Regulation of Murine TGFβ2 by Pax3 during Early Embryonic Development

Abstract

Pax3 encodes a paired homeobox containing transcription factor that is expressed in neuroepithelium, neural crest, and presomitic mesoderm (1). Homozygous mouse embryos carrying a loss-of-function Pax3 allele (Pax3 Ϫ/Ϫ ) develop open neural tube defects, such as exencephaly or spina bifida (2), and die around embryonic day 14 (E14) 4 as a consequence of heart defects (3). More recently, Pax3 has been shown to function at the nodal point in melanocyte stem cell differentiation (4). Heterozygous embryos (Pax3 ϩ/Ϫ ) are viable but exhibit white patches on their bellies caused by defective development of neural crest-derived melanocytes. This suggests that disruption of the Pax3-dependent developmental program may cause defects in the development of neural crest-derived structures.Two main Pax3-binding sites have been identified and are found in most Pax3 target elements as follows: (i) a binding site derived from the Drosophila Paired (ATTA N5 GTTCC), and (ii) a Pax3 paired domain binding site (CGTCAC(G/A)(C/ G)TT) identified by Epstein et al. (5) by CASTing (DNA-binding site selection assays) in the c-Met promoter region. In addition several paired domains, such as GTTCC, CAGTGT, GTTAT, GTGTGA, and CAAGG (6), as well as the homeodomain ATTA, have been suggested to be "putative Pax3-binding motifs" (7,8). More recently, Corey and Underhill (9) demonstrated that Pax3 can regulate target genes through alternative modes of DNA recognition. They observed that although the microphthalmia-associated transcription factor element is characterized by suboptimal recognition motifs for the paired domain and homeodomain, it sustains a higher level of Pax3 binding than TRP-1, which contains a canonical paired domain site. The basis for this difference involved a context-dependent cooperative binding event requiring both the paired and homeodomain, whereas the paired domain alone was sufficient for TRP-1 recognition.Since Pax3 is important in diverse cellular functions during development, we wanted to identify additional genes regulated by Pax3. To accomplish this we utilized oligonucleotide arrays and RNA isolated from Pax3-transfected cell lines and promoter-based data mining (6). Based on the putative Pax3-binding

Histone Deacetylase 10 Relieves Repression on the Melanogenic Program by Maintaining the Deacetylation Status of Repressors

“…Therefore, which enzyme functions as an upstream deacetylase remains to be a critical question. It has been shown that HDAC10 interacts with HDAC2 and HDAC3 (5,8), and one recent report showed that HDAC1 coimmunoprecipitates with acetylated Pax3 in a medulloblastoma cell line with stably transfected Pax3 (32). However, in our laboratory we observed that Pax3 failed to interact with HDAC1, HDAC2, HDAC3, or HDAC8 in coimmunoprecipitation experiments.…”

“…Nevertheless, we do not exclude the possibility that other HDACs also participate in the modulation of the activities of proteins targeted by HDAC10. In fact, Mayanil et al (32) showed that SirT1 binds to transforming growth factor-␤ promoter fragments where Pax3 binds, suggesting that SirT1 or other NAD ϩ -dependent HDACs might participate in HDAC10-mediated regulatory events as upstream deacetylases of target proteins.…”

Perplexing Pax: From puzzle to paradigm

“…In vivo assays performed during mouse embryonic development show that Pax7 targets a complex array of receptors and intracellular signaling pathways, including integral components of Ras-MAPK, JAK-STAT, and calmodulin-dependent signaling pathways (White and Ziman, 2008). Importantly, this echoes multiple studies implicating Pax3 in the regulation of receptors and components of signaling pathways such as the secretory glycoprotein Wnt1 (Fenby et al, 2008), HGF / c-Met (Epstein et al, 1996;Mayanil et al, 2001;Relaix et al, 2004;Tomescu et al, 2004), c-RET (Lang et al, 2000;Lang and Epstein, 2003), as well as both TGF-␣ (Barber et al, 2002) and TGF-␤2 (Mayanil et al, 2006). Multiple isoforms of Pax3 are also known to independently regulate signaling and morphogen response pathways by means of the Shh functional homologue Dhh, Fgf17, Kitl, and Rac1 to control cell differentiation and proliferation (Wang et al, 2007).…”

Transcriptional regulation by Pax3 and TGFbeta2 signaling: a potential gene regulatory network in neural crest development

“…Work from our lab established a link between Pax3 and TGFβ2 (Mayanil et al, 2006). Pax3 regulates the TGFβ2 promoter by binding to its cis-regulatory elements, and TGFβ2 expression is diminished in Pax3 -/-embryos.…”

“…Pax3 regulates the TGFβ2 promoter by binding to its cis-regulatory elements, and TGFβ2 expression is diminished in Pax3 -/-embryos. Thus a regulatory relationship exists between Pax3 and TGFβ2 (Mayanil et al, 2006).…”