A comprehensive analysis of sequence variants and putative disease-causing mutations in photoreceptor-specific nuclear receptor NR2E3.
OBJECTIVE
The photoreceptor-specific orphan nuclear receptor NR2E3 is a key regulator of transcriptional events during photoreceptor differentiation in mammalian retina. Mutations in NR2E3 are associated with enhanced S-cone syndrome and related retinal phenotypes that reveal characteristic excess of S-cone function. This study was undertaken to determine biochemical as well as functional consequences of reported sequence variants and disease-causing mutations in NR2E3.


METHODS
Twenty-five different mutations in the wild-type NR2E3 expression construct were generated by site-directed mutagenesis and performed nuclear localization, gel-shift, rhodopsin promoter activity assays, and co-immunoprecipitation in cultured mammalian cells.


RESULTS
Of the 25 mutant proteins, 15 mislocalize at least partially to the cytoplasm. Eight of the nine changes in the DNA-binding domain (DBD) and 12 of the 14 mutations in the ligand-binding domain (LBD) of NR2E3 exhibited reduced DNA-binding and transcriptional activation of the rhodopsin promoter. Moreover, these mutations dramatically altered the interaction of NR2E3 with NRL as well as with CRX. Two NR2E3 variants between DBD and LBD showed no effect on any biochemical or functional parameter tested.


CONCLUSIONS
These data provide a better understanding of sequence variants, validate disease-causing mutations, and demonstrate the significance of DBD and LBD in mediating NR2E3 function. These studies contribute to molecular mechanisms underlying retinal phenotypes caused by NR2E3 mutations.
Kanda
Atsuhiro
A
Neurobiology Neurodegeneration and Repair Laboratory (N-NRL), National Eye Institute, NIH, Bethesda, MD 20892, USA. kandaa@nei.nih.gov
Swaroop
Anand
A
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D050976:Basic-Leucine Zipper Transcription Factors / Q000378:metabolism; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D005136:Eye Proteins / Q000378:metabolism; D018398:Homeodomain Proteins / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000378:metabolism*; D009154:Mutation / Q000235:genetics*; D057093:Orphan Nuclear Receptors / Q000737:chemistry / Q000235:genetics*; D011485:Protein Binding; D021381:Protein Transport; D012164:Retinal Diseases / Q000235:genetics*; D013347:Subcellular Fractions / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation / Q000235:genetics
D050976:Basic-Leucine Zipper Transcription Factors; D005136:Eye Proteins; D018398:Homeodomain Proteins; D050505:Mutant Proteins; C403073:NR2E3 protein, human; C490037:NRL protein, human; D057093:Orphan Nuclear Receptors; D015534:Trans-Activators; C109288:cone rod homeobox protein; D004247:DNA