Background: Smad interacting protein 1 (SIP1) is a transcriptional inhibitor that binds to the DNA sequence, 5'-CACCT-3', in different promoters. SIP1 has been shown to repress the transcription of E-cadherin. Defects in the gene which encodes for SIP1, ZEB2, are the cause of Hirschsprung disease-mental retardation syndrome (Hirschsprung disease) also known as Mowat-Wilson syndrome (MWS). Hirschsprung disease is a rare autosomal dominant complex developmental disorder [taken from the Universal Protein Resource (UniProt) O60315].