Justin C Recknor | PubMed Health

PubMed2006

Transcriptional profiling of myostatin-knockout mice implicates Wnt signaling in postnatal skeletal muscle growth and hypertrophy.

Myostatin is an inhibitor of skeletal muscle growth. Disruption of the Mstn gene in mice results in muscles that weigh two to three times those of controls, but precisely how myostatin signals to exert its effects on muscle is unclear. We used the Affymetrix GeneChip system to identify differences in gene expression between myostatin null and wild-type mice. The results indicated a switch in muscle fiber type, from slow to fast, in the absence of myostatin. They also indicated that myostatin may act upstream of Wnt pathway components. Notably, it repressed expression of Wnt4. Wnt4 was capable of stimulating satellite cell proliferation, while inhibition of Wnt signaling down-regulated satellite cell proliferation. This evidence points to a role for Wnt/calcium signaling in the growth and maintenance of postnatal skeletal muscle. This study offers new insight into potential downstream targets of myostatin, which will be beneficial for elucidation of the mechanism through which myostatin acts to inhibit muscle growth.

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PubMed2005

Transcriptional profiling using a novel cDNA array identifies differential gene expression during porcine embryo elongation.

A novel porcine cDNA array, containing 1,015 PCR products selected for embryonic expression, was used for transcriptional profiling of conceptuses at four stages of peri-implantation development. Total conceptus RNA from small spherical, large spherical, tubular, and filamentous stages was amplified, converted to cDNA, and hybridized to membranes. Initially, normalized signal intensities obtained using cDNA from total RNA or from amplified RNA were compared. Uniform distribution of P-values associated with t-tests conducted for each gene indicated no evidence that amplification introduced bias. Analysis of data obtained by using amplified targets and the novel array identified genes differentially expressed across stages. Such genes were identified by testing for significant stage effects in gene-specific mixed models. A total of nine genes were declared differentially expressed. Six of the nine genes had P-values less than 0.001, and a false discovery rate of approximately 17% was associated with this significance threshold. Two out of six genes were significant when using the Bonferroni method to control the probability of one or more false positives. The other three genes had P-values between 0.001 and 0.01 and exhibited differences greater than twofold between stages. All four genes selected for confirmation (steroidogenic acute regulatory protein, interleukin 1 beta, transforming growth factor beta 3, and thymosin beta 10) were shown to be differentially expressed by using quantitative real time RT-PCR. Our study shows that RNA amplification is useful for transcriptional profiling with limiting porcine embryonic RNA, and that this novel targeted array can detect differential gene expression during trophoblastic elongation. Finally, our results contribute to an increased understanding of the temporal patterns of expression of known genes controlling conceptus development, as well as identify novel genes also differentially regulated during implantation.

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