Gene mapping on mouse chromosome 8 by interspecific crosses: new data on a linkage group conserved on human chromosome 16q

Association of metallothionein 2A rs10636 with low mean corpuscular volume (MCV), low mean corpuscular haemoglobin (MCH) in healthy Taiwanese

Human metallothionein-2A (MT2A) protein participates in metal homeostasis, detoxification, oxidative stress reduction, and immune defense. It decreases heavy metal ions and reactive oxygen species (ROS) during injury of cells and tissues. The single nucleotide polymorphisms at the MT2A gene have been associated in various human diseases including cancer. The current study aimed to elucidate associations between MT2A genotypes with the clinical, biochemical, and molecular characteristics that potentially related to lowered MT2A ex-pression. One hundred and forty-one healthy Taiwanese subjects were enrolled from Changhua Show-Chwan Memorial Hospital. Clinical, biochemical and molecular characteristics including the frequent minor allele SNPs, rs28366003 and rs10636, within the MT2A gene were determined. The genotype distribution of MT2A rs10636 fits the Hardy-Weinberg equilibrium. The significant associations with gradually decline of mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) were identified with MT2A rs10636 and rs28366003 using analysis of variance (ANOVA) with Tukey's analysis as a post hoc test. We further validated the correlations between the expressions of genes in erythropoiesis, cholesterol synthesis, platelet synthesis, insulin with MT2A using the web-based Gene Expression Profiling Interactive Analysis (GEPIA) databases. The results revealed that hypoxia-inducible factor 1α (HIF-1α), erythropoietin (EPO), lipoprotein lipase (LPL), and lecithin-cholesterol acyltransferase (LCAT) mRNA ex-pression are significantly correlated with MT2A mRNA expression. In conclusion, these results suggested that genetic variations of MT2A rs10636 and rs28366003 might be an important risk factor for erythropoiesis in the Taiwanese general population.

Molecular characterization, expression profile and association analysis with carcass traits of porcine LCAT gene

The lecithin cholesterol acyltransferase gene (LCAT) plays an important role in lipoprotein metabolism, especially in the process termed 'reverse cholesterol transport'. In this study, we obtained the 1,434 bp mRNA sequence of porcine LCAT including the full coding region and encoding a protein of 472 amino acids. The sequence was deposited into the GenBank under the accession no. EU717835. The genomic sequence of this gene which contains six exons and five introns, is 3,712 bp in length (GQ379050). Bioinformatic analysis of the 5' regulatory region has revealed that some transcription factor Sp1, AP-1, AP-2 and NF-kappaB were represented in this region. Tissue expression analysis showed that the porcine LCAT gene is ubiquitously expressed in all examined tissues. Phylogenetic tree was constructed by aligning the amino acid sequences of different species. Moreover, we found a single nucleotide polymorphism (SNP, C/G266) in intron 1 of the LCAT gene and association analysis showed that it was significantly associated with ratio of lean to fat (P < 0.05), caul fat weight (P < 0.01), leaf fat weight (P < 0.05), carcass length (P < 0.05) and bone percentage (P < 0.05). Our study will lay the groundwork for the further investigations on the detailed physiological function of LCAT in pig models.

The E-cadherin-catenin complex in tumour metastasis: structure, function and regulation

E-cadherin and the associated catenin complex have been recognised as performing a key role in cell adhesion. Loss of cell adhesion is seen as a key step in the cascade leading to tumour metastasis. The ability of both extra- and intracellular factors to regulate E-cadherin-mediated cell adhesion in physiological processes has provided insight into both the interactions of the E-cadherin-catenin complex, and possible mechanisms utilised by tumours in the process of metastasis. The interaction of the E-cadherin-catenin complex with various regulating factors, their effect on cell signalling pathways, and the relationship with the metastatic potential of tumours are reviewed.

Regulation of E-cadherin: does hypoxia initiate the metastatic cascade?

The ability of tumours to metastasis is regarded as one of the hallmarks of malignancy. The process through which tumours evolve to achieve this has been termed the metastatic cascade. This cascade has been the subject of much investigation over many years. One of the vital events identified by these investigations is the reduction of adhesion between tumour cells facilitating invasion of the surrounding tissues and vascular channels, ultimately leading to the development of a distant metastasis. E-cadherin and its associated catenin complex have been identified as key molecules in cell adhesion. This review looks at the structure and interaction of the E-cadherin-catenin complex and the factors that appear to regulate E-cadherin expression and thus cell adhesion. From the data gathered, it has become possible to propose the hypothesis that the development of tumour hypoxia is the initiating factor that sets the tumour on the road to metastasis.

High-resolution mapping of a linkage group on mouse chromosome 8 conserved on human chromosome 16Q

We have performed a high-resolution linkage analysis for the conserved segment on distal mouse Chromosome (Chr) 8 that is homologous to human Chr 16q. The interspecific backcross used involved M. m. molossinus and an M. m. domesticus line congenic for an M. spretus segment from Chr 8 flanked by phenotypic markers Os (oligosyndactyly) and e, a coat colormarker. From a total of 682 N2 progeny, the 191 animals revealing a recombination event between these phenotypic markers were typed for 23 internal loci. The following locus order with distances in cM was obtained: (centromere)-Os-4.1-Mmp2-0.2-Ces1,Es1, Es22-1.2-Mt1,D8Mit15-2.2-Got2, D8Mit11-3.7-Es30-0.3-Es2, Es7-0.9-Ctra1,Lcat-0.3-Cdh1, Cadp, Nmor1, D8Mit12-0.2-Mov34-2.5-Hp,Tat-0.2-Zfp4-1.6-Zfp1,+ ++Ctrb-10.9-e. In a separate interspecific cross involving 62 meioses, Dpep1 was mapped together with Aprt and Cdh3 at 12.9 cM distal to Hp, Tat, to the vicinity of e. Our data give locus order for markers not previously resolved, add Mmp2 and Dpep1 as new markers on mouse Chr 8, and indicate that Ctra1 is the mouse homolog for human CTRL. Comparison of the order of 17 mouse loci with that of their human homologs reveals that locus order is well conserved and that the conserved segment in the human apparently spans the whole long arm of Chr 16.

Quantitative trait loci influencing cholesterol and phospholipid phenotypes map to chromosomes that contain genes regulating blood pressure in the spontaneously hypertensive rat

The frequent coincidence of hypertension and dyslipidemia suggests that related genetic factors might underlie these common risk factors for cardiovascular disease. To investigate whether quantitative trait loci (QTLs) regulating lipid levels map to chromosomes known to contain genes regulating blood pressure, we used a genome scanning approach to map QTLs influencing cholesterol and phospholipid phenotypes in a large set of recombinant inbred strains and in congenic strains derived from the spontaneously hypertensive rat and normotensive Brown-Norway (BN.Lx) rat fed normal and high cholesterol diets. QTLs regulating lipid phenotypes were mapped by scanning the genome with 534 genetic markers. A significant relationship (P < 0.00006) was found between basal HDL2 cholesterol levels and the D19Mit2 marker on chromosome 19. Analysis of congenic strains of spontaneously hypertensive rat indicated that QTLs regulating postdietary lipid phenotypes exist also on chromosomes 8 and 20. Previous studies in the recombinant inbred and congenic strains have demonstrated the presence of blood pressure regulatory genes in corresponding segments of chromosomes 8, 19, and 20. These findings provide support for the hypothesis that blood pressure and certain lipid subfractions can be modulated by linked genes or perhaps even the same genes.

Anchored reference loci for comparative genome mapping in mammals

Recent advances in gene mapping technologies have led to increased emphasis in developing representative genetic maps for several species, particularly domestic plants and animals. These maps are being compiled with two distinct goals: to provide a resource for genetic analysis, and to help dissect the evolution of genome organization by comparing linkage relationships of homologous genes. We propose here a list of 321 reference anchor loci suitable for comparative gene mapping in mammals and other vertebrate classes. We selected cloned mouse and human functional genes spaced an average of 5-10 centiMorgans throughout their respective genomes. We also attempted to include loci that are evolutionarily conserved and represented in comparative gene maps in other mammalian orders, particularly cattle and the domestic cat. We believe that the map may provide the basis for a unified approach to comparative analysis of mammalian species genomes.

Re-localization of Actsk-1 to mouse chromosome 8, a new region of homology with human chromosome 1

We present here the genetic mapping of the alpha-skeletal actin locus (Actsk-1) on mouse Chromosome (Chr) 8, on the basis of the PCR analysis of a microsatellite in an interspecific backcross. Linkage and genetic distances were established for four loci by analysis of 192 (or 222) meiotic events and indicated the following gene order: (centromere)-Es-1-11.7 cM-Tat-8.3 cM-Actsk-1-0.5 cM-Aprt. Mapping of ACTSK to human Chr 1 and of TAT and APRT to human Chr 16 demonstrates the existence of a new short region of homology between mouse Chr 8 and human Chr 1. Intermingling on this scale between human and mouse chromosomal homologies that occurred during evolution creates disorders in comparative linkage studies.

Gene order and genetic distance of 13 loci spanning murine chromosome 15

Thirteen genetic loci spanning murine chromosome 15 from 15A2 (Mlvi-2) to 15F2-3 (Gdc-1) have been mapped. The genetic distance extends to 55.4 cM. Among 151 animals, only 1 animal with a double cross-over was found. The linear order is unambiguous, with the exception of the distal end on 15F1-3. Our analysis favors the order cen-Ela-1/Hox-3-Wnt-1-Gdc-1-ter. This ordering makes necessary the introduction of three tightly spaced double recombination events around and within the Hox-3 locus. Alternatively, Hox-3 may be most distal, and several double recombinations at the telomere lead to map expansion. Despite the unequal distribution along chromosome 15 of G-versus R-bands, a comparison of distances determined by physical and genetic mapping does not indicate an overt difference in distance between both mapping techniques.

DNA variants with telomere probe enable genetic mapping of ends of mouse chromosomes

Dde I-digested DNA fragments from 11 inbred mouse strains were separated by electrophoresis, blotted and probed with a labeled oligomer, TELO, containing five repeats of the consensus mammalian telomere sequence, TTAGGG. Each strain produced a unique set of hybridizing fragments. Segregation analysis of TELO-hybridizing fragments from the BXD RI strains indicated that each fragment segregated as expected for a single gene. One fragment from strain DBA/2J was genetically linked to locus Xmv-9, previously mapped near the distal end of the map of chromosome (Chr) 4 and three fragments to Cck, near the distal end of Chr 9, suggesting that these fragments are telomeric and represent the ends of the chromosome maps. Confirmation of these map positions was obtained from a backcross. Fragments associated with the short arm of the Y Chr were found in DNA from strains C57BL/6J and DBA/2J. TELO-hybridizing fragments from DBA/2J were digested by the exonuclease Bal 31, under conditions in which fragments hybridizing to a cDNA probe for the metallothionein locus, located at the middle of mouse Chr 8, remained intact. Thus both biochemical and genetic tests indicate that several TELO-hybridizing fragments from Dde I-digested DNA are at the ends of chromosomes and probably derive from mouse telomeres. Using this approach should allow the mapping of genes relative to the ends of other mouse chromosomes.

A multilocus linkage map of mouse chromosome 8

We present a genetic linkage map of mouse chromosome 8 that spans 53 cM and includes eight cloned loci. This map was derived from analysis of 100 progeny of an interspecific backcross between Mus spretus and Mus musculus domesticus. Genes that were mapped in this analysis include L7, Plat, Lpl, Ucp, Es, Mt-1, Um, and Tat. This analysis positions a new extremely proximal marker on chromosome 8, which is discussed as a potential candidate gene for the nervous locus. These linkage data will be useful for the mapping of additional loci on chromosome 8.

Characterization of a murine cDNA encoding a member of the carboxylesterase multigene family

We have characterized a mRNA sequence containing the entire coding region of a mouse carboxylesterase (EC 3.1.1.1). pEs-N, an 1840-bp composite of five overlapping cDNA clones, contains an open reading frame of 554 amino acids that display a high degree of similarity with rat and rabbit carboxylesterases. Genetic mapping studies place this carboxylesterase in cluster 1 of the esterase region on chromosome 8. Results of blot hybridization analysis of genomic DNA probed with a pEs-N cDNA under both low and high stringency conditions suggest membership in a carboxylesterase multigene family, as would be expected for a nonspecific carboxylesterase. A message size of 1850-1900 nucleotides was revealed by RNA blot hybridization analysis. S1 nuclease protection analyses with a probe representing a segment of pEs-N detected message in liver, kidney, and lung, but not in spleen, brain, testes, and submandibular gland, with higher levels in female than in male kidney. Additional S1 nuclease-protected mRNA species were found, suggesting the expression of distinct members of a multigene family. In vitro translation of a full-size transcript of pEs-N resulted in a product of 51.5 kDa. Upon the addition of microsomes, this product was processed into a protein of 60.4 kDa, which is within the size range of monomeric units of mouse carboxylesterases.

Genetic characterization of esterase 28 (ES-28) of the house mouse

The genetics of esterase-28, the major esterase of cauda epididymidis of the house mouse, has been studied after separation by polyacrylamide gel electrophoresis and isoelectric focusing. Four phenotypes are distinguished. Segregation of Es-28 in two backcross series indicated linkage to Es-1, Es-9, and Es-22. The Es-28 locus was placed into esterase cluster 1 on chromosome 8.

Meiotic mapping of murine chromosome 17: the string of loci around l(17)-2Pas

We describe a genetic analysis of l(17)-2Pas, an embryonic lethal mutation on murine chromosome 17. Males transmitted the l(17)-2 allele to only 38% of their offspring, whereas females transmitted this allele at 50%. Two-point crosses revealed tight linkage between l(17)-2 and brachyury (T), and deletion mapping placed l(17)-2 outside of the hairpin-tail deletion (Thp). To map this mutation more precisely, we intercrossed hybrid mice that carry distinct alleles at many classical and DNA loci on chromosome 17 and obtained 172 animals recombinant in the T to H-2 region. Strong positive interference was observed over the 14 cM interval from T to H-2K. Thus, a single recombinant can be informative; one such recombinant places l(17)-2 distal of the molecular marker D17Leh66D. Robust genetic maps can be constructed with multilocus crosses that share anchor loci. DNA markers can be interpolated onto these maps retrospectively.