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Crybb2 coding for βB2-crystallin affects sensorimotor gating and hippocampal function.

Sun M, Hölter SM, Stepan J, Garrett L, Genius J, Kremmer E, Hrabě de Angelis M, Wurst W, Lie DC, Bally-Cuif L, Eder M, Rujescu D, Graw J - Mamm. Genome (2013)

Bottom Line: These results point to an important function of βB2-crystallin in the hippocampal network.They indicate pleiotropic effects of mutations in the Crybb2 gene, which previously had been considered to be specific to the ocular lens.Moreover, our results are the first to demonstrate that βB2-crystallin has a role in hippocampal function and behavioral phenotypes.

View Article: PubMed Central - PubMed

Affiliation: Institute of Developmental Genetics, Helmholtz Center Munich - National Research Center for Environmental Health, Ingolstädter Landstrasse 1, 85764, Neuherberg, Germany.

ABSTRACT
βB2-crystallin (gene symbol: Crybb2/CRYBB2) was first described as a structural protein of the ocular lens. This gene, however, is also expressed in several regions of the mammalian brain, although its function in this organ remains entirely unknown. To unravel some aspects of its function in the brain, we combined behavioral, neuroanatomical, and physiological analyses in a novel Crybb2 mouse mutant, O377. Behavioral tests with male O377 mutants revealed altered sensorimotor gating, suggesting modified neuronal functions. Since these mouse mutants also displayed reduced hippocampal size, we concentrated further investigations on the hippocampus. Free intracellular Ca(2+) levels were increased and apoptosis was enhanced in the hippocampus of O377 mutants. Moreover, the expression of the gene encoding calpain 3 (gene symbol Capn3) was elevated and the expression of genes coding for the NMDA receptor subunits was downregulated. Additionally, the number of parvalbumin-positive interneurons was decreased in the hippocampus but not in the cortex of the mutants. High-speed voltage-sensitive dye imaging demonstrated an increased translation of input-to-output neuronal activity in the dentate gyrus of this Crybb2 mutant. These results point to an important function of βB2-crystallin in the hippocampal network. They indicate pleiotropic effects of mutations in the Crybb2 gene, which previously had been considered to be specific to the ocular lens. Moreover, our results are the first to demonstrate that βB2-crystallin has a role in hippocampal function and behavioral phenotypes. This model can now be further explored by future experiments.

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Altered expression levels of Capn3 and Grin1-Grin2C at P14. a–cCapn3 was detected to be expressed in the cerebellum, hippocampus, rostral migratory stream, and olfactory bulb of wild-type (a) and O377 mutant mice (b); no staining was ever observed with the sense control (c). d–f Close-up of the Capn3 expression in the hippocampus (d wild-type; eO377; f sense control). gCapn3 was detected by RT-PCR in the hippocampus at different developmental stages (E14.5–E18.5) and postnatally (P0–P30) in wild-type and O377 mice. h–l Normalized expression ratios of Capn3 (h), Grin1 (i), Grin2A (j), Grin2B (k), and Grin2C (l) in wild-type and O377 mutant mice determined by real-time PCR at P14. The relative gene expression levels were calculated by the ratio of the mRNA level of the gene of interest versus the expression level of the mRNA of a housekeeping gene, Tuba1a, according to the 2−ΔΔCt method (WT = 100 %).*p ≤ 0.05, Student’s t test, n ≥ 4. Error bar SEM
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Fig4: Altered expression levels of Capn3 and Grin1-Grin2C at P14. a–cCapn3 was detected to be expressed in the cerebellum, hippocampus, rostral migratory stream, and olfactory bulb of wild-type (a) and O377 mutant mice (b); no staining was ever observed with the sense control (c). d–f Close-up of the Capn3 expression in the hippocampus (d wild-type; eO377; f sense control). gCapn3 was detected by RT-PCR in the hippocampus at different developmental stages (E14.5–E18.5) and postnatally (P0–P30) in wild-type and O377 mice. h–l Normalized expression ratios of Capn3 (h), Grin1 (i), Grin2A (j), Grin2B (k), and Grin2C (l) in wild-type and O377 mutant mice determined by real-time PCR at P14. The relative gene expression levels were calculated by the ratio of the mRNA level of the gene of interest versus the expression level of the mRNA of a housekeeping gene, Tuba1a, according to the 2−ΔΔCt method (WT = 100 %).*p ≤ 0.05, Student’s t test, n ≥ 4. Error bar SEM

Mentions: Previous work demonstrated the upregulation of calpain 3 (gene symbol Capn3) expression in the brain of adult O377 mutants (Ganguly et al. 2008). Calpains are calcium-dependent proteases and highly associated with apoptosis (Raynaud and Marcilhac 2006). Given the results above that point to early changes in calcium homeostasis and neuronal death in βB2-crystallin mutants, we analyzed the expression of Capn3 in the brain of wild-type and O377 mutant mice at the age of 1 and 3 months. Capn3 was found to be widely expressed in the brains of both genotypes. We observed positive staining in Purkinje cells and granular cells of the cerebellum, in all layers of the cerebral cortex, in the CA1, CA2, CA3, and DG regions of the hippocampus, and in the glomerular layer, mitral layer, and granule cells of the olfactory bulb pointing to an overlapping expression pattern of Capn3 and Crybb2 (Fig. 4a–g). We also detected Capn3 expression in the hippocampus from E14.5 onward; it reached its maximum level at birth and remained constant at least up to 3 months (Fig. 4h). It might be important to mention that the Capn3 expression pattern in the hippocampus is almost identical to the Crybb2 expression pattern in the hippocampus, as described previously (Ganguly et al. 2008).Fig. 4


Crybb2 coding for βB2-crystallin affects sensorimotor gating and hippocampal function.

Sun M, Hölter SM, Stepan J, Garrett L, Genius J, Kremmer E, Hrabě de Angelis M, Wurst W, Lie DC, Bally-Cuif L, Eder M, Rujescu D, Graw J - Mamm. Genome (2013)

Altered expression levels of Capn3 and Grin1-Grin2C at P14. a–cCapn3 was detected to be expressed in the cerebellum, hippocampus, rostral migratory stream, and olfactory bulb of wild-type (a) and O377 mutant mice (b); no staining was ever observed with the sense control (c). d–f Close-up of the Capn3 expression in the hippocampus (d wild-type; eO377; f sense control). gCapn3 was detected by RT-PCR in the hippocampus at different developmental stages (E14.5–E18.5) and postnatally (P0–P30) in wild-type and O377 mice. h–l Normalized expression ratios of Capn3 (h), Grin1 (i), Grin2A (j), Grin2B (k), and Grin2C (l) in wild-type and O377 mutant mice determined by real-time PCR at P14. The relative gene expression levels were calculated by the ratio of the mRNA level of the gene of interest versus the expression level of the mRNA of a housekeeping gene, Tuba1a, according to the 2−ΔΔCt method (WT = 100 %).*p ≤ 0.05, Student’s t test, n ≥ 4. Error bar SEM
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
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Fig4: Altered expression levels of Capn3 and Grin1-Grin2C at P14. a–cCapn3 was detected to be expressed in the cerebellum, hippocampus, rostral migratory stream, and olfactory bulb of wild-type (a) and O377 mutant mice (b); no staining was ever observed with the sense control (c). d–f Close-up of the Capn3 expression in the hippocampus (d wild-type; eO377; f sense control). gCapn3 was detected by RT-PCR in the hippocampus at different developmental stages (E14.5–E18.5) and postnatally (P0–P30) in wild-type and O377 mice. h–l Normalized expression ratios of Capn3 (h), Grin1 (i), Grin2A (j), Grin2B (k), and Grin2C (l) in wild-type and O377 mutant mice determined by real-time PCR at P14. The relative gene expression levels were calculated by the ratio of the mRNA level of the gene of interest versus the expression level of the mRNA of a housekeeping gene, Tuba1a, according to the 2−ΔΔCt method (WT = 100 %).*p ≤ 0.05, Student’s t test, n ≥ 4. Error bar SEM
Mentions: Previous work demonstrated the upregulation of calpain 3 (gene symbol Capn3) expression in the brain of adult O377 mutants (Ganguly et al. 2008). Calpains are calcium-dependent proteases and highly associated with apoptosis (Raynaud and Marcilhac 2006). Given the results above that point to early changes in calcium homeostasis and neuronal death in βB2-crystallin mutants, we analyzed the expression of Capn3 in the brain of wild-type and O377 mutant mice at the age of 1 and 3 months. Capn3 was found to be widely expressed in the brains of both genotypes. We observed positive staining in Purkinje cells and granular cells of the cerebellum, in all layers of the cerebral cortex, in the CA1, CA2, CA3, and DG regions of the hippocampus, and in the glomerular layer, mitral layer, and granule cells of the olfactory bulb pointing to an overlapping expression pattern of Capn3 and Crybb2 (Fig. 4a–g). We also detected Capn3 expression in the hippocampus from E14.5 onward; it reached its maximum level at birth and remained constant at least up to 3 months (Fig. 4h). It might be important to mention that the Capn3 expression pattern in the hippocampus is almost identical to the Crybb2 expression pattern in the hippocampus, as described previously (Ganguly et al. 2008).Fig. 4

Bottom Line: These results point to an important function of βB2-crystallin in the hippocampal network.They indicate pleiotropic effects of mutations in the Crybb2 gene, which previously had been considered to be specific to the ocular lens.Moreover, our results are the first to demonstrate that βB2-crystallin has a role in hippocampal function and behavioral phenotypes.

View Article: PubMed Central - PubMed

Affiliation: Institute of Developmental Genetics, Helmholtz Center Munich - National Research Center for Environmental Health, Ingolstädter Landstrasse 1, 85764, Neuherberg, Germany.

ABSTRACT
βB2-crystallin (gene symbol: Crybb2/CRYBB2) was first described as a structural protein of the ocular lens. This gene, however, is also expressed in several regions of the mammalian brain, although its function in this organ remains entirely unknown. To unravel some aspects of its function in the brain, we combined behavioral, neuroanatomical, and physiological analyses in a novel Crybb2 mouse mutant, O377. Behavioral tests with male O377 mutants revealed altered sensorimotor gating, suggesting modified neuronal functions. Since these mouse mutants also displayed reduced hippocampal size, we concentrated further investigations on the hippocampus. Free intracellular Ca(2+) levels were increased and apoptosis was enhanced in the hippocampus of O377 mutants. Moreover, the expression of the gene encoding calpain 3 (gene symbol Capn3) was elevated and the expression of genes coding for the NMDA receptor subunits was downregulated. Additionally, the number of parvalbumin-positive interneurons was decreased in the hippocampus but not in the cortex of the mutants. High-speed voltage-sensitive dye imaging demonstrated an increased translation of input-to-output neuronal activity in the dentate gyrus of this Crybb2 mutant. These results point to an important function of βB2-crystallin in the hippocampal network. They indicate pleiotropic effects of mutations in the Crybb2 gene, which previously had been considered to be specific to the ocular lens. Moreover, our results are the first to demonstrate that βB2-crystallin has a role in hippocampal function and behavioral phenotypes. This model can now be further explored by future experiments.

Show MeSH