Rewritable digital data storage in live cells via engineered control of recombination directionality

The use of synthetic biological systems in research, healthcare, and manufacturing often requires autonomous history-dependent behavior and therefore some form of engineered biological memory. For example, the study or reprogramming of aging, cancer, or development would benefit from genetically encoded counters capable of recording up to several hundred cell division or differentiation events. Although genetic material itself provides a natural data storage medium, tools that allow researchers to reliably and reversibly write information to DNA in vivo are lacking. Here, we demonstrate a rewriteable recombinase addressable data (RAD) module that reliably stores digital information within a chromosome. RAD modules use serine integrase and excisionase functions adapted from bacteriophage to invert and restore specific DNA sequences. Our core RAD memory element is capable of passive information storage in the absence of heterologous gene expression for over 100 cell divisions and can be switched repeatedly without performance degradation, as is required to support combinatorial data storage. We also demonstrate how programmed stochasticity in RAD system performance arising from bidirectional recombination can be achieved and tuned by varying the synthesis and degradation rates of recombinase proteins. The serine recombinase functions used here do not require cell-specific cofactors and should be useful in extending computing and control methods to the study and engineering of many biological systems.     

In vitro vessel-forming capacity of endothelial progenitor cells in high glucose conditions

In type 2 diabetes, the impairment of vascular repair processes and angiogenesis are due to endothelial progenitor cell (EPC) dysfunction. In this study, we established a quantitative methodology to assess EPC function by using an in vitro 5-(6)-carboxyfluorescein diacetate succinimidyl ester-labeling vessel formation assay. The EPCs were cultured in three different glucose concentrations (100, 189.5, and 295.5 mg/dl of d-glucose) representing normal control and diabetes with either good or poor glycemic control, respectively. We found that the in vitro vessel-forming capacity was impaired in EPCs cultured in high glucose concentrations compared to normal control (43.4 ± 0.8% and 34.7 ± 0.7% vs. 50.8 ± 2.1%). We further studied expression of various genes involved in vessel formation. There was a lower level of angiopoietin 1 gene expression in EPCs cultured in high glucose concentrations. The addition of recombinant angiopoietin 1 significantly increased the vessel-forming capacity of EPCs cultured in high glucose concentration (35.3 ± 2.0% to 48.8 ± 2.7%), whereas the addition of angiopoietin 2 (a competitive inhibitor of angiopoietin 1) impaired the vessel-forming capacity of EPCs cultured in normal glucose concentration (51.8 ± 1.3% to 41.3 ± 0.6%). We conclude that the in vitro vessel-forming capacity of EPCs cultured in high glucose concentration is impaired due to low levels of angiopoietin 1.     

Energetics and optical properties of carbon impurities in rutile TiO2

Titanium dioxide is one of the most promising materials for many applications such as photovoltaics and photocatalysis. Non-metal doping of TiO₂ is widely used to improve the photoconversion efficiency by shifting the absorption edge from the UV to visible-light region. Here, we employ hybrid density-functional calculations to investigate the energetics and optical properties of carbon (C) impurities in rutile TiO₂. The predominant configurations of the C impurities are identified through the calculated formation energies under O-poor and O-rich growth conditions. Under the O-poor condition, we find that C occupying the oxygen site (C_O) is energetically favorable for Fermi-level values near the conduction band minimum (n-type TiO₂), and acts as a double acceptor. Under the O-rich condition, the C_i–V_Ti complex is energetically favorable, and is exclusively stable in the neutral charge state. We also find that interstitial hydrogen (H_i) can bind to C_O, forming a C_O–H_i complex. Our results suggest that C_O and C_O–H_i are a cause of visible-light absorption under oxygen deficient growth conditions.

The substitutional C on O site and its complex with H are a cause of visible-light absorption in rutile TiO₂.     

Cytochrome P450 2E1 polymorphism and nasopharyngeal carcinoma development in Thailand: a correlative study

Background  

Nasopharyngeal carcinoma (NPC) is a rare tumor in most parts of the world but occurs at relatively high frequency among people of Chinese descent. The cytochrome P450 2E1 enzyme (CYP2E1) is responsible for the metabolic activation of nitrosamines, and has been shown to be a susceptibility gene for NPC development in Taiwan [RR = 2.6; 95%CI = 1.2-5.7]. Since there has been only one report of this link, it was decided to investigate the susceptibility of CYP2E1 to NPC development in other populations. Therefore, the correlation between the RsaI polymorphism of this gene and NPC was studied in-patients including Thai and Chinese in Thailand. The present study comprised 217 cases diagnosed with NPC and 297 healthy controls.     

Promoter hypermethylation of CCNA1, RARRES1, and HRASLS3 in nasopharyngeal carcinoma

In search for putative tumor suppressor genes critical of nasopharyngeal carcinoma (NPC), we analyzed the available information from the expression profiling in conjunction with the comprehensive alleotyping published data relevant to this malignancy. Integration of this information suggested eight potential candidate tumor suppressor genes, CCNA1, HRASLS3, RARRES1, CLMN, EML1, TSC22, LOH11CR2A and MCC. However, to confirm the above observations, we chose to investigate if promoter hypermethylation of these candidate genes would be one of the mechanisms responsible for the de-regulation of gene expression in NPC in addition to the loss of genetic materials. In this study, we detected consistent hypermethylation of the 5' element of CCNA1, RARRES1, and HRASLS in NPC tissues with prevalence of 48%, 51%, and 17%, respectively. Moreover, we found a similar profile of promoter hypermethylation in primary cultured NPC cells but none in normal nasopharyngeal epithelium or leukocytes, which further substantiate our hypothesis. Our data indicate that CCNA1, RARRES1, and HRASLS3 may be the putative tumor suppressor genes in NPC.     

Effect of mating on sperm numbers and weight of the epididymis

In man, a decrease in sperm count occurs after ejaculation. Approximately three days are needed for complete recovery to preejaculation levels. Our experiment evaluated the possibility that a similar recovery period is also required in the rat. The total spermatozoa in the epididymis and the weight of the epididymis decreased for four and two days after mating, respectively. These data demonstrate that a recovery period for epididymal sperm counts and weight is required in the male rat following mating.     

Recurrent short-to-shield phenomenon requiring LVAD exchange: a rare complication

Journal of Artificial Organs - Left ventricular assist device (LVAD) therapy is a common alternative approach for a patient with end-stage heart failure with HeartMate II (HM II) being one of the...     

Whole genome analysis of human papillomavirus genotype 11 from cervix, larynx and lung

The prevalence of human papillomavirus genotypes differs in various target organs. HPV16 is the most prevalent genotype in the cervix while genotypes 6 and 11 are highly prevalent in skin and aero-digestive tract infections. In this study HPV11 positive specimens were selected from cervix, larynx and lung biopsy tissue to analyze the whole genome by PCR and direct sequencing. Five HPV11 whole genomes were characterized, consisting of two cervical specimens, two laryngeal specimens and one lung specimen. The results showed high homology of HPV11 in these organs. Phylogenetic analysis showed that all HPV11 derived from various organs belonged to the same lineage. Molecular characterization and functional studies can further our understanding of virulence, expression or transmission. Additional studies on functional protein expression at different organ sites will also contribute to our knowledge of HPV infection in various organs.