In light of the recent post on translational selection, I give you this paper from PLoS Genetics on tissue specific differences in tRNA expression from humans. From the abstract:
We found tissue-specific differences in the expression of individual tRNA species, and tRNAs decoding amino acids with similar chemical properties exhibited coordinated expression in distinct tissue types. Relative tRNA abundance exhibits a statistically significant correlation to the codon usage of a collection of highly expressed, tissue-specific genes in a subset of tissues or tRNA isoacceptors. Our findings demonstrate the existence of tissue-specific expression of tRNA species that strongly implicates a role for tRNA heterogeneity in regulating translation and possibly additional processes in vertebrate organisms.
Genes may not become optimized for translation in all tissues, but could be optimized for specific tissues. Additionally, protein secondary structure could be tissue dependent if translation rate influences protein folding.
Dittmar KA, Goodenbour JM, Pan T. 2006. Tissue-specific differences in human transfer RNA expression. PLoS Genet. 2: e221 DOI:10.1371/journal.pgen.0020221
Oh, that's neat! thanks!