Mutation of a nuclear receptor gene, NR2E3, causes enhanced S cone syndrome, a disorder of retinal cell fate

Abstract

Hereditary human retinal degenerative diseases usually affect the mature photoreceptor topography by reducing the number of cells through apoptosis, resulting in loss of visual function. Only one inherited retinal disease, the enhanced S-cone syndrome (ESCS), manifests a gain in function of photoreceptors. ESCS is an autosomal recessive retinopathy in which patients have an increased sensitivity to blue light; perception of blue light is mediated by what is normally the least populous cone photoreceptor subtype, the S (short wavelength, blue) cones. People with ESCS also suffer visual loss, with night blindness occurring from early in life, varying degrees of L (long, red)- and M (middle, green)-cone vision, and retinal degeneration. The altered ratio of S- to L/M-cone photoreceptor sensitivity in ESCS may be due to abnormal cone cell fate determination during retinal development. In 94% of a cohort of ESCS probands we found mutations in NR2E3 (also known as PNR), which encodes a retinal nuclear receptor recently discovered to be a ligand-dependent transcription factor. Expression of NR2E3 was limited to the outer nuclear layer of the human retina. Our results suggest that NR2E3 has a role in determining photoreceptor phenotype during human retinogenesis.

Genotype–phenotype correlation and mutation spectrum in a large cohort of patients with inherited retinal dystrophy revealed by next-generation sequencing

“…However, a pathogenic homozygous mutation in the NR2E3 gene (c.290G>A, p.R97H) was identified (Supplementary Figure S1 online) that was reported to cause enhanced S cone syndrome (ESCS) in previous studies. 20,21 To explain this inconsistency, proband W29-1 was sent for a clinical reassessment. Full-field electroretinography showed extinguished rod responses (Supplementary Figure S1 online).…”

Regulation of photoreceptor gene expression by Crx-associated transcription factor network

“…Nr2e3 is expressed in retinal photoreceptor cells beginning around E18 in the mouse, peaking during rod differentiation and persisting into adulthood at a decreased level (Kobayashi et al, 1999;Takezawa et al, 2007). Expression appears primarily localized to the outer nuclear layer (Kobayashi et al, 1999;Haider et al, 2000;Haider et al, 2001). This persistent expression, mainly in rods in mammals (Bumsted O'Brien et al, 2004;Chen et al, 2005;, suggests that Nr2e3 plays a major role in rod differentiation and maintenance.…”

“…Human genetic studies: Mutations in human NR2E3 cause enhanced S-cone syndrome (ESCS), an autosomal recessive disease featuring hyperfunction of blue cones, defective function of rods, and blindness in the late stages (Haider et al, 2000;Jacobson et al, 2004;Wright et al, 2004). Histopathological studies showed excess S-cones in the retina, some of which express both S-and M-cone opsins (Milam et al, 2002), which is unusual in humans (Lukats et al, 2005;Peichl, 2005).…”

FIZ1 is expressed during photoreceptor maturation, and synergizes with NRL and CRX at rod-specific promoters in vitro

“…NR2E3 (a nuclear receptor) is required for normal photoreceptor development, and recent studies have demonstrated NR2E3 can interact with CRX and regulate transcription at Opsin promoters. (Cheng, et al, 2004, Haider, et al, 2000 Nuclear receptors, as a family, are noted for both repression and activation effects that are mediated through Znfinger proteins. (Belandia, et al, 2002) Recent studies also indicate that the interaction of NR2E3 with NRL or CRX may not be direct and additional transcriptional regulatory proteins might be necessary for the formation of a stable complex in vivo.…”

“…(Akagi, et al, 2004, Brown, et al, 1998, Brown, et al, 2001, Hojo, et al, 2000, Kanekar, et al, 1997, Marquardt and Gruss, 2002, Moore, et al, 2002, Morrow, et al, 1999, Yan and Wang, 1998 Several transcription factors are clearly essential for photoreceptor development, and their mutations cause retinal degenerations: NRL, CRX, Otx2, Trβ2 (thyroid hormone receptor β2), and NR2E3. (Bessant, et al, 1999, DeAngelis, et al, 2002, Freund, et al, 1997, Haider, et al, 2000, Haider, et al, 2001, Martinez-Gimeno, et al, 2001, Ng, et al, 2001, Nishida, et al, 2003, Swain, et al, 1997 However, our knowledge of the interactions of these cell-specific proteins with each other and upstream signal transduction proteins remains sparse. We do not know how this pool of cell-specific transcription factors interacts with the pool of ubiquitous proteins, which include the general transcription machinery and epigenetic regulators of chromatin/DNA structure.…”