VDR and psoriasis: Caudal-type homeobox protein 2 (Cdx-2) is a transcription factor (TF) with a polymorphic binding site (TaaI/Cdx-2) in the VDR. The molecular mechanism underlying the Cdx-2 association with conditions like psoriasis, which depends on VDR expression and vitamin D absorption, is believed to be due to higher affinity of Cdx-2 for the G allele compared to the A allele.