Monoallelic and biallelic mutations in MAB21L2 cause a spectrum of major eye malformations - PubMed (original) (raw)

. 2014 Jun 5;94(6):915-23.

doi: 10.1016/j.ajhg.2014.05.005.

Davut Pehlivan 2, Stefan Johansson 3, Hemant Bengani 1, Luis Sanchez-Pulido 4, Kathleen A Williamson 1, Mehmet Ture 5, Heather Barker 6, Karen Rosendahl 7, Jürgen Spranger 8, Denise Horn 9, Alison Meynert 1, James A B Floyd 10, Trine Prescott 11, Carl A Anderson 10, Jacqueline K Rainger 1, Ender Karaca 2, Claudia Gonzaga-Jauregui 2, Shalini Jhangiani 12, Donna M Muzny 12, Anne Seawright 1, Dinesh C Soares 13, Mira Kharbanda 14, Victoria Murday 14, Andrew Finch 6; UK10K; Baylor-Hopkins Center for Mendelian Genomics; Richard A Gibbs 15, Veronica van Heyningen 1, Martin S Taylor 1, Tahsin Yakut 5, Per M Knappskog 3, Matthew E Hurles 10, Chris P Ponting 4, James R Lupski 15, Gunnar Houge 16, David R FitzPatrick 17

Collaborators, Affiliations

Monoallelic and biallelic mutations in MAB21L2 cause a spectrum of major eye malformations

Joe Rainger et al. Am J Hum Genet. 2014.

Abstract

We identified four different missense mutations in the single-exon gene MAB21L2 in eight individuals with bilateral eye malformations from five unrelated families via three independent exome sequencing projects. Three mutational events altered the same amino acid (Arg51), and two were identical de novo mutations (c.151C>T [p.Arg51Cys]) in unrelated children with bilateral anophthalmia, intellectual disability, and rhizomelic skeletal dysplasia. c.152G>A (p.Arg51His) segregated with autosomal-dominant bilateral colobomatous microphthalmia in a large multiplex family. The fourth heterozygous mutation (c.145G>A [p.Glu49Lys]) affected an amino acid within two residues of Arg51 in an adult male with bilateral colobomata. In a fifth family, a homozygous mutation (c.740G>A [p.Arg247Gln]) altering a different region of the protein was identified in two male siblings with bilateral retinal colobomata. In mouse embryos, Mab21l2 showed strong expression in the developing eye, pharyngeal arches, and limb bud. As predicted by structural homology, wild-type MAB21L2 bound single-stranded RNA, whereas this activity was lost in all altered forms of the protein. MAB21L2 had no detectable nucleotidyltransferase activity in vitro, and its function remains unknown. Induced expression of wild-type MAB21L2 in human embryonic kidney 293 cells increased phospho-ERK (pERK1/2) signaling. Compared to the wild-type and p.Arg247Gln proteins, the proteins with the Glu49 and Arg51 variants had increased stability. Abnormal persistence of pERK1/2 signaling in MAB21L2-expressing cells during development is a plausible pathogenic mechanism for the heterozygous mutations. The phenotype associated with the homozygous mutation might be a consequence of complete loss of MAB21L2 RNA binding, although the cellular function of this interaction remains unknown.

Copyright © 2014 The American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.

PubMed Disclaimer

Figures

Figure 1

Figure 1

Family Structures and MAB21L2 Mutations (A–E) Diagrammatic representation of the structure of the five families—1463 (A), 676 (B), 131 (C), 4480 (D), and 4468 (E)—in whom mutations were identified in MAB21L2. The family number is given above each pedigree, and the sequencing chromatograms of the mutated base are given below each pedigree. Clinical images associated with each of the probands are located on the right-hand side of each cognate pedigree. (F) The location of each missense mutation is provided on a schematic representation of MAB21L2.

Figure 2

Figure 2

Mab21l2 Expression during Mouse Eye Development OPT images of Mab21l2 expression at mouse Theiller stage 17 (TS17; 10.5 dpc). Hatched lines indicate the digital sections presented. (A) Lateral 3D OPT projection showing Mab21l2 expression in the eye (E), pharyngeal arches (PAs), and forelimbs (FLs). The transverse digital section presented alongside shows specific expression in the eyes, and an enlarged image (box) illustrates Mab21l2 expression at the distal regions of the neural retina (NR), but not in the lens vesicle (LV). (B) Posterior 3D OPT view illustrating specific Mab21l2 expression in the FLs. The sagittal digital section presented alongside and the enlarged box illustrate that Mab21l2 expression was highest dorsally but continued ventrally into the margins of the optic fissure (OF). Further abbreviations are as follows: HB, hindbrain; and TV, telencephalic vesicle.

Figure 3

Figure 3

Structural Modeling of MAB21L2 and Prediction of Nucleotidyltransferase Activity (A) A model of MAB21L2 was generated with PDB

4K9B

as a template and is shown in purple; the nucleotide monophosphates are shown in green, blue, and red. This analysis suggests that MAB21L2 has both a nucleotidyltransferase active site and a DNA- and/or RNA-binding domain (double-stranded DNA is shown in pink in the foreground). The position of the residues that were altered in the affected individuals is shown in white text in black boxes. The arginine residues (Arg51 [R51] and Arg247 [R247]) are highlighted in blue, and the glutamic acid residue (Glu49 [E49]) is shown in orange. (B) A graph showing the absence of OAS-like activity in purified MAB21L2. When OAS protein purified in the same way as MAB21L2 was incubated with ATP and double-stranded RNA (dsRNA), significant pyrophosphate release was detected, indicating nucleotidyltransferase activity. MAB21L2 showed no activity above background with ATP (or other nucleoside triphosphates [Figure S2]) using dsRNA, double-stranded DNA, ssRNA, or ssDNA as an activator. (C) An electromobility shift assay (EMSA) using fluorescently labeled I:C oligonucleotides shows binding of wild-type MAB21L2 to ssRNA, but not ssDNA. The ssRNA binding could be completed efficiently with unlabeled ssRNA, but not ssDNA. (D) Solution-based assay showing that wild-type MAB21L2 could efficiently bind a digoxigenin-labeled ssRNA molecule (this was an antisense riboprobe against FZD5, but all probes tested behaved in an identical fashion). None of the altered proteins could bind the ssRNA probe at levels above background. The error bars in (B) and (D) represent SE. Each experiment represents readings from two biological replicates, and all experiments were repeated twice.

Figure 4

Figure 4

Protein Stability Estimations and Induction of ERK Signaling by MAB21L2 (A) Time-course analysis of protein stability with the use of anti-GFP immunoblotting of MAB21L2 at various time points since tetracycline (Tet) removal. Data presented are representative of five independent replicates. (B) Quantification of immunoblots indicates higher protein stability for the proteins with substitutions at Glu49 or Arg51 than for the WT, whereas p.Arg247Gln displayed a pattern of protein stability similar to that of the WT. Error bars represent 95% confidence intervals. (C) Increase in the level of the 44 kDa phospho-ERK band after 5 hr of Tet induction of WT and p.Arg51His MAB21L2 in inducible HEK293 cells. (D) Graph representing quantification of this induction. Error bars represent 95% confidence intervals.

References

    1. Haddad M.A., Sei M., Sampaio M.W., Kara-José N. Causes of visual impairment in children: a study of 3,210 cases. J. Pediatr. Ophthalmol. Strabismus. 2007;44:232–240. - PubMed
    1. Rudanko S.L., Laatikainen L. Visual impairment in children born at full term from 1972 through 1989 in Finland. Ophthalmology. 2004;111:2307–2312. - PubMed
    1. Fantes J., Ragge N.K., Lynch S.A., McGill N.I., Collin J.R., Howard-Peebles P.N., Hayward C., Vivian A.J., Williamson K., van Heyningen V., FitzPatrick D.R. Mutations in SOX2 cause anophthalmia. Nat. Genet. 2003;33:461–463. - PubMed
    1. Ragge N.K., Lorenz B., Schneider A., Bushby K., de Sanctis L., de Sanctis U., Salt A., Collin J.R., Vivian A.J., Free S.L. SOX2 anophthalmia syndrome. Am. J. Med. Genet. A. 2005;135:1–7. discussion 8. - PubMed
    1. Ragge N.K., Brown A.G., Poloschek C.M., Lorenz B., Henderson R.A., Clarke M.P., Russell-Eggitt I., Fielder A., Gerrelli D., Martinez-Barbera J.P. Heterozygous mutations of OTX2 cause severe ocular malformations. Am. J. Hum. Genet. 2005;76:1008–1022. - PMC - PubMed

Publication types

MeSH terms

Substances

Supplementary concepts

Grants and funding

LinkOut - more resources