Erbb is linked to the alpha-globin locus on mouse chromosome 11.

A fragment of the human gene for c-erb-B was used to map homologous sequences in mice. Analysis of somatic cell hybrids and recombinant inbred and congenic mouse strains indicated that this gene, designated Erbb, is closely linked to the gene for alpha-globin on mouse chromosome 11. Several genes controlling hematopoietic differentiation map to mouse chromosome 11.     

The antibody response to bacteriophage is linked to the lymphopenia gene in congenic BioBreeding rats

Congenic BioBreeding (BB) rats, homozygous for the autosomal lymphopenia (Lyp) gene (Lyp/Lyp), heterozygous (Lyp/+), or wild-type (+/+), were immunized with the T cell-dependent bacteriophage PhiX174 to determine effects of Lyp on primary and secondary antibody responses. The primary PhiX174 antibody response did not differ between the three different genotypes. In contrast, the secondary immune response, expressed as the peak neutralizing titer, was markedly reduced in Lyp/Lyp (9.9+/-3.2; mean value+/-S.E.M. for seven rats) compared to both Lyp/+ (51+/-12; n=13; P=0.006) and +/+ (100+/-20; n=7; P=0.004) BB rats. We suggest that the secondary antibody response to the T cell-dependent neoantigen PhiX174 is linked in a recessive manner to genetic factor(s) in the Lyp gene region.     

The cardiac actin locus (Actc-1) is not on mouse chromosome 17 but is linked to beta 2-microglobulin on chromosome 2

A restriction fragment variant and recombinant inbred strains were used to show that the cardiac actin locus (Actc-1) is closely linked to beta 2-microglobulin (B2m) and several other loci on chromosome 2 of the mouse. Close linkage of Actc-1 and B2m in both man and mouse provides another example of a chromosomal segment that has been conserved since the divergence of the lineages leading to these two species.     

Control of the antibody response of C57BL/6 Lyt-congenic strains to the Lyt-3.1 alloantigen by a gene linked to theLyt-2 locus

Congenic anti-Lyt-3.1 sera have recently been produced by immunizing B6-Lyt-2^a mice with thymocytes from either B6-Lyt-2^a, Lyt-3^a or B6-Lyt-2^a, Lyt-3^a, H-2^k mice (Boos et al. 1978). Surprisingly, mice of the congenic strain B6 failed to produce either anti-Lyt-2.1 or anti-Lyt-3.1 cytotoxic antibodies after identical immunizations. To determine the genetic basis for the difference in response to Lyt-3.1, (B6 × B6-Lyt-2^a)F_a mice and progeny of the backcross, (B6 × B6-Lyt-2^a)F₁ × B6-Lyt-2^a, were immunized with B6-Lyt-2^a, Lyt-3^a, H-2^k thymocytes. In addition, thymic biopsies of backcross progeny were performed and thymocytes tested for the Lyt-2.2 antigenic specificity. Results indicate that gene(s) governing the immune response to Lyt-3.1 is (are) linked to theLyt-2 locus, and that the responder allele (linked toLyt-2 ^a ) shows very poor penetrance in Lyt-2^a/Lyt-2^b mice.     

Rapid blood clearance of mouse IgG2a and human IgG1 in many nude and nu/+ mouse strains is due to low IgG2a serum concentrations

 We reported previously that the blood clearance of injected mouse IgG2a was extremely rapid in many strains of nude and nu/+ mice. In an attempt to determine the cause of this phenomenon, the levels of endogenous IgG2a in the blood of these mice was assayed. It was found that the serum level of IgG2a was extremely low in many of these mice, below 50 μg/ml, which is 20–100 times lower than the expected normal value. Great heterogeneity between individual mice was observed in their blood level of IgG2a, and there was an excellent correlation between low blood IgG2a levels and rapid clearance of injected IgG2a. Thus, the blood IgG2a levels are so low that a novel, previously undescribed effect occurs, namely the rapid clearance of small amounts of injected IgG2a. The clearance is due primarily to binding sites in the spleen and liver. The low level of endogenous IgG2a is not due to the lack of a thymus, since it occurs in nu/+ as well as nude mice, but can probably be attributed to the very clean environment in which these mice are raised. In assays of sera from approximately 50 mouse strains, low IgG2a levels were found in all nude colonies and also in some normal mouse strains. Some nude mice displayed relatively normal IgG2a clearance rates despite having low levels of endogenous IgG2a. In repeated bleedings of individual mice, IgG2a levels were found to fluctuate greatly. A similar clearance effect was observed with a human IgG1 Ab injected into mice. This rapid clearance of injected IgG, of certain subclasses, represents a practical problem for many experiments in which antibodies are used for diagnosis or therapy, and several methods of circumventing the problem are discussed. Received: 15 August 1977 / Accepted: 14 October 1997     

A locus controlling the activity of UDP-galactose:GM2(NeuGc) galactosyltransferase in mouse liver is linked to the H-2 complex

Genetic polymorphism in the expression of the G_M1(NeuGc) ganglioside has been shown in the liver of inbred strains of mice. Through analysis of the gangliosides of H-2 congenic and recombinant strains, this polymorphism was demonstrated to be controlled by a locus mapped left outside of the H-2 complex on chromosome 17, and the locus was assumed to control the level of the activity of G_M1(NeuGc) synthetase, UDP-galactose:G_M2(NeuGc) galactosyltransferase (E.C.2.4.1.62) [Hashimotoet al., J Biochem (1983) 94:2049-54].In the present study we analyzed the genetic linkage between the activity of the galactosyltransferase and the H-2 haplotype. For this purpose, we selected two inbred strains of mice, WHT/Ht and BALB/c, because they have different levels of the transferase activity and show different H-2 haplotypes; the specific activity of the transferase obtained with BALB/c was one-eighth of that with WHT/Ht, and BALB/c expressed the la.7 antigen as one of the products encoded in their H-2^d complex, whereas WHT/Ht did not. To analyze the linkage between these two phenotypes, WHT/Ht were mated with BALB/c to obtain the F₁ mice, and the female F₁ mice were then backcrossed to WHT/Ht. It was found that one half of the backcross generation expressed the la.7 antigen derived from BALB/c and had a significantly lower specific activity of the transferase than that of WHT/Ht, while the other half did not express the la.7 antigen but had the same specific activity of the transferase as that obtained with WHT/Ht.These results suggest that the locus controlling the level of the transferase activity in mouse liver is linked to the H-2 complex on chromosome 17.Abbreviations NeuGc N-glycolylneuraminic acid The ganglioside nomenclature is based on the system of Svennerholm, J Neurochem (1963) 10:613-23. The sialic acid species present is shown in parentheses after the ganglioside abbreviation.     

Non-random conformation of a mouse IgG2a monoclonal antibody at low pH

The pH dependence of the conformation of a mouse IgG2a, kappa monoclonal antibody (MN12) was investigated by several physical techniques, including fluorescence spectroscopy, near-ultraviolet and far-ultraviolet CD, and electric-field-induced transient birefringence measurements. The intensity of the intrinsic tryptophan fluorescence remained constant in the pH range from 3.5 to 10.0. A conformational alteration in the MN12 molecule was observed in the pH region between pH 3.5 and 2.5, as reflected by a substantial enhancement of the fluorescence quantum yield. This effect was more pronounced at high ionic strengths. The fluorescence emission was unaltered, indicating that the acid-induced conformational state is different from a completely unfolded state. This was confirmed by CD and fluorescence polarisation measurements. Iodide and acrylamide fluorescence quenching studies indicated a gradually increasing accessibility of MN12 tryptophan residues with decreasing pH. At low pH precipitation was observed in the presence of iodide. One rotational relaxation time (0.16-0.18 microseconds) was observed for MN12 by electric-field-induced transient birefringence measurements at low ionic strength. After exposure of MN12 to low pH for 1 h, the relaxation time was increased to 0.23 microseconds; a further increase to 0.30 microseconds was observed after 24 h. The combined results suggest an acid-induced expansion and enhanced flexibility of MN12, which eventually leads to irreversible aggregation.     

The carbohydrate structures of a mouse monoclonal IgG antibody OKT3

A mouse monoclonal antibody OKT3, of IgG2a isotype, was isolated from hybridoma culture fluid. Sugar analysis showed the presence of sialic acid, galactose, mannose, fucose, and N-acetylglucosamine, i.e. sugars typical for N-glycosidically linked carbohydrate chains. The absence of N-acetylgalactosamine revealed that O-glycosidically linked carbohydrates were not present. The purified antibody was reduced, alkylated, and separated into heavy and light chains, and all carbohydrates were shown to be associated with the heavy chains. The N-linked carbohydrate chains were isolated as alditols using strong alkaline-borohydride degradation and further fractionated on a concanavalin A-Sepharose column and high performance ion exchange chromatography with pulsed amperometric detection. Structural analysis was carried out on the isolated oligosaccharide alditols by chemical analyses, fast atom bombardment mass spectrometry, and 500-MHz 1H NMR spectroscopy. Triantennary and biantenary types of structures were found. The triantennary structures were present as trisialo and tetrasialo forms without fucose; the tetrasialo forms were shown to contain a sequence of Neu5Ac alpha 2-3Gal beta 1-3[Neu5Ac alpha 2-6]GlcNAc beta 1- on one of the branches. The biantennary structures were present as completely sialylated nonfucosylated species and as asialo-, agalacto-, and partially fucosylated structures.     

The locus for apolipoprotein CII is closely linked to the apolipoprotein E locus on chromosome 19 in man

Summary We have demonstrated close linkage between the genes for apolipoprotein E (apoE) and apolipoprotein CII (apoCII). Families segregating for apoE protein variants were screened for a DNA restriction fragment length polymorphism close to the apoCII gene by using an apoCII cDNA clone. The maximum lod score is 4.52 (sexes combined) at a recombination frequency of zero. Given linkage, it may be assumed that no recombinations have happened in altogether 33 observed meioses. It is therefore evident that the apoCII gene is situated on chromosome 19, close to the apoE gene.     

A three-megabase yeast artificial chromosome contig spanning the C57BL mouse Igh locus

The mouse Ig H chain (Igh) complex locus is composed of >100 gene segments encoding the variable, diversity, joining, and constant portions of the Ab H chain protein. To advance the characterization of this locus and to identify all the V(H) genes, we have isolated the entire region from C57BL/6 and C57BL/10 as a yeast artificial chromosome contig. The mouse Igh locus extends approximately three megabases and contains at least 134 V(H) genes classified in 15 partially interspersed families. Two non-Igh pseudogenes (Odc-rs8 and Rpl32-rs14) were localized in the distal part of the locus. This physical yeast artificial chromosome map will provide important structure and guidance for the sequencing of this large, complex, and highly repetitive locus.     

T15 idiotype expression in the murine response to phosphorylcholine is actively regulated by genes linked to the Igh-C locus

In this report, we demonstrate the existence of a regulatory system that can determine the relative expression of individual clones (idiotypes) within the total immune response to PC. Studies of Igh-C-congenic mice and backcross analysis demonstrate that this regulation is controlled by genes linked to the immunoglobulin heavy chain locus. The regulation acts in a trans fashion. The regulatory genes of one parental allele can control the expression of idiotopes coded for by both parental alleles. This regulation does not appear to affect the quantity of the response, but could affect the quality of the response, depending on the potential repertoire and avidity of the individual clones available to respond to a given antigenic challenge.     

Interaction ofH-2 and nonH-2 linked genes in the regulation of antibody response to a threshold dose of sheep erythrocytes

The antibody response to a threshold dose (¹⁰) of SE was studied in the High responder line (H) and the Low responder line (L) of mice obtained by bidirectional selective breeding for the character quantitative agglutinin response to an optimal dose of SE, and in interline hybrids: F₁, F₁ and both backcrosses. Whereas the interline difference in agglutinin responses at the optimal dose is due to the additive effect of about ten independently segregating loci, one of which isH-2 linked, the responsiveness to the threshold dose is determined by the effect of two loci. The direction of the dominance effect also varies with the antigen dose: high responsiveness is partially dominant at the optimal dose while at the threshold dose nonresponder character is partially dominant. The role of theH-2 linked locus was investigated. It has been demonstrated that on an identical background (equivalent to that of F₁ hybrids) this locus is responsible for 12% of the interline difference at the optimal antigen dose, and for 61% at the threshold antigen dose. For the two antigen doses, the quantitative effect of theH-2 locus is in agreement with the estimate of the number of loci obtained by variance analysis. The intervention of a second gene, non-H-2 linked, in the regulation of responsiveness to 10⁶ SE is demonstrated by appropriate assortative matings. The interaction between the two genes is discussed.     

Regulation of autoimmune response to mouse thyroglobulin: influence of H-2D-end genes.

Studies were initiated to define the H-2-linked genetic control of response to self-determinants of MTg. In addition to the Ir gene control of H-2K end, a modifying effect of D end was seen. The extent of regulation depended upon the derivation of the K-end Ir-Tg gene(s) as well as the D-end genes. When the Ir-Tg gene was from good responder H-2k and H-Ss strains, and the H-2D-end gene from the d allele, antibody levels were moderate to high but cellular infiltration was significantly reduced. These findings demonstrate genetic interaction between I-region and D-end gene products in the response to a self-antigen, MTg.     

A locus on the X Chromosome is linked to body length in mice

Linkage between body length (anus to nose (AN) length) and three markers on the mouse X Chromosome was found in an interspecific backcross ((C57BL/6J×Mus spretus) F1 ×C57BL/6J), designated BSB. A cross of 409 mice were scored for 148 genetic markers distributed on all chromosomes except the Y Chromosome. Statistical analysis revealed highly significant linkage (LOD score 5.5) between body length and a locus in the middle portion of the X Chromosome, the nearest markers being the microsatellite marker DXMit73 and a farnesyl pyrophosphate locus (Fpsl9) 3.1 cM proximal to DXMit73. The locus explains 10% of the variance in AN length and affects both males and females to about the same extent. Received: 17 April 1995 / Accepted: 13 October 1995     

Open sesame: activating dormant replication origins in the mouse immunoglobulin heavy chain (Igh) locus

Chromosomal DNA replication in mammals initiates from replication origins whose activity differs in accordance with cell type and differentiation state. In addition to origins that are active in unperturbed conditions, chromosomes also contain dormant origins that can become functional in response to certain genotoxic stress conditions. Improper regulation of origin usage can cause genomic instability leading to tumorigenesis. We review findings from recent single-molecule DNA fiber studies examining replication of the mouse immunoglobulin heavy chain (Igh) locus, in which origin activity over a 400kb region is subject to dramatic developmental regulation. Possible models are discussed to explain such differential origin usage, particularly during replication stress conditions that can activate dormant origins.