RNU4-2 and neurodevelopmental disorder: Interestingly, GSidentified a causal diagnosis in 23.6% of patients with a previous negative ES.GS has the advantage over ES of identifying structural and non-exonicvariations, as recently demonstrated by the identification of sporadic variantsin the non-coding spliceosomal snRNA gene RNU4-2 as afrequent cause of syndromic neurodevelopmental disorders.13