A more complex class of diseases are those arising from defects in minor spliceosome components of which the TALS/MOPD1 (Taybi-Linder syndrome or microcephalic osteodysplastic primordial dwarfism type I) is a recent example. This evidence concerns the gene RNU4ATAC and microcephalic osteodysplastic primordial dwarfism type I.