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Chromosome substitution strain assessment of a Huntington's disease modifier locus.

Ramos EM, Kovalenko M, Guide JR, St Claire J, Gillis T, Mysore JS, Sequeiros J, Wheeler VC, Alonso I, MacDonald ME - Mamm. Genome (2015)

Bottom Line: Crosses were performed to assess the possibility of dominantly acting chr10 AJ-B6J variants of strong effect that may modulate CAG-dependent Hdh(Q111/+) phenotypes.These findings in relatively small cohorts are suggestive of dominant chr10 AJ-B6 variants that may modify effects of the CAG expansion, and encourage a larger study with CSS10 and sub-strains.This cross-species approach may therefore be suited to functional in vivo prioritisation of genomic regions harbouring genes that can modify the early effects of the HD mutation.

View Article: PubMed Central - PubMed

Affiliation: Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA, 02114, USA, esilvaramos@mgh.harvard.edu.

ABSTRACT
Huntington's disease (HD) is a dominant neurodegenerative disorder that is due to expansion of an unstable HTT CAG repeat for which genome-wide genetic scans are now revealing chromosome regions that contain disease-modifying genes. We have explored a novel human-mouse cross-species functional prioritisation approach, by evaluating the HD modifier 6q23-24 linkage interval. This unbiased strategy employs C57BL/6J (B6J) Hdh(Q111) knock-in mice, replicates of the HD mutation, and the C57BL/6J-chr10(A/J)/NaJ chromosome substitution strain (CSS10), in which only chromosome 10 (chr10), in synteny with the human 6q23-24 region, is derived from the A/J (AJ) strain. Crosses were performed to assess the possibility of dominantly acting chr10 AJ-B6J variants of strong effect that may modulate CAG-dependent Hdh(Q111/+) phenotypes. Testing of F1 progeny confirmed that a single AJ chromosome had a significant effect on the rate of body weight gain and in Hdh(Q111) mice the AJ chromosome was associated subtle alterations in somatic CAG instability in the liver and the formation of intra-nuclear inclusions, as well as DARPP-32 levels, in the striatum. These findings in relatively small cohorts are suggestive of dominant chr10 AJ-B6 variants that may modify effects of the CAG expansion, and encourage a larger study with CSS10 and sub-strains. This cross-species approach may therefore be suited to functional in vivo prioritisation of genomic regions harbouring genes that can modify the early effects of the HD mutation.

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Related in: MedlinePlus

HdhQ111 knock-in mice with different chr10 genetic backgrounds. Representative diagram of the breeding scheme showing the manner in which both chr10—AJ or B6J—and Htt alleles—wild type (+) or HdhQ111 knock-in allele (Q111)—were passed to the F1 progeny mice used in this study. The actual CAG size of the HdhQ111 knock-in allele in the paternal mice was 139 CAGs while in the F1 progeny ranged from 133 to 149 CAGs
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Fig1: HdhQ111 knock-in mice with different chr10 genetic backgrounds. Representative diagram of the breeding scheme showing the manner in which both chr10—AJ or B6J—and Htt alleles—wild type (+) or HdhQ111 knock-in allele (Q111)—were passed to the F1 progeny mice used in this study. The actual CAG size of the HdhQ111 knock-in allele in the paternal mice was 139 CAGs while in the F1 progeny ranged from 133 to 149 CAGs

Mentions: The C57BL/6J-Chr10A/J/NaJ (CSS10) mice that carry both chr10 from strain AJ on an otherwise C57BL/6J (shortened here to B6J) background (Nadeau et al. 2000) and wild type B6J mice were obtained from The Jackson Laboratories (Jackson Laboratories, Bar Harbor, ME). The congenic HdhQ111 knock-in line of mice used in this study carry the targeted Htt CAG expansion allele (Wheeler et al. 1999; White et al. 1997) on the B6J background. The renaming of the human HD gene, from HD to HTT, and of its murine homologue, from Hdh to Htt, has obscured connexions to previous research. Therefore, to maintain consistency with the literature and with the names of the lines of mice deposited in repositories, we use HdhQ111 to denote the published name of the specific line of mice that we have utilised. The locus name Htt is used to refer to the general knock-in approach (e.g. Htt CAG knock-in) and to the precise size of the expanded CAG repeat allele, which varies in any given progeny due to intergenerational CAG repeat instability. Thus, the actual genotyped Htt CAG repeat size of the parental HdhQ111 mice was 139 CAG repeats. As shown in Fig. 1, crosses between HdhQ111 knock-in and wild type (CSS10 and B6J) mice were made in one direction—HdhQ111/+ male × B6J and CSS10 females—in order to control for possible parental effects of the Htt mutant allele. Briefly, male heterozygous HdhQ111/+ knock-in mice were crossed with CSS10 female mice in order to generate wild type Hdh+/+.C57BL/6J.Chr10A/J (Hdh+/+B6J.AJ10) and mutant HdhQ111/+.C57BL/6J.Chr10A/J (HdhQ111/+B6J.AJ10) mice that carried one chr10 from strain AJ on an otherwise B6J background. Subsequently, the same male heterozygous HdhQ111/+ knock-in mice were crossed with B6J female mice in order to generate wild type Hdh+/+.C57BL/6J (Hdh+/+B6J) and mutant HdhQ111/+.C57BL/6J (HdhQ111/+B6J) mice on a complete B6J background. Animal experiments were performed to minimise pain and discomfort, under an approved protocol of the Massachusetts General Hospital Subcommittee on Research Animal Care.Fig. 1


Chromosome substitution strain assessment of a Huntington's disease modifier locus.

Ramos EM, Kovalenko M, Guide JR, St Claire J, Gillis T, Mysore JS, Sequeiros J, Wheeler VC, Alonso I, MacDonald ME - Mamm. Genome (2015)

HdhQ111 knock-in mice with different chr10 genetic backgrounds. Representative diagram of the breeding scheme showing the manner in which both chr10—AJ or B6J—and Htt alleles—wild type (+) or HdhQ111 knock-in allele (Q111)—were passed to the F1 progeny mice used in this study. The actual CAG size of the HdhQ111 knock-in allele in the paternal mice was 139 CAGs while in the F1 progeny ranged from 133 to 149 CAGs
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4372682&req=5

Fig1: HdhQ111 knock-in mice with different chr10 genetic backgrounds. Representative diagram of the breeding scheme showing the manner in which both chr10—AJ or B6J—and Htt alleles—wild type (+) or HdhQ111 knock-in allele (Q111)—were passed to the F1 progeny mice used in this study. The actual CAG size of the HdhQ111 knock-in allele in the paternal mice was 139 CAGs while in the F1 progeny ranged from 133 to 149 CAGs
Mentions: The C57BL/6J-Chr10A/J/NaJ (CSS10) mice that carry both chr10 from strain AJ on an otherwise C57BL/6J (shortened here to B6J) background (Nadeau et al. 2000) and wild type B6J mice were obtained from The Jackson Laboratories (Jackson Laboratories, Bar Harbor, ME). The congenic HdhQ111 knock-in line of mice used in this study carry the targeted Htt CAG expansion allele (Wheeler et al. 1999; White et al. 1997) on the B6J background. The renaming of the human HD gene, from HD to HTT, and of its murine homologue, from Hdh to Htt, has obscured connexions to previous research. Therefore, to maintain consistency with the literature and with the names of the lines of mice deposited in repositories, we use HdhQ111 to denote the published name of the specific line of mice that we have utilised. The locus name Htt is used to refer to the general knock-in approach (e.g. Htt CAG knock-in) and to the precise size of the expanded CAG repeat allele, which varies in any given progeny due to intergenerational CAG repeat instability. Thus, the actual genotyped Htt CAG repeat size of the parental HdhQ111 mice was 139 CAG repeats. As shown in Fig. 1, crosses between HdhQ111 knock-in and wild type (CSS10 and B6J) mice were made in one direction—HdhQ111/+ male × B6J and CSS10 females—in order to control for possible parental effects of the Htt mutant allele. Briefly, male heterozygous HdhQ111/+ knock-in mice were crossed with CSS10 female mice in order to generate wild type Hdh+/+.C57BL/6J.Chr10A/J (Hdh+/+B6J.AJ10) and mutant HdhQ111/+.C57BL/6J.Chr10A/J (HdhQ111/+B6J.AJ10) mice that carried one chr10 from strain AJ on an otherwise B6J background. Subsequently, the same male heterozygous HdhQ111/+ knock-in mice were crossed with B6J female mice in order to generate wild type Hdh+/+.C57BL/6J (Hdh+/+B6J) and mutant HdhQ111/+.C57BL/6J (HdhQ111/+B6J) mice on a complete B6J background. Animal experiments were performed to minimise pain and discomfort, under an approved protocol of the Massachusetts General Hospital Subcommittee on Research Animal Care.Fig. 1

Bottom Line: Crosses were performed to assess the possibility of dominantly acting chr10 AJ-B6J variants of strong effect that may modulate CAG-dependent Hdh(Q111/+) phenotypes.These findings in relatively small cohorts are suggestive of dominant chr10 AJ-B6 variants that may modify effects of the CAG expansion, and encourage a larger study with CSS10 and sub-strains.This cross-species approach may therefore be suited to functional in vivo prioritisation of genomic regions harbouring genes that can modify the early effects of the HD mutation.

View Article: PubMed Central - PubMed

Affiliation: Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA, 02114, USA, esilvaramos@mgh.harvard.edu.

ABSTRACT
Huntington's disease (HD) is a dominant neurodegenerative disorder that is due to expansion of an unstable HTT CAG repeat for which genome-wide genetic scans are now revealing chromosome regions that contain disease-modifying genes. We have explored a novel human-mouse cross-species functional prioritisation approach, by evaluating the HD modifier 6q23-24 linkage interval. This unbiased strategy employs C57BL/6J (B6J) Hdh(Q111) knock-in mice, replicates of the HD mutation, and the C57BL/6J-chr10(A/J)/NaJ chromosome substitution strain (CSS10), in which only chromosome 10 (chr10), in synteny with the human 6q23-24 region, is derived from the A/J (AJ) strain. Crosses were performed to assess the possibility of dominantly acting chr10 AJ-B6J variants of strong effect that may modulate CAG-dependent Hdh(Q111/+) phenotypes. Testing of F1 progeny confirmed that a single AJ chromosome had a significant effect on the rate of body weight gain and in Hdh(Q111) mice the AJ chromosome was associated subtle alterations in somatic CAG instability in the liver and the formation of intra-nuclear inclusions, as well as DARPP-32 levels, in the striatum. These findings in relatively small cohorts are suggestive of dominant chr10 AJ-B6 variants that may modify effects of the CAG expansion, and encourage a larger study with CSS10 and sub-strains. This cross-species approach may therefore be suited to functional in vivo prioritisation of genomic regions harbouring genes that can modify the early effects of the HD mutation.

Show MeSH
Related in: MedlinePlus