EPHA2 Segregates with Microphthalmia and Congenital Cataracts in Two Unrelated Families

Abstract

EPHA2 is a transmembrane tyrosine kinase receptor that, when disrupted, causes congenital and age-related cataracts. Cat-Map reports 22 pathogenic EPHA2 variants associated with congenital cataracts, variable microcornea, and lenticonus, but no previous association with microphthalmia (small, underdeveloped eye, ≥2 standard deviations below normal axial length). Microphthalmia arises from ocular maldevelopment with >90 monogenic causes, and can include a complex ocular phenotype. In this paper, we report two pathogenic EPHA2 variants in unrelated families presenting with bilateral microphthalmia and congenital cataracts. Whole genome sequencing through the 100,000 Genomes Project and cataract-related targeted gene panel testing identified autosomal dominant heterozygous mutations segregating with the disease: (i) missense c.1751C>T, p.(Pro584Leu) and (ii) splice site c.2826-9G>A. To functionally validate pathogenicity, morpholino knockdown of epha2a/epha2b in zebrafish resulted in significantly reduced eye size ± cataract formation. Misexpression of N-cadherin and retained fibre cell nuclei were observed in the developing lens of the epha2b knockdown morphant fish by 3 days post-fertilisation, which indicated a putative mechanism for microphthalmia pathogenesis through disruption of cadherin-mediated adherens junctions, preventing lens maturation and the critical signals stimulating eye growth. This study demonstrates a novel association of EPHA2 with microphthalmia, suggesting further analysis of pathogenic variants in unsolved microphthalmia cohorts may increase molecular diagnostic rates.

Real-world clinical and molecular management of 50 prospective patients with microphthalmia, anophthalmia and/or ocular coloboma

“…All monogenic causes were previously associated with MAC except EPHA2, for which association with microphthalmia was validated and published, 19 3, figure 2B). [19][20][21][22][23][24][25][26][27] According to Association for Clinical Genomic Science classification guidelines, ALDH1A3 variant c.104T>C;p.(Phe35Ser) in patient 22-1 is a variant of 'uncertain significance'.…”

“…All monogenic causes were previously associated with MAC except EPHA2, for which association with microphthalmia was validated and published, 19 3, figure 2B). [19][20][21][22][23][24][25][26][27] According to Association for Clinical Genomic Science classification guidelines, ALDH1A3 variant c.104T>C;p.(Phe35Ser) in patient 22-1 is a variant of 'uncertain significance'. However, the multidisciplinary team considered this patient's phenotype to be compatible with reported ALDH1A3 cases and there were no other relevant mutations found in MAC panels applied to this patient's genome data.…”

“…All monogenic causes were previously associated with MAC except EPHA2 , for which association with microphthalmia was validated and published, 19 and novel variants were identified in MAC-associated genes SOX2 c.867del;p.(Ser290Alafs*81), KMT2D c.6354del;p.(Ala2119Leufs*25), MAB21L2 c.379A>T; p.(Lys127*), ALDH1A3 c.104T>C;p.(Phe35Ser), BCOR c.856del;p.(Ser286Alafs*92) and FOXE3 c.763dup;p.(Ala255Glyfs*30) ( table 3 , figure 2B ). 19–27 According to Association for Clinical Genomic Science classification guidelines, ALDH1A3 variant c.104T>C;p.(Phe35Ser) in patient 22–1 is a variant of ‘uncertain significance’. However, the multidisciplinary team considered this patient’s phenotype to be compatible with reported ALDH1A3 cases and there were no other relevant mutations found in MAC panels applied to this patient’s genome data.…”

Identification of Novel Coloboma Candidate Genes through Conserved Gene Expression Analyses across Four Vertebrate Species

“…Ephrin receptorligand interactions at cell surfaces mediate numerous dynamic developmental processes, such as migration, proliferation, and cell fate determination, mediated through changes to cytoskeletal dynamics [49], and can also act as tumour suppressor genes [50]. A role for Ephrin signaling in eye development is also emerging: dominant mutations in EPHA2 cause isolated congenital cataracts, and its ligand EFNA5 is important for normal lens development [51][52][53][54]. Heterozygous pathogenic EPHA2 variants have also been reported in two families presenting with congenital cataract and non-syndromic microphthalmia, widening the phenotype associated with this gene [55].…”

Identification of novel coloboma candidate genes through conserved gene expression analyses across four vertebrate species

“…A role for Ephrin signaling in eye development is also emerging: dominant mutations in EPHA2 cause isolated congenital cataracts, and with its ligand EFNA5 are important for normal lens development [51][52][53][54]. Heterozygous pathogenic EPHA2 variants have also been reported in two families presenting with congenital cataract and non-syndromic microphthalmia, widening the phenotype associated with this gene [55]. Even more recently, biallelic mutations in EPHA2 have been found in a syndromic form of microphthalmia with anterior segment dysgenesis [56].…”