Regional assignment of five genes on human chromosome 19

A human-mouse hybrid segregant HM76Dd40-6 with new characteristics was derived from the hybrid cell line HM76Dd containing human chromosome 19 as the only human chromosome. Three virus sensitivities located on human chromosome 19 (PVS, E11S and RDRC) were lost in HM76Dd40-6, while six other genes (C3, LDLR, EF2, GPI, PEPD and MANB) were retained. Cytogenetic analysis and in situ hybridization using human or mouse repeated sequences as probes showed that the region q13.1-qter of human chromosome 19 had been replaced by a fragment of mouse chromosome. Our results permit further regional assignment for the following five genes on human chromosome 19: GPI in the region cen-q12, MANB in p13.2-q12, E11S and RDRC in q13.1-qter, and EF2 in pter-q12.     

The human Y chromosome: an evolutionary marker comes of age

Until recently, the Y chromosome seemed to fulfil the role of juvenile delinquent among human chromosomes--rich in junk, poor in useful attributes, reluctant to socialize with its neighbours and with an inescapable tendency to degenerate. The availability of the near-complete chromosome sequence, plus many new polymorphisms, a highly resolved phylogeny and insights into its mutation processes, now provide new avenues for investigating human evolution. Y-chromosome research is growing up.     

Localisation on human chromosome 19 of three genes for cell surface antigens defined by monoclonal antibodies

Expression of three distinct human cell surface antigens defined by monoclonal antibodies (mAbs) was examined in a series of rodent-human somatic cell hybrids retaining different subsets of human chromosomes. Cell surface reactivity with mAbs F8 and G253, detecting a 95 kilodalton (kD) glycoprotein (gp95); with mAbs F10 and A103, detecting a 50 kD glycoprotein (gp50); and with mAb S7 was found to cosegregate with human chromosome 19. However, differential antigen expression was observed with hybrids containing fragments of the 19 and hybrids constructed with different human cell types. Comparison of results from the serological typing with the presence of a number of chromosome 19 DNA markers in hybrid cells and cytogenetic analysis suggests that MSK20, the gene coding for the F10/A103 antigen gp50, is located in chromosome region 19pter----19p13.2. The genes coding for the F8/G253 antigen, gp95 (gene symbol MSK19) and the S7 antigen (MSK37) are located in region 19p13.2----19q13.2. Thus, the cell surface antigens described in this study may be used as selectable markers for specific portions of human chromosome 19.     

Gene duplication is an evolutionary mechanism for expanding spectral diversity in the long-wavelength photopigments of butterflies

Butterfly long-wavelength (L) photopigments are interesting for comparative studies of adaptive evolution because of the tremendous phenotypic variation that exists in their wavelength of peak absorbance (lambda(max) value). Here we present a comprehensive survey of L photopigment variation by measuring lambda(max) in 12 nymphalid and 1 riodinid species using epi-microspectrophotometry. Together with previous data, we find that L photopigment lambda(max) varies from 510-565 nm in 22 nymphalids, with an even broader 505- to 600-nm range in riodinids. We then surveyed the L opsin genes for which lambda(max) values are available as well as from related taxa and found 2 instances of L opsin gene duplication within nymphalids, in Hermeuptychia hermes and Amathusia phidippus, and 1 instance within riodinids, in the metalmark butterfly Apodemia mormo. Using maximum parsimony and maximum likelihood ancestral state reconstructions to map the evolution of spectral shifts within the L photopigments of nymphalids, we estimate the ancestral pigment had a lambda(max) = 540 nm +/- 10 nm standard error and that blueshifts in wavelength have occurred at least 4 times within the family. We used ancestral state reconstructions to investigate the importance of several amino acid substitutions (Ile17Met, Ala64Ser, Asn70Ser, and Ser137Ala) previously shown to have evolved under positive selection that are correlated with blue spectral shifts. These reconstructions suggest that the Ala64Ser substitution has indeed occurred along the newly identified blueshifted L photopigment lineages. Substitutions at the other 3 sites may also be involved in the functional diversification of L photopigments. Our data strongly suggest that there are limits to the evolution of L photopigment spectral shifts among species with only one L opsin gene and that opsin gene duplication broadens the potential range of lambda(max) values.     

The GLN family of murine endogenous retroviruses contains an element competent for infectious viral particle formation

Several families of endogenous retroviruses (ERVs) have been identified in the mouse genome, in several instances by in silico searches, but for many of them it remains to be determined whether there are elements that can still encode functional retroviral particles. Here, we identify, within the GLN family of highly reiterated ERVs, one, and only one, copy that encodes retroviral particles prone to infection of mouse cells. We show that its envelope protein confers an ecotropic host range and recognizes a receptor different from mCAT1 and mSMIT1, the two previously identified receptors for other ecotropic mouse retroviruses. Electron microscopy disclosed viral particle assembly and budding at the cell membrane, as well as release of mature particles into the extracellular space. These particles are closely related to murine leukemia virus (MLV) particles, with which they have most probably been confused in the past. This study, therefore, identifies a new class of infectious mouse ERVs belonging to the family Gammaretroviridae, with one family member still functional today. This family is in addition to the two MLV and mouse mammary tumor virus families of active mouse ERVs with an extracellular life cycle.     

The role of the Y chromosome in human evolutionary studies

Analyses of molecular genetic data have added a new dimension to human evolutionary research. Pioneering studies of variation in human populations were based on analyses of blood groups¹ and electromorphs,² both of which represent qualitative multistate phenotypes. With the development of recombinant DNA methods in the 1970s and 1980s, the focus shifted from gene products to a new and plentiful source of human variability, restriction fragment length polymorphisms (RFLPs).^3,4 Finally, the addition of DNA sequencining survey data to the rapidly growing RFLP data base made it feasible for the first time to determine the exact number of nucleotide substitutions between different alleles, as well as to construct gene trees and reconstruct the phylogenetic history of populations.^5–7     

Flower nectar of an autogamous perennialRorippa indica as an indirect defense mechanism against herbivorous insects

This report shows that one of the most important roles of the flower nectar of an autogamous perennialRorippa indica (L.) Hieron is as an attractant for employing some ant species as a defense against herbivorous insects. The plant has flowers from spring to early winter. Its flower nectar is frequently stolen by some ant species (hereafter cited as ants) which also feed on small herbivorous insects on the plant. Internations among the tritrophic levels (R. indica, herbivores, ants) were experimentally examined and the followings became clear. (1) Ants were attracted toR. indica in search of its flower nectar. (2) The gradual secretion of flower nectar seemed to detain ants on the plant. (3)Pieris butterfly lavae were the major herbivores onR. indica and were potentially harmful to the plant. (4) The presence of ants reduced the survival rate ofP. rapae larvae onR. indica. (5) The presence of ants reduced the feeding damage toR. indica. (6) The disadvantage of nectar use by ants seemed to be minimal for the plant since the ants did not disturb the other flower visitors. These facts suggest a mutualistic relationship betweenR. indica and ants. That is, the flower nectar serves as an indirect defense against herbivorous insects.     

Duplication of CXC chemokine genes on chromosome 4q13 in a melanoma-prone family

Copy number variations (CNVs) have been shown to contribute substantially to disease susceptibility in several inherited diseases including cancer. We conducted a genome-wide search for CNVs in blood-derived DNA from 79 individuals (62 melanoma patients and 17 spouse controls) of 30 high-risk melanoma-prone families without known segregating mutations using genome-wide comparative genomic hybridization (CGH) tiling arrays. We identified a duplicated region on chromosome 4q13 in germline DNA of all melanoma patients in a melanoma-prone family with three affected siblings. We confirmed the duplication using quantitative PCR and a custom-made CGH array design spanning the 4q13 region. The duplicated region contains 10 genes, most of which encode CXC chemokines. Among them, CXCL1 (melanoma growth-stimulating activity α) and IL8 (interleukin 8) have been shown to stimulate melanoma growth in vitro and in vivo. Our data suggest that the alteration of CXC chemokine genes may confer susceptibility to melanoma.     

Structure of a complex of human lactoferrin N-lobe with pneumococcal surface protein a provides insight into microbial defense mechanism

Human lactoferrin, a component of the innate immune system, kills a wide variety of microorganisms including the Gram positive bacteria Streptococcus pneumoniae. Pneumococcal surface protein A (PspA) efficiently inhibits this bactericidal action. The crystal structure of a complex of the lactoferrin-binding domain of PspA with the N-lobe of human lactoferrin reveals direct and specific interactions between the negatively charged surface of PspA helices and the highly cationic lactoferricin moiety of lactoferrin. Binding of PspA blocks surface accessibility of this bactericidal peptide preventing it from penetrating the bacterial membrane. Results of site-directed mutagenesis, in vitro protein binding assays and isothermal titration calorimetry measurements corroborate that the specific electrostatic interactions observed in the crystal structure represent major associations between PspA and lactoferrin. The structure provides a snapshot of the protective mechanism utilized by pathogens against the host's first line of defense. PspA represents a major virulence factor and a promising vaccine candidate. Insights from the structure of the complex have implications for designing therapeutic strategies for treatment and prevention of pneumococcal diseases that remain a major public health problem worldwide.     

Sublocalization of an invasion-inducing locus and other genes on human chromosome 7.

By somatic cell fusion studies between noninvasive mouse T-lymphoma cells and invasive human activated normal T-cells we have previously shown that the genetic information responsible for the induction of invasive and metastatic potential in interspecies T-cell hybrids is located on human chromosome 7. Apparently, genes derived from normal activated T-cells are dominantly expressed in the hybrids and control the invasive and, as a consequence, metastatic potential of these T-lymphoma cells. To sublocalize the invasion-inducing locus on chromosome 7 we have generated hybrids that harbor only specific regions of human chromosome 7 with or without a small fragment of human chromosome 21. Analysis of these hybrids revealed that the invasion-inducing locus maps to 7p12----cen. The human DNA complement of the hybrids was confirmed by Southern blot analysis using a large panel of chromosome 7-specific DNA probes. Several of these genes could be further sublocalized. These included: ARAF2 to 7p12----cen, D7S21 to 7pter----p12, ACTB to 7p15----p12, EGFR to 7p12, MDH2 to 7cen----q22, and PDGFA to 7pter----p15.     

Evidence for the presence of endogenous 19-norandrosterone in human urine

In 1997, in the scope of antidoping control in sport, a not inconsiderable number of urine analysed by official laboratories revealed the presence of 19-nortestosterone (19-NT: 17β-hydroxyestr-4-en-3-one) metabolites: 19-norandrosterone (19-NA: 3α-hydroxy-5α-estran-17-one) and 19-noretiocholanolone (19-NE: 3α-hydroxy-5β-estran-17-one). These repeated results on a short period of time generated some investigations and especially the verification of the possible production of these metabolites by an unknown endogenous route in adult entire male. Some experiences were led on different persons known to be non-treated with steroids and more precisely with nandrolone. Extractive methods were developed focusing on their selectivity, i.e. searching to eliminate at best matrix interferences from the target analytes. Gas chromatography coupled to mass spectrometry (quadrupole and magnetic instruments) was used to detect, identify and quantify the suspected signals. Two types of derivatization (TMS and TBDMS), a semi-preparative HPLC as well as co-chromatography proved unambiguously the presence, in more than 50% of the analysed urine (n=40), of 19-NA at concentrations between 0.05 and 0.60 ng/ml. 19-NE was not detected with the developed methods (LOD<0.02 ng/ml). Experiments led on athletes showed that after a prolonged intense effort, the 19-NA concentration can be increased by a factor varying between 2 and 4. Even if some complementary researches have to be done in order to determine the maximal physiological level of 19-NA and 19-NE, these results should considerably change the strategy of antidoping laboratories.     

Analysis of bymovirus resistance genes on proximal barley chromosome 4HL provides the basis for precision breeding for BaMMV/BaYMV resistance

Key message

Unlocking allelic diversity of the bymovirus resistance gene rym11 located on proximal barley chromosome 4HL and diagnostic markers provides the basis for precision breeding for BaMMV/BaYMV resistance.

Abstract

The recessive resistance gene rym11 on barley chromosome 4HL confers broad-spectrum and complete resistance to all virulent European isolates of Barley mild mosaic virus and Barley yellow mosaic virus (BaMMV/BaYMV). As previously reported, rym11-based resistance is conferred by a series of alleles of naturally occurring deletions in the gene HvPDIL5-1, encoding a protein disulfide isomerase-like protein. Here, a novel resistance-conferring allele of rym11 is reported that, in contrast to previously identified resistance-conferring variants of the gene HvPDIL5-1, carries a single non-synonymous amino acid substitution. Allelism was confirmed by crossing to genotypes carrying previously known rym11 alleles. Crossing rym11 genotypes with a cultivar carrying the recessive resistance gene rym1, which was reported to reside on the same chromosome arm 4HL like rym11, revealed allelism of both loci. This allelic state was confirmed by re-sequencing HvPDIL5-1 in the rym1 genotype, detecting the haplotype of the rym11-d allele. Diagnostic PCR-based markers were established to differentiate all seven resistance-conferring alleles of the rym11 locus providing precise tools for marker-assisted selection (MAS) of rym11 in barley breeding.     

The physical map ofMus musculus chromosome 11 reveals evolutionary relationship with different syntenic groups of genes inHomo sapiens

Summary The physical localization of sequences homologous to three cloned genes was determined by in situ hybridization to metaphase chromosomes. Previous work had assigned the skeletal myosin heavy chain gene cluster (Myh), the functional locus for the cellular tumor antigen p53 (Trp53-1), and the cellular homologue of the viral erb-B oncogene (Erbb) toMus musculus chromosome 11 (MMU11). Our results provide regional assignments ofMyh andTrp53-1 to chromosome bands B2C, and ofErbb to bands A1A4. Taken together with in situ mapping of three other loci on MMU 11 (Hox-2 homeobox-containing gene cluster, theSparc protein, and theColla-1 collagen gene), which have been reported elsewhere, these data allowed us to construct a physical map of MMU11 and to compare it with the linkage map of this chromosome. The map positions of the homologous genes on human chromosomes suggest evolutionary relationships of distinct regions of MMU11 with six different human chromosome arms: 1p, 5q, 7p, 16p, 17p, and 17q. The delineation of conserved chromosome regions has important implications for the understanding of karyotype evolution in mammalian species and for the development of animal models of human genetic diseases.     

TRPM7 provides an ion channel mechanism for cellular entry of trace metal ions

Trace metal ions such as Zn(2+), Fe(2+), Cu(2+), Mn(2+), and Co(2+) are required cofactors for many essential cellular enzymes, yet little is known about the mechanisms through which they enter into cells. We have shown previously that the widely expressed ion channel TRPM7 (LTRPC7, ChaK1, TRP-PLIK) functions as a Ca(2+)- and Mg(2+)-permeable cation channel, whose activity is regulated by intracellular Mg(2+) and Mg(2+).ATP and have designated native TRPM7-mediated currents as magnesium-nucleotide-regulated metal ion currents (MagNuM). Here we report that heterologously overexpressed TRPM7 in HEK-293 cells conducts a range of essential and toxic divalent metal ions with strong preference for Zn(2+) and Ni(2+), which both permeate TRPM7 up to four times better than Ca(2+). Similarly, native MagNuM currents are also able to support Zn(2+) entry. Furthermore, TRPM7 allows other essential metals such as Mn(2+) and Co(2+) to permeate, and permits significant entry of nonphysiologic or toxic metals such as Cd(2+), Ba(2+), and Sr(2+). Equimolar replacement studies substituting 10 mM Ca(2+) with the respective divalent ions reveal a unique permeation profile for TRPM7 with a permeability sequence of Zn(2+) approximately Ni(2+) > Ba(2+) > Co(2+) > Mg(2+) >/= Mn(2+) >/= Sr(2+) >/= Cd(2+) >/= Ca(2+), while trivalent ions such as La(3+) and Gd(3+) are not measurably permeable. With the exception of Mg(2+), which exerts strong negative feedback from the intracellular side of the pore, this sequence is faithfully maintained when isotonic solutions of these divalent cations are used. Fura-2 quenching experiments with Mn(2+), Co(2+), or Ni(2+) suggest that these can be transported by TRPM7 in the presence of physiological levels of Ca(2+) and Mg(2+), suggesting that TRPM7 represents a novel ion-channel mechanism for cellular metal ion entry into vertebrate cells.