PLAC1 affects cell to cell communication by interacting with the desmosome complex.

INTRODUCTION: X-linked PLAC1 is highly expressed in placenta during embryogenesis, and when ablated in mice, causes aberrant placental cell layer organization. It is also highly expressed in many types of cancer cell-lines. Although it has been shown that it promotes AKT phosphorylation in cancer cells, the exact mechanism by which it influences placental layer differentiation is unclear. METHODS: To investigate the mechanism of action of PLAC1 we did cell fractionation and immunoprecipitation of the protein and Mass Spectrometry analysis to identify its interaction partners. The associated proteins were directly tested for interactions by co-transfection with PLAC1 and immunoprecipitation. Mutations in the ZP-N domain of PLAC1 were introduced to assess its involvement in the interactions. RESULTS: We provide evidence that Desmoglein-2 (DSG2), a component of the membrane-associated desmosomal complex, directly interacts with PLAC1. Mutations of cysteines in ZP-N domain disrupt the interaction between PLAC1 and DSG-2. DISCUSSION: Because desmosomes are responsible for establishing lateral cell-cell junctions, we suggest that direct interaction with the lateral junction protein complex may be implicated in the PLAC1 effects on cell-cell interactions, and thereby on the layer structure of the placenta.

Eda-activated RelB recruits an SWI/SNF (BAF) chromatin-remodeling complex and initiates gene transcription in skin appendage formation.

Ectodysplasin A (Eda) signaling activates NF-κB during skin appendage formation, but how Eda controls specific gene transcription remains unclear. Here, we find that Eda triggers the formation of an NF-κB-associated SWI/SNF (BAF) complex in which p50/RelB recruits a linker protein, Tfg, that interacts with BAF45d in the BAF complex. We further reveal that Tfg is initially induced by Eda-mediated RelB activation and then bridges RelB and BAF for subsequent gene regulation. The BAF component BAF250a is particularly up-regulated in skin appendages, and epidermal knockout of BAF250a impairs skin appendage development, resulting in phenotypes similar to those of Eda-deficient mouse models. Transcription profiling identifies several target genes regulated by Eda, RelB, and BAF. Notably, RelB and the BAF complex are indispensable for transcription of Eda target genes, and both BAF complex and Eda signaling are required to open chromatin of Eda targets. Our studies thus suggest that Eda initiates a signaling cascade and recruits a BAF complex to specific gene loci to facilitate transcription during organogenesis.

PLAC1 (Placenta-specific 1): a novel, X-linked gene with roles in reproductive and cancer biology.

Placenta-specific 1 (PLAC1) is a recently described X-linked gene with expression restricted primarily to cells derived from trophoblast lineage during embryonic development. PLAC1 localizes to a region of the X chromosome thought to be important in placental development although its role in this process has not been defined. This review summarizes our current understanding of its expression, regulation, and function. PLAC1 is expressed throughout human pregnancy by the differentiated trophoblast and localizes to membranous structures in the syncytiotrophoblast, including the microvillous plasma membrane surface. Recent studies have demonstrated that PLAC1 is also expressed by a wide variety of human cancers. Studies of the PLAC1 promoter regions indicate that its expression in both normal placenta and cancer cells is driven by specific interactions involving a combination of transcription factors. Although functional insight into PLAC1 in the normal trophoblast is lacking, preliminary studies suggest that cancer-derived PLAC1 has the potential to promote tumor growth and function. In addition, it also appears to elicit a specific immunologic response that may influence survival in some cancer patients, suggesting that it may provide a therapeutic target for the treatment of some cancers. We also discuss a potential role for PLAC1 as a biomarker predictive of specific pregnancy complications, such as preeclampsia.

Uncovering early response of gene regulatory networks in ESCs by systematic induction of transcription factors.

To examine transcription factor (TF) network(s), we created mouse ESC lines, in each of which 1 of 50 TFs tagged with a FLAG moiety is inserted into a ubiquitously controllable tetracycline-repressible locus. Of the 50 TFs, Cdx2 provoked the most extensive transcriptome perturbation in ESCs, followed by Esx1, Sox9, Tcf3, Klf4, and Gata3. ChIP-Seq revealed that CDX2 binds to promoters of upregulated target genes. By contrast, genes downregulated by CDX2 did not show CDX2 binding but were enriched with binding sites for POU5F1, SOX2, and NANOG. Genes with binding sites for these core TFs were also downregulated by the induction of at least 15 other TFs, suggesting a common initial step for ESC differentiation mediated by interference with the binding of core TFs to their target genes. These ESC lines provide a fundamental resource to study biological networks in ESCs and mice.

Phosphodiesterase 8B gene variants are associated with serum TSH levels and thyroid function.

Thyroid-stimulating hormone (TSH) controls thyroid growth and hormone secretion through binding to its G protein-coupled receptor (TSHR) and production of cyclic AMP (cAMP). Serum TSH is a sensitive indicator of thyroid function, and overt abnormalities in thyroid function lead to common endocrine disorders affecting approximately 10% of individuals over a life span. By genotyping 362,129 SNPs in 4,300 Sardinians, we identified a strong association (p = 1.3 x 10(-11)) between alleles of rs4704397 and circulating TSH levels; each additional copy of the minor A allele was associated with an increase of 0.13 muIU/ml in TSH. The single-nucleotide polymorphism (SNP) is located in intron 1 of PDE8B, encoding a high-affinity cAMP-specific phosphodiesterase. The association was replicated in 4,158 individuals, including additional Sardinians and two genetically distant cohorts from Tuscany and the Old Order Amish (overall p value = 1.9 x 10(-20)). In addition to association of TSH levels with SNPs in PDE8B, our genome scan provided evidence for association with PDE10A and several biologically interesting candidates in a focused analysis of 24 genes. In particular, we found evidence for association of TSH levels with SNPs in the THRB (rs1505287, p = 7.3 x 10(-5)), GNAQ (rs10512065, p = 2.0 x 10(-4)), TG (rs2252696, p = 2.2 x 10(-3)), POU1F1 (rs1976324, p = 3.9 x 10(-3)), PDE4D (rs27178, p = 8.3 x 10(-3)), and TSHR (rs4903957, p = 8.6 x 10(-3)) loci. Overall, the results suggest a primary effect of PDE8B variants on cAMP levels in the thyroid. This would affect production of T4 and T3 and feedback to alter TSH release by the pituitary. PDE8B may thus provide a candidate target for the treatment of thyroid dysfunction.

Cartilage hair hypoplasia mutations that lead to RMRP promoter inefficiency or RNA transcript instability.

Cartilage hair hypoplasia (CHH; MIM 250250) is an autosomal recessive disease with diverse clinical manifestations. It is caused by mutations in RMRP gene, the RNA component of the ribonucleoprotein complex RNase MRP. Mutations in RMRP have been found in patients in the core promoter region or in the transcribed region, but the pathogenetic effect of the mutations is unclear. Real-time PCR assays confirmed that both promoter (c.-16_-1 dup and c.-15_+2 dup) and transcribed mutations (c.168G > A and c.218A > G) lower the expression level of RMRP. Experiments with 5'RACE, showed that the reduced transcription in the promoter mutants was accompanied by shifting of the transcription initiation sites to nucleotides 5'-upstream of the authentic site. Low levels of RMRP expression levels with transcript mutations were also seen when constructs encoding the wild-type and mutant genes were transfected into cultured cells. The reduced transcription was correlated with greater instability of mutant RMRP transcripts compared to controls. A comparable reduction was seen when a mouse gene containing the c.70A > G mutation (the major mutation in humans with CHH) was introduced into ES cells in place of one of the wild-type alleles. The low expression level of the c.70A > G Rmrp RNA was confirmed by expression assays into cultured cells, and was again correlated with RNA instability. Our results indicate that a loss of mutant RNA transcripts is a critical feature of pathogenesis.