PT  - JOURNAL ARTICLE
AU  - Gajewski, Martin
AU  - Sieger, Dirk
AU  - Alt, Burkhard
AU  - Leve, Christian
AU  - Hans, Stefan
AU  - Wolff, Christian
AU  - Rohr, Klaus B.
AU  - Tautz, Diethard
TI  - Anterior and posterior waves of cyclic <em>her1</em> gene expression are
differentially regulated in the presomitic mesoderm of zebrafish
AID  - 10.1242/dev.00627
DP  - 2003 Sep 15
TA  - Development
PG  - 4269--4278
VI  - 130
IP  - 18
4099  - http://dev.biologists.org/content/130/18/4269.short
4100  - http://dev.biologists.org/content/130/18/4269.full
SO  - Development2003 Sep 15; 130
AB  - Somite formation in vertebrates depends on a molecular oscillator in the presomitic mesoderm (PSM). In order to get a better insight into how oscillatory expression is achieved in the zebrafish Danio rerio, we have analysed the regulation of her1 and her7, two bHLH genes that are co-expressed in the PSM. Using specific morpholino oligonucleotide mediated inhibition and intron probe in situ hybridisation, we find that her7 is required for initiating the expression in the posterior PSM, while her1 is required to propagate the cyclic expression in the intermediate and anterior PSM. Reporter gene constructs with the her1 upstream sequence driving green fluorescent protein (GFP) expression show that separable regulatory regions can be identified that mediate expression in the posterior versus intermediate and anterior PSM. Our results indicate that the cyclic expression is generated at the transcriptional level and that the resulting mRNAs have a very short half-life. A specific degradation signal for her1 mRNA must be located in the 5′-UTR, as this region also destabilises the GFP mRNA such that it mimics the dynamic pattern of the endogenous her1 mRNA. In contrast to the mRNA, GFP protein is stable and we find that all somitic cells express the protein, proving that her1 mRNA is transiently expressed in all cells of the PSM.