title: Microarray profiling reveals CXCR4a is downregulated by blood flow in vivo and mediates collateral formation in zebrafish embryos.
abstract: The response to hemodynamic force is implicated in a number of pathologies including collateral vessel development. However, the transcriptional effect of hemodynamic force is extremely challenging to examine in vivo in mammals without also detecting confounding processes such as hypoxia and ischemia. We therefore serially examined the transcriptional effect of preventing cardiac contraction in zebrafish embryos which can be deprived of circulation without experiencing hypoxia since they obtain sufficient oxygenation by diffusion. Morpholino antisense knock-down of cardiac troponin T2 (tnnt2) prevented cardiac contraction without affecting vascular development. Gene expression in whole embryo RNA from tnnt2 or control morphants at 36, 48, and 60 h postfertilization (hpf) was assessed using Affymetrix GeneChip Zebrafish Genome Arrays (>14,900 transcripts). We identified 308 differentially expressed genes between tnnt2 and control morphants. One such (CXCR4a) was significantly more highly expressed in tnnt2 morphants at 48 and 60 hpf than controls. In situ hybridization localized CXCR4a upregulation to endothelium of both tnnt2 morphants and gridlock mutants (which have an occluded aorta preventing distal blood flow). This upregulation appears to be of functional significance as either CXCR4a knock-down or pharmacologic inhibition impaired the ability of gridlock mutants to recover blood flow via collateral vessels. We conclude absence of hemodynamic force induces endothelial CXCR4a upregulation that promotes recovery of blood flow.
authors.affiliation: Medical Research Council Centre for Developmental and Biomedical Genetics, United Kingdom.
authors.forename: Ian M
authors.initials: IM
authors.lastname: Packham
authors.forename: Caroline
authors.initials: C
authors.lastname: Gray
authors.forename: Paul R
authors.initials: PR
authors.lastname: Heath
authors.forename: Paul G
authors.initials: PG
authors.lastname: Hellewell
authors.forename: Philip W
authors.initials: PW
authors.lastname: Ingham
authors.forename: David C
authors.initials: DC
authors.lastname: Crossman
authors.forename: Marta
authors.initials: M
authors.lastname: Milo
authors.forename: Timothy J A
authors.initials: TJ
authors.lastname: Chico
mesh_terms: D000818:Animals; D001160:Arterioles / Q000254:growth & development; D001783:Blood Flow Velocity; D016000:Cluster Analysis; D003097:Collateral Circulation; D015536:Down-Regulation; D004625:Embryo, Nonmammalian / Q000196:embryology / Q000378:metabolism*; D005260:Female; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D055785:Gene Knockdown Techniques / Q000379:methods; D017403:In Situ Hybridization; D008297:Male; D009200:Myocardial Contraction; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods*; D016376:Oligonucleotides, Antisense; D019718:Receptors, CXCR4 / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020107:Troponin T / Q000235:genetics; D015027:Zebrafish / Q000196:embryology / Q000235:genetics*; D029961:Zebrafish Proteins / Q000235:genetics*
chemical_list: C532358:CXCR4a protein, zebrafish; D016376:Oligonucleotides, Antisense; D019718:Receptors, CXCR4; D020107:Troponin T; D029961:Zebrafish Proteins; C480681:tnnt2a protein, zebrafish