Mouse Chromosome 5

Chair of Committee for Mouse Chromosome 5     

The murine Il-6 gene maps to the proximal region of chromosome 5

Murine Il-6 cDNAs were isolated by cross-hybridization with a human IL-6 cDNA from an IL-1 activated bone marrow stromal cell line (W20). Mouse-hamster somatic cell hybrids were utilized to localize murine Il-6 to chromosome 5. Genetic mapping with respect to En-2, AlbH, and Gus in backcross progeny from an interspecific mating between C57BL/6J and Mus spretus positioned Il-6 3 cM distal to En-2. The syntenic relationships of Il-6 and En-2 in mouse and man, as well as the potential role of IL-6 in tumorigenesis, are discussed.     

Inactivation of Mxi1 induces Il-8 secretion activation in polycystic kidney

The Mxi1 proteins are biochemical and biological antagonists of c-myc oncoprotein. It has been reported that the overexpression pattern of c-myc might be similar to a molecular feature of early and late stages of human autosomal dominant polycystic kidney disease. We identified the cyst phenotype in Mxi1-deficient mice aged 6-12 months using H&E staining. Some chemokines containing a protein domain similar to human IL-8, which is associated with the inflammatory response, were subsequently selected from the up-regulated genes. We confirmed the expression level of these chemokines and measured protein concentrations of IL-8 using ELISA in the Mxi1-knockdown cells. IL-8 was found to be significantly increased in Mxi1-knockdown cells. We found that p38 MAP kinase activation was involved in the signal transduction of the Mxi1-inactivated secretion of IL-8. Therefore, we could suggest that the inactivation of Mxi1 leads to the inflammatory response and has the potential to induce polycystic renal disease.     

Knockout of Mkp-1 exacerbates colitis in Il-10-deficient mice

Il-10-deficient mice develop colitis associated with exaggerated Th1/Th17 responses and are a valuable model of inflammatory bowel disease. Mkp-1 is a major negative regulator of MAPKs, and its expression is enhanced by IL-10. To understand the role of Mkp-1 in the regulation of intestinal mucosal immune responses, we studied the effect of Mkp-1 deletion on the pathogenesis of colitis in Il-10(-/-) mice. We found that knockout of Mkp-1 on an Il-10(-/-) background accelerated the development of colitis. Compared with Il-10(-/-) mice, colitis not only appeared earlier but also was more severe in Il-10(-/-)/Mkp-1(-/-) mice. Il-10(-/-) mice exhibited a mild intestinal inflammation in the specific pathogen-free environment, and rectal prolapse rarely appeared before 6 mo of age. In contrast, the majority of Il-10(-/-)/Mkp-1(-/-) mice developed severe colitis rapidly and presented with rectal prolapse after only 2-3 mo. The colon of Il-10(-/-)/Mkp-1(-/-) mice showed diffuse transmural chronic inflammation and mucosal hyperplasia, with significantly more proliferating crypt epithelial cells than those of Il-10(-/-) mice. In addition to the severe colitis, Il-10(-/-)/Mkp-1(-/-) mice also developed conjunctivitis and blepharitis. The colon of Il-10(-/-)/Mkp-1(-/-) mice contained significantly higher levels of proinflammatory cytokines and exhibited greater MAPK activities than did the colon of Il-10(-/-) mice. Splenocytes and lymphocytes from Il-10(-/-)/Mkp-1(-/-) mice produced higher levels of Th1 cytokines ex vivo upon activation than did cells from Il-10(-/-) mice. Our studies support a pivotal role of Mkp-1 as a negative regulator of mucosal immune responses and highlight its protective function against inflammatory bowel disease.     

Re-localization of Actsk-1 to mouse Chromosome 8, a new region of homology with human Chromosome 1

We present here the genetic mapping of the -skeletal actin locus (Actsk-1) on mouse Chromosome (Chr) 8, on the basis of the PCR analysis of a microsatellite in an interspecific backcross. Linkage and genetic distances were established for four loci by analysis of 192 (or 222) meiotic events and indicated the following gene order: (centromere)-Es-1-11.7 cM-Tat-8.3 cM-Actsk-1-0.5 cM-Aprt. Mapping of ACTSK to human Chr 1 and of TAT and APRT to human Chr 16 demonstrates the existence of a new short region of homology between mouse Chr 8 and human Chr 1. Intermingling on this scale between human and mouse chromosomal homologies that occurred during evolution creates disorders in comparative linkage studies.     

Interleukin 1 and protein kinase C activator are dissimilar in their effects on Il-2 receptor expression and Il-2 secretion by T lymphocytes

T lymphocytes respond to mitogenic stimulation by expressing the receptor for interleukin 2 (Il-2) and secreting Il-2; once the receptor is expressed, Il-2 induces these cells to proliferation. In the present report using mouse T lymphocytes, thymocytes, and the lymphoma cell line EL4, we studied receptor expression and Il-2 secretion as early parameters for T-lymphocyte activation in response to ionomycin, concanavalin A (Con A), 12-O-tetradecanoyl-phorbol 13-acetate (TPA), and interleukin 1 (Il-1). Il-1 is required for mitogenic response of lymphocyte preparations that are rigorously depleted of macrophages. On its own, Il-1 had very little effect on Il-2 secretion and Il-2 receptor expression by T lymphocytes. TPA strongly synergized with ionomycin both for Il-2 secretion and for Il-2 receptor expression whereas Il-1 did not. Il-1 required the simultaneous presence of ionomycin and TPA to have any demonstrable effect on T lymphocytes from spleen and on thymocytes. However, on EL4 cells which were also partially responsive to TPA alone, Il-1 showed strong synergy with TPA to induce Il-2 secretion and Il-2 receptor expression. The effect of Il-1 on EL4 cells was dose dependent where increasingly higher concentrations of Il-1 in the presence of a fixed concentration of TPA caused higher percentage of EL4 cells to become Il-2 receptor positive. The present results suggest that Il-1 does not cause its effect on T lymphocytes via the same mechanism of protein kinase C activation that has been proposed for TPA.     

Assignment of three rat integrin genes to Chromosome 19 (ITGB1), Chromosome 3 (ITGA4), and Chromosome 7 (ITGA5)

By means of somatic cell, hybrids segregating rat chromosomes, we determined the chromosome localization of three rat 1 family integrin genes. ITGB1 was assigned to Chromosome (Chr) 19, ITGA4 to Chr 3, and ITGA5 to Chr 7. These chromosome assignments reveal or confirm homology between two pairs of rat and human chromosomes (rat Chr 3-human Chr 2; rat Chr 7-human Chr 12).     

Chromosome mapping of the owl monkey CSF1R and IL5 genes.

We mapped the owl monkey colony-stimulating factor 1 receptor (CSF1R) locus to the proximal region of chromosome 3q of karyotype VI(K-VI) and karyotype V(K-V) and the interleukin 5 (IL5) locus to the mid-region of chromosome 3q(K-VI) and 19q(K-IV) using a combination of Southern hybridization of somatic cells and in situ chromosomal hybridization methodologies. The findings support the proposed evolution of owl monkey chromosome 3(K-VI) from a fusion of two smaller structures, the homologs of chromosomes 6 and 19 (K-IV). The data also indicate genomic conservation of the HSA 5q23-q35 segment in the higher primates.