetal H19 alleles is associated with offspring size at birth and alterations in maternal glucose concentrations in pregnancy. Inferred parent of origins of transmitted alleles from 13 haplotype tag SNPs in the H19 gene region from 845 family (mother, partner, offspring) trios from the prospective Cambridge Baby Growth Study and 315 trios from the retrospective Cambridge Wellbeing Study cohorts were tested for association with offspring size at birth measures, as well as maternal glucose concentrations 1 h after a glucose load at week 28 of pregnancy. The foetal rs2071094 allele inherited from the mother was associated with increased birth weight (p = 0.0015) adjusted for gestational age, parity and sex. In the Cambridge Baby Growth Study it was also associated with increased head circumference (p = 0.004), length (p = 0.017) and sum of skinfold thicknesses (p = 0.017) at birth. In contrast to these results there was no association between offspring birth weight and either the maternal rs2071094 genotype or the foetal allele from the father. None of the foetal alleles or maternal genotypes were associated with maternal glucose concentrations, neither were there any other associations with offspring birth weight. In conclusion, consistent with imprinting, common polymorphic variation in foetal H19 alleles transmitted only from the mother are associated with birth weight and other markers of size at birth. Polymorphic variation in H19 is not associated with significant changes in maternal glucose tolerance in the third trimester of pregnancy.     

Characterization of highly polymorphic nuclear microsatellite loci in Juniperus communis L.

We developed five nuclear microsatellite markers in Juniperus communis L. using an enriched library method. Samples from 28 juniper individuals were collected in Spain, Germany and Slovakia and were analysed at the five loci. A high level of allelic diversity with values ranging from nine to 23 alleles was found. These highly polymorphic markers will be used in ongoing population genetic studies to evaluate the genetic resources and to contribute to the maintenance of genetic diversity of juniper in Middle Europe.     

Variation in the mating system of Sitka spruce (Picea sitchensis): evidence for partial assortative mating

Five allozyme polymorphisms were used to analyze the mating system in a Sitka spruce seed orchard in Saanichton, British Columbia. Allelic frequencies differed between the pollen and maternal pools at three of the five loci, with alleles rare in the maternal pool being even rarer in the effective pollen pool. Minor differences in pollen allelic frequencies were observed in the upper vs. lower crown. The multilocus outcrossing rate of the upper crown (t_m = 0.909) exceeded that of the lower crown (t_m = 0.764). Single-locus estimates of the outcrossing rate were significantly heterogeneous, with the lowest estimate of outcrossing, t = 0.773, observed for PGM-2 locus. Analyses of the mating system for the three maternal PGM-2 genotypes revealed heterogeneous pollen allelic frequencies and heterogeneous outcrossing rates, possibly due to assortative mating at this locus.     

Global allele polymorphism indicates a high rate of allele genesis at a locus under balancing selection

When selection favours rare alleles over common ones (balancing selection in the form of negative frequency-dependent selection), a locus may maintain a large number of alleles, each at similar frequency. To better understand how allelic richness is generated and maintained at such loci, we assessed 201 sequences of the complementary sex determiner (csd) of the Asian honeybee (Apis cerana), sampled from across its range. Honeybees are haplodiploid; hemizygotes at csd develop as males and heterozygotes as females, while homozygosity is lethal. Thus, csd is under strong negative frequency-dependent selection because rare alleles are less likely to end up in the lethal homozygous form. We find that in A. cerana, as in other Apis, just a few amino acid differences between csd alleles in the hypervariable region are sufficient to trigger female development. We then show that while allelic lineages are spread across geographical regions, allelic differentiation is high between populations, with most csd alleles (86.3%) detected in only one sample location. Furthermore, nucleotide diversity in the hypervariable region indicates an excess of recently arisen alleles, possibly associated with population expansion across Asia since the last glacial maximum. Only the newly invasive populations of the Austral-Pacific share most of their csd alleles. In all, the geographic patterns of csd diversity in A. cerana indicate that high mutation rates and balancing selection act together to produce high rates of allele genesis and turnover at the honeybee sex locus, which in turn leads to its exceptionally high local and global polymorphism.Subject terms: Evolutionary genetics, Rare variants, Ecological genetics     

Genetic variation in island populations of tuatara (<Emphasis Type="Italic">Sphenodon</Emphasis> spp) inferred from microsatellite markers

Tuatara (Sphenodon spp) populations are restricted to 35 offshore islands in the Hauraki Gulf, Bay of Plenty and Cook Strait of New Zealand. Low levels of genetic variation have previously been revealed by allozyme and mtDNA analyses. In this new study, we show that six polymorphic microsatellite loci display high levels of genetic variation in 14 populations across the geographic range of tuatara. These populations are characterised by disjunct allele frequency spectra with high numbers of private alleles. High F _ST (0.26) values indicate marked population structure and assignment tests allocate 96% of all individuals to their source populations. These genetic data confirm that islands support genetically distinct populations. Principal component analysis and allelic sequence data supplied information about genetic relationships between populations. Low numbers of rare alleles and low allelic richness identified populations with reduced genetic diversity. Little Barrier Island has very low numbers of old tuatara which have retained some relictual diversity. North Brother Island’s tuatara population is inbred with fixed alleles at 5 of the 6 loci.     

Population genetics of chimpanzee blood groups

A series of 60 chimpanzees (Pan troglodytes) were tested for their human-type A-B-O blood groups and for ten simian-type blood factors. Of the 60 chimpanzees four were group O and 56 group A; combining this with our previous results, among 274 chimpanzees there were 36 group O and 238 group A. Gene frequency analysis of the V-A-B types (determined by three antisera, anti- V ^c, anti- A ^c and anti- B ^c) of the 60 chimpanzees indicated inheritance by four allelic genes, namely, the amorphic gene v and the three additional alleles v^A, v^B and V. This theory allows for the existence of ten genotypes but only seven V-A-B phenotypes, since the type V.AB is excluded. Gene frequency analysis confirmed that C^c and c^c are contrasting antigens determined by corresponding allelic genes. The distribution of the C-c-E-F types among the 60 chimpanzees, as well as among 133 chimpanzees previously tested, is compatible with the postulation of five allelic genes, namely, the amorph c, and the alleles C^E, C^F, C^EF and the very rare allele C. The blood factor G ^c appears to define a separate blood group system, independent of the V-A-B and C-E-F systems. The newly defined blood factor Lindsay appears to be related to the V-A-B system, while factor H ^c may be related to the C-E-F system.     

Effect of a Founder Event on Variation in the Genetic Sex-Determining System of the Fire Ant Solenopsis Invicta

Effects of a recent founder event on genetic diversity in wild populations of the fire ant Solenopsis invicta were studied, with particular attention given to the genetic sex-determining system. Diploid males are far more common relative to haploid males in introduced populations than in native populations of fire ants, and queens that produce diploid males account for a significantly larger proportion of the mated queens in introduced than in native populations. Differences between native and introduced populations in attributes of the mating systems (i.e., queen mating frequency or level of inbreeding) can be excluded as factors contributing to these different levels of diploid male production. Thus, we conclude that diploid males have increased in frequency in introduced populations because of a loss of allelic diversity at the sex-determining locus (loci). This loss of sex alleles has generated a substantial increase in the estimated segregational genetic load associated with production of sterile diploid males in introduced populations over the load in native populations. The loss of allelic diversity in the sex-determining system in introduced S. invicta is paralleled by a loss of electrophoretically detectable rare alleles at protein-encoding loci. Such concordance between these different types of markers is predicted because each of the many sex alleles present in the native populations is expected to be rare. Estimates of expected heterozygosity (H(exp)) based on 76 electrophoretic loci do not differ significantly between the native and introduced fire ant populations, illustrating the lack of sensitivity of this measure for detecting many types of bottlenecks.     

Molecular analysis of a major locus for resistance to downy mildew in sunflower with specific PCR-based markers

Resistance of sunflower to the obligate parasite Plasmopara halstedii is conferred by specific dominant genes, denoted Pl. The Pl6 locus confers resistance to all races of P. halstedii except one, and must contain at least 11 tightly linked genes each giving resistance to different downy mildew races. Specific primers were designed and used to amplify 13 markers covering a genetic distance of about 3 cM centred on the Pl6 locus. Cloning and sequence analysis of these 13 markers indicate that Pl6 contains conserved genes belonging to the TIR-NBS-LRR class of plant resistance genes. Received: 9 April 2001 / Accepted: 10 August 2001     

Developmental Exposure to Bisphenol A: Interaction with Endogenous Estradiol During Pregnancy in Mice

Individual variability in endogenous hormones can confound theinterpretation of effects of developmental exposure to endocrinedisrupting chemicals. In single-birth species, such as humans,there are many sources of variability in fetal sex hormone levels,such as birth order or race. In litter-bearing species a sourceof fetal variability in serum levels of estradiol and testosteroneis the sex of adjacent fetuses due to fetus-to-fetus steroidtransport (called the intrauterine position phenomenon or IUP).Distinct phenotypes of reproductive physiology and behaviorare due to IUP in house mice and other litter-bearing animals.We review here the effects of background levels of sex steroidsin fetuses due to IUP in an experiment in which pregnant micewere exposed to an environmentally relevant low dose of theestrogen-mimicking chemical, bisphenol A. Bisphenol A is themonomer used to make polycarbonate plastic products (such asbaby bottles), the resin lining of food and beverage cans, dentalsealants, and a host of other products. Fetal exposure via themother to bisphenol A increased the rate of postnatal growthin males and females and also advanced the timing of pubertyin females. However, the greatest response to bisphenol A occurredin males and females with the highest background levels of endogenousestradiol during fetal life due to their IUP, while fetuseswith the lowest endogenous levels of estradiol showed no responseto maternal bisphenol A treatment. This finding suggests thatestrogen-mimicking chemicals interact with endogenous estrogenin altering the course of development.