This family consists of proteins from different gene families: Ndr1/RTP/Drg1, Ndr2, and Ndr3. Their similarity was previously noted. The precise molecular and cellular function of members of this family is still unknown. Yet, they are known to be involved in cellular differentiation events. The Ndr1 group was the first to be discovered. Their expression is repressed by the proto-oncogenes N-myc and c-myc, and in line with this observation, Ndr1 protein expression is down-regulated in neoplastic cells, and is reactivated when differentiation is induced by chemicals such as retinoic acid. Ndr2 and Ndr3 expression is not under the control of N-myc or c-myc. Ndr1 expression is also activated by several chemicals: tunicamycin and homocysteine induce Ndr1 in human umbilical endothelial cells; nickel induces Ndr1 in several cell types. Members of this family are found in wide variety of multicellular eukaryotes, including an Ndr1 type protein in Helianthus annuus (sunflower), known as Sf21. Interestingly, the highest scoring matches in the noise are all alpha/beta hydrolases pfam00561, suggesting that this family may have an enzymatic function (Bateman A pers. obs.).