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Synchronizing allelic effects of opposing quantitative trait loci confirmed a major epistatic interaction affecting acute lung injury survival in mice.

Prows DR, Gibbons WJ, Burzynski BB - PLoS ONE (2012)

Bottom Line: Interestingly, analysis of these recombinant populations supported opposite within-strain effects on survival for the two major-effect QTLs.Our previous QTL results predicted that substituting Shali1 B alleles onto the resistant X1 background would add sensitivity.Reciprocal congenic lines confirmed the opposing allelic effects of Shali1 and Shali2 on HALI survival time and provide unique models to identify their respective quantitative trait genes and to critically assess the apparent bidirectional epistatic interactions between these major-effect loci.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America. daniel.prows@cchmc.org

ABSTRACT
Increased oxygen (O(2)) levels help manage severely injured patients, but too much for too long can cause acute lung injury (ALI), acute respiratory distress syndrome (ARDS) and even death. In fact, continuous hyperoxia has become a prototype in rodents to mimic salient clinical and pathological characteristics of ALI/ARDS. To identify genes affecting hyperoxia-induced ALI (HALI), we previously established a mouse model of differential susceptibility. Genetic analysis of backcross and F(2) populations derived from sensitive (C57BL/6J; B) and resistant (129X1/SvJ; X1) inbred strains identified five quantitative trait loci (QTLs; Shali1-5) linked to HALI survival time. Interestingly, analysis of these recombinant populations supported opposite within-strain effects on survival for the two major-effect QTLs. Whereas Shali1 alleles imparted the expected survival time effects (i.e., X1 alleles increased HALI resistance and B alleles increased sensitivity), the allelic effects of Shali2 were reversed (i.e., X1 alleles increased HALI sensitivity and B alleles increased resistance). For in vivo validation of these inverse allelic effects, we constructed reciprocal congenic lines to synchronize the sensitivity or resistance alleles of Shali1 and Shali2 within the same strain. Specifically, B-derived Shali1 or Shali2 QTL regions were transferred to X1 mice and X1-derived QTL segments were transferred to B mice. Our previous QTL results predicted that substituting Shali1 B alleles onto the resistant X1 background would add sensitivity. Surprisingly, not only were these mice more sensitive than the resistant X1 strain, they were more sensitive than the sensitive B strain. In stark contrast, substituting the Shali2 interval from the sensitive B strain onto the X1 background markedly increased the survival time. Reciprocal congenic lines confirmed the opposing allelic effects of Shali1 and Shali2 on HALI survival time and provide unique models to identify their respective quantitative trait genes and to critically assess the apparent bidirectional epistatic interactions between these major-effect loci.

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Mean survival times of mice grouped by genotypes at markers with peak LOD scores for Shali1 and Shali2.The F2 population (n=840) generated from sensitive B and resistant X1 mice [25] was sorted into groups based on their genotypes (X1-X1, H, or B-B) at the peak MIT marker representing Shali1 (D1Mit303; 1–303) or Shali2 (D4Mit308; 4–308) (panel A) or at both peak markers (panel B). Survival times of mice for each genotype group was determined and plotted as the mean (MST) ± SEM. Groups that differed from each other are marked with the same symbol. Panel A shows a near mirror image of the genotype bar plots, indicative of the reciprocal allelic effects of Shali1 and Shali2. For Shali1 (D1Mit303), F2 mice for all three genotype groups differed from each other (indicated by *). For Shali2 (D4Mit308), F2 mice homozygous for X1 alleles differed from mice H or B-B (+), and mice B-B differed from those X1-X1 (#). Panel B shows a gradation of effect for the 9 different pairwise genotypes, with the polar extremes for MSTs (i.e., bars 1 vs. 9) occurring with the B-B, X1-X1 (high sensitivity) and X1-X1, B-B (high resistance) reciprocal genotypes at Shali1 and Shali2, respectively. Moving inward from each end gives group comparisons for each reciprocal genotype pair (i.e., bars 2 vs. 8, bars 3 vs. 7 and bars 4 vs. 6). The group of mice heterozygous for both markers fell in the center (bar 5), with a MST intermediate to all other groups. n, represents the number of F2 mice successfully genotyped for each (or both) MIT marker(s). F2 mice with genotype 9 (i.e., X1-X1, B-B at D1Mit303 and D4Mit308, respectively) were the most resistant and differed from all other genotypes (indicated by *). F2 mice with the reciprocal B-B, X1-X1 genotype were the most sensitive and, besides differing from genotype 9, also differed from genotypes 5, 7, and 8 (+).
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pone-0038177-g001: Mean survival times of mice grouped by genotypes at markers with peak LOD scores for Shali1 and Shali2.The F2 population (n=840) generated from sensitive B and resistant X1 mice [25] was sorted into groups based on their genotypes (X1-X1, H, or B-B) at the peak MIT marker representing Shali1 (D1Mit303; 1–303) or Shali2 (D4Mit308; 4–308) (panel A) or at both peak markers (panel B). Survival times of mice for each genotype group was determined and plotted as the mean (MST) ± SEM. Groups that differed from each other are marked with the same symbol. Panel A shows a near mirror image of the genotype bar plots, indicative of the reciprocal allelic effects of Shali1 and Shali2. For Shali1 (D1Mit303), F2 mice for all three genotype groups differed from each other (indicated by *). For Shali2 (D4Mit308), F2 mice homozygous for X1 alleles differed from mice H or B-B (+), and mice B-B differed from those X1-X1 (#). Panel B shows a gradation of effect for the 9 different pairwise genotypes, with the polar extremes for MSTs (i.e., bars 1 vs. 9) occurring with the B-B, X1-X1 (high sensitivity) and X1-X1, B-B (high resistance) reciprocal genotypes at Shali1 and Shali2, respectively. Moving inward from each end gives group comparisons for each reciprocal genotype pair (i.e., bars 2 vs. 8, bars 3 vs. 7 and bars 4 vs. 6). The group of mice heterozygous for both markers fell in the center (bar 5), with a MST intermediate to all other groups. n, represents the number of F2 mice successfully genotyped for each (or both) MIT marker(s). F2 mice with genotype 9 (i.e., X1-X1, B-B at D1Mit303 and D4Mit308, respectively) were the most resistant and differed from all other genotypes (indicated by *). F2 mice with the reciprocal B-B, X1-X1 genotype were the most sensitive and, besides differing from genotype 9, also differed from genotypes 5, 7, and 8 (+).

Mentions: Our previous QTL data suggested that the Shali1 and Shali2 allelic effects opposed each other in HALI survival time [24]–[26]. To quantitate and compare these QTL effects on survival time, allelic analysis of the major QTLs was performed in the F2 dataset [25]. For this, the allelic effects of the peak markers for Shali1 and Shali2 loci were calculated, first for the separate QTLs and then for both QTLs. F2 mice with homozygous X1 alleles for D1Mit303 were the most HALI resistant, with heterozygotes intermediate in MST and mice homozygous for B alleles at D1Mit303 being most sensitive. This directly correlated with X1 being the resistant strain. In contrast, F2 mice that were homozygous for B alleles at D4Mit308 were the most HALI resistant, even though the inbred B strain is HALI sensitive. Similarly, F2 mice that were homozygous for X1 alleles at D4Mit308 were most sensitive, even though inbred X1 mice are a resistant strain. Mice heterozygous at D4Mit308 were again intermediate in survival time. Because this data provided a key finding that formed the basis of the breeding strategies reported in this study, we have re-plotted these data to clearly demonstrate this inverse relationship. In this format, the opposing actions of the homozygous B and X1 alleles for Shali1 and Shali2 can be seen as near mirror images, showing a similar, but opposite effect of the two QTLs and HALI survival times (Figure 1A). The overall survival time with homozygous X1 alleles at D1Mit303 (145 hrs) was similar to that for homozygous B alleles at D4Mit308 (140 hrs). Heterozygotes for either QTL marker also had similar MSTs to each other (both ∼130 hrs) and to the control X1 strain (133 hrs).


Synchronizing allelic effects of opposing quantitative trait loci confirmed a major epistatic interaction affecting acute lung injury survival in mice.

Prows DR, Gibbons WJ, Burzynski BB - PLoS ONE (2012)

Mean survival times of mice grouped by genotypes at markers with peak LOD scores for Shali1 and Shali2.The F2 population (n=840) generated from sensitive B and resistant X1 mice [25] was sorted into groups based on their genotypes (X1-X1, H, or B-B) at the peak MIT marker representing Shali1 (D1Mit303; 1–303) or Shali2 (D4Mit308; 4–308) (panel A) or at both peak markers (panel B). Survival times of mice for each genotype group was determined and plotted as the mean (MST) ± SEM. Groups that differed from each other are marked with the same symbol. Panel A shows a near mirror image of the genotype bar plots, indicative of the reciprocal allelic effects of Shali1 and Shali2. For Shali1 (D1Mit303), F2 mice for all three genotype groups differed from each other (indicated by *). For Shali2 (D4Mit308), F2 mice homozygous for X1 alleles differed from mice H or B-B (+), and mice B-B differed from those X1-X1 (#). Panel B shows a gradation of effect for the 9 different pairwise genotypes, with the polar extremes for MSTs (i.e., bars 1 vs. 9) occurring with the B-B, X1-X1 (high sensitivity) and X1-X1, B-B (high resistance) reciprocal genotypes at Shali1 and Shali2, respectively. Moving inward from each end gives group comparisons for each reciprocal genotype pair (i.e., bars 2 vs. 8, bars 3 vs. 7 and bars 4 vs. 6). The group of mice heterozygous for both markers fell in the center (bar 5), with a MST intermediate to all other groups. n, represents the number of F2 mice successfully genotyped for each (or both) MIT marker(s). F2 mice with genotype 9 (i.e., X1-X1, B-B at D1Mit303 and D4Mit308, respectively) were the most resistant and differed from all other genotypes (indicated by *). F2 mice with the reciprocal B-B, X1-X1 genotype were the most sensitive and, besides differing from genotype 9, also differed from genotypes 5, 7, and 8 (+).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3362546&req=5

pone-0038177-g001: Mean survival times of mice grouped by genotypes at markers with peak LOD scores for Shali1 and Shali2.The F2 population (n=840) generated from sensitive B and resistant X1 mice [25] was sorted into groups based on their genotypes (X1-X1, H, or B-B) at the peak MIT marker representing Shali1 (D1Mit303; 1–303) or Shali2 (D4Mit308; 4–308) (panel A) or at both peak markers (panel B). Survival times of mice for each genotype group was determined and plotted as the mean (MST) ± SEM. Groups that differed from each other are marked with the same symbol. Panel A shows a near mirror image of the genotype bar plots, indicative of the reciprocal allelic effects of Shali1 and Shali2. For Shali1 (D1Mit303), F2 mice for all three genotype groups differed from each other (indicated by *). For Shali2 (D4Mit308), F2 mice homozygous for X1 alleles differed from mice H or B-B (+), and mice B-B differed from those X1-X1 (#). Panel B shows a gradation of effect for the 9 different pairwise genotypes, with the polar extremes for MSTs (i.e., bars 1 vs. 9) occurring with the B-B, X1-X1 (high sensitivity) and X1-X1, B-B (high resistance) reciprocal genotypes at Shali1 and Shali2, respectively. Moving inward from each end gives group comparisons for each reciprocal genotype pair (i.e., bars 2 vs. 8, bars 3 vs. 7 and bars 4 vs. 6). The group of mice heterozygous for both markers fell in the center (bar 5), with a MST intermediate to all other groups. n, represents the number of F2 mice successfully genotyped for each (or both) MIT marker(s). F2 mice with genotype 9 (i.e., X1-X1, B-B at D1Mit303 and D4Mit308, respectively) were the most resistant and differed from all other genotypes (indicated by *). F2 mice with the reciprocal B-B, X1-X1 genotype were the most sensitive and, besides differing from genotype 9, also differed from genotypes 5, 7, and 8 (+).
Mentions: Our previous QTL data suggested that the Shali1 and Shali2 allelic effects opposed each other in HALI survival time [24]–[26]. To quantitate and compare these QTL effects on survival time, allelic analysis of the major QTLs was performed in the F2 dataset [25]. For this, the allelic effects of the peak markers for Shali1 and Shali2 loci were calculated, first for the separate QTLs and then for both QTLs. F2 mice with homozygous X1 alleles for D1Mit303 were the most HALI resistant, with heterozygotes intermediate in MST and mice homozygous for B alleles at D1Mit303 being most sensitive. This directly correlated with X1 being the resistant strain. In contrast, F2 mice that were homozygous for B alleles at D4Mit308 were the most HALI resistant, even though the inbred B strain is HALI sensitive. Similarly, F2 mice that were homozygous for X1 alleles at D4Mit308 were most sensitive, even though inbred X1 mice are a resistant strain. Mice heterozygous at D4Mit308 were again intermediate in survival time. Because this data provided a key finding that formed the basis of the breeding strategies reported in this study, we have re-plotted these data to clearly demonstrate this inverse relationship. In this format, the opposing actions of the homozygous B and X1 alleles for Shali1 and Shali2 can be seen as near mirror images, showing a similar, but opposite effect of the two QTLs and HALI survival times (Figure 1A). The overall survival time with homozygous X1 alleles at D1Mit303 (145 hrs) was similar to that for homozygous B alleles at D4Mit308 (140 hrs). Heterozygotes for either QTL marker also had similar MSTs to each other (both ∼130 hrs) and to the control X1 strain (133 hrs).

Bottom Line: Interestingly, analysis of these recombinant populations supported opposite within-strain effects on survival for the two major-effect QTLs.Our previous QTL results predicted that substituting Shali1 B alleles onto the resistant X1 background would add sensitivity.Reciprocal congenic lines confirmed the opposing allelic effects of Shali1 and Shali2 on HALI survival time and provide unique models to identify their respective quantitative trait genes and to critically assess the apparent bidirectional epistatic interactions between these major-effect loci.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America. daniel.prows@cchmc.org

ABSTRACT
Increased oxygen (O(2)) levels help manage severely injured patients, but too much for too long can cause acute lung injury (ALI), acute respiratory distress syndrome (ARDS) and even death. In fact, continuous hyperoxia has become a prototype in rodents to mimic salient clinical and pathological characteristics of ALI/ARDS. To identify genes affecting hyperoxia-induced ALI (HALI), we previously established a mouse model of differential susceptibility. Genetic analysis of backcross and F(2) populations derived from sensitive (C57BL/6J; B) and resistant (129X1/SvJ; X1) inbred strains identified five quantitative trait loci (QTLs; Shali1-5) linked to HALI survival time. Interestingly, analysis of these recombinant populations supported opposite within-strain effects on survival for the two major-effect QTLs. Whereas Shali1 alleles imparted the expected survival time effects (i.e., X1 alleles increased HALI resistance and B alleles increased sensitivity), the allelic effects of Shali2 were reversed (i.e., X1 alleles increased HALI sensitivity and B alleles increased resistance). For in vivo validation of these inverse allelic effects, we constructed reciprocal congenic lines to synchronize the sensitivity or resistance alleles of Shali1 and Shali2 within the same strain. Specifically, B-derived Shali1 or Shali2 QTL regions were transferred to X1 mice and X1-derived QTL segments were transferred to B mice. Our previous QTL results predicted that substituting Shali1 B alleles onto the resistant X1 background would add sensitivity. Surprisingly, not only were these mice more sensitive than the resistant X1 strain, they were more sensitive than the sensitive B strain. In stark contrast, substituting the Shali2 interval from the sensitive B strain onto the X1 background markedly increased the survival time. Reciprocal congenic lines confirmed the opposing allelic effects of Shali1 and Shali2 on HALI survival time and provide unique models to identify their respective quantitative trait genes and to critically assess the apparent bidirectional epistatic interactions between these major-effect loci.

Show MeSH
Related in: MedlinePlus