Single-locus control of sucrose octaacetate tasting among mice

SWR/J mice avoid sucrose octaacetate (SOA) solutions at concentrations which other inbred strains do not. This phenotypic difference has been hypothesized to result from variation at a single autosomal locus with two alleles, one dominant (Soa ^a , aversion) and one recessive (Soa ^a , blind). Data from reciprocal F₁ and F₂ crosses of SWR/J (taster) and C57BL/6J (nontaster) mice and from four generations of selective lineal backcrossing to the C57BL/6J strain, in two-bottle preference tests with 10^–5 M SOA, were used to test this monogenic model against two polygenic models. The phenotypic ratios expected in the segregating generations according to the single-locus model were consistent with the observed ratios. The ratios expected with either two-locus model were inconsistent with those found. A strain distribution pattern, also consistent with monogenic variation, was found when a set of recombinant inbred strains (SWXL/Ty) derived from SWR/J and C57L/J (nontaster) mice was similarly tested. Outbred CFW mice (inbred substrains of which had been reported by separate laboratories to be both SOA tasters and SOA nontasters) were found to be polymorphic for SOA tasting. An allele identical by descent to that in the SWR/J strain may be segregating in this (distantly) related line.This research was supported in part by Grant NS 15560 from the NINCDS.     

C3.SW-SOA a heterozygous congenic taster mice

Sensitivity to the bitter acetylated sugar sucrose octaacetate (SOA) is mediated by a single-locus system with three alleles in mice. Inbred strains are classified according to SOA phenotype as tasters, nontasters, or demitasters (intermediate sensitivity). A congenic quartet created from taster and nontaster strains has been used to investigate the effect of theSoa locus on non-SOA aspects of taste sensitivity. In this study, we created a third congenic set, C3.SW-Soa ^a, from taster (SWR/J) and demitaster (C3HeB/FeJ) strains. After 11 lineal backcross generations these C3.SW mice carry the tasting allele on a 99% C3 demitaster background. After testing a total of 938 mice, taster-demitaster proportions across 12 generations were consistent with expectations from a monogenic model. The resultant three-strain congenic series will allow further examination of the mechanisms of taste.     

The B6.SW bilineal congenic sucrose octaacetate (SOA)-Taster mice

SWR/J inbred mice (Tasters) reliably avoid, whereas C57BL/6J inbred mice (Nontasters) are indifferent to, sucrose octaacetate (SOA) at certain concentrations. From these strains we have developed a set of bilineal congenic Taster mice. Approximately 4000 mice, from 2 isogenic and 12 segregating generations, were tested in a program designed to evaluate genetic models for SOA tasting during development of congenic strains. The criterion phenotype was avoidance or nonavoidance in preference tests of the bitter tastant SOA at concentrations of 10^–4 and 10^–5 M. Across the 12 segregating generations, the results were consistent with Mendelian expectations for a single autosomal locus with complete dominance of the Taster phenotype. The breeding program produced 12 replicate B6.SW lines containing the taster allele on the B6-Nontaster genomic background. The congenic Taster mice may facilitate a functional analysis of the sense of taste.This research was supported in part by Grant NS 15560 from the NINCDS.     

Sucrose octaacetate tasting in a heterogeneous population of CFW mice

Three experiments investigated the genetic underpinnings of the sucrose octaacetate (SOA) avoidance-indifference dimorphism that exists among outbred CFW mice. In the first experiment, results from 687 subjects across three generations of segregation were consistent with predictions from a single-autosomal, two-allele model, with dominance for the avoidance (Taster) phenotype. In the second experiment, heterogeneous CFW Tasters and Nontasters were mated with SWR/J (Taster) and C57BL/6J (Nontaster) inbred mice. The SWR and CFW mice are both derived from Swiss mice, and the results were consistent with the possibility that the Taster animals share an allele which is identical by descent. The second and third experiments also investigated sensitivity to SOA across an extended range of concentrations. Nontaster CFWs avoided SOA at the near-saturation 10^–3 M concentration but did not avoid any weaker concentrations. Taster CFWs avoided all concentrations down to approximately 10^–6 M SOA.This research was supported in part by NINCDS Grant NS 15560.     

Qed-1 – a target for unrestricted killing by T cells

Two prototype target determinants for unrestricted killing by T cells are defined: Qed-l^a, detected on B6.Tla^a targets by C3H/HeJ lymphocytes primed in vivo and restimulated in vitro by B 10.BR spleen cells; and Qed-1^b, detected on C57BL/6J lymphocytes by B 10.BR anti-C 3 HiHeJ effector cells generated in the same manner. Other mouse strains can be typed for Qed-1 by the ability of their lymphocytes to inhibit one of these lytic reactions. Of 55 inbred strains, 52 expressed either Qed-1^a or Qed-1^b, which thus behaved as products of alleles of a single locus, Qed-1. The remaining three strains, all H-2^r, did not compete against specific lysis of Qed-1^a, but inhibited Qed-1^b-specific lysis only in part; it is proposed that these strains carry a third allele or haplotype, Qed-1^c. The Qed-1 locus was mapped distal to Qa-2. Qed-1^h was found on both normal and mitogen-activated lymphocytes and did not appear confined to any lymphoid subpopulation. Cytotoxic responses, not restricted by H-2 and specific for antigens controlled by the Tla region, could be induced in several combinations of H-Zidentical strains differing at Qed-1. Cells of some strains, like B 10.BR, NZB, and SWR, responded directly in culture, even without priming in vivo.     

Quantitative trait loci (QTL) for circadian rhythms of locomotor activity in mice

The loomotor activity of male mice (Mus musculus) was monitored by infrared photoelectric beams under three lighting regimens: LD (12 h of light and 12 h of dark), DD (constant dark), and LL (constant broad-spectrum light, 10 lux). Circadian period of locomotor activioty (τ) was compared among 3 inbred strains of mice, C57BL/6J (B6), BALB/c (C), and DBA/2J (D2), and 26 recombinant inbred strains B×D (B6×D2). the τ under both continuous low-intensity light and continuous darkenss varied significantly among strains. Under DD the mean τ was 23.8 h for B6, 23.7 h for D2, and 23.6 h for C. Under LL the mean τ was 25.1 for B6, 23.9 h for D2, and 25.5 h for C. Frequency histograms of the mean τ of 26B×D RI mouse strains (three to seven animals per strain) in either DD or LL and the difference between them, Δτ, had distributions which appeared unimodal, suggesting polygenic inheritances. The narrow-sense heritability determined using 26 strains of B×D RI mice was about 55% for τ and about 38% for both τ in LL and Δτ. An estimated four loci contribute to the variance of τ in constant darkness and five to the variance of τ in constant low-intensity light among the strains studied. Quantitative trait locus (QTL) analysis identified several potential genetic loci associated with τ in constant darkness, τ in constant low-intensity light, and Δτ. The associations of highest probability for each of these traits were theD1Nds4 locus (p<0.001) on mouse chromosome 1, theD5Ncvs52 locus (p<.05) on mouse chromosome 5, and thePmv12 locus (p<.01) at 70 cM on mouse chromosome 5, respectively. A QTL identified for τ was associated (p<.05) with theD2NDS1 marker at 45 cM on chromsome 2 near the Ea 6 marker at 46 cM associated (p<.05) with that reported for the period of wheel running activity in seven C×B RI strains (Schwartz, W. J., and Zimmerman, P.,J. Neurosci. 10:3685 1990).     

Basidiomycetousras cDNA functionally replaces its homolog genes in yeast

It was shown by a plasmid exchange procedure that the Ras-encoding cDNA of the basidiomyceteLentinus edodes (namedLeras cDNA) can functionally replace its homolog genes (ScRAS1 andScRAS2) in the yeastSaccharomyces cerevisiae to maintain the viability of an yeast strain containing genetic disruptions of bothRAS genes. The strain replaced by aLeras–cDNA-carrying plasmid, however, grew slower than the strains replaced by aScRAS1– or aScRAS2–carrying plasmid. The intracellular level of cAMP in the strain harboring theLeras–cDNA-carrying plasmid was clearly higher than that of a parental strain which maintains a plasmid carrying theS. cerevisiae cAMP-dependent protein kinase catalytic subunit C₁ gene,TPK1, but was lower than that in a strain harboring anScRAS2–carrying plasmid. These results suggest that theLeras cDNA can complement theras1 ^– ras2^– mutation of yeast by virture of the stimulation of adenylate cyclase activity, although the complementation is not as efficient as that obtained by expressing theScRAS2 gene.     

A test for rare male mating advantage at an “enzyme locus” inDrosophila

Matings betweenDrosophila pseudoobscura strains differeing at the amylase (Amy) locus were observed in Elens-Wattiaux chambers. Males homozygous for eitherAmy ^1.00 orAmy ^0.84 alleles in the CH gene arrangement enjoyed a mating advantage when moderately rare, but none when quite rare. The minority male advantage for strains differing at theAmy locus, and other loci linked to it, was comparable in size to that observed between strains carrying the ST or CH gene arrangements, and either alike or different at theAmy locus. Although some features of our results are puzzling, there is evidence that theAmy locus and others for which it serves as a marker have effects on mating behavior which include some degree of rare male mating advantage.     

Single-locus control of saccharin intake in BXD/Ty recombinant inbred (RI) mice: Some methodological implications for RI strain analysis

Thesac locus, with a major effect on saccharin preference, was discovered by Fuller (1974) in C57BL/6J (B6), DBA/2J (D2), and derived crosses, and is now supported in the BXD/Ty recombinant inbred (RI) series by a marked bimodal distribution in saccharin preference among 20 strains. The B6 allele led to increased saccharin preference compared to the D2 allele. Since the search for bimodal distributions reflecting major gene loci is an essential part of RI strain analysis, a new statistical method is proposed to test for bimodality, and comparisons are made to previously proposed methods. Another new RI method, quantitative trait loci (QTL) analysis, allows provisional detection and mapping of minor as well as major gene loci. Using this method as a screen, significant associations with saccharin preference were suggested with marker loci on portions of six chromosomes. One of these, theD12nyu1 locus on chromosome 12, was independently supported in a panel of standard (non-RI) inbred strains also tested for saccharin preference. It is unclear whether this reflects thesac locus.This work was supported by NIDA Contracts 271-87-8120 and 271-90-7405, PHS Grants DA05228, AA08621, and AA08125, and two grants from the Department of Veterans Affairs.     

Identification of 46 novel SNPs in the 130-kb region containing a myocardial infarction susceptibility gene on chromosomal band 6p21

We identified a total of 187 single-nucleotide polymorphisms (SNPs) at 11 gene loci in the 130-kb region on chromosome 6p21 containing a gene strongly associated with myocardial infarction (MI). By comparing our data with SNPs deposited in the dbSNP database at the National Center for Biotechnology Information, 46 of these SNPs (24.6%) were considered to be novel: four were identified in the P5-1 locus, 14 in the MICB locus, nine in the BAT1 locus, one in the ATP6V1G2 locus, six in the NFKBIL1 locus, one in the LTA locus, one in the TNF locus, five in the LST1 locus, four in the LY117a locus, and one in the AIF-1 locus. The SNP map presented here should provide as useful resource not only for examining the relationships between genotypes and susceptibility to the MI phenotype, but also for scanning of complex diseases mapped to this local segment on chromosome 6.     

ANALYSIS OF Ly5 CHROMOSOME 1 POSITION USING ALLELIC DIFFERENCES AND RECOMBINANT INBRED MICE

Differences between the mouse Ly5^a and Ly5^b alleles can be distinguished on the basis of polymerase chain reaction (PCR)-restriction enzyme analysis and differential monoclonal antibody reactivities. To more precisely map the Ly5 gene on the mouse chromosome 1, analytical DNA and protein tests were performed on recombinant inbred strains of mice prepared from SJL/J (Ly5^a) and B ALB/cke (Ly5^b) progenitor strains. Each recombinant inbred strain was characterized to determine whether it carried the Ly5^a or Ly5^b allele. Both assays, DNA-PCR and protein-immunofluorescence, yielded identical results for each strain examined. Placement of the Ly5 gene with respect to other characterized markers of mouse chromosome 1 for these recombinant inbred mouse strains shows a gene order of Idh-1.Ity:Pep3:/Ly5, CfhJ.     

Quantitative trait loci associated with the behavioral response of B×D recombinant inbred mice to restraint stress: A preliminary communication

Quantitative trait loci (QTL) analysis was used to make provisional identification of loci containing genes influencing vulnerability to stress. The effect of restraint stress on openfield activity was measured in C57BL/6J and DBA/2J inbred strains of mice and in 22 B×D recombinant inbred strains of mice. QTL analyses were performed by correlating the behavioral delta scores for each group with the strain distribution pattern of 1300 markers for the B×D mice. A significant association was found between postrestraint rearings during min 5 through 8 in the open field and theLamb2 marker on chromosome 1 (r=.718,p<.0001). Significant associations at thep<.0001 level were also found between baseline open-field rearings of control mice during min 0 through 5 and theZp3, Ache, andMr66-1 markers on chromosome 5, baseline open-field rearings of control mice during min 5 through 8 and thePmv42 marker on chromosome 15, and open-field rearings of experimental mice during min 0 through 5 and theD11Ncvs61 marker on chromosome 11.     

pH sensitivity of Schizosaccharomyces pombe: effect on the cellular phenotype associated with lacZ gene expression

We report on a series of experiments inSchizosaccharomyces pombe to detect the blue-colour colony phenotype associated with expression of theEscherichia coli lacZ gene. Increasing the pH in solid minimal medium to optimize blue colony colour revealed a pH-sensitive phenotype in auxotrophic strains requiring uracil and leucine as external supplements. This phenotype was observed among commonS. pombe stock strains, 5-fluoroorotic acid (5-FOA)-selected strains, and random genetic segregants. Growth of prototrophicS. pombe strains 972 and 975 or the adenine auxotrophic strain NCYC 1860 were unaffected by an increase in external pH. Analysis of genetic segregants from three independent crosses indicated that a single auxotrophic marker (ura4 ^- orleu1-32) was sufficient for yeast cell-growth inhibition when the medium pH was increased above 6.6. In contrast, growth of aSaccharomyces cerevisiae strain isogenic to AH22, requiring uracil, leucine and histidine, was unaffected by changes in the pH of the medium. These observations suggest that uptake of uracil and leucine intoS. pombe cells is compromised by alterations in external pH. Our results have implications for detection of thelacZ gene-encoded bluecolour colony phenotype inS. pombe, which is optimized by growth in the presence of 5-bromo-4-chloro-3-indolyl--D-galactoside (Xgal) at pH 7.0. We discuss the conditions under which this blue-colour phenotype can be routinely observed inS. pombe.     

Differential sensitivity to gliotoxin of virulent and attenuated poliovirus strains and its possible use as a genetic marker

Summary Gliotoxin was shown to exert a less inhibitory effect on standard virulent type 1 and 2 poliovirus strains than on attenuated homotypie strains. This did not apply to type 3 standard strains since the virulent Saukett virus proved to be inhibited to the same degree as the attenuated Leon 12a₁b, WM III and USOL D bac strains. An increase in gliotoxin-resistance after several intra-human passages of different live polio vaccine strains occurred only in a vaccinee fed the type 1 LSc2ab strain.A strong correlation between the gliotoxin marker and therct/40 andMS characters was found in type 1 and 2 poliovirus strains isolated from patients and vaccinees. No correlation was observed between thegli marker and thermoinactivation at 50°C or sensitivity to dextran sulphate, guanidine and HBB.The covariation between therct/40 andgli characters seems to be asymmetrical sincegli ^r mutants of the LSc2ab strain maintained theirrct/40 ^– character, whilerct/40 ⁺ mutants of the same parental strain displayed increased gliotoxin-resistance. The value of thegli marker for genetic and epidemiological studies is discussed.     

Female sexual receptivity is defective in juvenile hormone-deficient mutants of theapterous gene ofDrosophila melanogaster

During reproductive maturation of female insects, the acquisition of sexual receptivity is coordinated with ovarian development. Juvenile homone regulates vitellogenesis in the ovaries, but the action of this hormone in the development of sexual behavior is less well-understood. A strain ofDrosophila melanogaster carrying a mutation in theapterous gene(ap ⁴) was known to exhibit arrested vitellogenesis (rescuable by applying exogenous juvenile hormone), sterility of both sexes, and a deficiency of juvenile hormone. In this study, we examined the effects of mutations ofap on female receptivity and its relationship to juvenile hormone. We observed abnormally low female receptivity in homozygousap strains, and heteroallelic combinations ofap mutations exhibited low receptivity. For female receptivity,ap showed no dominance (i.e.,ap/ap ⁺ was intermediate betweenap/ap andap ⁺/ap ⁺). Low receptivity mapped genetically to theap locus. The reduction in female receptivity in these mutants is positively correlated with levels of juvenile hormone synthesized by their corpora allata.This work was supported in part by The Scheinfeld Center for Humans Genetics in the Social Sciences (J.R.), The National Science Foundation (BNS-882 1339 to J.R.), BARD (No. IS-1664-89R to D.S.), The Israel Cancer Research Fund (grant to D.S.), The Rekanati Foundation of Tel Aviv University (grant to D.S.), and The Israeli Fruit Council (award to M.A.)     

A new genetic locus mapped from behavioral variation in mice: Audiogenic seizure prone (asp)

Audiogenic seizure susceptibility to the initial presentation of intense sound was studied in generations of mice derived from the susceptible DBA/2J and the resistant C57BL/6J inbred strains. The experimental results led to the detection, location, and position of a new genetic locus affecting behavior in mice. The locus is designatedasp (audiogenic seizure prone), and the pattern of inheritance for high seizure risk is recessive. Evidence for the mapping ofasp results from the following experimental findings: (1) frequencies of seizures for each of six segregating generations obtained by crossing C57BL/6J and DBA/2J conformed to expectations based upon a single locus model of genetic inheritance; (2) theasp-locus is loosely linked to theb-locus and thus resides on Linkage Group VIII of the mouse; (3) linkage relationships betweenasp and other named mutations on LG VIII, pintail (Pt),misty (m), brown (b), and autosomal glucose-6-phosphate dehydrogenase (Gpd-1), indicate that the position of theasp-locus is towards the centromeric end of the chromosome. The order of loci isasp-b-Pt-Gpd-1; (4) no linkage was observed betweenasp and thed-locus of Linkage Group II. These experiments illustrate that new genetic loci, whose allelic alternatives exert major effects on chosen behavioral characters, can be identified and mapped in a directed search.In memory of Dr. Margaret M. Dickie who died July 4, 1969. Supported by NIH Research Grant MH 11327 from the National Institute of Mental Health and partly by an allocation from the American Cancer Society Institutional grant IN-19 to the Jackson Laboratory. The principles of laboratory animal care as advocated by the National Society for Medical Research are observed in this laboratory.     

Host genetic control of mouse hepatitis virus type-4 (JHM strain) replication. II. The gene locus for susceptibility is linked to the Svp-2 locus on mouse chromosome 7

Peritoneal macrophages were used to analyze host genetic control of MHV-4 infection in the 14 recombinant-inbred strains between susceptible SWR/J and resistant SJL/J progenitor strains. 4 strains were resistant to MHV-4 infection, while the remaining 10 strains were productively infected. Based upon the strain distribution pattern of susceptibility the gene locus for MHV-4 susceptibility is linked to the Svp-2 locus on the proximal end of mouse chromosome 7. This strain distribution pattern of susceptibility, and hence linkage, was determined to be identical for another MHV strain, MHV-A59. We have suggested that this locus-controlling susceptibility to MHV-4 and MHV-A59 be designated Hv-2.     

Mapping of two genes that influence susceptibility to audiogenic seizures in crosses of C57BL/6J and DBA/2J mice

The difference in susceptibility to audiogenic seizures (AGS) between C57BL/6J and DBA/2J inbred strains of mice is due to multiple genetic factors. AGS susceptibility was tested in 21-day-old mice from classical crosses, BXD recombinant inbred (RI) strains, a congenic DBA/2N.B6N-Ah ^b inbred strain and crosses between the BXD RI strains and DBA/2J. Analysis of these data reveals that the variation in AGS susceptibility between these two strains results from allelic differences at three or more loci. Most of the variation is due to allelic differences at two loci. The first,Asp-1 (formerlyIas), is a major gene located on chromosome 12, betweenAh andD12 Nyul. The second,Asp-2 (formerlyasp), is a minor gene located on chromosome 4, tightly linked tob. The negative correlation of brain stem Ca²⁺-ATPase activity and AGS susceptibility in the BXD RI strains suggests that the strain difference in Ca²⁺-ATPase activity is inherited as a polygenic trait and thatAsp-1 andAsp-2 are linked to, or identical to, factors that influence Ca²⁺-ATPase activity.This work was supported by grants from the HRC Foundation, NIH (NS 20820, NS 23355, and NS 24826), and NSF (BNS 8305449).     

Hypothetical quantitative trait loci (QTL) for circadian period of locomotor activity in CXB recombinant inbred strains of mice

The locomotor activity of male mice (Mus musculus) of 13 CXB (BALB/cBy × C57BL/6J) recombinant inbred (RI) strains and their progenitor strains was monitored for 4 to 6 weeks by infrared photoelectric beams under constant dark. The circadian period (τ) of locomotor activity was calculated and used in quantitative trait locus (QTL) analysis of strains' means. Results were compared with potential QTL found in a previous study of the BXD RI series. The mean τ of 13 CXB RI mouse strains (three to six animals per strain) in constant dark had a unimodal distribution suggesting polygenic inheritance. A number of potential QTL were found for this trait. There were two associations atp<.001,H23 on chromosome 3 andPmv16 on chromosome 16. A region of chromosome 1 was associated with τ in both CXB and BXD RI series. There was also a conjunction with a locus determined from QTL analysis of the previously reported τ of wheel running activity in seven CXB RI strains (Schwartz and Zimmerman, 1990).     

Resistance to cadmium is under the control of the CAD2 gene in the yeast Saccharomyces cerevisiae

Summary A cadmium-resistant strain, X3382-3A, which is able to grow in a medium containing 0.2 mM cadmium sulfate, was picked out from our laboratory stock strains of Saccharomyces cerevisiae. The cadmium resistance of this strain is controlled by a single dominant nuclear gene, denoted as CAD2. The locus of CAD2 was mapped by gene linkage to a site 15.5 centimorgans to the right of the his7 locus on the right arm of chromosome II. The cadmium resistance of the strain carrying CAD2 was evaluated for its properties of cadmium uptake, cadmium distribution and cadmium-metallothionein formation, in comparison with those of some other strains. The results suggest that the novel type of cadmium resistance controlled by CAD2 does not involve production of a cadmiumm-metallothionein.