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Abstract
The tubby mouse is characterized by progressive retinal and cochlear degeneration and late-onset obesity. These phenotypes are caused by a loss-of-function mutation in the tub gene and are shared with several human syndromes, suggesting the importance of tubby protein in central nervous system (CNS) functioning. Although evidence suggests that tubby may act as a transcription factor mediating G-protein coupled receptor (GPCR) signaling, any downstream gene regulated by tubby has yet to be identified. To explore potential target genes of tubby with region-specific transcription patterns in the brain, we performed a microarray analysis using the cerebral cortex and hypothalamus of tubby mice. We also validated the changes of gene expression level observed with the microarray analysis using real-time RT-PCR. We found that expression of erythroid differentiation factor 1 (Erdr1) and caspase 1 (Casp1) increased, while p21-activated kinase 1 (Pak1) and cholecystokinin 2 receptor (Cck2r) expression decreased in the cerebral cortex of tubby mice. In the hypothalamic region, Casp 1 was up-regulated and μ-crystallin (CRYM) was down-regulated. Based on the reported functions of the differentially expressed genes, these individual or grouped genes may account for the phenotype of tubby mice. We discussed how altered expression of genes in tubby mice might be understood as the underlying mechanism behind tubby phenotypes.
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Fig. 1.
Validation of array-based gene expression profiles in the cerebral cortex of tubby mice using real-time RT-PCR. mRNA levels of genes were determined using real-time RT-PCR. Expression profiles of up-regulated (A) and down-regulated genes (B) are presented as fold changes compared to the cerebral cortex of control mice. Expression levels of β-actin were used to normalize the values. ∗p<0.05 and ∗∗p<0.01.
Fig. 2.
Validation of array-based gene expression profiles in the hypothalamus of tubby mice using real-time RT-PCR. mRNA levels of genes were determined using real-time RT-PCR. Hypothalamic Casp1 and Erdr1 expressions (A), the up-regulated genes in the cortex, and the expression profiles of other down-regulated genes in the hypothalamus (B) are represented as fold changes compared to the hypothalmus of control mice. Expression levels of β-actin were used to normalize the values. ∗p<0.05.
Table 1.
Sequences of primers used in real-time RT-PCR
Table 2.
A selection of genes up- or down-regulated in the cerebral cortex of tubby mice compared to control mice. Gene profiling was performed using microarray analysis. Expression level is presented as the mean of fold change (n=3). Negative fold change values indicate decreased gene expression in tubby mice
Table 3.
A selection of genes up- or down-regulated in the hypothalamus of tubby mice compared to control mice. Gene profiling was performed using microarray analysis. Expression level is presented as the mean of fold change (n=3). Negative fold change values indicate decreased gene expression in tubby mice
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