A survey of protein tyrosine kinase mRNAs expressed in normal human melanocytes

We have used the reverse transcription-polymerase chain reaction to survey the repertoire of protein tyrosine kinases expressed in cultured normal human melanocytes, a differentiated cell type derived from the neural crest. We identified 25 different tyrosine kinase cDNAs among a total of 608 protein tyrosinase kinase-related cDNAs analyzed. Six encode receptor tyrosine kinases for known ligands, several of which have been implicated in controlling melanocyte proliferation in vitro. Two others encode apparent receptor tyrosine kinases for unknown ligands. Four encode known non-receptor tyrosine kinases and five encode previously identified anonymous protein tyrosine kinases. Of the eight other melanocyte-associated protein tyrosine kinases, most or all appear to be novel. These 25 protein tyrosine kinase genes exhibit distinct patterns of expression in cultured human melanocytes, human erythroleukemia cells, and a variety of normal human tissues. We mapped 16 of the corresponding protein tyrosine kinase genes to specific human chromosomes, identifying a total of 19 human genetic loci, some of which may constitute candidate genes for genetic disorders of mammalian development.