It is long established that the graded distribution of Dorsal transcription factor influences spatial domains of gene expression along the dorsoventral axis of Drosophila melanogaster embryos.However, the more recent realization that Dorsal levels also change in time raises the question of whether these dynamics are instructive. Here, an overview of dorsoventral axis patterning is provided focusing on new insights identified through quantitative analysis of temporal changes in Dorsal target gene expression from one nuclear cycle to the next ('steps'). Possible roles for the step-wise progression of this patterning program are discussed including (i) tight, temporal regulation of signaling pathway activation, (ii) control of gene expression cohorts, and (iii) to ensure irreversibility of the patterning and cell fate specification process.
KeywordsDorsal transcription factor; Drosophila embryo; dorsal-ventral patterning; dynamics; morphogen gradients; spatiotemporal gene expression
Transcription factor dynamics regulate target gene expressionSubdividing the embryo into distinct domains of gene expression by combinatorial control of transcription factors is an important function of regulatory networks acting in early embryos including those of Drosophila [1][2][3][4][5]. These early patterning events influence the activation of signaling pathways to support tissue differentiation and also control cell movements required for the generation of a multilayered embryo; the developmental actions that encompass gastrulation [6,7]. To study these events at the transcriptional level in Drosophila embryos, previous studies of early zygotic gene expression have considered one or two time-points spanning the first four hours of early embryo development [8][9][10][11], and yet recent studies suggest gene expression patterns change on the order of minutes rather than hours [e.g. 12, 13, 14]. Furthermore, only recently has it come to light that transcription factors in the early embryo exhibit changes in levels over time [15][16][17][18]. At least in part these dynamics relate to the fast nuclear divisions that encompass Drosophila early embryonic * Correspondence: angelike@caltech.edu (A. Stathopoulos). Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Author ManuscriptAuthor Manuscript development and result in oscillatory inputs to target genes. Transcription factor dynamics appear to be a general mechanism of regulating gene expression [19,20] and highlight the need to study temporal regulation of developmental gene expression...