Mutations in ADAMTSL4 cause a unique form of autosomal-recessive congenital ectopia lentis

Several unique mutations of ADAMTSL4 leading to congenital ectopia lentis (CEL) have been previously reported by our team. The purpose of this study is to find out the possible mechanism of a recurrent novel intronic variant in ADAMTSL4 led to CEL. Twelve novel ADAMTSL4 mutations with a unique form congenital ectopic lentis were detected previously by panel-based NGS. Genetic analysis verified a novel heterozygous ADAMTSL4 variation c.2177+4A > G on Intron 11 in two unrelated patients with iris and lens abnormalities. MINI-Gene assay showed two splicing modes of mRNA that process two different bands A and B, and mutant-type shows replacement with the splicing mode of Exon 11 skipping. Construction of wild-type and mutant ADAMTSL4 vector showed the appearance of premature termination codons (PTC). In vitro expression detection showed significant down-regulated expression level of ADAMTSL4 mRNAs and proteins in cells transfected with mutant vectors compared with in wild-type group. On the contrary, translation inhibitor CHX and small interfering RNA of UPF1 (si-UPF1) significantly increased mRNA or protein expression of ADAMTSL4 in cells transfected with the mutant vectors. 12 novel mutations in ADAMTSL4 gene have been previously reported by our team in 6 CEL patients with a unique series of ocular abnormalities. The recurrent novel ADAMTSL4 mutation c.2177+4A > G triggering the splicing mode of Exon 11 skipping and NMD would cause the decrease of ADAMTSL4 proteins that participate in biosynthesis and assembly of microfibers, which might lead to CEL, and suggest that sequencing of certain intronic splicing varition might be a vital tool for genetic counseling and prenatal diagnoses.