Expression Atlas of the mouse orthologues of the human chromosome 21 genes

Down syndrome (DS), due to an extra copy of human chromosome 21 (HC21), is the most common genetic cause of mental retardation. To define where HC21 genes exert their function and identify their possible role in the DS phenotypes we performed a systematic analysis of the expression profile of 170 murine genes which represent (almost all) the orthologues of the HC21 genes. To obtain an high resolution expression pattern several complementary methods were combined: RT-PCR on a mouse cDNA panel of 12 adult tissues and 4 developmental stages; wholemount in situ of E9.5 and E10.5 embryos and section in situ of E14.5 embryos. These stages correspond to mid and late embryonic and fetal human periods, when the major organs and body regions are organized. Genes showing interesting and/or restricted expression pattern were analyzed further on appropriate sections at more developmental timepoints. 91% of the tested genes showed a clear expression pattern during murine development. In 37% of the cases expression was ubiquitous while 50% of the cDNAs showed a differential expression pattern in the embryonal tissues. The topographical catalogue of expression of the murine orthologues of human chromosome 21 genes will be instrumental to the understanding of the pathogenesis of trisomy 21 as well as of other chromosome 21 linked disorders. Some of analyzed genes display a pattern of expression relevant to the congenital heart disease and/or to the mental retardation observed in DS. The entire data set will be made available to the scientific community via a web site.