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

The nemo-like kinase (Nlk) connects the MAP kinase and Wnt signalling pathways. We have found that invertebrate (Caenorhabditis elegans, Drosophila melanogaster) and mammalian genomes (Mus musculus and Homo sapiens) each contain only a single functional Nlk gene. The mouse genome also harbours a transcriptionally silent processed Nlk pseudogene residing on chromosome 2. Thus, while genes encoding upstream (such as Wnts and frizzelds) and downstream (such as TCF/LEF) components of the Wnt signalling pathway have been extensively diversified during evolution, genes encoding components of the common core of the connecting signalling structure (such as beta -catenin, GSK beta and Nlk) have been maintained in single copies. (C) 2001 Elsevier Science B.V. All rights reserved.