Dynamic gene expression of Lin-28 during embryonic development in mouse and chicken

Abstract

The Caenorhabditis elegans heterochronic gene lin-28 regulates developmental timing in the nematode trunk. We report the dynamic expression patterns of Lin-28 homologues in mouse and chick embryos. Whole mount in situ hybridization revealed specific and intriguing expression patterns of Lin-28 in the developing mouse and chick limb bud. Mouse Lin-28 expression was detected in both the fore-limb and hindlimb at E9.5, but disappeared from the forelimb at E10.5, and finally from the forelimb and hindlimb at E11.5. Chicken Lin-28, which was first detected in the limb primordium at stage 15/16, was also downregulated as the stage proceeded. The amino acid sequences of mouse and chicken Lin-28 genes are highly conserved and the similar expression patterns of Lin-28 during limb development in mouse and chicken suggest that this heterochronic gene is also conserved during vertebrate limb development. KeywordsHeterochronic gene; Whole mount in situ hybridization; Mouse; Chick; Limb bud; Lin-28; MicroRNAs; Developmental timing; Dynamic expression; Embryo Results and discussionEmbryonic development is tightly regulated by spatio-temporal gene expression; however, systems regulating developmental timing are largely unknown. A series of mutagenesis studies using the nematode Caenorhabditis elegans as a model have identified a cluster of genes, the so-called "heterochronic genes," which is expressed at the specific period of time during embryogenesis and play a critical role in determining the relative timing of developmental events (Ambros and Horvitz, 1984;Lee et al., 1993). Among these heterochronic genes, * Corresponding author. Address: Department of Systems Biomedicine, National Research Institute for Child Health and Development, 2-10-1 Okura, Setagaya, Tokyo, Japan. Tel/fax: +81 3 3417 2498., E-mail address: asahara@nch.go.jp (H. Asahara). Publisher's Disclaimer: This article was published in an Elsevier journal. The attached copy is furnished to the author for non-commercial research and education use, including for instruction at the author's institution, sharing with colleagues and providing to institution administration. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. To further examine the spatio-temporal expression patterns of Lin-28 in developing embryos, we performed whole mount in situ hybridization using mouse and chicken embryos at different developmental stages.Although Lin-28 was ubiquitously expressed throughout the mouse embryo at E9.5 (Fig. 1a, a′), strong expression was observed in the most distal mesenchyme adjacent to the apical ectodermal ridge (AER) of both forelimb and hindlimb buds (Fig. 1b, b′, white arrow). Interestingly, at E10.5, the expression of Lin-28 in forelimb almost disappeared, and expression was restricted to the hindlimb and more caudal trunk at the hindlimb level ( Fig. 1c-e). In a ...

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