One of the first stages of biogenesis is the post-transcriptional formation of primary transcripts (pri-miRNA) with a cap at the 5’ end and a poly(A) tail, which are then capped and spliced by the nuclear protein DGCR8 (DiGeorge syndrome critical region) combined with the Drosha enzyme which contains two RNase III domains, each of which cleaves one strand of the dsRNA [53]. This evidence concerns the gene DROSHA and 22q11.2 deletion syndrome.