ANTISENSE TRANSCRIPTION OF A MURINE FGFR-3 PSEUDOGENE DURING FETAL DEVELOPMENT

In a search for new protein tyrosine kinases (PTKs) in early hemopoiet ic cells, we have identified a sequence closely related to the Fibrobl ast Growth Factor Receptor (FGFR) family. A cDNA isolated from a mouse embryo library was 89% identical to FGFR-3 in both its coding and 3' untranslated regions. However, the region homologous to exons 5 to 9 o f FGFR-3 was missing. In addition, the ORF was interrupted by several stop codons and frame shifts, indicating that this sequence is not fun ctional. These transcripts were therefore copied from a novel FGFR-3 p seudogene, that we called psi FGFR-3. Partial analysis of this gene sh owed the absence of introns, which is a characteristic feature of a pr ocessed pseudogene. psi FGFR-3 gene was localized on Chromosome 1H4-6. Its transcription was shown to be antisense and its expression was re stricted to fetal tissues. These results indicate that psi FGFR-3 has been inserted in Chromosome 1 in antisense orientation dose to a heter ologous promoter.