bmp1 and mini fin are functionally redundant in regulating formation of the zebrafish dorsoventral axis

Abstract

Drosophila metalloproteinase Tolloid (TLD) is responsible for cleaving the antagonist Short gastrulation (SOG), thereby regulating signaling by the bone morphogenetic protein (BMP) Decapentaplegic (DPP). In mice there are four TLD-related proteinases, two of which, BMP1 and mammalian Tolloid-like 1 (mTLL1), are responsible for cleaving the SOG orthologue Chordin, thereby regulating signaling by DPP orthologues BMP2 and 4. However, although TLD mutations markedly dorsalize Drosophila embryos, mice doubly homozygous null for BMP1 and mTLL1 genes are not dorsalized in early development. Only a single TLD-related proteinase has previously been reported for zebrafish, and mutation of the zebrafish TLD gene (mini fin) results only in mild dorsalization, manifested by loss of the most ventral cell types of the tail. Here we identify and map the zebrafish BMP1 gene bmp1. Knockdown of BMP1 expression results in a mild tail phenotype. However, simultaneous knockdown of mini fin and bmp1 results in severe dorsalization resembling the Swirl (swr) and Snailhouse (snh) phenotypes; caused by defects in major zebrafish ventralizing genes bmp2b and bmp7, respectively. We conclude that bmp1 and mfn gene products functionally overlap and are together responsible for a key portion of the Chordin processing activity necessary to formation of the zebrafish dorsoventral axis.

The bone morphogenetic protein 1/Tolloid-like metalloproteinases

“…mTLL2 may provide such activity in vivo, since it has Chordinase activity in vitro in the presence of the modulator protein twisted gastrulation (TSG) ; also see below). In contrast to mammals, knockdown of the expression of the bmp1a and tll1 genes in zebrafish is sufficient to severely dorsalize embryos (Jasuja et al, 2006;Muraoka et al, 2006), indicating less redundancy for Chordin cleavage in teleosts than in mammals. In addition to their roles in patterning, BMPs 2 and 4 are potently osteoinductive .…”

“…Apparently due to partial genome duplication in teleosts, two genes exist for BMP1 in zebrafish (bmp1a and bmp1b) (Muraoka et al, 2006;Jasuja et al, 2006), although only sequences for longer mTLD-like proteinases have been described for these genes, and it has yet to be determined whether they also encode alternatively spliced mRNAs for shorter BMP1 forms. In contrast, cDNA encoding the short form of BMP1 (suBMP), has been described in the sea urchin S. purpuratus (Hwang et al, 1994), with a longer alternatively spliced form yet to be described.…”

Efficient Mapping and Cloning of Mutations in Zebrafish by Low-Coverage Whole-Genome Sequencing

“…A morpholino directed against the translation initiation site of bmp1a (MO1) (Jasuja et al 2006) was injected at a concentration of 0.3 mM into one-cell stage Tü embryos. The phenotype was assessed at 3 days postfertilization (dpf).…”

BMP and non-canonical Wnt signaling are required for inhibition of secondary tail formation in zebrafish

“…mfn, dvl2, dvl3 and cdh2 morpholinos have been described previously (Lele et al, 2002;Angers et al, 2006;Jasuja et al, 2006). The standard control morpholino by Gene Tools was used in some experiments.…”