Multigenic control of skin tumor susceptibility in SENCARA/Pt mice

Skin tumors induced in mice by initiation-promotion (2 microg DMBA-2 microg TPA) protocols were found to be under multigenic control. Eighty-one N2 mice from the cross (BALB/cAnPt x SENCARA/Pt)F1 x SENCARA/Pt that were either solidly resistant (no papillomas) or highly susceptible (> or = 7 papillomas/mouse) were subjected to a 'genome scan' using 89 microsatellite markers to check for associations with susceptible and resistant phenotypes. A locus on Chr 5 (Skts4) was found to control the susceptibility of SENCARA/Pt mice and the resistance of BALB/cAnPt mice to papilloma formation. In addition, higher than expected linkage scores were seen for the markers D9Mit271, D11Mit268 and D12Mit56. Further work is required to establish whether genes determining papilloma formation are located in these regions of the genome. In general, no evidence was seen for loss of heterozygosity in microsatellite markers on Chrs 5, 9 and 11 in 17 microdissected papillomas from (BALB/c x SENCARA)F1 hybrid mice.

Cdkn2a, the cyclin-dependent kinase inhibitor encoding p16INK4a and p19ARF, is a candidate for the plasmacytoma susceptibility locus, Pctr1

Plasma cell tumor induction in mice by pristane is under multigenic control. BALB/c mice are susceptible to tumor development; whereas DBA/2 mice are resistant. Restriction fragment length polymorphisms between BALB/c and DBA/2 for Cdkn2a(p16) and Cdkn2b(p15), and between BALB/c and Mus spretus for Cdkn2c(p18(INK4c)) were used to position these loci with respect to the Pctr1 locus. These cyclin-dependent kinase (CDK) inhibitors mapped to a 6 cM interval of chromosome 4 between Ifna and Tal1. C.D2-Chr 4 congenic strains harboring DBA/2 alleles associated with the Pctr1 locus contained DBA/2 "resistant" alleles of the CDK4/CDK6 inhibitors p16 and p15. On sequencing p16 and p18 cDNAs, two different allelic variants within ankyrin repeat regions of p16 were found between BALB/c and DBA/2 mice. By using an assay involving PCR amplification and restriction enzyme digestion, allelic variants were typed among several inbred strains of mice. One of the variants, G232A, was specific to two inbred strains, BALB/cAn and ABP/Le, of mice and occurred in a highly conserved amino acid in both human and rat p16. When tested with wild-type (DBA/2) p16, both A134C and G232A BALB/c-specific variants of p16 were inefficient in their ability to inhibit the activity of cyclin D2/CDK4 in kinase assays with retinoblastoma protein, suggesting this defective, inherited allele plays an important role in the genetic susceptibility of BALB/c mice for plasmacytoma induction and that p16(INK4a) is a strong candidate for the Pctr1 locus.

Gene organization and chromosome location of the neural-specific RNA binding protein Elavl4

We have isolated the gene that encodes the neural-specific RNA binding protein HuD in the mouse (Elavl4), and have mapped its location to the mid-distal region of chromosome 4, close to the neurological mutant clasper. The coding region of the Elavl4 gene covers approximately 44 kb; the first two RNA binding domains (RBDs) that are homologous to the two RBDs found in the Drosophila sex-lethal gene are each encoded in two exons, whereas the third RBD is encoded in a single exon. Elavl4 mRNAs are alternatively spliced in the region between RBDs 2 and 3 due to the variable use of two micro-exons, and RNase protection analysis indicates that two of four possible splice variants are the predominant isoforms expressed in the central nervous system. The high degree of sequence conservation between the Hu proteins suggests that the exon organization of all the Hu protein genes will be similar, if not identical, to the Elavl4 gene.

The plasmacytoma resistance gene, Pctr2, delays the onset of tumorigenesis and resides in the telomeric region of chromosome 4

Mouse plasmacytomas share pathogenetic features in common with both multiple myeloma and Burkitt's lymphoma in humans. Susceptibility to plasmacytoma induction by intraperitoneal pristane in mice is controlled by multiple genes. At least two of these genes reside on mouse chromosome 4 in regions of the genome sharing linkage homology with human chromosomes 9p21, 1p32, and 1p36. A series of congenic strains recombinant for regions of mouse chromosome 4 in the vicinity of the Pctr2 predisposition locus were created and typed for their tumor susceptibility/resistance phenotypes. These strains were derived by introgressively backcrossing alleles from resistant DBA/2 mice onto the susceptible BALB/cAnPt background. Six resistant and two susceptible strains were allelotyped for 10 genes and 49 random DNA markers to identify the smallest region of overlap in the resistant strains. These studies have determined that the Pctr2 locus resides in either a 500-kb interval proximal to Nppa, or in a 1- to 2-centiMorgan (cM) interval distal to Nppa. In these congenic strain analyses, the Nppa and Fv1 loci, in addition to genes within about 1 cM of these loci, have been excluded as candidates for the Pctr2 locus. A relevant locus that may reside in this interval is Rep2; it is associated with the efficiency of repairing X-ray induced DNA damage sustained during the G2 phase of the mitotic cycle. The Pctr2 locus acts in a codominant fashion. F1 hybrids between resistant and susceptible congenic strains exhibit a reduced tumor incidence and a significant delay in the onset of tumorigenesis. Identification and eventual cloning of the Pctr2 locus may assist in the identification of genes involved in many types of cancer showing aberrations in human chromosome 1p36.

The B-lymphocyte maturation promoting transcription factor BLIMP1/PRDI-BF1 maps to D6S447 on human chromosome 6q21-q22.1 and the syntenic region of mouse chromosome 10

The human PRDI-BF1 or BLIMP1 gene and its mouse homolog Blimp1 are members of the recently realized PR domain family that includes the retinoblastoma interacting zinc finger gene RIZ and the MDS1-EVI1 leukemia cancer gene. The specific high-level expression of Blimp1 in late B and plasma cells, its induction during B-cell differentiation, and its ability to drive B-cell maturation suggest that this gene may play a role in the differentiation and pathogenesis of B cells. We have now mapped the physical location of BLIMP1 near the marker D6S447 on human chromosome 6q21-q22.1; we have also mapped Blimp1 to mouse Chromosome 10 at 14 cM distal to the Myb locus and to a region homologous to the location of BLIMP1. Deletions of the 6q21-q22 region are common in several human malignancies, particularly in B-cell non-Hodgkin lymphoma (B-NHL). The data led us to suggest that BLIMP1 may be a candidate B-NHL tumor suppressor gene.

Plasmacytoma-associated neuronal glycoprotein, Pang, maps to mouse chromosome 6 and human chromosome 3

A new member of the immunoglobulin/fibronectin superfamily of adhesion molecules, Pang (plasmacytoma-associated neuronal glycoprotein), was recently isolated from a plasmacytoma. In previous studies, Pang was found to be normally expressed in the brain and ectopically activated by intracisternal A-type particle long terminal repeats in plasmacytomas. In this study, Pang was initially mapped to mouse Chr 6 by somatic cell hybrid analysis and further positioned on the chromosome between Wnt7a and Pcp1. Southern blot analysis of human-rodent somatic cell hybrids together with predictions from the mouse map location indicate that human PANG is located at 3p26.

Molecular cloning, chromosomal mapping, and expression of the mouse p107 gene

Progression through the G1 phase of the cell cycle is regulated, in part, by the pRB-family proteins, pRB and p107. The basis for this regulation is due to a network of interactions between the pRB-family proteins, pRB, p107, and p130; the E2F-family of transcription factors; and cyclins D, E, and A. One of the pRB-family proteins, p107, has also been found to bind to the transactivation domain of the c-Myc proto-oncogene. This region in c-Myc is frequently mutated in tumors such as Burkitt's lymphoma, HIV-associated lymphoma, and multiple myeloma. The binding of p107 and regulation of c-Myc may conceivably be disrupted not only by mutations in c-Myc, but possibly by mutations in p107. In order to determine if mutations in p107 are indeed present in mouse B-cell tumors which exhibit a lower frequency of c-Myc mutation, we have cloned the mouse p107 cDNA and compared this sequence with its human counterpart. We find that the extreme N-terminal and C-terminal regions are the most conserved between human and mouse p107 sequences. Chromosomal positioning of the locus for p107 (designated Rbl1) as well as E2f1 to the distal end of mouse Chromosome (Chr) 2 also suggests a close but unlinked genetic relationship between these cell cycle regulatory transcription factors.

Interleukin 6 is essential for in vivo development of B lineage neoplasms

Interleukin (IL) 6 has been suggested to be the major cytokine responsible for proliferation of neoplastic plasma cells in both human myeloma and mouse plasmacytoma. Much of the evidence supporting this suggestion is derived from in vitro studies in which the survival or proliferation of some plasma cell tumors has been found to be IL-6 dependent. However, it remains unclear whether this dependency is the consequence of in vivo or in vitro selective pressures that preferentially expand IL-6-responsive tumor cells, or whether it reflects a critical in vivo role for IL-6 in plasma cell neoplasia. To address this question, we have attempted to induce plasma cell tumors in normal mice and in IL-6-deficient mice generated by introduction of a germline-encoded null mutation in the IL-6 gene. The results demonstrate that mice homozygous (+/+) or heterozygous (+/-) for the wild-type IL-6 allele yield the expected incidences of plasma cell tumors. In contrast, mice homozygous for the IL-6-null allele (-/-) are completely resistant to plasma cell tumor development. These studies define the essential role of IL-6 in the development of B lineage tumors in vivo and provide experimental support for continued efforts to modulate this cytokine in the treatment of appropriate human B cell malignancies.

CHUK, a conserved helix-loop-helix ubiquitous kinase, maps to human chromosome 10 and mouse chromosome 19

Helix-loop-helix proteins contain stretches of DNA that encode two amphipathic alpha-helices joined by a loop structure and are involved in protein dimerization and transcriptional regulation essential to a variety of cellular processes. CHUK, a newly described conserved helix-loop-helix ubiquitous kinase, was mapped by somatic cell hybrid analyses to human Chr 10q24-q25. Chuk and a related sequence, Chuk-rs1, were mapped to mouse chromosomes 19 and 16, respectively, by a combination of somatic cell hybrid, recombinant inbred, and backcross analyses.

Nonrandom chromosomal change (trisomy 11) in murine plasmacytomas induced by an ABL-MYC retrovirus

Trisomy of chromosome 11 (Ts11) is the second most frequent nonrandom chromosomal change in murine plasmacytomas (PCTs). The frequency of Ts11 is significantly higher in PCTs induced in pristane-conditioned mice infected by Abelson-murine leukemia virus (52%) compared to those induced by pristane alone (8.1%). Although the significance of Ts11 in mouse plasmacytomagenesis is not clearly understood it is hypothesized that a gene or genes located on chromosome (Chr) 11 may specifically promote the development of PCTs in which both oncogenes, c-myc and v-abl, are abundantly expressed. To test this assumption we induced PCTs by three highly effective plasmacytomagenic retroviruses: ABL-MYC, J3V1, and RIM. Nearly 90% of PCTs that arose in BALB/c, (BALB/c x DBA/2N)F1, BALB/c-nu/nu, and 5-month-old SCID mice infected with ABL-MYC virus were trisomic for Chr 11. In contrast, < 10% of PCTs induced by J3V1 or RIM retroviral constructs encompassing either v-myc and v-raf or c-myc and v-Ha-ras oncogenes, respectively, contained Ts11. We have also investigated whether the entire Chr 11 or any particular subregion is preferentially duplicated in the process of ABL-MYC plasmacytomagenesis. By inducing PCTs in F1 heterozygous mice that are carriers of reciprocal translocations involving Chr 11 we found that the duplicated chromosomal region is located distal to the T4Dn breakpoint (11B5 band) on the telomeric segment of Chr 11. The regular duplication of this chromosomal segment strongly suggests the presence of a gene or genes whose amplification is of critical importance for v-abl associated murine plasmacytomagenesis.

Genetic regulation of leishmanial and mycobacterial infections: the Lsh/Ity/Bcg gene story continues

A common basis to genetic regulation of leishmanial and mycobacterial infections is provided by the action of the murine Lsh/Ity/Bcg gene in controlling the priming/activation of macrophages for antimicrobial activity. This relies on the TNF-alpha-dependent sustained expression of the inducible nitric oxide synthase (iNOS) gene responsible for the generation of large amounts of toxic nitric oxide (NO). The Lsh/Ity/Bcg gene has many pleiotropic effects, including differential expression of the early response gene KC following stimulation of macrophages with bacterial lipopolysaccharide (LPS) and mycobacterial lipoarabinomannan (LAM). The major signal transduction pathway involved in KC induction requires the generation of low levels of NO via constitutive nitric oxide synthase (cNOS) activity, leading to activation of guanylate cyclase and the cGMP-dependent kinase pathway. NO therefore appears to provide a common link between the early influence of Lsh in regulating the expression of genes which mediate many pleiotropic effects, and the later production of NO as the final effector mechanism for kill. The recently cloned candidate for Lsh/Ity/Bcg, designated Nramp for Natural resistance associated macrophage protein, encodes a polytopic integral membrane protein that has structural features common to prokaryotic and eukaryotic transporters and includes a conserved binding-protein-dependent transport motif which may be involved in interaction with peripheral ATP-binding subunits. The N-terminal sequence also carries a proline/serine rich putative SH3 binding domain, consistent with a role for tyrosine kinases in regulating Nramp function. (ABSTRACT TRUNCATED AT 250 WORDS)

Genetic and physical mapping of 2q35 in the region of the NRAMP and IL8R genes: identification of a polymorphic repeat in exon 2 of NRAMP

Recent interest has focused on the region of conserved synteny between mouse chromosome 1 and human 2q33-q37, particularly over the region encoding the murine macrophage resistance gene Ity/Lsh/Bcg (candidate Nramp) and members of the Il8r interleukin-8 (IL8) receptor gene cluster. In this paper, identification of a restriction fragment length polymorphism in the IL8RB gene in 35 pedigrees previously typed for markers in the 2q33-q37 interval provided evidence (lod scores > 3) for linkage between IL8RB and the 2q34-q35 markers FN1, TNP1, VIL1, and DES. Physical mapping, using yeast artificial chromosomes isolated with VIL1, confirmed that IL8RA, IL8RB, and the IL8RB pseudogene map within the NRAMP-VIL1 interval, with the physical distance (155 kb) from 5' LSH to 3' VIL1 representing approximately 3-fold that observed in the mouse. Partial sequencing of NRAMP confirmed the presence of the N-terminal proline/serine-rich putative SH3 binding domain in exon 2 of the human gene. Further analysis of Brazilian leprosy and visceral leishmaniasis pedigrees identified a rare second allele varying in a 9-nucleotide repeat motif of the exon 2 sequence but segregating independently of the disease phenotype.

Construction of a BALB/c congenic mouse, C.C3H-Lpsd, that expresses the Lpsd allele: analysis of chromosome 4 markers surrounding the Lps gene

Development of a congenic BALB/c mouse strain that contains a segment of chromosome 4 including the Lpsd allele of the lipopolysaccharide (LPS)-hyporesponsive C3H/HeJ strain is presented. On the basis of LPS-induced spleen cell mitogenesis, macrophage tumor necrosis factor secretion, and tyrosine phosphorylation in vitro and lethality in galactosamine-sensitized mice in vivo, the C.C3H-Lpsd strain provides a model of LPS hyporesponsiveness that is comparable to that of the parental C3H/HeJ strain. Analysis of markers in this region indicates that length of the donor fragment is approximately 5.5 centimorgans. Thus, the C.C3H-Lpsd strain provides an important genetic tool for analysis of markers in this region and for examining functional effects of Lpsd expression on the BALB/c background.

The inducible form of nitric oxide synthase (NOS2) isolated from murine macrophages maps near the nude mutation on mouse chromosome 11

Nitric oxide synthase has been shown to mediate streptozocin-induced diabetes and to act as an antimicrobial agent in murine macrophages. Using a cDNA probe for the inducible form of nitric oxide synthase (Nos2) isolated from murine macrophages we have determined that the gene maps within 1 cM of the nude mutation on mouse Chromosome 11. The position of Nos2 was also mapped relative to the markers 115, Evi2, Cchlbl (previously unmapped), and Gfap. This map location is discussed relative to map locations for disease susceptibility loci involved in mediating cutaneous leishmaniasis (ScII) and autoimmune type-I diabetes (Idd4).

Identification of two genes on chromosome 4 that determine resistance to plasmacytoma induction in mice

BALB/cAn mice are highly susceptible to the induction of plasmacytomas (PCTs) by the i.p. injection of paraffin oils, whereas DBA/2 mice are solidly resistant. To search for genes that control the dominant resistant phenotype of DBA/2, BALB/c.DBA/2 (C.D2) congenic strains were constructed, and the susceptibility and resistance to PCT development were determined. PCT formation takes place over an extended period of 365 days but begins morphologically in focal proliferations of atypical plasma cells (foci) in the reactive oil granuloma that forms on mesenteric surfaces. Cells from some of these foci spread to other locations in oil granuloma tissue, forming new foci. Mice that develop six or more foci appear to be progressing towards eventual overgrowth and replacement of all peritoneal tissues with PCT cells. From Days 100 to 250, between 28 and 56% of PCT-susceptible BALB/cAn mice had 6 or more foci, whereas less than 5% of resistant DBA/2, BALB/c x DBA/2 F1 (hereafter called CD2F1), C57BL/6, and BALB/cJ mice had 6 or more foci. Four CD2 congenic strains carrying D2 alleles of genes on chromosomes other than chromosome 4 were highly susceptible. Between 0 and 20% of the mice in C.D2-Chr 4 congenic strains C.D2-MIA, C.D2-TF3, C.D2-Fv-1n/n, C.D2-Pnd7, C.D2-Lgm-1A, C.D2-Lgm-1B, C.D2-Lgm-1C, and C.D2-Lgm-1H developed 6 or more foci from 125 to 260 days, indicating resistance. The segments of DBA/2 chromosome 4 chromatin in C.D2-Fv-1n/n and C.D2-Pnd7 were discontinuous with those in C.D2-TF3, C.D2-Lgm-1A, C.D2-Lgm-1B, C.D2-Lgm-1C, and C.D2-Lgm-1H, indicating there are at least two genes (Pctr1 and Pctr2) in the distal half of this chromosome that confer resistance. Pctr1 is located between Ifa and D4Rck41, and Pctr2 is between Tnfr-1 and Pkcz. Each locus acting alone distinctly conferred a partial resistant phenotype. Pctr1 and Pctr2 did not appear to prevent the formation of clonal foci but did appear to limit the ability of the plasma cells in foci to acquire greater autonomy; thus, these genes affect tumor progression.

Construction of a series of congenic mice with recombinant chromosome 1 regions surrounding the genetic loci for resistance to intracellular parasites (Ity, Lsh, and Bcg), DNA repair responses (Rep-1), and the cytoskeletal protein villin (Vil)

The interval of mouse chromosome 1 extending from Idh-1 to Pep-3 harbors the natural resistance gene Ity/Lsh/Bcg; it controls the outcome of infection with Salmonella typhimurium, Leishmania donovani, and several Mycobacterium species. This region also contains a DNA repair gene, Rep-1, which determines the rapidity with which double-strand breaks in chromatin are repaired. BALB/cAnPt and DBA/2N mice differ in their phenotypic expression of these genes. To generate appropriate strains of mice for the study of these genes, a series of 10 C.D2 congenic strains recombinant across a 28-centimorgan interval of mouse chromosome 1 extending from Idh-1 to Pep-3 were derived from crosses of the C.D2-Idh-1 Pep-3 congenic strain back to BALB/cAn. Analyses of these recombinant strains will allow the correlation of biological-immunological phenotypes with defined genetic regions.

The murine homologue of the human interleukin-8 receptor type B maps near the Ity-Lsh-Bcg disease resistance locus

Interleukin-8 (IL-8), a member of the chemokine alpha subfamily, is a chemoattractant for neutrophils. Cell surface receptors for IL-8 have been cloned from rabbits and humans. Two related but different IL-8 receptors (IL-8R) have been characterized from humans. IL-8RA and IL-8RB bind IL-8 at high affinity but IL-8RB also binds GRO/MGSA and NAP-2 at high affinity. Using the human IL-8RB cDNA as a probe, we have determined that the homologous murine gene maps near the Ity-Lsh-Bcg disease resistance locus. A murine homologue of the human IL-8RB was isolated from a genomic library. This gene would encode a protein of 359 amino acids and would have a 68 and 71% amino acid identity with human IL-8RA and IL-8RB, respectively. Additional mapping data using the murine gene revealed the following genetic distances (in cM +/- 1 standard error) from the centromere: Mylf--7.9 +/- 2.7--Lsh-Ity-Bcg--1.9 +/- 1.4--Il8rb--1.9 +/- 1.4--Vil-- 5.9 +/- 2.3--Acrg--2.9 +/- 1.7--Bcl-2.

Genetic mapping of tumor susceptibility genes involved in mouse plasmacytomagenesis

Plasmacytomas (PCTs) were induced in 47% of BALB/cAnPt mice by the intraperitoneal injection of pristane, in 2% of (BALB/c x DBA/2N)F1, and in 11% of 773 BALB/cAnPt x (BALB/cAnPt x DBA/2N)F1 N2 backcross mice. This result indicates a multigenic mode of inheritance for PCT susceptibility. To locate genes controlling this complex genetic trait, tumor susceptibility in backcross progeny generated from BALB/c and DBA/2N (resistant) mice was correlated with alleles of 83 marker loci. The genotypes of the PCT-susceptible progeny displayed an excess homozygosity for BALB/c alleles within a 32-centimorgan stretch of mouse chromosome 4 (> 95% probability of linkage) with minimal recombination (12%) near Gt10. Another susceptibility gene on mouse chromosome 1 may be linked to Fcgr2 (90% probability of linkage); there were excess heterozygotes for Fcgr2 among the susceptible progeny and excess homozygotes among the resistant progeny. Regions of mouse chromosomes 4 and 1 that are correlated with PCT susceptibility share extensive linkage homology with regions of human chromosome 1 that have been associated with cytogenetic abnormalities in multiple myeloma and lymphoid, breast, and endocrine tumors.

Mapping of genes controlling Leishmania major infection in CXS recombinant inbred mice

Previous studies demonstrated that growth of the primary lesion following Leishmania major infection in inbred mice comes under the control of a single major gene designated Scl-1. Preliminary mapping studies had suggested a chromosome 8 location for the gene. In this paper a more detailed study of different disease phenotypes (lesion growth, splenomegaly, liver parasite load) in 14 CXS recombinant inbred (RI) mouse strains was undertaken in order to obtain a more definitive map location for the gene. Using the Kruskal-Wallis generalization of the Wilcoxon Rank-Sum Test to assign RI strains to parental phenotypes, high concordances with genes at the mid (Il-3) to distal end (Dlb-1, Hox-2, Sigje, Mtv-3 and Es-3) of chromosome 11 were demonstrated with two strains (LV39 and NIH173) of L. major given as promastigotes subcutaneously into the shaven rump. The results suggest that the most likely location for the previously described single major gene (Scl-1) regulating early lesion expansion is at the distal end of mouse chromosome 11, with the possibility that a gene located more proximally influences later phases of the infection.