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ADAMTSL4 assessment in ectopia lentis reveals a recurrent founder mutation in Polynesians
Katherine A van Bysterveldt1, Rasha Al Taie1,2, Will Ikink1
1a Department of Ophthalmology, FMHS, New Zealand National Eye Centre , University of Auckland , Auckland , New Zealand.
Background:
To clinically characterize a cohort of patients with ectopia lentis (EL), or Marfanoid features in whom a definite genetic diagnosis of Marfan syndrome (MFS) had been excluded (atypical MFS), and to evaluate the contribution of mutations in ADAMTSL4 (OMIM * 610113), and P3H2 (LEPREL1; OMIM * 610341) to disease in this population.
Materials And Methods:
Subjects underwent comprehensive ophthalmic examination, including keratometry. Mutational analysis of ADAMTSL4 and P3H2 was undertaken using PCR, high resolution melting analysis, and sequencing. The frequency of c.2237G>A; p.(Arg746His) was determined in an unaffected Polynesian cohort. Haplotype analysis used tagged single nucleotide polymorphic markers.
Results:
Mutational analysis of ADAMTSL4 identified two pathogenic variants in ADAMTSL4 in 11/31 (35%) probands, consistent with the autosomal recessive EL phenotype. A recurrent, rare missense variant in ADAMTSL4, c.2237G>A; p.(Arg746His), was present in 10 probands -(8 homozygotes), predominantly of Polynesian descent, and all shared the same haplotype. p.(Arg746His) affects the Thrombospondin1 (TSP1) domain of the protein and is predicted to be pathogenic. No pathogenic variants in P3H2 were identified.
Conclusion:
A recurrent pathogenic ADAMTSL4 variant is a major cause of early onset autosomal recessive EL in a Cook Island Māori population and associated with a common haplotype, suggesting a founder effect. Children presenting under the age of 5 years, particularly of Cook Island or New Zealand Māori descent, with isolated ectopia lentis, should in the first instance be tested for this single variant.