Limits...
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.

Show MeSH

Related in: MedlinePlus

HdhQ111/+B6J.AJ10 mice showed a mild increase of neuronal intranuclear inclusions when compared to HdhQ111/+B6J mice. a Micrographs of striata stained with EM48 and counterstained with thionine of representative 5 months mice with Hdh+/+B6J, HdhQ111/+B6J (139 CAGs), Hdh+/+B6J.AJ10 and HdhQ111/+B6J.AJ10 (140 CAGs) genotypes. b Quantification of the percentage of EM48-positive cells containing an inclusion (line represents mean of values for each genotype) and c its correlation with constitutive Htt CAG repeat size (the best fit linear regression line of inclusion/EM48 nuclei by CAG repeat size for HdhQ111/+B6J is represent with solid line and for HdhQ111/+B6J.AJ10 with the thinner solid line). HdhQ111/+B6J (n = 9) mice are represented in squares and HdhQ111/+B6J.AJ10 (n = 9) mice in triangles. Each individual value represents the mean observed on three consecutive striatal sections for each mouse
© Copyright Policy - OpenAccess
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4372682&req=5

Fig6: HdhQ111/+B6J.AJ10 mice showed a mild increase of neuronal intranuclear inclusions when compared to HdhQ111/+B6J mice. a Micrographs of striata stained with EM48 and counterstained with thionine of representative 5 months mice with Hdh+/+B6J, HdhQ111/+B6J (139 CAGs), Hdh+/+B6J.AJ10 and HdhQ111/+B6J.AJ10 (140 CAGs) genotypes. b Quantification of the percentage of EM48-positive cells containing an inclusion (line represents mean of values for each genotype) and c its correlation with constitutive Htt CAG repeat size (the best fit linear regression line of inclusion/EM48 nuclei by CAG repeat size for HdhQ111/+B6J is represent with solid line and for HdhQ111/+B6J.AJ10 with the thinner solid line). HdhQ111/+B6J (n = 9) mice are represented in squares and HdhQ111/+B6J.AJ10 (n = 9) mice in triangles. Each individual value represents the mean observed on three consecutive striatal sections for each mouse

Mentions: Another early, dominant, CAG-length-dependent phenotype in HdhQ111 mice is the time-dependent immunostaining of mutant huntingtin in the nuclei of striatal neurons. Previous studies have detected early (~2.5 months) diffuse-immunostaining nuclear mutant huntingtin and later (6–12 months) intranuclear inclusions of mutant huntingtin amino-terminal fragments, using the anti-huntingtin antibody EM48 (Lloret et al. 2006; Wheeler et al. 2000, 2002). In order to determine the effect of the chr10 background on the nuclear mutant huntingtin phenotype, we immunostained striatal sections from 5-month mice with EM48 antibody (Fig. 6a). As expected, EM48 staining was not detected in the wild type mice (Fig. 6a, right panel). When comparing Htt CAG knock-in mice, we found a similar number of nuclei with diffuse mutant huntingtin stain (data not shown) and some nuclei exhibited intranuclear inclusions (Fig. 6a, left panel). We found that, compared to HdhQ111/+B6J mice, the percentage of EM48-positive nuclei with intranuclear inclusions was higher in HdhQ111/+B6J.AJ10 mice (35.88 ± 11.45 vs 46.69 ± 12.11, respectively), although the difference did not reach statistical significance (Fig. 6b; p = 0.0694). Moreover, the number of intranuclear inclusions was found to depend on the constitutive CAG repeat length of HdhQ111/+B6J.AJ10 mice, with longer CAG lengths resulting in an increased percentage of EM48 nuclei with inclusions (and higher when compared with HdhQ111/+B6J mice with similar CAG repeat length) (Fig. 6c).Fig. 6


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/+B6J.AJ10 mice showed a mild increase of neuronal intranuclear inclusions when compared to HdhQ111/+B6J mice. a Micrographs of striata stained with EM48 and counterstained with thionine of representative 5 months mice with Hdh+/+B6J, HdhQ111/+B6J (139 CAGs), Hdh+/+B6J.AJ10 and HdhQ111/+B6J.AJ10 (140 CAGs) genotypes. b Quantification of the percentage of EM48-positive cells containing an inclusion (line represents mean of values for each genotype) and c its correlation with constitutive Htt CAG repeat size (the best fit linear regression line of inclusion/EM48 nuclei by CAG repeat size for HdhQ111/+B6J is represent with solid line and for HdhQ111/+B6J.AJ10 with the thinner solid line). HdhQ111/+B6J (n = 9) mice are represented in squares and HdhQ111/+B6J.AJ10 (n = 9) mice in triangles. Each individual value represents the mean observed on three consecutive striatal sections for each mouse
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig6: HdhQ111/+B6J.AJ10 mice showed a mild increase of neuronal intranuclear inclusions when compared to HdhQ111/+B6J mice. a Micrographs of striata stained with EM48 and counterstained with thionine of representative 5 months mice with Hdh+/+B6J, HdhQ111/+B6J (139 CAGs), Hdh+/+B6J.AJ10 and HdhQ111/+B6J.AJ10 (140 CAGs) genotypes. b Quantification of the percentage of EM48-positive cells containing an inclusion (line represents mean of values for each genotype) and c its correlation with constitutive Htt CAG repeat size (the best fit linear regression line of inclusion/EM48 nuclei by CAG repeat size for HdhQ111/+B6J is represent with solid line and for HdhQ111/+B6J.AJ10 with the thinner solid line). HdhQ111/+B6J (n = 9) mice are represented in squares and HdhQ111/+B6J.AJ10 (n = 9) mice in triangles. Each individual value represents the mean observed on three consecutive striatal sections for each mouse
Mentions: Another early, dominant, CAG-length-dependent phenotype in HdhQ111 mice is the time-dependent immunostaining of mutant huntingtin in the nuclei of striatal neurons. Previous studies have detected early (~2.5 months) diffuse-immunostaining nuclear mutant huntingtin and later (6–12 months) intranuclear inclusions of mutant huntingtin amino-terminal fragments, using the anti-huntingtin antibody EM48 (Lloret et al. 2006; Wheeler et al. 2000, 2002). In order to determine the effect of the chr10 background on the nuclear mutant huntingtin phenotype, we immunostained striatal sections from 5-month mice with EM48 antibody (Fig. 6a). As expected, EM48 staining was not detected in the wild type mice (Fig. 6a, right panel). When comparing Htt CAG knock-in mice, we found a similar number of nuclei with diffuse mutant huntingtin stain (data not shown) and some nuclei exhibited intranuclear inclusions (Fig. 6a, left panel). We found that, compared to HdhQ111/+B6J mice, the percentage of EM48-positive nuclei with intranuclear inclusions was higher in HdhQ111/+B6J.AJ10 mice (35.88 ± 11.45 vs 46.69 ± 12.11, respectively), although the difference did not reach statistical significance (Fig. 6b; p = 0.0694). Moreover, the number of intranuclear inclusions was found to depend on the constitutive CAG repeat length of HdhQ111/+B6J.AJ10 mice, with longer CAG lengths resulting in an increased percentage of EM48 nuclei with inclusions (and higher when compared with HdhQ111/+B6J mice with similar CAG repeat length) (Fig. 6c).Fig. 6

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