Platelet genomics and proteomics in human health and disease

Abstract

Proteomic and genomic technologies provide powerful tools for characterizing the multitude of events that occur in the anucleate platelet. These technologies are beginning to define the complete platelet transcriptome and proteome as well as the protein-protein interactions critical for platelet function. The integration of these results provides the opportunity to identify those proteins involved in discrete facets of platelet function. Here we summarize the findings of platelet proteome and transcriptome studies and their application to diseases of platelet function.

Figure 1

Platelet transcript profiling by microarray. Generally, 1 of 2 approaches can be used to identify expressed transcripts in platelets. (A) With single-channel oligonucleotide arrays, mRNA is isolated from platelets, labeled, and hybridized to the microarray. The array is then processed and scanned, and genes are identified as “present,” “marginal,” or “absent.” Comparisons between samples can then be made in silico to identify differentially expressed genes. (B) In a 2-channel experiment, RNA from 2 individuals is isolated, each sample is labeled with a different fluorescent dye, and the 2 are compared directly on a microarray. In this case, the individuals have a different dose-response curve for a platelet agonist. Differentially expressed genes can then be directly identified.

Figure 2

Analyzing the platelet proteome. 2D-GE has been extensively applied to the characterization of the platelet proteome. Published studies have analyzed the platelet proteome as a whole (36, 38, 44) or in subfractions (16, 40, 42). Proteins are separated on the gel by charge (pI) and molecular weight (MW). The protein spots are then digested with a proteolytic enzyme, typically trypsin, and the resultant peptides are characterized by mass spectrometry to generate partial sequence information for the protein. This information can then be used to identify the protein by comparison of the sequence with databases of known protein and nucleic acid sequences.

Figure 3

Integration of proteome and transcriptome data. Global studies of the platelet transcriptome and proteome will allow complete characterization of the platelet system. The functional significance of changes in both proteome and transcriptome can be considered by comparison of healthy and diseased individuals, as well as those individuals with extreme platelet phenotypes. Further genomics, involving case-control genotyping studies, will permit determination of the genetic components that underlie normal variation in platelet function. Finally, bioinformatic integration of these approaches, along with the study of protein function using model organisms or in vitro examination of protein interactions, will expand upon current models of platelet function in health and disease. This map was generated using CellDesigner version 2.0 (http://www.systems-biology.org/index.html).