Genetic control of glucuronidase in mice

Two electrophoretically distinct components of glucuronidase have been resolved in extracts of murine liver. A mutation which results in a ten-fold reduction in liver glucuronidase activity leads to a reduction in intensity of both components. Since the substrate dependencies of both mutant (gg) and wild-type (GG) glucuronidase have previously been shown to be identical, it is suggested that the mutation results in a decreased concentration of liver glucuronidase molecules. Furthermore, the anodal electrophoretic component is shown to be preferentially localized in lysosomes, while the cathodal component is primarily microsomal. The difference in mobility of the two components may reflect a difference in membranous elements attached to the extracted glucuronidase molecule.This paper was presented at a symposium entitled Genetic Control of Mammalian Metabolism held at The Jackson Laboratory, Bar Harbor, Maine, June 30–July 2, 1969. The symposium was supported in part by an allocation from NIH General Research Support Grant FR 05545 from the Division of Research Resources to The Jackson Laboratory.This investigation was supported by a grant from the Pharmaceutical Manufacturers Association Foundation.     

Genetic control of tolerance induction to human gamma-globulin in mice.

Susceptibility to tolerance induction with monomeric human gamma-globulin (HGG) was tested in different inbred strains of mice. The results indicated a differential tolerance susceptibility among the strains and that the basis for the variation is genetic in nature. By using a protocol that permits genetic analysis, F1, F2, and backcross generations of the parental strains SJL/J and C3H/Bi were examined. A multigenic control model by H-2-linked and non-H-2-linked genes showing Mendelian autosomal inheritance is proposed.     

Genetic control of catalepsy in mice

Pinch-induced immobility (catalepsy) was studied in mice of 9 inbred strains. CBA mice were found to be different from those of other strains both by the highest percent of cataleptics (56%) and by the highest duration of immobility. The Mendelian analysis of predisposition to catalepsy was performed on CBA and AKR mice strains contrasting in this feature. Reciprocal F1 hybrids did not display any catalepsy. Manifestation of cataleptics in the F2 and in CBA x F2 backcrosses suggested that catalepsy was inherited as a recessive, monogenic, autosomal feature.     

Genetic effects on male mouse kidney glucuronidase activity

Kidney β-glucuronidase activity in C57BL/Kl and DBA/2/Kl male mice differs about tenfold, C57 giving low and DBA high values. Another C57 subline, C57BL/6J, has slightly higher activity than C57BL/Kl. There is an association between the kidney glucuronidase activity and coat color determined by the buff locus, which indicates that part of the variation is due to differences at the Gur locus. The bf allele per se raises the activity of the enzyme. The backcross distributions give evidence that at least one more locus is involved.     

Genetic control of glucokinase activity in mice

Inbred strains of mice were surveyed for liver glucokinase activity. Mice of all strains studied could be distributed into three groups with high, intermediate, and low levels of enzyme activity. Genetic analysis using crosses and backcrosses with prototype high (C3H/HeJ) and low (RF/J) strains revealed that glucokinase activity was controlled by a single gene. The name glucokinase and gene symbol Gk are suggested for this gene. The Gk ^a allele designates the strain with high glucokinase activity, while Gk ^b represents the allele in the strain with the low enzyme activity. The interaction of fasting and diabetes on the activity of glucokinase in these two strains is described.Supported in part by United States Public Health Service Research Grant CA 05873 from the National Cancer Institute. The Jackson Laboratory is fully accredited by the American Association for the Accreditation of Laboratory Animal Care.     

Genetic control of ganglioside biosynthesis in mice

The enzymatic basis for the differences in hepatic ganglioside patterns in the mouse strains C57Bl/6 and Swiss White (SW) was investigated. SW has a “Swiss-type” ganglioside profile, expressing G_M1 ^? and G_D1a ^? in addition to G_M2 ^? as major hepatic gangliosides, whereas C57Bl/6 shows a “G_M2-type” profile, expressing only G_M2 ^? as the major hepatic ganglioside. The enzyme UDP-galactose:G_M2 ganglioside galactosyltransferase (G_M2-GalT), which catalyzes the synthesis of G_M1 ganglioside, showed a four- to fivefold elevation in intact and solubilized liver Golgi membrane fractions of the SW strain compared to C57Bl/6. Crosses between C57Bl/6 and SW produced an F₁ generation with a hepatic ganglioside and enzymatic phenotype intermediate between those of the two parental strains. All three genotypic groups show two forms of the Golgi apparatus enzyme with isoelectric points of 6.5–6.8 and 8.3–9.0. The simplest mode of action of genes which control the enzymatic phenotype that would be consistent with these findings are one or two structural genes or one or two cis-regulatory genes affecting the rate of enzyme synthesis.     

Genetic control of ornithine transcarbamylase induction in chick kidney

After ornithine transcarbamylase (OTC) induction by egg-yolk feeding, OTC activity increases rapidly in chicks bearing an Ocb gene. This response to an egg yolk diet does not appear in chicks having no Ocb gene (showing low OTC activity). The chicks showing intermediate OTC activity also respond to the diet, but moderately. Crossing experiments revealed that OTC induction by egg yolk-diet feeding is inherited as a simple autosomal dominant trait. Since a chick develops during embryonic life by utilizing egg yolk from the yolk sac, the variation of OTC activity among chicken breeds and within a breed in 2-day-old chicks seems to depend on a genetically controlled difference of inducibility by egg yolk. The Ocb is an autosomal gene which controls the induction of OTC activity, but it is difficult to explain the consistent difference in OTC activity between sexes by involving this gene or this locus alone.     

Genetic control of novel food preference in mice

In food preference studies, mammals are often categorized as being either neophilic or neophobic, i.e., preferring or disliking a novel-tasting food. To date, the genetic factors influencing novel food preference have not been elucidated. To understand this phenomenon, we investigated the genetics of food preference in eight inbred strains of mice. We gave them plain-, cinnamon-, or cocoa-flavored powdered food on day 0 for 45 min and then a choice of cinnamon- or cocoa-flavored food 14 days later. We determined their preference for novel versus already-experienced flavored food and found that some inbred strains chose the food that they had been given previously, while others chose a different food. In particular, the DBA/2 strain chose more cinnamon-flavored food after it was pre-exposed to cinnamon, while the B6 strain chose less cinnamon-flavored food after this initial exposure. The BXD recombinant inbred (RI) strain set was then used to map quantitative trait loci (QTLs) that influence this novel food preference. One of these QTLs was found to map to the distal end of Chromosome (Chr) 8.     

Enzymic effects of beta-glucosidase destruction in mice. Changes in glucuronidase levels.

1. The injection into mice of a single dose of conduritol B epoxide, a covalent inhibitor of glucosidases, quickly produced changes in tissue levels of beta-D-glucuronidase (EC 3.2.1.31). The specific activity of the enzyme decreased in liver, spleen and kidney while brain showed little change. The inhibitor did not act on glucuronidase in vitro, so the effect of the inhibitor is complex, possibly a result of the loss of glucosidase activity. Since glucuronidase contains glucose, we suggest that the transport of the enzyme between subcellular regions and tissues involves loss of part of the glucose moieties. 2. Levels of glucocerebrosidase (D-glucosyl-N-acylsphingosine glucohydrolase, EC 3.2.1.45) dropped very rapidly after epoxide injection, reaching a minimum at 1 h in liver. There was a noticeable restoration of activity within the next 1--2 h. Aryl beta-glucosidase (EC 3.2.1.21) decrease somewhat less than cerebrosidase, reaching a minimum within 2 h. It too showed some recovery of activity within 3 h. 3. Acid phosphatase rose slightly in liver but not in brain. alpha-L-Fucosidase and angiotensin-converting enzyme were not affected by the epoxide injection. The latter two enzymes are known to contain glucose. 4. Injection of a hemolyzing agent, phenylhydrazine, produced an increased level of glucuronidase in liver and spleen within 6 days, but not in kidney. This enhancement was a little less in mice previously injected with the glucosidase inhibitor. 5. Mice injected with the epoxide once a day eight times showed a distinct rise in brain glucuronidase level, as well as a rise in brain weight. However, the other organs showed only the same decrease in glucuronidase specific activity noted with the single injection protocol. It is suggested that the difference is due to the blood-brain barrier, which could slow the loss of brain glucuronidase from the extracellular fluid.     

Genetic control of T-Cell subset representation in inbred mice

Lyt-2+ T cells constitute a significantly greater proportion of the total peripheral T-cell population in C57BL mice than in BALB/c and other mouse strains. The inheritance of this differential representation of Lyt-2- vs. Lyt-2+ T cells was studied by two-color immunofluorescence analysis of peripheral T cell subsets in BALB/c, C57BL, F1 and F2 generations, and in CXB recombinant inbred strains. It was shown that the C57BL phenotype (low Lyt-2-/Lyt-2+ ratio) is a dominant Mendelian character. Studies of subpopulations of thymocytes and of early thymus emigrants indicate that the representation of mature Lyt-2- and Lyt-2+ T cells is influenced by mechanisms of selection or differential turnover in the peripheral lymphoid organs, but that thymic and prethymic influences may also play a role.     

Genetic control of scrapie and Creutzfeldt-Jakob disease in mice

Genetic control of experimental scrapie and Creutzfeldt-Jakob disease (CJD) was studied in inbred strains of mice by measuring the times from intracerebral inoculation with the agents to the onset of neurological dysfunction. Every strain of mice examined was susceptible to infection; however, a wide range of incubation times was found for both scrapie and CJD. New Zealand (NZ) mice, which eventually develop an autoimmune disorder, were inoculated intracerebrally with 10(6) ID50 units of the scrapie agent in a Chandler isolate. NZW mice showed incubation periods of less than 95 days; this is the shortest period recorded for any murine host with scrapie. In NZB and NZB X W F1 mice, the incubation periods were approximately 130 days and were similar to those in BALB/c and C57BL mice. Male and female NZ mice exhibited scrapie incubation periods of the same length. Similar results were obtained when B10.Q and C57BL/6J mice were inoculated intracerebrally with 10(4) ID50 units of the CJD agent in a K.Fu. isolate. These observations define a genetic locus or loci controlling the length of scrapie and CJD incubation periods; alleles coding for longer incubation times appear to be autosomal dominant. When congenic mice with a C57BL/10J background differing only in their H-2 haplotypes were studied, the results showed that the D subregion of the H-2 complex played a central role in controlling the length of the CJD incubation period. The q allele at the D subregion resulted in shorter incubation times, whereas the d allele resulted in long incubation times. The p, s, b, and k alleles gave intermediate incubation times. We propose the symbol PID-1 for designating this genetic locus which is located within the D subregion of the major histocompatibility (H-2) complex on murine chromosome 17. In addition, observations on congenic mice provide evidence for the influence of sex on CJD incubation periods. In some strains of inbred mice, males showed significantly shorter incubation periods compared with those for females with experimental CJD. These studies with inbred mice have defined previously unrecognized genes that control the length of scrapie and CJD incubation periods.     

Genetic control of hormone-induced ovulation rate in mice.

The nature of genetic differences in ovarian responsiveness to gonadotropins was examined in mouse strains and subspecies. Hormone-induced ovulation rate (HIOR) differed 5-fold between Mus musculus strains A/J (10.3 +/- 1.6 eggs in cumulus) and C57BL/6J (B6) (47.3 +/- 2.5 eggs in cumulus), and 6-fold among Mus spretus lines and crosses. Subspecies differed up to 10-fold in HIOR (Mus spretus/Ros: 4.8 +/- 1.0 eggs in cumulus versus B6). An additional experiment examined the genetics of HIOR in crosses. The number of eggs ovulated in response to equine chorionic gonadotropin (CG)/human CG averaged 8.4 +/- 0.9 in A/J, 40.7 +/- 1.7 in B6, 33.9 +/- 1.6 in B6AF1, and 20.2 +/- 0.3 in (B6xA)xA backcrosses. The 5-fold genetic differences in hormone-induced ovulation rate between Mus musculus strains A/J and B6 segregated in backcrosses as though they were controlled by the action of approximately 3 loci with major effects. This study demonstrates genetic variation in HIOR both within and between mouse subspecies, and provides confirmation that genetic differences are a major source of variation in the regulation of ovarian responsiveness to gonadotropins.     

Genetic control of streptococcus-induced hepatic granulomatous lesions in mice

Hepatic granulomatous lesions were induced in mice by a single intraperitoneal injection of 3 mg of disrupted Streptococcus pyogenes cell-wall material. Mice carrying the H-2 ^b or H-2 ^k haplotypes were highly susceptible to the induction and three weeks after the injection produced numerous granulomas. In contrast, mice of the H-2 ^d haplotype were resistant and produced only a few hepatic granulomas. Resistance was inherited as a dominant trait and in the backcross generation segregated together with the H-2 ^d phenotype. Testing of the H-2-recombinant mice indicated that the putative gene(s) determining resistance/susceptibility is located to the right of the S and to the left of the D region. Thes location corresponds to the recently described gene cluster consisting of tumor necrosis factor (TNF) and lymphotoxin genes and several BAT sequences. The known effect of TNF on granuloma formation in mice is consistent with a possible effect of TNF genes, and their variants, on S. pyogenes-inducibility of hepatic granulomas in mice. Address correspondence and offprint requests to: M. B. Zaleski.     

Genetic control of interleukin-2 production in inbred mice

BALB/c mice (H-2d haplotype) produced IL 2 better than C57BL/6 mice (H-2d haplotype). However genetic analysis in F2 generation demonstrated independent segregation of the IL 2 production intensity and H-2 haplotype. Investigation of the IL 2 production intensity in BALB/c, C57BL/6 and their F1 and F2 generation revealed that this was controlled by only one gene.     

Genetic control of retroviral disease in aging wild mice

Different populations of wild mice (Mus musculus domesticus) in Los Angeles and Ventura Counties were observed over their lifespan in captivity for expression of infectious murine leukemia virus (MuLV) and murine mammary tumor virus (MMTV) and for the occurrence of cancer and other diseases. In most populations of feral mice these indigenous retroviruses were infrequently expressed and cancer seldom occurred until later in life (>2 years old). MMTV was found in the milk of about 50% of wild mice, but was associated with only a low incidence (>1%) of breast cancer after one year of age. By contrast, in several populations, most notably at a squab farm near Lake Casitas (LC), infectious MuLV acquired at birth via milk was highly prevalent, and the infected mice were prone to leukemia and a lower motor neuron paralytic disease after one year of age. These two diseases were both caused by the same infectious (ecotropic)strain of MuLV and were the principal cause of premature death in these aging LC mice. A dominant gene called FV-4^R restricting the infection with ecotropic MuLV was found segregating in LC mice. Mice inheriting this FV-4^R allele were resistant to the ecotropic MuLV associated lymphoma and paralysis. The FV-4^R allele represents a defective endogenous MuLV provirus DNA segment that expresses an ecotropic MuLV envelope-related glycoprotein (gp70) on the cell surface. This FV-4^R encoded gp70 presumably occupies the receptor for ecotropic MuLV and blocks entry of the virus. The FV-4^R gene was probably acquired by the naturally occurring crossbreeding of LC feral mice with another species of feral mice (Mus castaneus) from Southeast Asia. The FV-4^R gp70 does not block entry of the amphotropic MuLV that uses a separate cell surface receptor. Therefore LC mice continued to be susceptible to the highly prevalent but weakly lymphogenic and nonparalytogenic amphotropic strain of MuLV. The study points out the potential of feral populations to reveal genes associated with specific disease resistance.     

Genetic variation in spontaneous ovulation rate and LH receptor induction in mice

Selection for litter size (Line S1) and for post-weaning body weight gain (Line G) increased spontaneous ovulation rate in mature females by 69 and 73%, respectively, over that of randomly bred control mice (Line C). Inbreeding from S1 mice with selection for litter size produced highly inbred lines with elevated ovulation rates. Inbreeding from Line C mice produced a 21% divergence among lines, but did not depress the mean ovulation rate. Crosses of these lines revealed little heterosis in ovulation rate. LH receptors were induced by treating females from 22 days of age with diethylstilboestrol for 4 days and FSH for 2 days. The in-vitro binding of 125I-labelled hCG per microgram DNA decreased 56% in response to selection for litter size and increased 57% in response to selection for body weight gain, indicating high susceptibility of this trait to genetic change. Inbreeding from Line C mice produced a 135% divergence amongst lines, but did not depress the mean LH receptor induction. Body weight had significant effects on ovulation rate and LH receptor induction. These results show that selection for litter size and for rapid post-weaning body weight gain increases ovulation rate, but we suggest that different mechanisms are involved in these responses.     

Genetic control of serine dehydratase and phosphoenolpyruvate carboxykinase in mice

Inbred strains of mice were found to differ with regard to their endogenous activities of the liver enzymes serine dehydratase (SD) and phosphoenolpyruvate carboxykinase (PEPCK). The strain distribution patterns for the activity of each enzyme were identical. On feeding of high-protein diets or on fasting, the activities of both enzymes were induced in a concordant fashion which suggested the control of both enzymes by a single gene. Genetic analysis established that the induction of both enzymes on feeding of high-protein diets was controlled by a single gene (Sdr-1), whereas the induction of SD, but not of PEPCK, on fasting was controlled by different single gene (Sdr-2). The lack of segregation of the backcross generations with respect to PEPCK activities obtained on fasting precluded the establishment of any association of the response of PEPCK to fasting with either the Sdr-1 or Sdr-2 locus. The strain of mice (BALB/cJ) that had the ability to maximally induce both gluconeogenic enzymes under both dietary treatments failed to survive a fast as long as those strains with less ability to induce. This suggests that the ability to induce key enzymes in gluconeogenesis when food is unavailable is of little consequence with regard to their ability to produce essential nutrients necessary for survival.     

Genetic control of acquired resistance to visceral Leishmaniasis in mice

A series ofH-2 and non-H-2 congenic resistant (CR) strains on a C57BL/10Sn background were infected with 10⁷ amastigotes ofLeishmania donovani. Non-H-2 congenic strains B10.LP-H-3 ^b and B10.CE(30NX) and (B10.LP-H-3 ^b × B10)F₁ hybrids showed a very rapid decrease in liver-parasite burdens beyond day 21. Parasite counts for these strains at day 35 were significantly lower than for all other strains tested. The rapid decrease in parasite numbers, massive lymphocellular infiltration into the liver and strong delayed hypersensitivity reactions to parasite antigens in strains congenic for a portion of chromosome 2 indicated that acquired immunity toL. donovani was controlled by a dominant gene at or near theIr-2 locus. In addition, B10.129(10M) mice, which differ from C57BL/10Sn at theH-11 locus, showed highly significant increases in parasite numbers at day 35. Other observations supporting the absence of acquired immunity in B10.129(10M) included negative delayed hypersensitivity tests to parasite antigens and the absence of lymphocellular infiltrate into the liver. Although the differences were not as pronounced,H-2 CR strains withH-2 ^b ,H-2 ^a , andH-2 ^k haplotypes also showed significantly greater decreases in parasite numbers by day 35 as compared to otherH-2 CR strains.