A new era for the dark genome

A landmark study by Quinodoz et al. revealed that variants in noncoding small nuclear RNA genes, RNU4-2 and four RNU6 paralogs, represent a previously unrecognized cause of autosomal dominant retinitis pigmentosa. This uncovers pleiotropy in RNU4-2 variants and expands the genetic architecture of Mendelian disease into the ‘dark genome’.