Homeobox gene transcription factors play critical roles in normal placental development and are expressed in specialised trophoblast cells. Abnormal trophoblast cell function is associated with pregnancy disorders including fetal growth restriction. Our studies show homeobox gene HLX expression in trophoblast cells (1) and that HLX is significantly decreased in fetal growth restriction (2). HLX gene inactivation in cultured trophoblast cells shows that HLX is a regulator of cytokine-dependent trophoblast proliferation (3). Hepatocyte growth factor (HGF) activates trophoblast cell migration in a paracrine fashion and its receptor, c-met, is expressed in trophoblast cells. This study investigates the regulation of HGF/c-met mediated trophoblast migration by HLX, in two human trophoblast cell lines SGHPL-4 and HTR-8/SVNeo. HGF stimulation significantly increased HLX mRNA expression (e.g. 43.2 ± 2.5, HGF v. 18.4 ± 1.7 control, densitometric units, P < 0.001, n = 3). siRNA-mediated inactivation of HLX resulted in significantly decreased trophoblast migration (e.g. 32 ± 4, siRNA v. 127 ± 12 control, migrated cells, P < 0.05, n = 4). When HLX was inactivated in the presence of HGF stimulation, migration remained significantly decreased (e.g. 112 ± 15, siRNA + HGF v. 368 ± 44 HGF, migrated cells, P < 0.05, n = 4). In order to determine if HGF is acting via the c-met receptor, the Met tyrosine kinase inhibitor, SU11274, was employed to inhibit c-met activity. c-met inhibition resulted in significantly reduced HLX mRNA expression (e.g. 2.1 ± 0.32, SU11274 v. 12.3 ± 1.4 control, densitometric units, P < 0.05, n = 3). HLX expression remained significantly reduced with HGF stimulation and SU11274 mediated c-met inhibition (e.g. 8.02 ± 1.3, SU11274 v. 38.3 ± 5.4 HGF, densitometric units, P < 0.05, n = 3). This is the first study to show that homeobox gene HLX is a downstream effector gene of HGF, that HLX regulates trophoblast migration and that HGF, via its receptor c-met, acts through HLX to control cell migration.
(1) Rajaraman G, Murthi P, Quinn L, Brennecke SP, Kalionis B. Homeodomain protein HLX is expressed primarily in cytotrophoblast cell types in the early human placenta. (2008) Reproduction, Fertility a
(2) Murthi P, Doherty V, Said J, Donath S, Brennecke SP, Kalionis B. Homeobox gene HLX1 expression is decreased in idiopathic human fetal growth restriction. (2006) Am J Pathol. 2006 Feb;168(2):511–8.
(3) Rajaraman G, Murthi P, Leo B, Brennecke SP, Kalionis B. Homeobox gene HLX1 is a regulator of colony stimulating factor-1 dependent cell proliferation. (2007) Placenta Volume 28, Issue 10, October
H19 long noncoding RNA alters trophoblast cell migration and invasion by regulating TβR3 in placentae with fetal growth restriction
