Embedding permanent watermarks in synthetic genes

As synthetic biology advances, labeling of genes or organisms, like other high-value products, will become important not only to pinpoint their identity, origin, or spread, but also for intellectual property, classification, bio-security or legal reasons. Ideally information should be inseparably interlaced into expressed genes. We describe a method for embedding messages within open reading frames of synthetic genes by adapting steganographic algorithms typically used for watermarking digital media files. Text messages are first translated into a binary string, and then represented in the reading frame by synonymous codon choice. To aim for good expression of the labeled gene in its host as well as retain a high degree of codon assignment flexibility for gene optimization, codon usage tables of the target organism are taken into account. Preferably amino acids with 4 or 6 synonymous codons are used to comprise binary digits. Several different messages were embedded into open reading frames of T7 RNA polymerase, GFP, human EMG1 and HIV gag, variously optimized for bacterial, yeast, mammalian or plant expression, without affecting their protein expression or function. We also introduced Vigenère polyalphabetic substitution to cipher text messages, and developed an identifier as a key to deciphering codon usage ranking stored for a specific organism within a sequence of 35 nucleotides.

17β-estradiol increases volume, apical surface and elasticity of human endothelium mediated by Na+/H+ exchange

OBJECTIVE

17beta-estradiol is known to delay the onset of atherosclerosis in women but cellular mechanisms are still unclear. Estrogens bind to specific receptors and initiate a signaling cascade that involves the activation of plasma membrane Na(+)/H(+) exchange. We hypothesized that estrogens interfere with ion transport across the plasma membrane and thus control endothelial structure and function. Therefore, we investigated the effects of the sex steroids 17beta-estradiol, progesterone, and testosterone on volume, apical surface and elasticity in human endothelium.

METHODS

The atomic force microscope was used as an imaging tool and as an elasticity sensor. We applied the antiestrogen tamoxifen, the Na(+)/H(+) exchange blocker cariporide and the epithelial Na(+)channel blocker amiloride to elucidate the role of transmembrane ion transport in hormone-treated human umbilical vein endothelial cells (HUVEC).

RESULTS

Incubation with 17beta-estradiol for 72 h led to a dose-dependent increase of endothelial cell volume (41%), apical cell surface (22%), and cell elasticity (53%) as compared to non-17beta-estradiol treated controls. Block of the 17beta-estradiol receptor by tamoxifen and of plasma membrane Na(+)/H(+) exchange by cariporide prevented the hormone-induced changes. Progesterone and testosterone were ineffective.

CONCLUSIONS

17beta-estradiol increases HUVEC water content and HUVEC elasticity mediated by activated estrogen receptors. The estrogen response depends on the activation of plasma membrane Na(+)/H(+) exchange. The increase in endothelial cell elasticity could be one of the vasoprotective mechanisms postulated for 17beta-estradiol.