Body and major organ weights of A/J-Chr 11(SM) consomic mice

Neonatal lethality of mouse A/J-7SM consomic strain is caused by an insertion mutation in the Dchs1 gene

Homosomic mice of the A/J-7^SM consomic mouse strain that introduced the entire chromosome 7 (Chr 7) of SM/J into the A/J strain exhibited neonatal lethality. We tentatively maintained segregating inbred strains (A/J-7A^SM and A/J-7D^SM) in which the central portion of Chr 7 was heterozygous for the A/J and SM/J strains, and the centromeric and telomeric sides of Chr 7 were homozygous for the SM/J strain, instead of the A/J-7^SM strain. Based on the chromosomal constitution of Chr 7 in A/J-7A^SM and A/J-7D^SM mice, the causative gene for neonatal lethality in homosomic mice was suggested to be located within an approximately 1.620 Mb region between D7Mit125 (104.879 Mb) and D7Mit355 (106.499 Mb) on Chr 7. RT-PCR analysis revealed that homosomic mice lacked dachsous cadherin-related 1 (Dchs1), which is located within the D7Mit125 to D7Mit355 region and functions in the regulation of planar cell polarity. Screening for mutations in Dchs1 indicated that homosomic mice possessed an early transposable (ETn)-like sequence in intron 1 of Dchs1. Moreover, an allelism test between Dchs1 ETn-like-insertion alleles detected in homosomic mice and CRISPR/Cas9-induced Dchs1 deletion alleles revealed that Dchs1 is a causative gene for neonatal lethality in homosomic mice. Based on these results, we concluded that in the A/J-7^SM strain, ETn-like elements were inserted into intron 1 of SM/J-derived Dchs1 during strain development, which dramatically reduced Dchs1 expression, thus resulting in neonatal lethality in homosomic mice. Additionally, it was suggested that the timing of lethality in Dchs1 mutant mice is influenced by the genetic background.

Acute benzo[a]pyrene treatment causes different antioxidant response and DNA damage in liver, lung, brain, stomach and kidney

Acute effects of oxidative damage induced by benzo[a]pyrene (B[a]P) on various organs are still not clear. In this study, we investigated oxidative stress and DNA damage in liver, lung, stomach, brain and kidney of ICR male mice induced by acute B[a]P treatment. B[a]P treatment led to a significant decrease at the different doses in body weight. For the variations of superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), glutathione (GSH) and GSH/GSSG, significant increases were observed at 24 h, then decreased till 72 h after B[a]P injection. The increase percent indicated in a dose- dependent decrease manner. However, glutathione peroxidase (GPx), GSSG and MDA were significantly increased in a time- and dose-dependent increase manner. DNA damage showed the significant and top levels at 24 h, and increased in proportion to the doses of B[a]P treatment. The total induction could be indicated by the variation of MDA at 24 h after B[a]P injection and showed the following order of predominance: lung > liver > kidney = stomach > brain. This was further certificated by histopathological changes in the examined organs. Additionally, the levels of serum glutamic-oxaloacetic transaminase (GOT), glutamic-pyruvic transaminase (GPT), and blood urea nitrogen (UN), creatinine were also significantly increased at 24 h after B[a]P injection. These findings suggested the disturbance of antioxidant responses and aggravation of DNA damages, and the different responses on various organs induced by acute B[a]P treatment in organism.

Congenic mapping and candidate gene analysis for streptozotocin-induced diabetes susceptibility locus on mouse chromosome 11

Streptozotocin (STZ) has been widely used to induce diabetes in rodents. Strain-dependent variation in susceptibility to STZ has been reported; however, the gene(s) responsible for STZ susceptibility has not been identified. Here, we utilized the A/J-11^SM consomic strain and a set of chromosome 11 (Chr. 11) congenic strains developed from A/J-11^SM to identify a candidate STZ-induced diabetes susceptibility gene. The A/J strain exhibited significantly higher susceptibility to STZ-induced diabetes than the A/J-11^SM strain, confirming the existence of a susceptibility locus on Chr. 11. We named this locus Stzds1 (STZ-induced diabetes susceptibility 1). Congenic mapping using the Chr. 11 congenic strains indicated that the Stzds1 locus was located between D11Mit163 (27.72 Mb) and D11Mit51 (36.39 Mb). The Mpg gene, which encodes N-methylpurine DNA glycosylase (MPG), a ubiquitous DNA repair enzyme responsible for the removal of alkylated base lesions in DNA, is located within the Stzds1 region. There is a close relationship between DNA alkylation at an early stage of STZ action and the function of MPG. A Sanger sequence analysis of the Mpg gene revealed five polymorphic sites in the A/J genome. One variant, p.Ala132Ser, was located in a highly conserved region among rodent species and in the minimal region for retained enzyme activity of MPG. It is likely that structural alteration of MPG caused by the p.Ala132Ser mutation elicits increased recognition and excision of alkylated base lesions in DNA by STZ.

Depletion of mitochondrial enzyme system in liver, lung, brain, stomach and kidney induced by benzo(a)pyrene

Mitochondrial dysfunction has recently received considerable attention as it plays an important role in adult human pathology caused by various drugs, endogenous agents and environmental agents. Benzo(a)pyrene (BaP), is a ubiquitous environmental contaminant mainly derived from anthropogenic activity during incomplete combustion of organic materials from various sources. The present study aimed to evaluate the effects of benzo(a)pyrene (BaP) on mitochondrial enzymes in the multiple organs including liver, lung, brain, stomach and kidney. ICR mice were exposed to different doses of BaP (2.5, 5 and 10mg/kg body weight) through oral gavage and intraperitoneal injection treatment for 13 weeks consecutively. The induced mitochondrial damage in the examined organs was assayed in terms of significant increase in lipid peroxidation (LPO) and prominent decrease in antioxidant enzymes. Non enzymatic antioxidants and Krebs cycle's enzymes were also significantly decreased in mitochondria. Additionally, BaP induced the body growth retardation and decrease in relative liver weight, increase in relative lung, stomach, kidney and brain weights, and this was further certified through histopathological lesions. Liver and lungs were more prominently damaged by BaP. The mitochondrial depletion increased in BaP dose-dependent manner.

First-trimester nonsystemic corticosteroid use and the risk of oral clefts in Norway

PURPOSE

Exposure of pregnant mice to corticosteroids can produce oral clefts in offspring. Although data in humans are more mixed, recent reports have suggested that dermatologic steroids are associated with oral clefts.

METHODS

We investigated maternal first-trimester exposure to corticosteroids (focusing on dermatologic uses) and oral clefts in offspring using two population-based studies. The Norway Cleft Study (1996-2001) is a national case-control study including 377 infants with cleft lip ± palate (CLP), 196 infants with cleft palate only (CPO), and 763 controls. The Norwegian Mother and Child Cohort Study (MoBa, 1998-2008) is a national birth cohort including 123 infants with CLP, 61 infants with CPO, and 551 controls.

RESULTS

In the case-control study, there was the suggestion of an association of dermatologic corticosteroids with both CLP (adjusted OR [aOR], 2.3; 95% confidence interval [CI], 0.71-7.7) and CPO (aOR, 3.4; CI, 0.87-13). There was no evidence of this association in the cohort data (odds ratio for CLP, 1.2; CI, 0.50-2.8 and odds ratio for CPO, 1.0; CI, 0.30-3.4), although exposure to dermatologic steroids was less specifically ascertained. There were no associations with other types of corticosteroids.

CONCLUSIONS

Our data add to the suggestive but inconsistent findings for this association.

Establishment of consomic strains derived from A/J and SM/J mice for genetic analysis of complex traits

Consomic strains, in which one chromosome is derived from a donor strain and the other chromosomes are derived from the recipient strain, provide a powerful tool for the dissection of complex genetic traits. In this study we established ten consomic strains (A-2(SM), A-6(SM), A-11(SM), A-12(SM), A-13(SM), A-15(SM), A-17(SM), A-18(SM), A-19(SM), A-Y(SM)) using the SM/J strain as the donor and the A/J strain as the recipient; these are the parental strains of a set of SMXA recombinant inbred (RI) strains that we had developed previously. We analyzed body weights and blood lipid levels in the consomic and parental strains. The mean values for each trait showed a continuous range of variation in the consomic strains suggesting that they are controlled by multiple genes. We previously identified suggestive QTLs for body weight on chromosome 6 in SMXA RI strains and (SM/J × A/J)F(2) mice. The observation that the A-6(SM) consomic strain had a significantly lower mean body weight than the A/J strain supports the presence of this QTL on chromosome 6. Similarly, the higher blood triglyceride level in the A-11(SM) strain shows the existence of a previously mapped QTL on chromosome 11, and the A-12(SM) strain provides evidence of a QTL for blood total cholesterol level on chromosome 12. These consomic strains, along with the previously developed set of SMXA RI strains from A/J and SM/J mice, offer an invaluable and powerful resource for the analysis of complex genetic traits in mice.