Related Experiment Video
Updated: Aug 21, 2026
Quantifying the Activity of cis-Regulatory Elements in the Mouse Retina by Explant Electroporation
Published on: June 28, 2011
Deciphering the contribution of known cis-elements in the mouse cone arrestin gene to its cone-specific expression
Shiyi Wei Pickrell1, Xuemei Zhu, Xiaopeng Wang
1The Mary D. Allen Laboratory for Vision Research, Doheny Eye Institute, Los Angeles, CA 90033-9224, USA.
Purpose:
Cone arrestin (CAR) is highly expressed in all cone photoreceptors of the retina and a subset of pinealocytes in the pineal gland. This study was initiated to examine the cis-elements responsible for the cell-specific expression pattern of CAR.
Methods:
Mutagenesis and specific deletions of known cis-elements in the proximal promoter of the mouse CAR (mCAR) gene were introduced and analyzed in vitro and in vivo. A series of mCAR promoter-luciferase reporter constructs were transiently transfected into COS-7 or Weri-Rb-1 retinoblastoma cells and tested in in vitro promoter assays. Transgenic Xenopus laevis were created with deletional or mutated promoter fragments driving an enhanced green fluorescent protein (EGFP) reporter gene. The resultant EGFP expression pattern in the transgenic animals was analyzed by fluorescence microscopy and immunocytochemistry.
Results:
A significant decrease in in vitro transcriptional activities was observed when the minimal 215-bp promoter fragment was mutated in each of the four cone-rod homeobox (CRX)-binding elements (CBEs) or in either of the two TATA-elements. The 215-bp mCAR proximal promoter drove EGFP expression to cone photoreceptors and pinealocytes in transgenic Xenopus laevis; however, the truncated 147-bp fragment drove expression to both cone and rod photoreceptors. Transgenic tadpoles carrying a single mutation in either the TATA-box, the TATA-element or the proximal CBE had undetectable EGFP expression in the retina. However, when one of the other three CBEs was mutated, EGFP expression was observed in muscle and brain tissues, in addition to the eyes. Also, when both TATA elements were mutated, transgenic animals had EGFP expression in all photoreceptors. Because no reporter activity was observed when either a 3.2-kb 5' extended region or the first intron of the mCAR gene was tested in Weri-Rb-1 cells, neither construct was examined in vivo.
Conclusions:
The data demonstrate that the regulatory functions of the known cis-elements in the mCAR promoter are highly dependent on location and nucleotide sequence conservation. The TATA elements and CBEs are crucial for driving both basal transcriptional activity and tissue specificity to cone photoreceptors and pinealocytes.
Insights
Cone arrestin (CAR) gene expression in photoreceptors and pinealocytes is regulated by specific DNA elements. TATA elements and CRX-binding elements (CBEs) are crucial for cell-specific transcription.
Area of Science:
- Molecular Biology
- Genetics
- Neuroscience
Background:
- Cone arrestin (CAR) is a protein highly expressed in cone photoreceptors and pinealocytes.
- Understanding the genetic regulation of CAR is essential for studying retinal and pineal gland function.
Purpose of the Study:
- To identify and analyze the cis-acting DNA elements responsible for the cell-specific expression of the mouse CAR (mCAR) gene.
Main Methods:
- In vitro promoter assays using luciferase reporter constructs in cell lines (COS-7, Weri-Rb-1).
- In vivo studies using transgenic Xenopus laevis with mutated or deleted mCAR promoter fragments driving an EGFP reporter gene.
- Analysis of EGFP expression patterns via fluorescence microscopy and immunocytochemistry.
Main Results:
- Mutations in TATA elements or CRX-binding elements (CBEs) within the mCAR promoter significantly reduced in vitro transcriptional activity.
- In transgenic Xenopus, the 215-bp promoter drove expression to cone photoreceptors and pinealocytes, while a truncated 147-bp fragment included rod photoreceptors.
- Specific mutations in TATA or proximal CBE abolished retinal EGFP expression, while mutations in other CBEs led to expression in muscle and brain tissues.
Conclusions:
- The location and sequence conservation of cis-elements are critical for mCAR gene regulation.
- TATA elements and CBEs are essential for both basal transcription and the tissue-specific expression of CAR in cone photoreceptors and pinealocytes.
