NORMAL GENOMIC

• Canty EG, Garrigue-Antar L, Kadler KE
• A complete domain structure of Drosophila tolloid is required for cleavageof short gastrulation.
• J Biol Chem. 2006; 281: 13258-67
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• Drosophila tolloid (TLD) is a member of a family of proteinases that playimportant roles in development and includes mammalian tolloid (mTLD) andbone morphogenetic protein (BMP)-1. TLD accentuates the activity ofdecapentaplegic (DPP), a transforming growth factor beta superfamilygrowth factor, by cleaving its antagonist Short gastrulation (Sog).Similarly, the activity of BMP-2/4 (vertebrate homologues of DPP) isaugmented by cleavage of chordin. However, whereas TLD is an effectiveSogase, mTLD is a poor chordinase and is functionally replaced by itssmaller splice variant BMP-1, which lacks the most C-terminal epidermalgrowth factor (EGF)-like and CUB domains of mTLD. Moreover, the minimalchordinase activity resides in the N-terminal half of BMP-1. This studyshowed that the proteolytic activity of TLD is considerably enhanced byCa2+ and tested the hypothesis that the Sogase activity of TLD resides inthe N-terminal half of the proteinase. Unexpectedly, it was found that TLDlacking the CUB4 and CUB5 domains and/or the EGF-like domains was unableto cleave Sog. Loss of function mutations have been reported in the tldgene that result in amino acid substitutions at E835K (in CUB4), S915L (inCUB5), and N760I (in EGF2) in TLD. The CUB mutants were found to beineffective Sogases, but the activity of the EGF2 mutant was unchanged.The results show that substrate recognition and cleavage by Drosophilatolloid and mTLD are different despite their identical domain structureand homologous functions in patterning. The result that the N760I mutanthas full Sogase activity suggests that novel substrates for TLD exist.

• Hoffmann U, Kroiher M
• A possible role for the cnidarian homologue of serum response factor indecision making by undifferentiated cells.
• Dev Biol. 2001; 236: 304-15
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• We have isolated the serum response factor (SRF) homologue from twohydrozoans, the freshwater polyp Hydra vulgaris and the marine colonialHydractinia echinata; we have termed the Hydra gene HvSRF and theHydractinia gene HeSRF. The MADS-box of both genes is identical insequence and more similar to SRFs of other organisms than to non-SRFMADS-box-containing proteins from other organisms. Within the N terminusof the predicted protein, a motif of 14 amino acids is nearly identicalbetween Hydra and Hydractinia. This motif is absent from other known SRFsequences. In the adult Hydra polyp, SRF is predominantly expressed incells of the interstitial cell (I-cell) lineage. Expression of SRF ceaseswhen I-cells differentiate into nerve cells, nematocytes, or gland cells.In the course of sexual reproduction in Hydractinia, SRF is expressed infemale germ cells. During embryogenesis, SRF transcripts are observed inall blastomeres. Later on, SRF expression is turned off in cells formingthe ectodermal layer but further on is expressed in cells of the centralcell mass, from which the endodermal epithelial cells and the I-celllineage originate. Expression eventually becomes restricted to the I-celllineage. We conclude that hydrozoan SRF is expressed in all these cells,which still have the property for differentiation. In adult Hydra, theabundance of SRF transcripts varies during the day. The pacemaker of thisdiurnal rhythm is the feeding regime. HvSRF expression decreases by 4 hafter feeding and returns to the initial level 12 h after feeding. Whenfeeding is stopped, the cycle of SRF expression persists through the firstday when the animals are not fed. It has been shown that feeding partlysynchronizes the cell cycle of the epithelial cells but not that of theI-cells. We suggest that the epithelial cells affect SRF expression inI-cells and thereby influence the decision of I-cells to enter adifferentiation pathway.

• Trudeau D, Witherell RA, Strand MR
• Characterization of two novel Microplitis demolitor polydnavirus mRNAsexpressed in Pseudoplusia includens haemocytes.
• J Gen Virol. 2000; 81: 3049-58
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• The braconid wasp Microplitis demolitor carries M. demolitor polydnavirus(MdPDV) and parasitizes the larval stage of the moth Pseudoplusiaincludens. M. demolitor injects MdPDV into P. includens larvae when itlays an egg and the virus infects various cells including haemocytes. Twonew MdPDV transcripts expressed in host haemocytes were characterized inthis study. Screening of an MdPDV-infected haemocyte cDNA libraryidentified a 0.4 kb cDNA encoding a predicted protein of 103 amino acidswhich was named Egf0. 4. This protein contained a cysteine-rich epidermalgrowth factor (EGF)-like motif at its N terminus that was similar to theEGF-like domains in the previously identified MdPDV genes egf1.5 andegf1.0. Sequencing of the genomic clone pMd-10 indicated that it containedthe egf0.4 gene, which consisted of two introns and three exons. This genewas located on MdPDV segment O and appeared to exist in multiple copies. Anucleic acid and expression screen identified a 1. 8 kb cDNA encoding apredicted protein of 515 amino acids designated Glc1.8. This proteinconsisted of a heavily glycosylated central core of six tandemly arrangedrepeats flanked by hydrophobic N- and C-terminal domains. Northernblotting and in situ hybridization studies indicated that both egf0.4 andglc1.8 were expressed in MdPDV-infected host haemocytes.Immunocytochemical studies also indicated that Glc1.8 localized to thecell surface.