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Spink2 modulates apoptotic susceptibility and is a candidate gene in the Rgcs1 QTL that affects retinal ganglion cell death after optic nerve damage.

Dietz JA, Maes ME, Huang S, Yandell BS, Schlamp CL, Montgomery AD, Allingham RR, Hauser MA, Nickells RW - PLoS ONE (2014)

Bottom Line: In this region, a single gene (Spink2) is the most likely candidate for this effect.This gene is also polymorphic between resistant and susceptible strains, containing a single conserved amino acid change (threonine to serine) and a 220 bp deletion in intron 1 that may quantitatively alter endogenous expression levels between strains.Overexpression of the different variants of Spink2 in D407 tissue culture cells also increases their susceptibility to the apoptosis-inducing agent staurosporine in a manner consistent with the differential susceptibility between the DBA/2J and BALB/cByJ strains.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, Wisconsin, United States of America.

ABSTRACT
The Rgcs1 quantitative trait locus, on mouse chromosome 5, influences susceptibility of retinal ganglion cells to acute damage of the optic nerve. Normally resistant mice (DBA/2J) congenic for the susceptible allele from BALB/cByJ mice exhibit susceptibility to ganglion cells, not only in acute optic nerve crush, but also to chronic inherited glaucoma that is characteristic of the DBA/2J strain as they age. SNP mapping of this QTL has narrowed the region of interest to 1 Mb. In this region, a single gene (Spink2) is the most likely candidate for this effect. Spink2 is expressed in retinal ganglion cells and is increased after optic nerve damage. This gene is also polymorphic between resistant and susceptible strains, containing a single conserved amino acid change (threonine to serine) and a 220 bp deletion in intron 1 that may quantitatively alter endogenous expression levels between strains. Overexpression of the different variants of Spink2 in D407 tissue culture cells also increases their susceptibility to the apoptosis-inducing agent staurosporine in a manner consistent with the differential susceptibility between the DBA/2J and BALB/cByJ strains.

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Narrowing of the Rgcs1 QTL to 1 Mb by SNP analysis.(A) A genome wide scanone of LOD scores for 252 mice generated by the F2 generation of a DBA/2J and BALB/cByJ cross. Data obtained from genome-wide microsatellite markers combined with 38 SNPs spaced throughout the 58 Mb region of chromosome 5 between Chr5:loc34-59 cM. A single significant peak with a LOD score of 6.81 was detected. (B) Detail of the scanone peak on chromosome 5 showing the highest association with SNP rs13478335. (C) Genomic map of mouse chromosome 5. The region highlighted in yellow indicates the size of the Rgcs1 QTL as defined by microsatellite markers in Dietz et al [11]. Black arrowheads indicate the positions of the first screen using SNPs across this region. Blue arrowheads indicate the position of SNPs between 76.7 and 77.7 Mb used in a second round of screening. No further narrowing of the interval was achieved in this second round. Known genes and putative coding regions (ENSEMBL genome browser) in this interval are shown.
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pone-0093564-g003: Narrowing of the Rgcs1 QTL to 1 Mb by SNP analysis.(A) A genome wide scanone of LOD scores for 252 mice generated by the F2 generation of a DBA/2J and BALB/cByJ cross. Data obtained from genome-wide microsatellite markers combined with 38 SNPs spaced throughout the 58 Mb region of chromosome 5 between Chr5:loc34-59 cM. A single significant peak with a LOD score of 6.81 was detected. (B) Detail of the scanone peak on chromosome 5 showing the highest association with SNP rs13478335. (C) Genomic map of mouse chromosome 5. The region highlighted in yellow indicates the size of the Rgcs1 QTL as defined by microsatellite markers in Dietz et al [11]. Black arrowheads indicate the positions of the first screen using SNPs across this region. Blue arrowheads indicate the position of SNPs between 76.7 and 77.7 Mb used in a second round of screening. No further narrowing of the interval was achieved in this second round. Known genes and putative coding regions (ENSEMBL genome browser) in this interval are shown.

Mentions: SNP analysis using 37 informative SNP markers, all within the region of the original limits of the Rgcs1 QTL, were conducted on 252 mice generated in an F2 cross (see Methods). This analysis defined further a significant association with a peak LOD score of 6.81 centered between 76.7 and 77.7 Mb (Figure 3), well above the estimated 99% confidence interval estimate of 4.15. A second round of mapping using 8 additional SNPs situated within this 1 Mb region confirmed this peak LOD score. LOD scores increased for all markers after normal transformation of the mapping population data, but did not change the position of peak association (data not shown). The fitted LOD curve on chromosome 5 using high resolution mapping with SNPs inside the 1 Mb region also yielded a potential bimodal structure suggestive of 2 QTLs in this region. This possibility was not supported by a “scantwo” analysis based on this assumption, however. Figure S1 shows the dominant inheritance pattern of the resistant phenotype as a function of the rs13478335 SNP. F2 animals, homozygous for the BALB/cByJ allele (CC), had significantly more cell loss (P<0.001) than mice either homozygous or heterozygous for the DBA/2J allele (DD and DC). Overall, this allele accounts for ∼11% of the cell death phenotype after optic nerve crush. This is consistent with the level of increased susceptibility in DBA/2J.BALBRgcs1 (CC) mice to optic nerve crush (Figure 1) and previous estimates calculated from the data obtained using microsatellite screening of a subset of this mapping population [11].


Spink2 modulates apoptotic susceptibility and is a candidate gene in the Rgcs1 QTL that affects retinal ganglion cell death after optic nerve damage.

Dietz JA, Maes ME, Huang S, Yandell BS, Schlamp CL, Montgomery AD, Allingham RR, Hauser MA, Nickells RW - PLoS ONE (2014)

Narrowing of the Rgcs1 QTL to 1 Mb by SNP analysis.(A) A genome wide scanone of LOD scores for 252 mice generated by the F2 generation of a DBA/2J and BALB/cByJ cross. Data obtained from genome-wide microsatellite markers combined with 38 SNPs spaced throughout the 58 Mb region of chromosome 5 between Chr5:loc34-59 cM. A single significant peak with a LOD score of 6.81 was detected. (B) Detail of the scanone peak on chromosome 5 showing the highest association with SNP rs13478335. (C) Genomic map of mouse chromosome 5. The region highlighted in yellow indicates the size of the Rgcs1 QTL as defined by microsatellite markers in Dietz et al [11]. Black arrowheads indicate the positions of the first screen using SNPs across this region. Blue arrowheads indicate the position of SNPs between 76.7 and 77.7 Mb used in a second round of screening. No further narrowing of the interval was achieved in this second round. Known genes and putative coding regions (ENSEMBL genome browser) in this interval are shown.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3974755&req=5

pone-0093564-g003: Narrowing of the Rgcs1 QTL to 1 Mb by SNP analysis.(A) A genome wide scanone of LOD scores for 252 mice generated by the F2 generation of a DBA/2J and BALB/cByJ cross. Data obtained from genome-wide microsatellite markers combined with 38 SNPs spaced throughout the 58 Mb region of chromosome 5 between Chr5:loc34-59 cM. A single significant peak with a LOD score of 6.81 was detected. (B) Detail of the scanone peak on chromosome 5 showing the highest association with SNP rs13478335. (C) Genomic map of mouse chromosome 5. The region highlighted in yellow indicates the size of the Rgcs1 QTL as defined by microsatellite markers in Dietz et al [11]. Black arrowheads indicate the positions of the first screen using SNPs across this region. Blue arrowheads indicate the position of SNPs between 76.7 and 77.7 Mb used in a second round of screening. No further narrowing of the interval was achieved in this second round. Known genes and putative coding regions (ENSEMBL genome browser) in this interval are shown.
Mentions: SNP analysis using 37 informative SNP markers, all within the region of the original limits of the Rgcs1 QTL, were conducted on 252 mice generated in an F2 cross (see Methods). This analysis defined further a significant association with a peak LOD score of 6.81 centered between 76.7 and 77.7 Mb (Figure 3), well above the estimated 99% confidence interval estimate of 4.15. A second round of mapping using 8 additional SNPs situated within this 1 Mb region confirmed this peak LOD score. LOD scores increased for all markers after normal transformation of the mapping population data, but did not change the position of peak association (data not shown). The fitted LOD curve on chromosome 5 using high resolution mapping with SNPs inside the 1 Mb region also yielded a potential bimodal structure suggestive of 2 QTLs in this region. This possibility was not supported by a “scantwo” analysis based on this assumption, however. Figure S1 shows the dominant inheritance pattern of the resistant phenotype as a function of the rs13478335 SNP. F2 animals, homozygous for the BALB/cByJ allele (CC), had significantly more cell loss (P<0.001) than mice either homozygous or heterozygous for the DBA/2J allele (DD and DC). Overall, this allele accounts for ∼11% of the cell death phenotype after optic nerve crush. This is consistent with the level of increased susceptibility in DBA/2J.BALBRgcs1 (CC) mice to optic nerve crush (Figure 1) and previous estimates calculated from the data obtained using microsatellite screening of a subset of this mapping population [11].

Bottom Line: In this region, a single gene (Spink2) is the most likely candidate for this effect.This gene is also polymorphic between resistant and susceptible strains, containing a single conserved amino acid change (threonine to serine) and a 220 bp deletion in intron 1 that may quantitatively alter endogenous expression levels between strains.Overexpression of the different variants of Spink2 in D407 tissue culture cells also increases their susceptibility to the apoptosis-inducing agent staurosporine in a manner consistent with the differential susceptibility between the DBA/2J and BALB/cByJ strains.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, Wisconsin, United States of America.

ABSTRACT
The Rgcs1 quantitative trait locus, on mouse chromosome 5, influences susceptibility of retinal ganglion cells to acute damage of the optic nerve. Normally resistant mice (DBA/2J) congenic for the susceptible allele from BALB/cByJ mice exhibit susceptibility to ganglion cells, not only in acute optic nerve crush, but also to chronic inherited glaucoma that is characteristic of the DBA/2J strain as they age. SNP mapping of this QTL has narrowed the region of interest to 1 Mb. In this region, a single gene (Spink2) is the most likely candidate for this effect. Spink2 is expressed in retinal ganglion cells and is increased after optic nerve damage. This gene is also polymorphic between resistant and susceptible strains, containing a single conserved amino acid change (threonine to serine) and a 220 bp deletion in intron 1 that may quantitatively alter endogenous expression levels between strains. Overexpression of the different variants of Spink2 in D407 tissue culture cells also increases their susceptibility to the apoptosis-inducing agent staurosporine in a manner consistent with the differential susceptibility between the DBA/2J and BALB/cByJ strains.

Show MeSH
Related in: MedlinePlus