Localization of the gene for the vitamin B12 binding protein,transcobalamin II,near the centromere on mouse chromosome 11, linked with the hemoglobin alpha-chain locus

Somatic cell hybrids, recombinant inbred (RI) mouse strains, and backcross breeding experiments were used to locate the gene of transcobalamin II (Tcn-2), the vitamin B12 binding protein in mouse serum. TCN-2 was found to be a useful genetic marker in the somatic cell hybrids. Selected hybrid clones were derived from fusions between GR mouse cells and the Chinese hamster cell line E36. Analysis of mouse specific chromosomal enzyme markers in relationship to TCN-2 secretion, in the hybrid clones, provided provisional evidence for assignment of the Tcn-2 locus to chromosome 11. The strain distribution pattern of the TCN-2 variants S and F in the RI series CXS, constructed from the cross of BALB/cHeA (TCN-2S) with STS/A (TCN-2F), implied a close linkage with the hemoglobin alpha-chain locus (Hba) on chromosome 11. Backcross breeding using inbred strains confirmed these findings and located the Tcn-2 gene closest to the centromere, linked with waved 2 (wa-2) and Hba with recombination frequencies of 6.9 and 19.2% each. The linkage group Tcn-2/wa-2/Hba was established.This work was supported by Swiss National Science Foundation Grants 3.023-0.81 and 3.728-0.80, Fritz Hoffmann-La Roche Stiftung 173, the Prof. Dr. Max Cloëtta Foundation, and the Kantonale Zürcher Liga für krebsbekämpfung, Switzerland. M. Prochazka was supported by the Postgraduate Training Program for Experimental Medicine and Biology of the University of Zürich, Switzerland.     

Genetic Variation at a Locus (TAM-1) for Submaxillary Gland Protease in the Mouse and Its Location on Chromosome 7

Electrophoretic and activity variants for a testosterone-induced esteroprotease have been discovered in submaxillary glands from inbred strains of mice. The enzyme is tentatively designated tamase (TAM-1) and the variant genetic locus is Tam-1. The alleles Tam-1^a and Tam-1^b determine electrophoretically distinct zones of tamase activity, while Tam-1^c produces no detectable enzyme activity. Data from recombinant inbred strains and B6AF₁ x B6 and B6D2F₁ x B6 backcrosses established linkage of Tam-1 to glucose phosphate isomerase (Gpi-1), pink-eyed dilution (p) and β-hemoglobin (Hbb) on chromosome 7. The gene order is Gpi-1—Tam-1—p—Hbb. Analysis of congenic resistant strains indicates that Tam-1 is closely linked to the minor histocompatibility locus, H-4. TAM-1 was not cross-reactive with antisera to mouse nerve growth factor, submaxillary renin, or tamases A and D.     

Genotype-specific environmental impact on the variance of blood values in inbred and F1 hybrid mice

Mice are important models for biomedical research because of the possibility of standardizing genetic background and environmental conditions, which both affect phenotypic variability. Inbred mouse strains as well as F₁ hybrid mice are routinely used as genetically defined animal models; however, only a few studies investigated the variance of phenotypic parameters in inbred versus F₁ hybrid mice and the potential interference of the genetic background with different housing conditions. Thus, we analyzed the ranges of clinical chemical and hematologic parameters in C3H and C57BL/6 inbred mice and their reciprocal F₁ hybrids (B6C3F1, C3B6F1) in two different mouse facilities. Two thirds of the blood parameters examined in the same strain differed between the facilities for both the inbred strains and the F₁ hybrid lines. The relation of the values between inbred and F₁ hybrid mice was also affected by the facility. The variance of blood parameters in F₁ hybrid mice compared with their parental inbred strains was inconsistent in one facility but generally smaller in the other facility. A subsequent study of F₁ hybrid animals derived from the parental strains C3H and BALB/c, which was done in the latter housing unit, detected no general difference in the variance of blood parameters between F₁ hybrid and inbred mice. Our study clearly demonstrates the possibility of major interactions between genotype and environment regarding the variance of clinical chemical and hematologic parameters.     

Genetic control of two electrophoretic variants of glucosephosphate isomerase in the mouse (Mus musculus)

The autosomal variation and the genetic control of GPI has been determined by a comparison of electrophoretic patterns of F₁ and backcross progeny of three inbred strains of mice. The locus controlling the production of GPI in the mouse has been designated Gpi-1. Two alleles at this locus have been described and designated Gpi-1 ^a and Gpi-1 ^b, which represent, respectively, the slow and fast electrophoretic forms. Twenty-seven inbred strains of mice have been classified for these two alleles. The absence of close linkage of Gpi-1 to seven other genetic loci has been determined. It has been demonstrated that the polymorphism of Gpi-1 is widely distributed in feral mice. GPI was expressed in vitro and in four types of malignant tumors.Supported by U.S. Public Health Service Grants GM-09966, from General Medical Sciences, and GY 4193.     

Genetics of an esterase in Aedes aegypti

Zymograms of single individuals of Aedes aegypti were obtained by means of starch gel electrophoresis, using alpha-naphthyl acetate as substrate. Inbred lines gave consistently homogeneous patterns; earlier results from random-breeding laboratory strains had shown considerable variability. Six distinct bands were observed. The furthest moving band, designated Esterase 6, showed differential migration in two inbred lines. Reciprocal crosses between these lines gave F₁ progeny showing both bands. Backcrosses of F₁ to either parental line gave a 1:1 segregation. These results are consistent with the hypothesis that the two forms of Esterase 6 are controlled by a single pair of codominant alleles at a single gene locus (Est 6 ^a and Est 6 ^b). Linkage tests with marker genes have demonstrated that Est 6 is on linkage group 2, with the following alignment: spot-abdomen (9.0±1.0) yellow-larva (17.4±1.3) Est 6. Crosses with another inbred line demonstrated a third band with intermediate mobility, designated Est 6 ^c. An additional electrophoretic variant which seems to have a simple Mendelian basis was found in esterase band 1.This work was supported by NIH Research Grant No. A1-02753.     

Mating preferences of F2 segregants of crosses between MHC-congenic mouse strains

Male and female F₂ homozygotes from crosses between MHC-congenic inbred mouse strains were tested for MHC-associated mating preference. In three instances, of the four genotypic combinations so tested, marked MHC-associated mating preference was observed. This result greatly reduces the possibility that the observed mating preferences of MHC-congenic inbred strains can be explained wholly in terms of non-MHC genetic drift, or of residual non-MHC genetic disparity, or of fortuitous acquired strain characteristics unrelated to MHC. In two of the four combinations investigated, the MHC-related mating bias of F₂ segregants was similar to that of the genotypically similar inbred parent strains. In a third combination, F² segregants did not show the mating bias exhibited by the corresponding parent strains. In a fourth combination, F₂ segregants displayed an MHC-related mating bias that was evident in the corresponding parental inbred strains only when the colonies of the parent strains had been maintained in isolation from other strains. While the exhibition of mating preference by mice of the same genotypes may differ according to circumstances, as indicated, in no instance was preference reversed. Mating preference in a given combination of MHC genotypes, whenever it was observed, always favored the same MHC haplotype of the two alternative haplotypes represented. It appears that the familial MHC genotypes of mice and the environment in which the colonies are maintained influence their MHC-related mating preference, but it has yet to be decided whether these factors operate by determining exposure to particular MHC haplotypes.Abbreviations used in this paper are as follows B6 C57BL/6 - B10 C57BL/10 - BALE BALB/c - BALB.B BALB.B10 - INB inbred - MHC major histocompatibility complex See also Figure 1     

Glutamate oxalate transaminase (GOT) genetics in Mus musculus: Linkage,polymorphism, and phenotypes of the Got-2 and Got-1 loci

A comparison of electrophoretic patterns of F₁ and backcross progeny of two inbred strains of mice has revealed a new autosomal variant of the mitochondrial form of GOT. The loci controlling the production of the soluble and mitochondrial forms of GOT have been designated Got-1 and Got-2, respectively. The two alleles of the Got-2 locus have been designated Got-2 ^a and Got-2 ^b, which represent the slow- and fast-migrating electrophoretic forms. Twenty-seven inbred strains of mice have been classified for Got-2 ^a and Got-2 ^b. It has been demonstrated that the polymorphism of Got-2 is widely distributed in feral mice. Got-2 was shown to be linked to Es-1, and evidence is also presented for linkage between Got-2 and Es-2, Es-5, and oligosyndactyly (Os). The absence of linkage of Got-2 to seven other loci has also been demonstrated. GOT was expressed in vitro in cell lines derived from human and mouse tissues.     

Quantitative trait loci for steady-state platelet count in mice

Platelet count in humans is a strongly genetically regulated trait, with approximately 85% of the interindividual variance in platelet numbers attributable to genetic factors. Inbred mouse strains also have strain-specific platelet count ranges. As part of a project to identify novel factors that regulate platelet count, we identified two inbred mouse strains, CBA/CaH and QSi5, with substantial differences in platelet count (mean values of 581 vs. 1062 × 10⁹/L). An F₂ intercross resource of 1126 animals was bred from these two parental strains for a genomewide scan for quantitative trait loci (QTL) for platelet count. QTL were identified on MMU1 (LOD 6.8, p < 0.0005) and MMU11 (LOD 11.2, p < 0.0005) by selectively genotyping animals from the extremes of the F₂ platelet count distribution. Three other QTL of suggestive statistical significance were also detected on MMU7, 13, and 17. It is noteworthy that no QTL were detected in the vicinity of the genes encoding thrombopoietin (Thpo), and its receptor (c-Mpl), both known to influence platelet production. Comparison of gene expression levels between the parental mouse strains by microarrays also showed little difference in the mRNA levels of these known candidate genes. These results represent the first published use of a genetic linkage-based approach in a mouse model toward the identification of genetic factors that regulate platelet count.     

Phosphoglucomutase electrophoretic variants in the mouse

The phosphoglucomutase (PGM) electrophoretic phenotype of the mouse (Mus musculus) consists of several distinct components which can be grouped into two major zones designated PGM-1 and PGM-2. Evidence presented here indicates that each zone is controlled by a single genetic locus denoted Pgm-1 and Pgm-2, respectively. Two variant forms segregated at the Pgm-1 locus. They were codominantly expressed and inherited as alleles at an autosomal locus. The alleles were termed Pgm-1 ^a (fast) and Pgm-1 ^b (slow). These alleles were separately fixed in a number of inbred strains of mice. Preliminary evidence based on wild mouse phenotypes indicates that variant forms also exist for PGM-2 which are inherited as alleles at an autosomal locus. Genetic linkage relationships have not been determined for these loci. PGM-1 variants and PGM-2 were expressed in mouse fibroblasts in vitro.Supported by U.S. Public Health Service grants GM-09966 and GM-07249 from General Medical Sciences and 5 F2 HD-35,531 from Child Health and Human Development; and Atomic Energy Commission contract AT(30-1)-3671.Postdoctoral Fellow of the U.S. Public Health Service.     

Genetic characterization of a polymorphic murine cell-surface glycoprotein

As described in the preceding paper, monoclonal antibodies have been raised by immunization of rats with mouse hematopoietic cells which detect a major cell-surface glycoprotein (M_r=95 000) of mouse bone-marrow cells of the granulocytic series. While most of the monoclonal antibodies detect this molecule on bone-marrow and spleen cells of all mouse strains, two antibodies recognize alternative allelic forms of the molecule. One alloantigen is expressed in all the remaining inbred strains examined. The alloantigens are codominantly expressed on the cells of F₁ mice. Backcrosses of DBA/2 and C57BL/6 with F₁ mice (B6D2F₁) confirmed that a single genetic locus is involved in the expression of the two antigenic forms and demonstrated linkage to Ly-m11 which has previously been mapped to mouse chromosome 2. These genetic mapping experiments and the biochemical properties of the glycoprotein suggested that it might be identical to a glycoprotein first identified on murine fibroblasts by Hughes and August and designated Pgp-1. This has been firmly established by exchange of monoclonal antibody reagents and sequential immunoprecipitations.     

Polymorphism of esterase-10 in Mus musculus

An esterase, esterase-10, in the house mouse, Mus musculus, is specific for esters of 4-methylumbelliferone and exhibits a polymorphism detectable by electrophoresis. Fifteen inbred strains and two outbred strains have been examined for this polymorphism, and two phenotypes, ES-10A and ES-10B, have been observed. Each phenotype manifests itself as a single band of enzyme activity, but under the electrophoretic conditions used the ES-10A phenotype has less anodal electrophoretic mobility than the ES-10B phenotype. In F₁ hybrids (C3H/He/Lac×C57BL/Gr) a third phenotype was observed, ES-10AB, consisting of three bands of enzyme activity, two of which correspond to the parental forms and the third with intermediate mobility. The triple-band pattern in the F₁ hybrids indicates that esterase-10 is a dimeric enzyme protein.This work was supported by the Medical Research Council.     

Esterase-8 (Es-8): Characterization,polymorphism, and linkage of an erythrocyte esterase locus on chromosome 7 of Mus musculus

An electrophoretic polymorphism of an erythrocyte esterase, esterase-8, specific for the substrates α- and β-naphthyl acetate has been observed in the Asian house mouse, Mus musculus castaneus. M. m. castaneus is interfertile with inbred strains of mice, and F₁ hybrids (C57BL/6J × castaneus)F₁ and (SWR/J × castaneus)F₁ show a double-banded phenotype similar to a mixture of parental forms. This pattern suggests codominant expression of a structural gene difference. In backcrosses, ES-8 segregated as a single autosomal gene, designated Es-8, linked to Gpi-1 on chromosome 7. A gene order of Es-8, Gpi-1, c, Mod-2, and Hbb was determined from a series of crosses.     

Genetic dissection of testis weight in mice: quantitative trait locus analysis using F2 intercrosses between strains with extreme testis weight, and association study using Y-consomic strains

In the present study, dissection of genetic bases of testis weight in mice was performed. Autosomes and the X chromosome were searched using traditional quantitative trait locus (QTL) scans, and the Y chromosome was searched by association studies of Y-consomic strains. QTL analysis was performed in ??DDD?×???CBA F₂ mice; the inbred mouse DDD has the heaviest testes, whereas the inbred mouse CBA has the lightest testes. Two significant testis weight QTLs were identified on chromosomes 1 and X. A DDD allele was associated with increased and decreased testis weight at the locus on chromosomes 1 and X, respectively. In the reciprocal cross ??CBA?×???DDD F₂ mice, QTL on chromosome 1, and not on chromosome X, had a significant effect on testis weight. The DDD allele at the X-linked locus could not sustain testis weight in combination with the Y chromosome of the CBA strain. The Y chromosome per se had a significant effect on testis weight, i.e., DH-Chr Y^DDD had significantly heavier testes than DH-Chr Y^CBA. On the basis of the results of Y-chromosome-wide association studies using 17 Y-consomic strains, variations in Uty, Usp9y, and Sry were significantly associated with testis weight. Thus, testis weight is a complex quantitative phenotype controlled by multiple genes on autosomes and sex chromosomes and their interactions.     

Characterizations of candidate genes for IDD susceptibility from the diabetes-prone NOD mouse strain

The nucleotide sequences of the NOD and C57BL/6J alleles of Glut-2, Sod-2, and Il-2 were determined by RT-PCR sequencing. Each of these loci is located in intervals that strongly correlated with susceptibility to diabetes in an (NOD/Uf x C57BL/6J)F₁ x NOD/Uf backcross. No significant variations in the alleles of Glut-2 at 16 cM on Chromosome (Chr) 3 or Sod-2 at 8 cM on Chr 17 were detected. However, the Il-2 allele in NOD at 20 cM on Chr 3 was found to differ from that in C57BL/6J by a complex mutation involving the contraction of a simple sequence repeat (SSR). Il-2 in NOD differs from the allele in C57BL/6J via a complex mutation involving a deletion of four CAG codons from the SSR together with a length-compensatory four-codon duplication of a segment 5 from the SSR. Two nonsynonymous mutations in the coding region 5 to the SSR were also detected. Only these two allelic forms of Il-2 were detected in a survey of 13 standard inbred lines and 4 wild mouse strains. We propose to designate these alleles as Il-2 ^a (for alleles such as C57BL/6J that contain 12 CAG repeats) and Il-2 ^b (for alleles such as NOD), which occurred in a variety of standard inbred strains and in all four wild Mus musculus domesticus tested. The distribution of these Il-2 alleles among inbred strains correlated with the detection of Chr 3 as an interval effecting diabetes susceptibility in three separate genetic crosses. However, functional characterizations of the quantity and functional characteristics of Il-2 produced by Il-2 ^a and Il-2 ^b failed to reveal any allele-specific variations.     

Transgressive segregation in a behavioural trait? Explorative strategies in two house mouse subspecies and their hybrids

Hybrid zones between genetically diverged populations are widespread among animals and plants. Their dynamics usually depend on selection against admixture and dispersal of parental forms in the zone. Although indirect estimates of selection have been the target of many studies, dispersal has been neglected. In this study we carried out open field experiments to test whether males of two house mouse subspecies, Mus musculus musculus and Mus musculus domesticus, differ in their propensity to disperse and in their character of exploration. We tested wild‐caught males and males of two wild‐derived inbred strains. In addition, we examined reciprocal F₁ crosses to test the prediction that these hybrids display intermediate behaviours. We revealed that M. m. musculus males were less hesitant to enter the experimental arena than were M. m. domesticus males, but once inside the arena their movements were more timid. F₁ males differed from both parental strains, with longer latencies to enter the arena, but explored the arena in a similar fashion as the M. m. domesticus males, thus displaying transgressive behavioural phenotypes. These results contribute to our knowledge of behavioural divergence between the mouse subspecies, and add a new facet to the study of speciation. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ●●, ●●–●●.     

The <Emphasis Type="Italic">C1473G</Emphasis> polymorphism in gene <Emphasis Type="Italic">tph2</Emphasis> is the main factor mediating the genetically defined variability of tryptophan hydroxylase-2 activity in the mouse brain

Brain neurotransmitter serotonin is involved in the regulation of many physiological functions and types of behavior. The key enzyme of serotonin synthesis in the brain is tryptophan hydroxylase-2 (TPH-2). Linkage between the C1473G polymorphism in gene tph2 causing the replacement of Pro⁴⁴⁷ by Arg⁴⁴⁷ in TPH-2 molecule and enzyme activity in the mouse brain of 10 inbred strains was found. Association of the polymorphism with the TPH-2 activity in the brain of F₂ hybrids between strains C57BL/6 and CC57BR was shown. The results indicate that the C1473G polymorphism in gene tph2 is the main factor determining the genetically defined variability of enzyme activity in the mouse brain.     

Influences of inbreeding and genetics on telomere length in mice

We measured telomere lengths of blood leukocytes in several inbred and outbred mammalian species, using a telomere-specific fluorescent probe and flow cytometry. Humans, non-human primates, and three outbred populations of Peromyscus mice (Peromyscus leucopus, Peromyscus maniculatus, and Peromyscus polionotus) have short telomeres. Two common strains of laboratory mice, C57BL/6J and DBA/2J, have telomeres several times longer than most other mammals surveyed. Moreover, the two inbred laboratory mouse strains display significantly different telomere lengths, suggesting the existence of strain-specific genetic determinants. To further examine the effects of inbreeding, we studied three Peromyscus leucopus inbred lines (GS109, GS16A1, and GS16B), all derived from the outbred P. leucopus stock. Telomeres of all three inbred lines are significantly lengthened relative to outbred P. leucopus, and the three lines display strain-specific significantly different telomere lengths, much like the C57BL/6J and DBA/2J strains of M. musculus. To further characterize the genetic inheritance of telomere length, we carried out several crosses to obtain hybrid F₁ mice between parental strains displaying the phenotype of long and short telomeres. In all F₁ mice assayed, peripheral blood leukocyte telomere length was intermediate to that of the parents. Additionally, we generated F₂ mice from a cross of the (P. leucopus outbred × GS16B)F₁. Based on the distribution of telomere length in the F₂ population, we determined that more than five loci contribute to telomere length regulation in Peromyscus. We concluded that inbreeding, through unknown mechanisms, results in the elongation of telomeres, and that telomere length for a given species and/or sub-strain is genetically determined by multiple segregating loci.     

Genetic control of nucleolar number in mouse

The number of nucleoli per cell was studied in embryonic tissues and neonatal livers of the mouse. Different inbred strains showed different mean nucleolar numbers. The f₁, F₂, and backcross progeny between two inbred strains, BALB/c and C3H, revealed that the number of nucleoli per cell was genetically determined and probably follows polygenic inheritance.     

Polymorphism of esterase 11 in Mus musculus,a further esterase locus on chromosome 8

A further esterase, esterase 11, which exhibits a polymorphism detectable by electrophoresis, has been observed in the house mouse, Mus musculus. In 15 inbred strains and two outbred strains, the ES-11A phenotype has been found, composed of two bands of enzyme activity of greater anodal electrophoretic mobility than the two bands of the ES-11B phenotype found in one inbred strain, one wild stock, and 101 wild mice. In F₁ hybrids (IS/Cam×C57 BL/Gr), the phenotype shown corresponds to a mixture of the two parental phenotypes. In backcrosses, ES-11 segregates as an autosomal gene, designated Es-11, closely linked to Es-2 and Es-5 on chromosome 8.This work was supported by the Medical Research Council.     

Monoallelic expression of mouse <Emphasis Type="Italic">Cd4</Emphasis> gene

A 7-bp deletion in the Cd4 gene, present in the strain MOLF/Ei of Mus musculus molossinus and absent in laboratory mouse strains (Mus musculus musculus), provided the means to distinguish the parental origin of the Cd4 alleles expressed in single cells of F₁ (AKR × MOLF/Ei) and F₁ (Balb/C × MOLF/Ei) hybrids. Single-cell RT-PCR showed that the individual CD4⁺ lymphocyte expresses either the maternal or the paternal Cd4 allele, never both. In situ hybridization proved that Cd4 alleles replicate asynchronously, as expected in the case of genes expressed monoallelically.