Developmental expression and CORT-regulation of TGF-β and EGF receptor mRNA during mouse palatal morphogenesis: Correlation between CORT-induced cleft palate and TGF-β2 mRNA expression

Abstract

Glucocorticoids (CORT) have been shown to induce cleft palate in mice. Although the pathogenetic pathway of CORT‐induced cleft palate has been investigated for several decades, the molecular details remain to be elucidated. Since growth factors have been shown to regulate palate morphogenesis, and the expression of several growth factors or their receptors, e.g. TGF‐β, EGF receptor (EGF‐R), are known to be modulated by CORT, we postulate that CORT modulation of growth factor (or receptor) gene expression is a key mechanism involved in CORT‐induced cleft palate. To test this hypothesis, we analyzed the steady‐state levels (Northern and RNase protection) and developmental expression (in situ hybridization) of four CORT‐responsive genes—TGF‐β1, TGF‐β2, TGF‐β3, and EGF receptor (EGF‐R)—in developing mouse palates in the presence or absence of exogenous CORT. Pregnant B10.A dams were injected on day 12 of gestation with CORT or sham‐injected and embryonic palates were collected at 1, 2, and 3 days postinjection (E13–E15). During mouse palate development, significant increases in TGF‐β1 and TGF‐β3 mRNA levels, as well as a significant decrease in TGF‐β2 mRNA levels, are detected; no significant difference in EGF‐R transcript level is observed with progressive development. In CORT‐exposed palates, we demonstrate no significant differences in the direction or magnitude of change with time in TGF‐β1, TGF‐β3, and EGF‐R mRNA levels compared to controls. However, CORT delays by 1 day the down‐regulation of palatal TGF‐β2 transcript normally seen on day 14 of gestation. TGF‐β2 is known to inhibit cell proliferation. The level of TGF‐β2 mRNA, the only isoform primarily expressed in the palatal mesenchyme, significantly decreases with progressive palatal development; this down‐regulation in TGF‐β2 expression is associated with increased mesenchymal cell proliferation and palatal shelf growth. CORT, at a critical stage of palatogenesis, induces a delay in the normal down‐regulation of TGF‐β2 gene expression. Given that CORT is known to inhibit mesenchymal cell proliferation and palatal shelf growth, we conclude that the CORT‐induced delay in the normal down‐regulation of TGF‐β2 gene expression is probably a key event in the pathogenesis of CORT‐induced cleft palate. © 1996 Wiley‐Liss, Inc.

EGF‐stimulated signaling by means of PI3K, PLCγ1, and PKC isozymes regulates branching morphogenesis of the fetal mouse submandibular gland

“…Umeda et al (2001) showed that HB‐EGF is also essential for branching morphogenesis of the fetal mouse SMG. In addition, signaling through the fibroblast growth factor family of receptors (DeMoerlooze et al, 2000; Hoffman et al, 2002; Jaskoll et al, 2002) and other pathways (Jaskoll et al, 1996; Jaskoll and Melnick, 1999; Melnick and Jaskoll, 2000; Melnick et al, 2001a, b; Davies, 2002; Jaskoll et al, 2002) is also critical for branching of this organ rudiment. Moreover, the final outcome of activating the Ras/MEK/ERK pathway has been shown recently to be modulated by both positive and negative feedback loops, demonstrating flexibility in signaling, with obvious functional significance (Bhalla et al, 2002).…”

Expression profiling of transforming growth factor β superfamily genes in developing orofacial tissue

“…Embryonic orofacial tissue contains functional type I, II, and III TGFβ receptors (Linask et al,1991; Cui and Shuler2002) that, when activated, elicit changes in palatal cell proliferation (Linask et al,1991), glycosaminoglycan synthesis (D'Angelo and Greene,1991), collagen metabolism (D'Angelo et al,1994), and the remodeling of the extracellular matrix via matrix metalloproteinases (MMPs) such as MMP2 and MMP9 (also known as gelatinases A and B, respectively) (D'Angelo et al,1994; Brown et al, 2002). Moreover, the TGFβs exhibit unique spatiotemporal patterns of expression in the developing orofacial region (Fitzpatrick et al,1990; Gehris et al,1991; Pelton et al,1991; Jaskoll et al,1996).…”

Environmental mechanisms of orofacial clefts

“…Homeostatic levels of endogenous cortisol are required for appropriate craniofacial morphogenesis, but the addition of exogenous GCs can cause cleft palate (Hu, Gao, Liao, Tang, & Lu, 2013; R. Pratt, 1980). Although excess of cortisol itself can cause cleft palate in mice (Jaskoll, Choy, Chen, & Melnick, 1996), some synthetic GCs may have a more potent effect of cleft palate induction. As an example, the synthetic GC dexamethasone is approximately 300 times more potent than cortisol for inducing cleft palate (Pinsky & Digeorge, 1965).…”