A Genome-Wide Association Study for Susceptibility to Axial Length in Highly Myopic Eyes

Abstract

High myopia has long been highly prevalent worldwide with a largely yet unexplained genetic contribution. To identify novel susceptibility genes for axial length (AL) in highly myopic eyes, a genome-wide association study (GWAS) was performed using the genomic dataset of 350 deep whole-genome sequencing data from highly myopic patients. Top single nucleotide polymorphisms (SNPs) were functionally annotated. Immunofluorescence staining, quantitative polymerase chain reaction, and western blot were performed using neural retina of form-deprived myopic mice. Enrichment analyses were further performed. We identified the four top SNPs and found that ADAM Metallopeptidase With Thrombospondin Type 1 Motif 16 (ADAMTS16) and Phosphatidylinositol Glycan Anchor Biosynthesis Class Z (PIGZ) had the potential of clinical significance. Animal experiments confirmed that PIGZ expression could be observed and showed higher expression level in form-deprived mice, especially in the ganglion cell layer. The messenger RNA (mRNA) levels of both ADAMTS16 and PIGZ were significantly higher in the neural retina of form-deprived eyes (p = 0.005 and 0.007 respectively), and both proteins showed significantly upregulated expression in the neural retina of deprived eyes (p = 0.004 and 0.042, respectively). Enrichment analysis revealed a significant role of cellular adhesion and signal transduction in AL, and also several AL-related pathways including circadian entrainment and inflammatory mediator regulation of transient receptor potential channels were proposed. In conclusion, the current study identified four novel SNPs associated with AL in highly myopic eyes and confirmed that the expression of ADAMTS16 and PIGZ was significantly upregulated in neural retina of deprived eyes. Enrichment analyses provided novel insight into the etiology of high myopia and opened avenues for future research interest.

Supplementary information: The online version contains supplementary material available at 10.1007/s43657-022-00082-x.

Keywords: ADAM Metallopeptidase With Thrombospondin Type 1 Motif 16; Axial length; High myopia; Phosphatidylinositol Glycan Anchor Biosynthesis Class Z; Whole-genome sequencing.

Fig. 1

Manhattan and quantile–quantile plot for genome-wide association study (GWAS) of axial length. a Manhattan plot showing the result of linear regression GWAS: the blue horizontal line indicates the suggestive genome-wide significance threshold at p = 1.0 × 10^–5; b quantile–quantile plot of p values from the linear regression GWAS: Y-axis shows observed negative log₁₀ p values and X-axis shows expected negative log₁₀ p values according to the null hypothesis of no genetic association. Diagonal line = line of unity (observed = expected)

Fig. 2

Expression of PIGZ in the retinal nerve fiber layer of deprived and control mouse. The nuclei were counterstained with DAPI in the merged image. The upper part of the images face toward the retinal pigment epithelium side, and the lower part of the images face toward the vitreous body side. Scale bars (lower right white line), 10 μm. GCL, ganglion cell layer; IPL, inner plexiform layer; INL, inner nuclear layer; OPL, outer plexiform layer; ONL, outer nuclear layer; PRL, photoreceptor layer

Fig. 3

Differential mRNA level of a ADAMTS16 and b PIGZ between form-deprived myopic eyes and control eyes in experimental mice (n = 10 for each group)

Fig. 4

ADAMTS16 and PIGZ protein expression in the neural retina. Representative example of western blot of a ADAMTS16 and b PIGZ expression in the neural retina. Densitometric analysis of c ADAMTS16 and d PIGZ protein expression in the neural retina (n = 5 for each group). Protein expression levels were normalized to the level of β-actin

Fig. 5

GO and KEGG pathway enrichment analysis of candidate genes for axial length. a GO enrichment items based on biological processes (BP), cellular components (CC) and molecular functions (MF); b KEGG pathway enrichment items. False discovery rate (FDR) < 0.05 was considered significant