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Published on: November 20, 2018
Molecular genetic characterization of the distal NKC recombination hotspot and putative murine CMV resistance control
Anthony A Scalzo1, Roy Wheat, Chad Dubbelde
1Department of Microbiology, University of Western Australia, 6907 Nedlands, Western Australia, Australia.
Abstract:
The NK gene complex (NKC) controls murine cytomegalovirus (MCMV) immunity through Cmv1-dependent natural killer (NK) cell responses. Ly49H expression correlates with Cmv1 phenotypes in different inbred strains, is required for MCMV resistance in C57BL/6 (B6) mice, and its interaction with the MCMV encoded m157 protein leads to NK cell-mediated destruction of virus-infected cells. However, genetic mapping studies have previously indicated that Cmv1 should reside in the D6Wum9-16 NKC interval, distal to Ly49h. Since these data suggested that multiple NKC-linked loci could regulate viral immunity, a putative MCMV resistance control ( Mrc) locus was pinpointed to within the D6Wum9-16 interval on a NKC-aligned bacterial artificial chromosome (BAC). Sequence analysis of BAC 151 revealed several novel G-protein coupled receptor genes, an HMG-1 remnant and many additional polymorphic microsatellites that were useful in determining the minimal genetic interval for the Mrc locus. Moreover, comparison of B6, BALB/c, A/J and recombinant Mrc alleles restricted the genetic interval to approximately 470 bp and showed that it was also a hotspot for recombination. MCMV challenge of novel NKC recombinant mice demonstrated that Mrc(B6) was not required for MCMV resistance nor could it directly complement the Ly49(BALB) haplotype to rescue MCMV susceptibility. Taken together, these data show that while Mrc apparently guides recombination, Ly49H expression is sufficient for MCMV resistance in B6 mice. A direct role for Mrc(B6) in virus resistance is excluded in the novel mice.
Insights
Murine cytomegalovirus (MCMV) resistance in mice is primarily governed by Ly49H expression, not the Mrc locus. The Mrc locus appears to influence recombination within the Natural Killer gene complex (NKC).
Area of Science:
- Immunology
- Genetics
- Virology
Background:
- The Natural Killer (NK) gene complex (NKC) regulates immunity to murine cytomegalovirus (MCMV) via Cmv1-dependent NK cell responses.
- Ly49H expression is crucial for MCMV resistance in C57BL/6 (B6) mice, mediating the destruction of infected cells through interaction with the viral m157 protein.
Purpose of the Study:
- To investigate the role of a putative MCMV resistance control (Mrc) locus within the NKC, distinct from Ly49H.
- To determine if the Mrc locus contributes to MCMV resistance independently or in conjunction with Ly49H.
Main Methods:
- Genetic mapping and sequence analysis of bacterial artificial chromosomes (BACs) within the NKC to pinpoint the Mrc locus.
- Generation and MCMV challenge of novel NKC recombinant mice to assess the function of Mrc alleles.
Main Results:
- Sequence analysis identified novel genes and microsatellites, refining the Mrc locus to a 470 bp interval, identified as a recombination hotspot.
- MCMV challenge revealed that the Mrc(B6) allele was not required for MCMV resistance in B6 mice.
- The Mrc locus did not complement the Ly49(BALB) haplotype to restore MCMV resistance.
Conclusions:
- Ly49H expression is sufficient for MCMV resistance in B6 mice.
- The Mrc locus's primary role appears to be guiding recombination within the NKC rather than directly conferring MCMV resistance.
