Abstract
Background
Mutations in the mouse formin (Fmn) gene result in limb deformities and incompletely penetrant renal aplasia. A molecular genetic approach was taken to characterize novel circular RNAs from the Fmn gene and to understand the developmental effects of gene-targeted mutations.
Materials and Methods
RT-PCR and ribonuclease protection analyses were done to characterize the circular RNA transcripts arising from the Fmn gene. Two lines of mice with gene-targeted deletions of specific Fmn exons, namely exon 4 or exon 5, were generated and analyzed.
Results
In our analysis of formin cDNAs, we discovered a class of transcripts in which the exon order is reversed such that downstream exons are joined to the acceptor end of a specific exon that lies 5′ to them in the genome. RT-PCR and ribonuclease protection analyses indicate that these transcripts are circular and are the major transcripts arising from this locus in adult brain and kidney. To gain insight into the biological function of these transcripts, we have systematically deleted the relevant exons using gene-targeted homologous recombination. The resulting mice fail to produce circular transcripts, but appear to produce normal amounts of the linear RNA isoforms from this locus. While these deficient mice have normal limbs, they display variably penetrant renal aplasia characteristic of other mutant formin alleles.
Conclusions
Our results demonstrate novel circular transcripts arising from the Fmn gene. Moreover, their high levels of expression suggest that they are not products of aberrant splicing events, but instead, may play important biological roles. Mice with gene-targeted deletions of Fmn exons 4 or 5 lack these circular transcripts and have an incompletely penetrant renal agenesis phenotype. While the biologic function of circular Fmn RNA transcripts is not entirely known, our work suggests their possible involvement in kidney development.
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Acknowledgments
We thank Mark Bedford and Chuxia Deng for their technical expertise and helpful discussions. We gratefully acknowledge technical help from Cathie Daugherty, Judy Dunmore, Anne Harrington, and Montserrat Michelman. We are grateful to Hsiuchen Chen, Ian Krane, Ben Stanger, and Christoph Westphal for careful reading of the manuscript. C. W. Chao and D. C. Chan were supported in part by the NIH Medical Scientist Training Program.
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Communicated by P. Leder.
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Chao, C.W., Chan, D.C., Kuo, A. et al. The Mouse formin (Fmn) Gene: Abundant Circular RNA Transcripts and Gene-Targeted Deletion Analysis. Mol Med 4, 614–628 (1998). https://doi.org/10.1007/BF03401761
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DOI: https://doi.org/10.1007/BF03401761