The isolation of the genes located in chromosome 21 and the characterisation of their function are essen tial steps towards the understanding of the physiopathological mechanisms involved in Down syndrome. We have used two complementary approaches to characterise the function of the novel gene DSCR2 (Down Syndrome Critical Region gene 2): the isolation and characterisation of the mouse gene homologue to the human DSCR2 gene, and the analysis of the expression of the gene in different human cell lines, We have isolated and characterised a 1012 bp of a mouse cDNA having a high homology to the human DSCR2 gene. The predicted mouse dscr2 protein has an identity of 85.4% as compared to the human protein, indicating that the DSCR2 protein has been conserved during the evolution. However, the amino acid sequence is not homologous to other known proteins, or to the known protein domains. The dscr2 gene is expressed throughout all the stages of the mouse embryo development. In the adult mouse the gene is expressed in testis, kidney, liver, brain, heart, skeletal muscle, and pancreas. The expression analysis of the DSCR2 gene in different human tumour derived cell lines indicates that the gene is expressed in all proliferating cell lines tested. The levels of the DSCR2 mRNA correlate with cellular growth of T98G and Jurkat cells in response to different treatments. The expression pattern throughout the foetal development together with the correlation observed with the cell cycle indicates a possible function for the DSCR2 gene related to cell proliferation.