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Presenting Author(s) Kevin J Beattie
Abstract Title MicroRNAs and non-coding RNAs in Chick limb development.
Full author List Kevin J Beattie, Elizabeth R Farrell , Cheryll Tickle and Stuart Wilson
Text of abstract

MicroRNAs are expressed as ~22nt sequences, having been processed from ~80nt hairpin loops through the action of DICER, an enzyme which catalyses this cleavage. MicroRNAs are found throughout nature, in plants, invertebrates and vertebrates. In C.elegans two microRNAs, lin-4 and let-7 have been found to be important in regulating the timing of embryonic development. One complex series of interactions required for the progression of embryonic to adult fates centres around let-7, which is transcribed as a 70nt hairpin loop near the end of the embryonic period and is then cleaved through the action of DICER into a 22nt sequence. This then binds to the 3'UTR of its target gene, lin-41, which is present in high levels during the embryonic period, thus reducing the levels of LIN-41 protein. This repression is necessary for upregulation of LIN-29 which is required for the differentiation of cells to adult fates.

We have found homologues of both lin-41 and let-7 in the chick EST database ( www.chick.umist.ac.uk ). Lin-41 is present in the stage 20-21 whole embryo and stage 22 limb libraries, with let-7 found in the stage 36 limb library. This suggests a possible parallel with the roles of this pathway in C.elegans. An in-situ hybridization analysis of the expression pattern was performed for lin-41, which was found to be expressed at the early stages of limb bud development and later was associated with the developing digits. PCR analysis revealed let-7 transcripts present at later stages of limb development. Homologs of other microRNAs also found in the chick EST database have been identified and in-situ hybridization analysis carried out.

We have recently also performed an in-situ hybridization screen of a number of other non-coding RNAs found in the chick EST database, which were confirmed using the chicken genome sequence. We found evidence of tissue specific expression, in addition to more general expression throughout the entire embryo. This indicates a possible role for these non-coding RNAs in embryonic development.

Which session is your work most relevant to: Limb patterning