Missense NR2F1 variant in monozygotic twins affected with the Bosch–Boonstra–Schaaf optic atrophy syndrome. Issue 7 (15th May 2020)

• Record Type: Journal Article
• Authors: Mio, Catia; Fogolari, Federico; Pezzoli, Laura; D'Elia, Angela V.; Iascone, Maria; Damante, Giuseppe
• Is Part Of: Molecular genetics & genomic medicine. Volume 8:Issue 7(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-05-15
• Subjects: BBSOAS -- monozygotic twins -- NR2F1 -- whole exome sequencing; Medical genetics -- Periodicals; Genomics -- Periodicals; 616.042
• DOI: 10.1002/mgg3.1278
• Languages: English
• ISSNs: 2324-9269

Abstract

Abstract: Background: The Bosch‐Boonstra‐Schaaf optic atrophy syndrome (BBSOAS) is an autosomal‐dominant disorder (OMIM615722) mostly characterized by optic atrophy and/or hypoplasia, mild intellectual disability, hypotonia, seizures/infantile epilepsy. This disorder is caused by loss‐of‐function alterations of NR2F1 (i.e., either whole gene deletions or single nucleotide variants) and, to date, 40 patients have been identified with deletions or mutations in this gene. Here we describe two monozygotic twins harboring a de novo missense variant in the DNA‐binding domain of NR2F1 (c.313G>A, p.Gly105Ser), with well‐characterized features associated to BBSOAS. Methods: Patients' DNA was analyzed by exome sequencing identifying the missense variant c.313G>A in NR2F1 (NM_005654.4). Furthermore, molecular modeling was performed to evaluate putative differences in DNA binding between wild‐type and mutated NR2F1. Results: The missense variant is predicted to be likely pathogenetic following the ACMG (American College of Medical Genetics and Genomics)/AMP (Association for Molecular Pathology) guidelines. Indeed, dynamic simulation experiments highlighted that the Gly105Ser substitution let the formation of a hydrogen bond between the S105 side chain and R142 and a base (G5) of the DNA sequence, allowing us to hypothesize that the G105 residue might be evolutionary conserved due to the absence of a side chain, besides glycine conformational features. Therefore, the G105S variation seems to cause a stiffening and a possible deformation in the protein‐DNA complex due to the interaction of residues R142‐S105 and G5 on the DNA, compared to the wild‐type. Conclusion: In summary, we described two monozygotic twins harboring a novel Gly105Ser mutation in NR2F1 DNA binding domain, displaying the classical phenotype of BBSOAS‐affected patients. Our computational data suggest a dominant negative effect of this newly characterized missense variant. To date, this is the first genetic report analyzing in silico structural consequences of NR2F1 Gly105Ser substitution. Abstract : Here we describe two monozygotic twins harboring a de novo missense variant in the DNA binding domain of NR2F1, with well‐characterized features associated to BBSOAS. Following the American College of Medical Genetics and Genomics (ACMG) guidelines, the variant is classified as likely pathogenic, matching 4 out of 6 specific criteria. Furthermore, molecular dynamics simulations highlighted that the complexes mutation introduces bonds in the triad R142‐S105‐G5 DNA base which could lead to a distortion and stiffening in this region, compromising the receptor functions.