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Behavioral defects in chaperone-deficient Alzheimer's disease model mice.

Ojha J, Karmegam RV, Masilamoni JG, Terry AV, Cashikar AG - PLoS ONE (2011)

Bottom Line: Molecular chaperones protect cells from the deleterious effects of protein misfolding and aggregation.We observed that the overall content of αB-crystallin, a small heat shock protein molecular chaperone, decreased in AD model mice in an age-dependent manner.Our results highlight a synergistic effect of combining chaperone deficiency in a transgenic mouse model for AD underscoring an important role for chaperones in protein misfolding diseases.

View Article: PubMed Central - PubMed

Affiliation: Center for Molecular Chaperones and Radiobiology, Medical College of Georgia, Augusta, Georgia, United States of America.

ABSTRACT
Molecular chaperones protect cells from the deleterious effects of protein misfolding and aggregation. Neurotoxicity of amyloid-beta (Aβ) aggregates and their deposition in senile plaques are hallmarks of Alzheimer's disease (AD). We observed that the overall content of αB-crystallin, a small heat shock protein molecular chaperone, decreased in AD model mice in an age-dependent manner. We hypothesized that αB-crystallin protects cells against Aβ toxicity. To test this, we crossed αB-crystallin/HspB2 deficient (CRYAB⁻/⁻HSPB2⁻/⁻) mice with AD model transgenic mice expressing mutant human amyloid precursor protein. Transgenic and non-transgenic mice in chaperone-sufficient or deficient backgrounds were examined for representative behavioral paradigms for locomotion and memory network functions: (i) spatial orientation and locomotion was monitored by open field test; (ii) sequential organization and associative learning was monitored by fear conditioning; and (iii) evoked behavioral response was tested by hot plate method. Interestingly, αB-crystallin/HspB2 deficient transgenic mice were severely impaired in locomotion compared to each genetic model separately. Our results highlight a synergistic effect of combining chaperone deficiency in a transgenic mouse model for AD underscoring an important role for chaperones in protein misfolding diseases.

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Generation of the required genotypes of mice.(A) Schematic diagram showing the mouse crosses that lead to the required genotypes. (B) Immunoblots showing αB-crystallin and Hsp27 expression in two sets of mice at 7 months of age. WT is CRYAB+/+HspB2+/+, Tg0/0; WTTg is CRYAB+/+HspB2+/+, Tg+/0; KO is CRYAB-/-HspB2-/-, Tg0/0 and KOTg is CRYAB-/-HspB2-/-, Tg+/0.
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pone-0016550-g002: Generation of the required genotypes of mice.(A) Schematic diagram showing the mouse crosses that lead to the required genotypes. (B) Immunoblots showing αB-crystallin and Hsp27 expression in two sets of mice at 7 months of age. WT is CRYAB+/+HspB2+/+, Tg0/0; WTTg is CRYAB+/+HspB2+/+, Tg+/0; KO is CRYAB-/-HspB2-/-, Tg0/0 and KOTg is CRYAB-/-HspB2-/-, Tg+/0.

Mentions: Based on our observations of reduced αB-crystallin in older transgenic but not in non-transgenic mice, we hypothesized that if this chaperone is protective, then its loss may show an exaggerated phenotype. To examine if decreased αB-crystallin levels were important for the manifestation of the behavioral phenotypes in the AD model mice we crossed Tg2576 mice (B6/SJL background) with wild-type (CRYAB+/+HSPB2+/+) or αB-crystallin/HspB2 knockout (CRYAB-/-HSPB2-/-) mice (129Sv background). The breeding scheme is shown in Figure 2A. This intercross resulted in litters with equal numbers of non-transgenic (Tg0/0) or hemizygous transgenic (Tg+/0) mice, which were heterozygous for αB-crystallin/HspB2 (CRYAB+/-HSPB2+/-). The litters were inbred to obtain mice of the following genotypes – (i) CRYAB+/+HSPB2+/+, Tg0/0; (ii) CRYAB+/+HSPB2+/+, Tg+/0; (iii) CRYAB-/-HSPB2-/-, Tg0/0 and (iv) CRYAB-/-HSPB2-/-, Tg+/0. From this point on, these mice are denoted as WT, WTTg, KO and KOTg, respectively. (Mice heterozygous for CRYAB (namely, CRYAB+/-HSPB2+/-, Tg0/0; and CRYAB+/- HSPB2+/-, Tg+/0) that were also generated in this cross were not used further.) By comparing only littermates for all experimental genotypes, we minimized the influence of genetic variation resulting from the parental strains. Further, any residual effects of genetic variation are expected to be evenly distributed between the four genotypes. The chaperone expression in each genotype was confirmed by western-blotting two sets of brain lysates from 7-month old mice for αB-crystallin, and Hsp27 (Figure 2B). The expression of Hsp27 was equal in all mice suggesting that the expression of Hsp27 was not increased to compensate for the loss of αB-crystallin/HspB2. The KO and KOTg samples were devoid of αB-crystallin as expected. WT samples showed higher amounts of αB-crystallin than WTTg samples as observed in Figure 1. Expression of APP was observed only in the transgenic samples (KOTg and WTTg) as expected (not shown). Although the WTTg mice express low levels of αB-crystallin, they are distinct from KOTg mice, which are devoid of αB-crystallin since embryogenesis.


Behavioral defects in chaperone-deficient Alzheimer's disease model mice.

Ojha J, Karmegam RV, Masilamoni JG, Terry AV, Cashikar AG - PLoS ONE (2011)

Generation of the required genotypes of mice.(A) Schematic diagram showing the mouse crosses that lead to the required genotypes. (B) Immunoblots showing αB-crystallin and Hsp27 expression in two sets of mice at 7 months of age. WT is CRYAB+/+HspB2+/+, Tg0/0; WTTg is CRYAB+/+HspB2+/+, Tg+/0; KO is CRYAB-/-HspB2-/-, Tg0/0 and KOTg is CRYAB-/-HspB2-/-, Tg+/0.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3040748&req=5

pone-0016550-g002: Generation of the required genotypes of mice.(A) Schematic diagram showing the mouse crosses that lead to the required genotypes. (B) Immunoblots showing αB-crystallin and Hsp27 expression in two sets of mice at 7 months of age. WT is CRYAB+/+HspB2+/+, Tg0/0; WTTg is CRYAB+/+HspB2+/+, Tg+/0; KO is CRYAB-/-HspB2-/-, Tg0/0 and KOTg is CRYAB-/-HspB2-/-, Tg+/0.
Mentions: Based on our observations of reduced αB-crystallin in older transgenic but not in non-transgenic mice, we hypothesized that if this chaperone is protective, then its loss may show an exaggerated phenotype. To examine if decreased αB-crystallin levels were important for the manifestation of the behavioral phenotypes in the AD model mice we crossed Tg2576 mice (B6/SJL background) with wild-type (CRYAB+/+HSPB2+/+) or αB-crystallin/HspB2 knockout (CRYAB-/-HSPB2-/-) mice (129Sv background). The breeding scheme is shown in Figure 2A. This intercross resulted in litters with equal numbers of non-transgenic (Tg0/0) or hemizygous transgenic (Tg+/0) mice, which were heterozygous for αB-crystallin/HspB2 (CRYAB+/-HSPB2+/-). The litters were inbred to obtain mice of the following genotypes – (i) CRYAB+/+HSPB2+/+, Tg0/0; (ii) CRYAB+/+HSPB2+/+, Tg+/0; (iii) CRYAB-/-HSPB2-/-, Tg0/0 and (iv) CRYAB-/-HSPB2-/-, Tg+/0. From this point on, these mice are denoted as WT, WTTg, KO and KOTg, respectively. (Mice heterozygous for CRYAB (namely, CRYAB+/-HSPB2+/-, Tg0/0; and CRYAB+/- HSPB2+/-, Tg+/0) that were also generated in this cross were not used further.) By comparing only littermates for all experimental genotypes, we minimized the influence of genetic variation resulting from the parental strains. Further, any residual effects of genetic variation are expected to be evenly distributed between the four genotypes. The chaperone expression in each genotype was confirmed by western-blotting two sets of brain lysates from 7-month old mice for αB-crystallin, and Hsp27 (Figure 2B). The expression of Hsp27 was equal in all mice suggesting that the expression of Hsp27 was not increased to compensate for the loss of αB-crystallin/HspB2. The KO and KOTg samples were devoid of αB-crystallin as expected. WT samples showed higher amounts of αB-crystallin than WTTg samples as observed in Figure 1. Expression of APP was observed only in the transgenic samples (KOTg and WTTg) as expected (not shown). Although the WTTg mice express low levels of αB-crystallin, they are distinct from KOTg mice, which are devoid of αB-crystallin since embryogenesis.

Bottom Line: Molecular chaperones protect cells from the deleterious effects of protein misfolding and aggregation.We observed that the overall content of αB-crystallin, a small heat shock protein molecular chaperone, decreased in AD model mice in an age-dependent manner.Our results highlight a synergistic effect of combining chaperone deficiency in a transgenic mouse model for AD underscoring an important role for chaperones in protein misfolding diseases.

View Article: PubMed Central - PubMed

Affiliation: Center for Molecular Chaperones and Radiobiology, Medical College of Georgia, Augusta, Georgia, United States of America.

ABSTRACT
Molecular chaperones protect cells from the deleterious effects of protein misfolding and aggregation. Neurotoxicity of amyloid-beta (Aβ) aggregates and their deposition in senile plaques are hallmarks of Alzheimer's disease (AD). We observed that the overall content of αB-crystallin, a small heat shock protein molecular chaperone, decreased in AD model mice in an age-dependent manner. We hypothesized that αB-crystallin protects cells against Aβ toxicity. To test this, we crossed αB-crystallin/HspB2 deficient (CRYAB⁻/⁻HSPB2⁻/⁻) mice with AD model transgenic mice expressing mutant human amyloid precursor protein. Transgenic and non-transgenic mice in chaperone-sufficient or deficient backgrounds were examined for representative behavioral paradigms for locomotion and memory network functions: (i) spatial orientation and locomotion was monitored by open field test; (ii) sequential organization and associative learning was monitored by fear conditioning; and (iii) evoked behavioral response was tested by hot plate method. Interestingly, αB-crystallin/HspB2 deficient transgenic mice were severely impaired in locomotion compared to each genetic model separately. Our results highlight a synergistic effect of combining chaperone deficiency in a transgenic mouse model for AD underscoring an important role for chaperones in protein misfolding diseases.

Show MeSH
Related in: MedlinePlus