Identification of differentially expressed genes in thyrotropin stimulated dog thyroid cells by the cDNA-AFLP technique

Pathophysiological Functions of Rnd3/RhoE

Rnd3, also known as RhoE, belongs to the Rnd subclass of the Rho family of small guanosine triphosphate (GTP)-binding proteins. Rnd proteins are unique due to their inability to switch from a GTP-bound to GDP-bound conformation. Even though studies of the biological function of Rnd3 are far from being concluded, information is available regarding its expression pattern, cellular localization, and its activity, which can be altered depending on the conditions. The compiled data from these studies implies that Rnd3 may not be a traditional small GTPase. The basic role of Rnd3 is to report as an endogenous antagonist of RhoA signaling-mediated actin cytoskeleton dynamics, which specifically contributes to cell migration and neuron polarity. In addition, Rnd3 also plays a critical role in arresting cell cycle distribution, inhibiting cell growth, and inducing apoptosis and differentiation. Increasing data have shown that aberrant Rnd3 expression may be the leading cause of some systemic diseases; particularly highlighted in apoptotic cardiomyopathy, developmental arrhythmogenesis and heart failure, hydrocephalus, as well as tumor metastasis and chemotherapy resistance. Therefore, a better understanding of the function of Rnd3 under different physiological and pathological conditions, through the use of suitable models, would provide a novel insight into the origin and treatment of multiple human diseases.

Hypoxia-independent angiogenesis in adipose tissues during cold acclimation

The molecular mechanisms of angiogenesis in relation to adipose tissue metabolism remain poorly understood. Here, we show that exposure of mice to cold led to activation of angiogenesis in both white and brown adipose tissues. In the inguinal depot, cold exposure resulted in elevated expression levels of brown-fat-associated proteins, including uncoupling protein-1 (UCP1) and PGC-1alpha. Proangiogenic factors such as VEGF were upregulated, and endogenous angiogenesis inhibitors, including thrombospondin, were downregulated. In wild-type mice, the adipose tissues became hypoxic during cold exposure; in UCP1(-/-) mice, hypoxia did not occur, but, remarkably, the augmented angiogenesis was unaltered and was thus hypoxia independent. Intriguingly, VEGFR2 blockage abolished the cold-induced angiogenesis and significantly impaired nonshivering thermogenesis capacity. Unexpectedly, VEGFR1 blockage resulted in the opposite effects: increased adipose vascularity and nonshivering thermogenesis capacity. Our findings have conceptual implications concerning application of angiogenesis modulators for treatment of obesity and metabolic disorders.

Thyroid-stimulating hormone/cAMP-mediated proliferation in thyrocytes

Current research on thyrotropin-activated proliferation in the thyrocyte needs to be aimed at a better understanding of crosstalk and negative-feedback mechanisms with other proliferative pathways, especially the insulin/IGF-1-induced phosphoinositol-3 kinase pathway and the serum-induced MAPK or Wnt pathways. Convergence of proliferative pathways in mTOR is a hotspot of current research, and combined treatment using double class inhibitors for thyroid cancer may bring some success. New thyroid-stimulating hormone receptor (TSHR)-interacting proteins, a better picture of cAMP targets, a deeper knowledge of the action of the protein kinase A regulatory subunits, especially their interactions with the replication machinery, and a further understanding of mechanisms that lead to cell cycle progression through G₁/S and G₂/M checkpoints are areas that need further elucidation. Finally, massive information coming from microarray data analysis will prompt our understanding of thyroid-stimulating hormone-promoted thyrocyte proliferation in health and disease.

Microarray analysis of thyroid stimulating hormone, insulin-like growth factor-1, and insulin-induced gene expression in FRTL-5 thyroid cells

To determine which genes are regulated by thyroid stimulating hormone (thyrotropin, TSH), insulin and insulin-like growth factor-1 (IGF-1) in the rat thyroid, we used the microarray technology and observed the changes in gene expression. The expressions of genes for bone morphogenetic protein 6, the glucagon receptor, and cyclin D1 were increased by both TSH and IGF-1; for cytochrome P450, 2c37, the expression was decreased by both. Genes for cholecystokinin, glucuronidase, beta, demethyl-Q 7, and cytochrome c oxidase, subunit VIIIa, were up-regulated; the genes for ribosomal protein L37 and ribosomal protein L4 were down-regulated by TSH and insulin. However, there was no gene observed to be regulated by all three: TSH, IGF-1, and insulin molecules studied. These findings suggest that TSH, IGF-1, and insulin stimulate different signal pathways, which can interact with one another to regulate the proliferation of thyrocytes, and thereby provide additional influence on the process of cellular proliferation.

AFLP-based transcript profiling (cDNA-AFLP) for genome-wide expression analysis

Although DNA microarrays are currently the standard tool for genome-wide expression analysis, their application is limited to organisms for which the complete genome sequence or large collections of known transcript sequences are available. Here, we describe a protocol for cDNA-AFLP, an AFLP-based transcript profiling method that allows genome-wide expression analysis in any species without the need for prior sequence knowledge. In essence, the cDNA-AFLP method involves reverse transcription of mRNA into double-stranded cDNA, followed by restriction digestion, ligation of specific adapters and fractionation of this mixture of cDNA fragments into smaller subsets by selective PCR amplification. The resulting cDNA-AFLP fragments are separated on high-resolution gels, and visualization of cDNA-AFLP fingerprints is described using either a conventional autoradiography platform or an automated LI-COR system. Observed differences in band intensities between samples provide a good measure of the relative differences in the gene expression levels. Identification of differentially expressed genes can be accomplished by purifying cDNA-AFLP fragments from sequence gels and subsequent sequencing. This method has found widespread use as an attractive technology for gene discovery on the basis of fragment detection and for temporal quantitative gene expression analysis. The protocol can be completed in 3-4 d.

cDNA-AFLP analysis of differential gene expression in human hepatoma cells (HepG2) upon dengue virus infection

In infectious diseases, the disease pathogenesis is the outcome of the interaction between the genome of the host and the genome of the pathogen. Despite the wide distribution of dengue infections in the world, and the large number of annual infections, few studies have investigated how the dengue genome alters the global transcriptional profile of the host cell. To investigate alterations in the liver cell transcriptome in response to dengue virus infection, liver cells (HepG2) were infected with dengue serotype 2 at MOI 5 and at 3 days post-infection RNA extracted and analyzed by cDNA-AFLP in parallel with mock-infected cells. From 73 primer combinations over 5,000 transcription-derived fragments (TDFs) were observed, of which approximately 10% were regulated differentially in response to infection. Sixty-five TDFs were subsequently cloned and sequenced and 27 unique gene transcripts identified. Semi-quantitative reverse transcription (RT)-PCR was used to validate the expression of 12 of these genes and 10 transcripts (CK2, KIAA509, HSP70, AK3L, NIPA, PHIP, RiboS4, JEM-1, MALT1, and HSI12044) were confirmed to be differentially regulated, with four transcripts (HSP70, NIPA, RiboS4, and JEM-1) showing a greater than twofold regulation. These results suggest that the expression of a large number of genes is altered in response to dengue virus infection of liver cells, and that cDNA-AFLP is a useful tool for obtaining information on both characterized and as yet uncharacterized transcripts whose expression is altered during the infection process.