We report the identification and characterization of a novel 32-kDa protein expressed in skeletal muscle and located in the Z-disc of the sarcomere. We found that this protein binds to three other Z-disc proteins; therefore, we have named it FATZ, ␥-filamin/ABP-L, ␣-actinin and telethonin binding protein of the Z-disc. From yeast twohybrid experiments we are able to show that the SR3-SR4 domains of ␣-actinin 2 are required to bind the COOH-terminal region of the FATZ as does ␥-filamin/ ABP-L. Furthermore, by using a glutathione S-transferase overlay assay we find that FATZ also binds telethonin. The level of FATZ protein in muscle cells increases during differentiation, being clearly detectable before the onset of myosin. Although FATZ has no known interaction domains, it would appear to be involved in a complex network of interactions with other Z-band components. On the basis of the information known about its binding partners, we could envisage a central role for FATZ in the myofibrillogenesis. After screening our muscle expressed sequence tag data base and the public expressed sequence tag data bases, we were able to assemble two other muscle transcripts that show a high level of identity with FATZ in two different domains. Therefore, FATZ may be the first member of a small family of novel muscle proteins.The Z-disc of vertebrate striated muscle is a region where the antiparallel actin filaments spanning the sarcomere are crosslinked. This supramolecular structure plays an important role in the regulation of contraction both in skeletal and cardiac muscle. Variation of the Z-disc structure is observed during development and differentiation of muscle cells and can be correlated with specific pathological or degenerative conditions associated with muscle injuries or atrophies.The number of different protein components of the Z-disc is far from being complete, and many of the newly discovered muscle proteins appear to be localized in this region, and very generally they can be divided into two groups based on their location. In the first group are proteins that are only partially in the Z-disc while extending into other portions of the sarcomere or the sarcolemma. An example of the first group is titin that acts as a ruler for the ordered distribution of sarcomeric proteins and is particularly important in Z-disc assembly. The NH 2 -terminal portion of titin extends into the Z-disc, where two different sub-domains have been shown to interact specifically with ␣-actinin (1-3) and also with the muscle-specific protein telethonin (4). Although telethonin binds to the NH 2 -terminal domain of titin, it also acts as one of the substrates of the titin serine kinase domain that is located outside of the Z-disc (5). The second group is composed of proteins, many of which have been recently discovered and characterized, that appear to be entirely located in the Z-disc (e.g. ␣-actinin, Nspl1, telethonin, ZASP1, and CapZ). Among these proteins, ␣-actinin plays a central role by directly cross-linking the actin molecules. ...

BackgroundSkeletal muscle is a complex, versatile tissue composed of a variety of functionally diverse fiber types. Although the biochemical, structural and functional properties of myofibers have been the subject of intense investigation for the last decades, understanding molecular processes regulating fiber type diversity is still complicated by the heterogeneity of cell types present in the whole muscle organ.Methodology/Principal FindingsWe have produced a first catalogue of genes expressed in mouse slow-oxidative (type 1) and fast-glycolytic (type 2B) fibers through transcriptome analysis at the single fiber level (microgenomics). Individual fibers were obtained from murine soleus and EDL muscles and initially classified by myosin heavy chain isoform content. Gene expression profiling on high density DNA oligonucleotide microarrays showed that both qualitative and quantitative improvements were achieved, compared to results with standard muscle homogenate. First, myofiber profiles were virtually free from non-muscle transcriptional activity. Second, thousands of muscle-specific genes were identified, leading to a better definition of gene signatures in the two fiber types as well as the detection of metabolic and signaling pathways that are differentially activated in specific fiber types. Several regulatory proteins showed preferential expression in slow myofibers. Discriminant analysis revealed novel genes that could be useful for fiber type functional classification.Conclusions/SignificanceAs gene expression analyses at the single fiber level significantly increased the resolution power, this innovative approach would allow a better understanding of the adaptive transcriptomic transitions occurring in myofibers under physiological and pathological conditions.

Denervation deeply affects muscle structure and function, the alterations being different in slow and fast muscles. Because the effects of denervation on fast muscles are still controversial, and high-throughput studies on gene expression in denervated muscles are lacking, we studied gene expression during atrophy progression following denervation in mouse tibialis anterior (TA). The sciatic nerve was cut close to trochanter in adult CD1 mice. One, three, seven, and fourteen days after denervation, animals were killed and TA muscles were dissected out and utilized for physiological experiments and gene expression studies. Target cDNAs from TA muscles were hybridized on a dedicated cDNA microarray of muscle genes. Seventy-one genes were found differentially expressed. Microarray results were validated, and the expression of relevant genes not probed on our array was monitored by real-time quantitative PCR (RQ-PCR). Nuclear- and mitochondrial-encoded genes implicated in energy metabolism were consistently downregulated. Among genes implicated in muscle contraction (myofibrillar and sarcoplasmic reticulum), genes typical of fast fibers were downregulated, whereas those typical of slow fibers were upregulated. Electrophoresis and Western blot showed less pronounced changes in myofibrillar protein expression, partially confirming changes in gene expression. Isometric tension of skinned fibers was little affected by denervation, whereas calcium sensitivity decreased. Functional studies in mouse extensor digitorum longus muscle showed prolongation in twitch time parameters and shift to the left in force-frequency curves after denervation. We conclude that, if studied at the mRNA level, fast muscles appear not less responsive than slow muscles to the interruption of neural stimulation.

BackgroundAtherosclerosis affects aorta, coronary, carotid, and iliac arteries most frequently than any other body vessel. There may be common molecular pathways sustaining this process. Plaque presence and diffusion is revealed by circulating factors that can mediate systemic reaction leading to plaque rupture and thrombosis.ResultsWe used DNA microarrays and meta-analysis to study how the presence of calcified plaque modifies human coronary and carotid gene expression. We identified a series of potential human atherogenic genes that are integrated in functional networks involved in atherosclerosis. Caveolae and JAK/STAT pathways, and S100A9/S100A8 interacting proteins are certainly involved in the development of vascular disease. We found that the system of caveolae is directly connected with genes that respond to hormone receptors, and indirectly with the apoptosis pathway.Cytokines, chemokines and growth factors released in the blood flux were investigated in parallel. High levels of RANTES, IL-1ra, MIP-1alpha, MIP-1beta, IL-2, IL-4, IL-5, IL-6, IL-7, IL-17, PDGF-BB, VEGF and IFN-gamma were found in plasma of atherosclerotic patients and might also be integrated in the molecular networks underlying atherosclerotic modifications of these vessels.ConclusionThe pattern of cytokine and S100A9/S100A8 up-regulation characterizes atherosclerosis as a proinflammatory disorder. Activation of the JAK/STAT pathway is confirmed by the up-regulation of IL-6, STAT1, ISGF3G and IL10RA genes in coronary and carotid plaques. The functional network constructed in our research is an evidence of the central role of STAT protein and the caveolae system to contribute to preserve the plaque. Moreover, Cav-1 is involved in SMC differentiation and dyslipidemia confirming the importance of lipid homeostasis in the atherosclerotic phenotype.

Highlights d Transcriptional networking distinguishes myofibers as glycolytic or oxidative d miR-27a-3p and miR-142-3p influence mitochondrial morphology d miR-27a-3p improves lipid use and increases glycogen storage d miR-142-3p reduces lipid use