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Insufficiently defined genetic background confounds phenotypes in transgenic studies as exemplified by malaria infection in Tlr9 knockout mice.

ABSTRACT: The use of genetically modified mice, i.e. transgenic as well as gene knockout (KO) and knock-in mice, has become an established tool to study gene function in many animal models for human diseases. However, a gene functions in a particular genomic context. This implies the importance of a well-defined homogenous genetic background for the analysis and interpretation of phenotypes associated with genetic mutations. By studying a Plasmodium chabaudi chabaudi AS (PcAS) malaria infection in mice bearing a TLR9 null mutation, we found an increased susceptibility to infection, i.e. higher parasitemia levels and increased mortality. However, this was not triggered by the deficient TLR9 gene itself. Instead, this disease phenotype was dependent on the heterogeneous genetic background of the mice, which appeared insufficiently defined as determined by single nucleotide polymorphism (SNP) analysis. Hence, it is of critical importance to study gene KO phenotypes on a homogenous genetic background identical to that of their wild type (WT) control counterparts. In particular, to avoid problems related to an insufficiently defined genetic background, we advocate that for each study involving genetically modified mice, at least a detailed description of the origin and genetic background of both the WT control and the altered strain of mice is essential.

SUBMITTER: Geurts N

PROVIDER: S-EPMC3214040 | biostudies-literature | 2011

REPOSITORIES: biostudies-literature

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Insufficiently defined genetic background confounds phenotypes in transgenic studies as exemplified by malaria infection in Tlr9 knockout mice.

Geurts Nathalie N Martens Erik E Verhenne Sebastien S Lays Natacha N Thijs Greet G Magez Stefan S Cauwe Bénédicte B Li Sandra S Heremans Hubertine H Opdenakker Ghislain G Van den Steen Philippe E PE

PloS one 20111111 11

The use of genetically modified mice, i.e. transgenic as well as gene knockout (KO) and knock-in mice, has become an established tool to study gene function in many animal models for human diseases. However, a gene functions in a particular genomic context. This implies the importance of a well-defined homogenous genetic background for the analysis and interpretation of phenotypes associated with genetic mutations. By studying a Plasmodium chabaudi chabaudi AS (PcAS) malaria infection in mice be ...[more]

PMID: 22096530

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Project description:IntroductionSystemic Lupus Erythematosus (SLE) impacts the central nervous system (CNS), leading to severe neurological and psychiatric manifestations known as neuropsychiatric lupus (NPSLE). The complexity and heterogeneity of clinical presentations of NPSLE impede direct investigation of disease etiology in patients. The limitations of existing mouse models developed for NPSLE obstruct a comprehensive understanding of this disease. Hence, the identification of a robust mouse model of NPSLE is desirable.MethodsC57BL/6 mice transgenic for human MeCP2 (B6.Mecp2Tg1) were phenotyped, including autoantibody profiling through antigen array, analysis of cellularity and activation of splenic immune cells through flow cytometry, and measurement of proteinuria. Behavioral tests were conducted to explore their neuropsychiatric functions. Immunofluorescence analyses were used to reveal altered neurogenesis and brain inflammation. Various signaling molecules implicated in lupus pathogenesis were examined using western blotting.ResultsB6.Mecp2Tg1 exhibits elevated proteinuria and an overall increase in autoantibodies, particularly in female B6.Mecp2Tg1 mice. An increase in CD3+CD4+ T cells in the transgenic mice was observed, along with activated germinal center cells and activated CD11b+F4/80+ macrophages. Moreover, the transgenic mice displayed reduced locomotor activity, heightened anxiety and depression, and impaired short-term memory. Immunofluorescence analysis revealed IgG deposition and immune cell infiltration in the kidneys and brains of transgenic mice, as well as altered neurogenesis, activated microglia, and compromised blood-brain barrier (BBB). Additionally, protein levels of various key signaling molecules were found to be differentially modulated upon MeCP2 overexpression, including GFAP, BDNF, Albumin, NCoR1, mTOR, and NLRP3.DiscussionCollectively, this work demonstrates that B6.Mecp2Tg1 mice exhibit lupus-like phenotypes as well as robust CNS dysfunctions, suggesting its utility as a new animal model for NPSLE.

Project description:Amino-terminal (Nt-) acetylation (NTA) is a common protein modification, affecting approximately 80% of all human proteins. The human essential X-linked gene, NAA10, encodes for the enzyme NAA10, which is the catalytic subunit in the N-terminal acetyltransferase A (NatA) complex, also including the accessory protein, NAA15, encoded by the autosomal gene, NAA15. Although NAA10 is an essential gene in humans, there is nonetheless extensive genetic variation in humans with missense, splice-site, and C-terminal frameshift variants in NAA10. Likewise, the genetic spectrum for NAA15 is also extensive, where the mechanism likely involves haploinsufficiency in heterozygous individuals. The phenotypic presentation in humans with NAA10 or NAA15 variants includes variable levels of intellectual disability, delayed milestones, autism spectrum disorder, craniofacial dysmorphology, cardiac anomalies, seizures, and visual abnormalities. In mice, Naa10 is not an essential gene, as there exists a paralogous gene, Naa12, that substantially rescues Naa10 knockout mice from embryonic lethality, whereas double knockouts (Naa10-/Y Naa12-/-) are embryonic lethal. However, the phenotypic variability in the mice is nonetheless quite extensive, including piebaldism, skeletal defects, small size, hydrocephaly, hydronephrosis, and neonatal lethality. Here we show that the mouse phenotypes are replicated with new genetic alleles, but are modulated by genetic background and environmental effects, as demonstrated by several new mouse strains and backcrossing of the original Naa10 null allele 20 generations to inbred C57BL/6J mice in a different animal facility. We cannot replicate a prior report of "maternal effect lethality" for heterozygous Naa10-/X female mice, but we do observe a small amount of embryonic lethality in the Naa10-/y male mice on the inbred genetic background in this different animal facility. We hypothesize that decreased NTA of many different target substrate proteins is the main explanation for the variable phenotypic outcomes, and future experiments will make use of these mice and human cell lines to address this hypothesis.

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Insufficiently defined genetic background confounds phenotypes in transgenic studies as exemplified by malaria infection in Tlr9 knockout mice.

Publications

Insufficiently defined genetic background confounds phenotypes in transgenic studies as exemplified by malaria infection in Tlr9 knockout mice.

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