Published online 13 July 2006
© 2006 The Author(s)
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Article |
The regulated expression of chimeric tyrosine hydroxylase–insulin transcripts during early development
Group of Growth Factors in Vertebrate Development, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC) Ramiro de Maeztu 9, E-28040 Madrid, Spain 1 Department of Animal Physiology II, Facultad de C. Biológicas, Universidad Complutense de Madrid E-28040 Madrid, Spain
*To whom correspondence should be addressed. Tel/Fax: +34 91 534 9201; Email: chernandez{at}cib.csic.es
Received April 20, 2006. Revised June 1, 2006. Accepted June 2, 2006.
Biological complexity does not appear to be simply correlated with gene number but rather other mechanisms contribute to the morphological and functional diversity across phyla. Such mechanisms regulate different transcriptional, translational and post-translational processes and include the recently identified transcription induced chimerism (TIC). We have found two novel chimeric transcripts in the chick and quail that result from the fusion of tyrosine hydroxylase (TH) and insulin into a single mature transcript. The th and insulin genes are located in tandem and they are generally transcribed independently. However, it appears that two chimeric transcripts containing exons from both the genes can also be produced in a regulated manner. The TH–INS1 and TH–INS2 chimeras differ in their insulin gene content, and they encode two novel isoforms of the TH protein with markedly reduced functionality when compared with the canonical TH. In addition, the TH–INS1 chimeric mRNA generates a small amount of insulin. We propose that TIC is an additional mechanism that can be employed to further regulate TH and insulin expression according to the specific needs of developing vertebrates.