The vit gene maps to the mi (microphthalmia) locus of the laboratory mouse.

The murine model for human vitiligo (the vit/vit mouse) develops progressive depigmentation of the pelage, skin, and eyes. The vit gene is inherited as an autosomal recessive. We have used classical breeding and isozyme marker analysis to map this vit gene that produces a vitiligo-like condition in the mouse. Crossbreeding the C57BL/6J-vit/vit mice with C57BL/6J mice carrying the Miwh and/or miws alleles at the microphthalmia locus resulted in mutant phenotypes, demonstrating absence of complementation. When vit is heterozygous with the Miwh allele, a "blotched" pigment pattern results. When it is heterozygous with the miws allele, a novel expression of the vitiliginous phenotype results. Further mating analysis of these crossbred populations demonstrates allelic inheritance between vit and the alleles at the microphthalmia locus. Other breeding studies using alleles at the agouti, belted, brown, dominant spotting, extension, mahogany, patch, and piebald loci did not demonstrate pigmentation explainable by allelic inheritance with the vit gene. Also, vit was tested for linkage with isozyme markers located on chromosomes 1, 4, 5, 7, 9, and 11, and results were negative. Therefore, the vit (vitiligo) gene of the laboratory mouse has been mapped to the mi (microphthalmia) locus on chromosome 6. The gene properly should be designated as mivit.     

Mapping of genetic modifiers of Eya1 bor/bor in CAST/EiJ and BALB/cJ that suppress cochlear aplasia and associated deafness

Mice homozygous for the hypomorphic allele Eya1 ( bor ) exhibit cochlear aplasia, with associated deafness, and renal hypoplasia, similar to Branchio-Oto-Renal syndrome (BOR) in humans. Although much is known about the genetics of the disease, little is known about the factors that modify its phenotypic expression. We have recently detailed two modifier loci (Mead1 and Mead2) in a C3HeB/FeJ-Eya1 ( bor/+ ) x C57BL/6 J intercross that suppress the ear-related phenotypes in our hypomorphic mutants. In this study we report corroborating evidence for our initial finding with the identification of two modifier loci mapping to the same region in CAST/EiJ and BALB/cJ. Furthermore, we describe an additional locus (Mead3) on chromosome 19 in CAST/EiJ, within which the previously cloned suppressor Nxf1 resides. The suppression effect on cochlear coiling was studied on congenic line(s) for each protective allele. The penetrance and suppressor strength of these alleles vary by strain and locus. Eya1 ( bor/bor ) hypomorphs, when homozygous for each of the three protective alleles (CAST/EiJ, C57BL/6 J, or BALB/cJ) at the Mead1 or Mead2 locus, exhibit completely penetrant suppression of cochlear agenesis. At the Mead1 locus, the C57BL/6 J and BALB/cJ alleles have comparable strengths. At the Mead2 locus, the C57BL/6 J and CAST/EiJ alleles have comparable strengths. In contrast, mice with genotype Eya1 ( bor/bor )Mead3(CAST/CAST) exhibit incomplete penetrance (50%) and a wide range of cochlear coiling (1/4-1(1/2) turns). The identification of these additional modifier alleles could provide crucial clues for evaluating the candidate genes.     

The phosphorylase kinase deficiency (Phk) locus in the mouse: Evidence that the mutant allele codes for an enzyme with an abnormal structure

Female (I/St X C57BL/St) F1 mice heterozygous at the sex-linked phosphorylase kinase deficiency locus (Phk) have phosphorylase kinase activities averaging 86% that of mice homozygous for the wild-type allele (C57BL/St), i.e., 72% greater than the sum of one-half the activities of the parental strains. Approximately one-half the phosphorylase kinase activity in the (I X C57BL) F1 muscle extracts had a stability at 42.5 C similar to that of the activity in C57BL extracts (t1/2 = 13.2 min); the other half of the activity in the F1 extracts was more labile (t1/2 = 3.9 min). Two species of phosphorylase kinase activity in F1 muscle extracts were also differentiated with an antiserum prepared in guinea pigs against purified rabbit skeletal muscle phosphorylase kinase. This anti-serum cross-reacted with phosphorylase kinase in C57BL muscle extracts but did not cross-react with skeletal muscle extracts of mice hemi- or homozygous for the mutant allele (I/LnJ). The guinea pig antiserum precipitated 52% as much protein from (I X C57BL)F1 muscle extracts compared to those of C57BL. However, an antiserum prepared against purified rabbit skeletal muscle phosphorylase kinase in the goat cross-reacted with the mutant phosphorylase kinase. The ratio C57BL:(I X C57BL)F1:I of immunoprecipitated protein from skeletal muscle extracts with this antiserum was 1:0.97:1.08. Polyacrylamide gel electrophoresis of the immunoprecipitates in the presence of 0.1% sodium dodecylsulfate showed three subunits for mouse phosphorylase kinase with molecular weights of 139,000, 118,000, and 41,000; these values are similar to the ones obtained with purified rabbit skeletal muscle phosphorylase kinase. These three subunits were also observed in immunoprecipitates from I/LnJ muscle extracts. These results offer substantial evidence (1) that in skeletal muscle extracts of mice heterozygous at the Phk locus the mutant phosphorylase kinase is active, (2) that the gene product of the mutant allele is an enzyme with an abnormal structure, and (3) that the phosphorylase kinase deficiency in I/LnJ skeletal muscle extracts is not the result of the absence of phosphorylase kinase or one of its subunits.     

Allelic polymorphism of murine IgE controlled by the seventh immunoglobulin heavy chain allotype locus

Two alloantisera against hybridoma-derived IgE detected allotypic determinants expressed on the murine s chain. An antiserum raised in BALB/c mice against monoclonal IgE of C57BL/6 origin reacted exclusively with IgE of strains having Igh-1^b (IgG_2a) allotype. The second antiserum, C57BL/6 anti-BALB/c monoclonal IgE, reacted with IgE of strains having Igh-1^a, Igh-1^d, Igh-1^e and Igh-1^j allotypes. The genetic studies of (BALB/c x C57BL/6)F₁ and backcross F₂ animals indicated that the locus controlling the IgE allotype is linked to the Igh-1 locus. This was further confirmed by the possession of respective IgE allotypes by Igh-C congenic mice, BALB/c and BAB-14, C3H.SW/Hz and CWB/Hz. Thus, the allotype detected on the chain is controlled by the seventh murine immunoglobulin allotype locus, and should be designated as the Igh-7 allotype.Abbreviations used in this paper PCA passive cutaneous anaphylaxis - RID radioimmunodiffusion - i.p. intraperitoneally - EA egg albumin - Igh-C immunoglobulin heavy chain constant region locus - DNP 2,4-dinitrophenyl - PBS phosphate-buffered saline - NMS normal mouse serum - KLH keyhole limpet hemocyanin Visiting investigator supported by the Scientific and Humanistic Development Council from the Central University of Venezuela, currently at the following address: Consejo de Desarrollo Cientifico y Universidad Central de Venezuela, Av. Principal Urb. La Floresta Ota., Silenia Caracas, Venezuela.     

Synergistic gene interactions control the induction of the mitochondrial uncoupling protein (Ucp1) gene in white fat tissue

Among a selected group of mouse strains susceptible to dietary obesity, those with an enhanced capacity for Ucp1 and brown adipocyte induction in white fat preferentially lost body weight following adrenergic stimulation. Based on the generality of this mechanism for reducing obesity, a genetic analysis was initiated to identify genes that control brown adipocyte induction in white fat depots in mice. Quantitative trait locus (QTL) analysis was performed using the variations of retroperitoneal fat Ucp1 mRNA expression in progeny of genetic crosses between the A/J and C57BL/6J parental strains and selected AXB recombinant inbred strains. Three A/J-derived loci on chromosomes 2, 3, and 8 and one C57BL/6J locus on chromosome 19 were linked to Ucp1 induction in retroperitoneal fat. Although A/J-derived alleles seemed to contribute to elevated Ucp1 expression, the C57BL/6J allele on chromosome 19 increased Ucp1 mRNA to levels higher than parental values. Thus, novel patterns of C57BL/6J and A/J recombinant genotypes among the four mapped loci resulted in a transgressive variation of Ucp1 phenotypes. Although the extent of the interchromosomal interactions have not been fully explored, strong synergistic interactions occur between a C57BL/6J allele on chromosome 19 and an A/J allele on chromosome 8. In addition to selective synergistic interactions between loci, variations in recessive and dominant effects also contribute to the final levels of Ucp1 expression.     

A new erythrocytic antigen of C57BL/10 (B10) mice

A new antigen, detectable on murine erythrocytes by hemagglutination assay with a (BALB/cCrl X SWR/J)F1 anti-B10.D2n/Sn alloantiserum, is described. Among the inbred and congenic mouse strains tested for reactivity with the antiserum, only the immunizing strain, B10.D2, and its congenic resistant partner, C57BL/10 (B10), reacted. Three other C57 strains, C57BL/6J, C57BL/6By, and C57L, were negative for the antigen. F1 hybrids between B10 and BALB/c, an antigen-negative strain, were positive for the antigen indicating that its expression is dominant. Typing of 39 (BALB/c X (BALB/c X B10)F1) and 62 [BALB/c X B10)F1 X BALB/c) backcross mice revealed that a single gene controls expression of the antigen. The gene is autosomal and not linked to H-2, Ly-4, or the c (albino) or b coat color genes.     

The effects of genetic variation in N-acetyltransferases on 4-aminobiphenyl genotoxicity in mouse liver

Inbred, congenic and transgenic strains of mice were characterized for acetylation of p-aminobenzoic (PABA) and the carcinogen 4-aminobiphenyl (4ABP). C57Bl/6 mice have the NAT2*8 allele, A/J mice have NAT2*9 and congenic B6.A mice have NAT2*9 on the C57Bl/6 background. The first transgenic strain with human NAT1, the functional equivalent of murine NAT2, was also tested. The murine NAT2*9 allele correlated with a slow phenotype measured with the murine NAT2 selective substrate PABA. The two strains having this allele also had a lower capacity to acetylate 4ABP. A line with five copies of the human NAT1 transgene was bred for at least five generations with either C57Bl/6 or A/J mice. There was no significant change in PABA NAT activity on the C57Bl/6 background but a 2.5-fold increase was seen in hNAT1:A/J compared with A/J. The effect of variation in NATs on 4ABP genotoxicity was assessed in these strains. Twenty-four hours after exposure to a single oral dose of 120 mg 4ABP/kg, hepatic 4ABP-DNA adducts were detected by immunofluoresence in all strains. Nuclear fluorescence intensities (mean+/-S.D.) were 41.1+/-3.6 for C57Bl/6, 37.9+/-1.11 for A/J and 36.3+/-2.44 for B6.A. There was no correlation between murine NAT2 alleles and 4ABP-DNA adduct levels. Similar results were seen with the transgenic strains. The data indicate that the range of variation present in these strains of mice was insufficient to alter susceptibility to 4ABP genotoxicity. The impact of these relatively modest differences in the acetylation of the activation of 4ABP may be masked by other competing biotransformation reactions since 4ABP is a substrate for both NAT1 and NAT2. Mouse models with variation in both isoforms are needed to adequately assess the role of variation in NATs in susceptibility to 4ABP genotoxicity.     

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.     

Genes of the H-2 complex regulate the antibody response to murine leukemia virus

The influence of the major histocompatibility complex of the mouse (H-2 complex) on the antibody response against murine leukemia virus (MuLV) was investigated after 3 different ways of virus presentation (milk transmission of virus, spontaneous virus activation, and immunization with inactivated virus). The antibody response against MuLV was measured in the sera of H-2 congenic C57BL V+ sublines (V+ denotes positive for milk-transmitted MuLV), (B10.AV+ X C57BL)F1 mice, (C57BL X AKR)F1 mice and of C57BL animals after immunization with inactivated AKR virus. The pattern of immune responsiveness of the different C57BL strains to MuLV was independent of virus replication and was similar for the 3 ways of virus presentation. Serum antibody levels were controlled by 2 genes within the H-2 complex. The first gene (Ir-MuLV-1) was located in the I-A region and was complemented by a second gene (Ir-MuLV-2), which was situated in the regions to the right of the I-B region. Presence of 2 responder alleles (Ir-MuLV-1+,2+) led to an optimal antibody response (H-2b haplotype). Animals that only expressed a responder allele in the I-A region (Ir-MuLV-1+,2-) were intermediate responders. Animals lacking a responder allele in the I-A region (Ir-MuLV-1-,2+ or Ir-MuLV-1-,2-) were low responders.     

Identification of Soat1 as a quantitative trait locus gene on mouse chromosome 1 contributing to hyperlipidemia

We previously identified two closely linked quantitative trait loci (QTL) on distal chromosome 1 contributing to major variations in plasma cholesterol and triglyceride levels in an intercross derived from C57BL/6 (B6) and C3H/HeJ (C3H) apolipoprotein E-deficient (apoE(-/-)) mice. Soat1, encoding sterol o-acyltransferase 1, is a functional candidate gene located underneath the proximal linkage peak. We sequenced the coding region of Soat1 and identified four single nucleotide polymorphisms (SNPs) between B6 and C3H mice. Two of the SNPs resulted in amino-acid substitutions (Ile147Val and His205Tyr). Functional assay revealed an increased enzyme activity of Soat1 in peritoneal macrophages of C3H mice relative to those of B6 mice despite comparable protein expression levels. Allelic variants of Soat1 were associated with variations in plasma cholesterol and triglyceride levels in an intercross between B6.apoE(-/-) and C3H.apoE(-/-) mice. Inheritance of the C3H allele resulted in significantly higher plasma lipid levels than inheritance of the B6 allele. Soat1 variants were also significantly linked to major variations in plasma esterified cholesterol levels but not with free cholesterol levels. Trangenic expression of C3H Soat1 in B6.apoE(-/-) mice resulted in elevations of plasma cholesterol and triglyceride levels. These results indicate that Soat1 is a QTL gene contributing to hyperlipidemia.     

Construction and properties of new Lyt-congenic strains and anti-Lyt-2.2 and anti-Lyt-3.1 monoclonal antibodies

Hybridomas producing mouse monoclonal IgM antibodies specific for Lyt-2.2 and Lyt-3.1 T-cell surface alloantigens have been constructed. Cytotoxic titers of ascites fluids were found to be 10(-6) or greater and no lysis of thymocytes of congenic strains bearing the alternative allele was observed at the lowest dilutions tested (1:2). The anti-Lyt-2.2 monoclonal antibody (HO-2.2) specifically precipiated from extracts of Lyt-2.2-positive thymocytes molecular species indistinguishable from those precipitated by conventional anti-Lyt-2.2 sera. However, by immunoprecipitation criteria (though not by cytotoxicity), the anti-Lyt-3.1 antibody (HO-3.1) demonstrated some cross-reactivity with similar molecular species from Lyt-3.1-negative thymocytes. In addition, three new strains of mice differing from existing strains in the region of the Lyt-2 and Lyt-3 loci have been constructed. They are: C.C58-Lyt-2a, Lyt-3a and C.AKR-Lyt-2a, Lyt-3a, congenic with Balb/cAn and bearing Lyt-2a and Lyt-3a alleles of C58/J and AKR/J, respectively; and AKR.C-Lyt-2b, Lyt-3b congenic with AKR/J and bearing the Lyt-2b and Lyt-3b alleles of Balb/cJ.     

Quantitative Trait Locus Analysis of Plasma Cholesterol and Triglyceride Levels in C57BL/6J × RR F2 Mice

A highly significant cholesterol quantitative trait locus (QTL) (Cq6) was identified on chromosome 1 in C57BL/6J x RR F2 mice. The Cq6 was located over the gene for apolipoprotein A-Il (Apoa2), and the RR allele was associated with increased plasma cholesterol. C57BL/6J has Apoa2a alleles and RR has Apoa2b alleles. Three different Apoa2 alleles are known on the basis of amino acid substitutions at four residues. Analysis with partial Apoa2 congenic strains possessing Apoa2a, Apoa2b, and Apoa2C alleles revealed that the Apoa2b allele is unique in the ability to increase cholesterol among the three Apoa2 alleles, and that the Ala-to-Val substitution at residue 61 may be crucial as far as cholesterol metabolism is concerned. We also investigated the question of whether the Apoa1 gene is responsible for the cholesterol QTLs (Cq4 and Cq5) that had been identified previously on chromosome 9 in C57BL/6J x KK-Ay/a F2 and in KK x RR F2, but not in C57BL/6J x RR F2 mice. Similar to Apoa2 alleles, three different Apoal alleles with two successive amino acid substitutions were revealed among the strains. However, we could not correlate Apoal polymorphisms with the occurrence of QTLs in these three sets of F2 mice.     

Correlation between structural variation and activity of murine kidney β-galactosidase: Implications for genetic control

Two closely linked regulatory genes have been reported to control activity levels of beta-galactosidases in murine tissues. The specific effects of these genes on murine glycolipid metabolism have not been elucidated. A/HeJ kidney 4-methylumbelliferyl-beta-galactosidase exhibited lower thermostability than the corresponding C57BL/6J and SWR/J enzymes. This altered response to heat segregated with the Bgsh allele among progeny derived from backcrosses of F1 (A/HeJ; SWR/J) mice to the respective parental strains. Restriction of the heat-sensitive A/HeJ beta-galactosidase to kidney tissue suggests that it is not determined by the Bgs locus, since the latter appears to be expressed in all tissues. More likely, the Bgs region of chromosome 9 contains a gene cluster consisting of a number of regulatory and structural loci. The proposed structural genes share affinity for the artificial substrates commonly employed for their assay but may differ in their relative affinities for glycosphingolipid substrates. Presence of the Bgsh allele results in an increase of kidney GM1-ganglioside-beta-galactosidase; however, galactosylceramide-beta-galactosidase appears unaffected by this allele.     

The occurrence of anti-3-fucosyllactosamine antibodies and their cross-reactive idiotopes in preimmune and immune mouse sera

The carbohydrate determinant 3-fucosyllactosamine (3-FL), Gal(beta 1-4)[Fuc alpha 1-3]GlcNAc-R, which is also known as SSEA-1 or as the X determinant, is very immunogenic in BALB/c mice. Many monoclonal antibodies directed against this structure have been obtained by immunization of mice with murine teratocarcinomas and human carcinomas and myeloid cells. We have undertaken an analysis of the regulation of these antibodies and of their idiotypic, structural, and genetic diversity. We have described previously the preparation of syngeneic monoclonal anti-idiotypic antibodies (6C4 and 6B1) that reacted with 50% of a panel of monoclonal anti-3-FL antibodies. In this study, we have examined the occurrence of anti-3-FL antibodies and their cross-reactive idiotopes in the sera of unimmunized and immunized mice. All BALB/c sera examined had more naturally occurring antibodies against 3-FL than against four other glycolipid antigens, and the 6C4 and 6B1 idiotopes were also detected in these sera. Approximately 25% of the anti-3-FL antibodies could be removed from a pool of BALB/c sera by a 6C4 affinity column, and the eluate from this column exhibited strong binding to 3-FL antigens. After a single i.v. injection of a 3-FL-positive glycolipid coated on Salmonella minnesota, anti-3-FL titers rose in BALB/c mice. The level of 6B1 idiotope rose in most mice, but the idiotope level showed no correlation with anti-3-FL titers. Naturally occurring antibodies against 3-FL were also noted in the sera of AKR, C3H/He, DBA/2, BALB/c-nu/nu, and CBA/CaHN mice but not in C57BL/6, SM, or CBA/N mice. A single i.v. injection of antigen elicited an antibody response in C3H/He mice but not in C57BL/6, SM, or DBA/2 mice. These data indicate that several strains of mice have more naturally occurring IgM antibodies against the 3-FL structure than against other glycolipids, and that this response may be genetically regulated. The 6C4 and 6B1 cross-reactive idiotopes that we have identified previously on monoclonal antibodies are also present in preimmune and immune sera. The existence of a population of B lymphocytes that are primed against the 3-FL determinant accounts in part for the immunogenicity of this structure.     

Efficiency alleles of the Pctr1 modifier locus for plasmacytoma susceptibility

The susceptibility of BALB/c mice to pristane-induced plasmacytomas is a complex genetic trait involving multiple loci, while DBA/2 and C57BL/6 strains are genetically resistant to the plasmacytomagenic effects of pristane. In this model system for human B-cell neoplasia, one of the BALB/c susceptibility and modifier loci, Pctr1, was mapped to a 5.7-centimorgan (cM) chromosomal region that included Cdkn2a, which encodes p16(INK4a) and p19(ARF), and the coding sequences for the BALB/c p16(INK4a) and p19(ARF) alleles were found to be polymorphic with respect to their resistant Pctr1 counterparts in DBA/2 and C57BL/6 mice (45). In the present study, alleles of Pctr1, Cdkn2a, and D4Mit15 from a resistant strain (BALB/cDAG) carrying DBA/2 chromatin were introgressively backcrossed to the susceptible BALB/c strain. The resultant C.DAG-Pctr1 Cdkn2a D4Mit15 congenic was more resistant to plasmacytomagenesis than BALB/c, thus narrowing Pctr1 to a 1.5-cM interval. Concomitantly, resistant C57BL/6 mice, from which both gene products of the Cdkn2a gene have been eliminated, developed pristane-induced plasma cell tumors over a shorter latency period than the traditionally susceptible BALB/cAn strain. Biological assays of the p16(INK4a) and p19(ARF) alleles from BALB/c and DBA/2 indicated that the BALB/c p16(INK4a) allele was less active than its DBA/2 counterpart in inducing growth arrest of mouse plasmacytoma cell lines and preventing ras-induced transformation of NIH 3T3 cells, while the two p19(ARF) alleles displayed similar potencies in both assays. We propose that the BALB/c susceptibility/modifier locus, Pctr1, is an "efficiency" allele of the p16(INK4a) gene.     

Patterns of instability of expanded CAG repeats at the ERDA1 locus in general populations.

A highly polymorphic CAG repeat locus, ERDA1, was recently described on human chromosome 17q21.3, with alleles as large as 50-90 repeats and without any disease association in the general population. We have studied allelic distribution at this locus in five human populations and have characterized the mutational patterns by direct observation of 731 meioses. The data show that large alleles (>/=40 CAG repeats) are generally most common in Asian populations, less common in populations of European ancestry, and least common among Africans. We have observed a high intergenerational instability (46. 3%+/-5.1%) of the large alleles. Although the mutation rate is not dependent on parental sex, paternal transmissions have predominantly resulted in contractions, whereas maternal transmissions have yielded expansions. Within this class of large alleles, the mutation rate increases concomitantly with increasing allele size, but the magnitude of repeat size change does not depend on the size of the progenitor allele. Sequencing of specific alleles reveals that the intermediate-sized alleles (30-40 repeats) have CAT/CAC interruptions within the CAG-repeat array. These results indicate that expansion and instability of trinucleotide repeats are not exclusively disease-associated phenomena. The implications of the existence of massively expanded alleles in the general populations are not yet understood.     

Mouse genotype affects inducible expression of cytokine genes.

The levels of circulating IFN in mice infected with Newcastle disease virus (NDV) are regulated by the If-1 locus. In this study we show that in NDV-infected C57BL/6 mice, which carry the If-1h allele and produce high levels of IFN, high levels of both IFN-alpha and -beta mRNA can be detected in the spleen. In contrast, only very low levels of IFN mRNA could be detected in spleens of infected BALB/c mice containing the If-1l allele and producing low levels of IFN or in B6.C-H28c mice that are congenic for the If-1l allele. The relative levels of all individual IFN-alpha 1, alpha 4, and alpha 6 mRNA in spleens of infected BALB/c were lower than in spleens of infected C57BL/6 mice, indicating that the If-1 locus affects the expression of all IFN-alpha subtypes and is not associated with the deletion or inactivation of a specific IFN gene. The relative levels of IFN regulatory factor-1 mRNA in infected mice carrying the If-1l and If-1h loci were comparable, suggesting that the If-1 regulation is not associated with the altered expression of the IFN regulatory factor-1 gene. Quantitative difference in the expression of IFN-alpha and -beta genes was also observed in in vitro-infected peritoneal macrophages isolated from either C57BL/6 or BALB/c mice. A surprise finding was that the If-1 locus also affected the NDV-induced expression of two other cytokine genes, TNF-alpha and IL-6. Priming of the macrophage cultures with murine IFN enhanced the expression of all cytokine genes, and the relative levels of IFN, TNF-alpha, and IL-6 mRNA induced by NDV in macrophages derived from C57BL/6 and BALB/c mice were comparable. We propose that the If-1 locus affects the early stages of a signal transduction pathway which are common to the virus-mediated induction of IFN, TNF-alpha, and IL-6 genes.     

Human MHC class III genes, Bf and C4. Polymorphism, complotypes and association with MHC class I genes in the Finnish population

Electrophoretically detected genetic polymorphism of human MHC class III genes, factor B (Bf) and complement C4A and C4B, was studied in the Finnish population. Bf alleles were determined in a panel of sera from 70 unrelated individuals. The common Bf alleles, Bf*S and Bf*F, had frequencies of 73% and 26%, respectively. Only in 1 individual was another allele, Bf*F1, detected. The frequencies of the C4A and C4B alleles were based on studies of 254 unrelated individuals. In this panel, five different alleles were detected at the C4A locus and four at the C4B locus. At both loci an allele without a gene product, i.e. a 'null' allele, was observed with high frequency, 11% for C4A 'null' and 17% for C4B 'null'. The association of complotypes to HLA haplotypes was analyzed in 70 chromosomes. The most common combination, defined by class I and class III alleles, was HLA-B7-S31 (13%), followed by HLA-B35-F20 (8.4%) and HLA-B8-S03 (7.1%). Some HLA-B specificities, for example B15, B27 and B40, were associated with a variety of complotypes. The importance of complotyping in HLA genetics is discussed.