Novel ADAMTSL4 gene mutations in Chinese patients with isolated ectopia lentis

Background: To characterise the phenotype and genetic defects of isolated ectopia lentis (IEL) and to determine the ADAMTSL4 gene mutation frequencies in a Chinese congenital ectopia lentis (CEL) cohort.

Methods: In total, 127 Chinese probands with a clinical CEL diagnosis were recruited for this study and underwent ocular and systemic examinations. Whole-exome sequencing was used to detect variants, and Sanger sequencing and bioinformatics analysis verified the pathogenic mutations.

Results: Overall, biallelic mutations in ADAMTSL4, involving 8 novel ADAMTSL4 mutations (c.21-2A>G, c.1174G>C, c.2169C>A, c.2236C>T, c.2263delG, c.2397C>A, c.2488dupC and c.2935T>C) were identified in 5 probands (5/127, 3.94%) with IEL. Additionally, four patients had combined congenital cataracts, and two patients had ectopia lentis et pupillae (ELP). One of eight mutations was a homozygous missense mutation, and the other seven mutations were compound heterozygous. These eight consisted of three missense (37.5%), three frameshift (37.5%), one stop-gain (12.5%) and one spicing mutation (12.5%). These mutations co-segregated with the IEL, and the substitution of amino acids greatly affected conserved residues. Most of the novel mutations were located in the thrombospondin type 1 (TSP1) domain, which ultimately alters the structure of the ADAMTSL4 protein.

Conclusions: This study reported five IEL probands with eight novel mutations in the ADAMTSL4 gene. The clinical IEL phenotypes caused by these mutations were variable and complex. This study thus establishes the ADAMTSL4 gene mutation frequency and expands the gene's mutation spectrum to help recognise ADAMTSL4-related IEL clinical manifestations.