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Expression and function of blimp1/krox, an alternatively transcribed regulatory gene of the sea urchin endomesoderm network

Livi, Carolina B. and Davidson, Eric H. (2006) Expression and function of blimp1/krox, an alternatively transcribed regulatory gene of the sea urchin endomesoderm network. Developmental Biology, 293 (2). pp. 513-525. ISSN 0012-1606. doi:10.1016/j.ydbio.2006.02.021.

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The blimp1/krox gene of Strongylocentrotus purpuratus, formerly krox1, encodes zinc finger transcription factors which play a central role in both early and late endomesoderm specification. Here we show that there are two alternative splice forms transcribed under the control of different regulatory regions. The blimp1/krox1b form was previously unknown, and is the form expressed during cleavage, beginning 6–9 h postfertilization. This form is required for the early events of endomesoderm specification. A different splice variant, blimp1/krox1a, is expressed only from gastrula stage onward. During cleavage stages the blimp1/krox gene is expressed in the large micromeres and veg2 descendents. Soon after, it is expressed in the ring of specified mesoderm cells at the vegetal pole of the blastula. Its expression is later restricted to the blastopore region and the posterior of the invaginating archenteron, and finally to the midgut and hindgut of the pluteus larva. The expression of blimp1/krox is dynamic, and involves several distinct spatial territories. A GFP recombinant BAC was created by substituting the GFP coding sequence for that of the second exon (1b), in order to distinguish the expression pattern of the early form from that of the late form. This construct closely mimics blimp1/krox1b expression during early stages of sea urchin development. To expand our knowledge of the downstream linkages of this gene, additional experiments were carried out using antisense morpholino oligos (MASO). We confirmed previously published data that blimp1/krox autoregulates its own expression, but discovered, surprisingly, that this gene represses rather than activates itself. This negative autoregulation is restricted to the mesodermal and probably skeletogenic territories during the blastula stage, as shown by in situ hybridization analysis of MASO injected embryos. The MASO perturbation analysis also revealed blimp1/krox inputs into other genes of the endomesoderm regulatory network.

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Additional Information:© 2006 Elsevier Inc. Received for publication 27 October 2005; revised 15 February 2006; accepted 16 February 2006. Available online 3 April 2006. We are grateful to Dr. William Klein for providing a full-length SpKrox1 clone obtained from a lambda library, which corresponds to the late form, Spblimp1/krox1a. C.-H. Yuh provided invaluable help with the RACE library, gel shifts, and she and Sagar Damle assisted as well with the BAC homologous recombination. We thank Jonathan Rast for the GFP-kanamycin cassette construct used in this process. Kevin Berney and Lee Rowen performed the BAC annotations and conceptual translations. We also thank Veronica Hinman and Joel Smith for discussions on blimp1/krox, and comments on drafts of the manuscript. This research was funded by NIH Grant HD37105 and DOE grant DE-FG02-03ER63584.
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Department of Energy (DOE)DE-FG02-03ER63584
Subject Keywords:Strongylocentrotus purpuratus; SET domain; PR domain; Cys2His2 zinc finger transcription factor; Endomesodermal specification; Gene regulatory network; Alternative splice forms
Issue or Number:2
Record Number:CaltechAUTHORS:20160121-135400170
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Official Citation:Carolina B. Livi, Eric H. Davidson, Expression and function of blimp1/krox, an alternatively transcribed regulatory gene of the sea urchin endomesoderm network, Developmental Biology, Volume 293, Issue 2, 15 May 2006, Pages 513-525, ISSN 0012-1606, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:63845
Deposited By: Ruth Sustaita
Deposited On:22 Jan 2016 17:06
Last Modified:10 Nov 2021 23:22

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