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Adrienne Silla Bugayong, Arnold Salazar, Peipei Pan, Nora Blanca Caberoy; Tubby Transcriptionally activates Estrogen Related Receptor Beta (Esrrβ). Invest. Ophthalmol. Vis. Sci. 2017;58(8):4518.
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A spontaneous mutation in the tubby gene results to progressive retinal and cochlear degeneration, and adult-onset obesity in mice. Structural analysis of the tubby C-terminal domain revealed that tubby may act as a transcription factor, but no gene target for tubby has been reported. This study aims to identify the genes regulated by tubby protein to understand how mutation in tubby leads to its disease phenotypes.
A list of genes potentially regulated by tubby was obtained from a limited microarray data. The expression of these genes was verified in tubby mutant and wildtype mice by quantitative real time RT-PCR. The promoter regions of these genes were scanned for potential binding sites for tubby. Furthermore, a biotin-labelled promoter of each gene was generated by PCR and used for protein-DNA pull down assays. Luciferase assay was performed to confirm transcriptional activity of tubby in vivo.
Scanning of the promoter regions of genes potentially regulated by tubby revealed a hallmark sequence called Estrogen-related Receptor Response Element (ERRE). One of the genes containing ERRE that was regulated by tubby was Estrogen related receptor beta (Esrrβ). Esrrβ is an orphan nuclear hormone receptor that does not bind to estrogen but regulates transcription by binding to ERRE’s of its target genes. Protein pull-down assays and electrophoretic mobility shift assays showed that tubby interacts with Esrrβ ERRE. Tubby was also shown to transcriptionally activate Esrrβ in vivo.
The results revealed that tubby regulates Esrrβ expression. Esrrβ is a critical regulator of rod photoreceptor function and survival by maintaining metabolic homeostasis. Tubby mice are defective for carbohydrate metabolism. Thus, tubby’s direct regulation of Esrrβ might be responsible for maintaining metabolic homeostasis in the retina.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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