RNU4ATAC and microcephaly: For example, mutations in RNU4atac, encoding a UsnRNA component of the U12-dependent spliceosome, may result either in microcephalic osteodysplastic primordial dwarfism type I (MOPDI) or Taybi-Linder syndrome, rare conditions characterised by intrauterine and post-natal growth restrictions, microcephaly and cerebellar hypoplasia44,45.