Biomedically relevant circuit-design strategies in mammalian synthetic biology.

The development and progress in synthetic biology has been remarkable. Although still in its infancy, synthetic biology has achieved much during the past decade. Improvements in genetic circuit design have increased the potential for clinical applicability of synthetic biology research.

Engineering of synthetic intercellular communication systems.

The introduction of synthetic devices that provide precise fine-tuning of transgene expression has revolutionized the field of biology. The design and construction of sophisticated and reliable genetic control circuits have increased dramatically in complexity in recent years. The norm when creating such circuits is to program the whole network in a single cell.

Increasing the dynamic control space of mammalian transcription devices by combinatorial assembly of homologous regulatory elements from different bacterial species.

Prokaryotic transcriptional regulatory elements are widely utilized building blocks for constructing regulatory genetic circuits adapted for mammalian cells and have found their way into a broad range of biotechnological applications. Prokaryotic transcriptional repressors, fused to eukaryotic transactivation or repression domains, compose the transcription factor, which binds and adjusts transcription from chimeric promoters containing the repressor-specific operator sequence. Escherichia coli and Chlamydia trachomatis share common features in the regulatory mechanism of the biosynthesis of l-tryptophan.

Synthetic two-way communication between mammalian cells.

The design of synthetic biology-inspired control devices enabling entire mammalian cells to receive, process and transfer metabolic information and so communicate with each other via synthetic multichannel networks may provide new insight into the organization of multicellular organisms and future clinical interventions. Here we describe communication networks that orchestrate behavior in individual mammalian cells in response to cell-to-cell metabolic signals. We engineered sender, processor and receiver cells that interact with each other in ways that resemble natural intercellular communication networks such as multistep information processing cascades, feed-forward-based signaling loops, and two-way communication.

The use of light for engineered control and reprogramming of cellular functions.

Could combating incurable diseases lie in something as simple as light? This scenario might not be too farfetched due to groundbreaking research in optogenetics. This novel scientific area, where genetically encoded photosensors transform light energy into specifically engineered biological processes, has shown enormous potential. Cell morphology can be changed, signaling pathways can be reprogrammed, and gene expression can be regulated all by the control of light.

Vitamin H-regulated transgene expression in mammalian cells.

Although adjustable transgene expression systems are considered essential for future therapeutic and biopharmaceutical manufacturing applications, the currently available transcription control modalities all require side-effect-prone inducers such as immunosupressants, hormones and antibiotics for fine-tuning. We have designed a novel mammalian transcription-control system, which is reversibly fine-tuned by non-toxic vitamin H (also referred to as biotin). Ligation of vitamin H, by engineered Escherichia coli biotin ligase (BirA), to a synthetic biotinylation signal fused to the tetracycline-dependent transactivator (tTA), enables heterodimerization of tTA to a streptavidin-linked transrepressor domain (KRAB), thereby abolishing tTA-mediated transactivation of specific target promoters.

A novel vector platform for vitamin H-inducible transgene expression in mammalian cells.

Inducible transgene control systems have been instrumental to gene therapy, biopharmaceutical manufacturing, drug discovery, synthetic biology and functional genomic research. The most widely used heterologous gene regulation systems are responsive to antibiotics of the tetracycline, streptogramin and macrolide classes. Although these antibiotics are clinically licensed, concerns about the emergence of resistant bacteria, side-effects in animal studies, and economic considerations associated with clearance of antibiotics in biopharmaceutical manufacturing, have limited the use of heterologous transgene control modalities to basic research activities.