Finally, syndromic sporadic DRS proband ENG_OA harbored a homozygous FRMD4B variant (c.380A>G, p.(Lys127Arg), ENST00000398540.8) located in the Band 4.1 domain, which is involved in cytoskeletal-membrane linkage (Fig. 8U, Supplementary Fig. S4B).27 Here, FRMD4B is linked to Duane retraction syndrome.