NR2F1 mutations cause optic atrophy with intellectual disability

Abstract

Optic nerve atrophy and hypoplasia can be primary disorders or can result from trans-synaptic degeneration arising from cerebral visual impairment (CVI). Here we report six individuals with CVI and/or optic nerve abnormalities, born after an uneventful pregnancy and delivery, who have either de novo heterozygous missense mutations in NR2F1, also known as COUP-TFI, or deletions encompassing NR2F1. All affected individuals show mild to moderate intellectual impairment. NR2F1 encodes a nuclear receptor protein that regulates transcription. A reporter assay showed that missense mutations in the zinc-finger DNA-binding domain and the putative ligand-binding domain decrease NR2F1 transcriptional activity. These findings indicate that NR2F1 plays an important role in the neurodevelopment of the visual system and that its disruption can lead to optic atrophy with intellectual disability.

Figure 1

Phenotype and Genotype of the Individuals with Optic Atrophy (A) Confirmation by Sanger sequencing of the de novo mutations in NR2F1 [NM_005654.4] found by exome sequencing (individuals 1, 2, and 6), the de novo mutation in NR2F1 found by cohort screening (individual 3), and segregation analyses. The pictures of the individuals show nonspecific facial dysmorphisms. (B) Schematic representation of NR2F1, containing a DNA-binding domain (DBD) and a ligand-binding domain (LBD). The positions of the mutations identified in the affected individuals are indicated. (C) Overview of the 5q14-q15 region encompassing the two overlapping microdeletions of individual 4 (lower red bar) and 5 (upper red bar) comprising NR2F1. The inheritance of the deletion in individual 4 was unknown, because the father was not available for testing and the deletion was on the paternal allele. The deletion of individual 5 was de novo. The pictures of the affected individuals show nonspecific facial dysmorphisms.

Figure 2

In Vitro Luciferase Reporter Assay for NR2F1 Point Mutations Effects of the Nr2f1 (COUP-TFI) mutations on activation of an NGFI-A promoter-driven reporter. Top shows that pXP2-NGFI-A was cotransfected with 5 ng FLAG-tagged Nr2f1 (COUP-TFI) WT, FLAG-tagged Nr2f1 (COUP-TFI) mutations or empty vector into HEK293T cells as indicated. The cell sample transfected with pXP2-NGFI-A and vector served as the control, and its value (relative luciferase activity) was set as 1. The relative luciferase activities of the other samples are normalized to this control. Data are means ± SD (n = 3). Bottom shows immunoblot analysis of Nr2f1 (COUP-TFI) expression in transfection. Results indicate similar expression of WT and mutant Nr2f1 (COUP-TFI) constructs.