Distribution of sequencing reads in human and mouse platelets. Pie charts represent the number and percentage of sequencing reads from human platelets (top) or mouse platelets (bottom) mapping to indicated genomic regions. Only high-quality alignments following Novoalignment are represented. Although the majority of reads map to known intronic and exonic regions (combined RefSeq, UCSC, and Ensembl annotations), the remaining 1.9% (human) and 2.9% (mouse) of reads map to previously unannotated regions. Novel gene and exon regions are defined as unannotated regions that are enriched, at a conservative threshold, in sequencing reads. All other reads are termed intergenic. Intergenic reads may therefore contain some reads that map to novel genes and exons expressed below the arbitrary threshold.