Only one nemo-like kinase gene homologue in invertebrate and mammalian genomes

The nemo-like kinase (Nlk) connects the MAP kinase and Wnt signalling pathw ays. We have found that invertebrate (Caenorhabditis elegans, Drosophila me lanogaster) and mammalian genomes (Mus musculus and Homo sapiens) each cont ain only a single functional Nlk gene. The mouse genome also harbours a tra nscriptionally silent processed Nlk pseudogene residing on chromosome 2. Th us, while genes encoding upstream (such as Wnts and frizzelds) and downstre am (such as TCF/LEF) components of the Wnt signalling pathway have been ext ensively diversified during evolution, genes encoding components of the com mon core of the connecting signalling structure (such as beta -catenin, GSK beta and Nlk) have been maintained in single copies. (C) 2001 Elsevier Sci ence B.V. All rights reserved.