Reciprocal congenic lines of mice capture the aliq1 effect on acute lung injury survival time - PubMed (original) (raw)

Reciprocal congenic lines of mice capture the aliq1 effect on acute lung injury survival time

Daniel R Prows et al. Am J Respir Cell Mol Biol. 2008 Jan.

Abstract

Acute lung injury (ALI) is a devastating condition resulting from diverse causes. Genetic studies of human populations indicate that ALI is a complex disease with substantial phenotypic variance, incomplete penetrance, and gene-environment interactions. To identify genes controlling ALI mortality, we previously investigated mean survival time (MST) differences between sensitive A/J (A) and resistant C57BL/6J (B) mice in ozone using quantitative trait locus (QTL) analysis. MST was significantly linked to QTLs (Aliq1-3) on chromosomes 11, 13, and 17, respectively. Additional QTL analyses of separate and combined backcross and F(2) populations supported linkage to Aliq1 and Aliq2, and established significance for previously suggestive QTLs on chromosomes 7 and 12 (named Aliq5 and Aliq6, respectively). Decreased MSTs of corresponding chromosome substitution strains (CSSs) verified the contribution of most QTL-containing chromosomes to ALI survival. Multilocus models demonstrated that three QTLs could explain the MST difference between progenitor strains, agreeing with calculated estimates for number of genes involved. Based on results of QTL genotype analysis, a double CSS (B.A-6,11) was generated that contained Aliq1 and Aliq4 chromosomes. Surprisingly, MST and pulmonary edema after exposure of B.A-6,11 mice were comparable to B mice, revealing an unpredicted loss of sensitivity compared with separate CSSs. Reciprocal congenic lines for Aliq1 captured the corresponding phenotype in both background strains and further refined the QTL interval. Together, these findings support most of the previously identified QTLs linked to ALI survival and established lines of mice to further resolve Aliq1.

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Figures

**Figure 1.

Phenotype analysis of chromosome substitution strains. To determine the importance of each linked quantitative trait locus (QTL) to the overall survival phenotype, chromosome substitution strains (shaded bars) carrying a significant or suggestive QTL (as determined in previous analyses; see Refs. , , and 36) were exposed to continuous 10 ppm ozone. The number at the base of each bar represents sample size. Results are presented as means ± SE. Because the mean survival times (MSTs) of control B-mice did not differ between institutions, they were combined in the analysis. MSTs of chromosome substitution strains (CSSs) exposed at each institution were compared against control B-mice using one-way repeated measures ANOVA, with the Holm–Sidak method of multiple comparisons among groups. #P < 0.05 from all other strains listed. *P < 0.05 from B-strain.

**Figure 2.

Lung wet-to-dry (W:D) weight ratios for representative CSSs. Lung W:D weight ratios for B.A-6 and B.A-13 CSSs were compared to A (A/J) and B (C57BL/6J) progenitor strains exposed to 0, 3, 6, 8, 12, or 14 hours of continuous 10 ppm ozone. Plotted values represent the mean ± SE for each strain, with 5–7 mice per exposure time. Before exposure, all lines had a lung W:D weight ratio of about 4.0.

**Figure 3.

QTL genotype analysis. Survival time differences were determined for combined backcross and F2 mice that were homozygous for sensitivity alleles versus mice with resistance alleles at microsatellite markers representing the putative QTL peaks for ozone- and/or nickel-induced ALI. The group on the far right represents the MSTs of A/J (A) and C57BL/6J (B) control strains. Open bars represent mice with an AA genotype and solid bars denote mice with a BB genotype for the indicated representative QTL markers on chromosomes 11, 7, 13, and 6. Values are the mean ± SE. All MST differences between AA (open bars) versus BB (solid bars) QTL genotypes were significant (P < 0.05, t test).

**Figure 4.

Phenotype analysis of B.A-11 single CSS and 6,11-double CSS mice. (A) Comparison of QTL genotype analysis with predicted and in vivo testing of the B.A-6,11 CSSs. Bars represent MSTs of all mice from the combine backcross and F2 dataset with homozygous A alleles (± SE) or homozygous B alleles (solid bars) for the respective markers and chromosomes. The far right bars compare QTL genotype predicted versus actual MSTs for the B.A-6,11 double CSS. (B) Lung W:D weight ratios for B.A-6,11 double CSSs are compared to B (C57BL/6J) control and B.A-11 CSS mice before and after exposure to 10 ppm ozone for 8 or 14 hours (n = 4–6 mice for each line). *P < 0.05 (t test) from control B strain at same time.

**Figure 4.

**Figure 5.

Chromosome 11 reciprocal congenic lines derived from A and B strains of mice. Reciprocal congenic lines of mice were constructed to contain different segments around the Aliq1 interval (D11Mit245_–_D11Mit146). Control A and B strains, and the B.A-11 CSS are displayed as controls. B.A11-x (where x is 5 and 6) are two congenic lines on the B-strain background and A.B11-x (where x is 1 and 2) are two congenic lines on the A-strain background. Solid regions represent alleles that derive from the B strain, and open segments are alleles that derive from the A strain. Vertical lined regions denote segments between typed markers that are unknown (i.e., AA, AB, or BB). A schematic of chromosome 11 is presented on the left, listing MIT microsatellite markers and mapping locations of the crossover points in the congenic lines. On the far right is an overview of the QTL interval. The Aliq1 interval from the original (orig) data is identified by the hatched region (D11Mit245_–_D11Mit146), from the B.A11-congenic (B.A) is the open bar (D11Mit67–ter), from the A.B11-congenics (A.B) is the solid bar (D11Mit119–D11Mit336), and the refined Aliq1 interval is depicted as the black and white checkerboard bar (D11Mit67_–_D11Mit336).

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Reciprocal congenic lines of mice capture the aliq1 effect on acute lung injury survival time - PubMed (original) (raw)