GenoCAD: Computer Assisted Design Application for Synthetic Biology

A computer-aided design tool was created for genetic languages to guide the design of biological systems known as GenoCAD, the open-source software was developed by researchers at the Virginia Bioinformatics Institute at Virginia Tech to help synthetic biologists capture biological rules to engineer organisms that produce useful products or health-care solutions from inexpensive, renewable materials.

GenoCAD helps researchers in the design of protein expression vectors, artificial gene networks, and other genetic constructs, essentially combining engineering approaches with biology.

Synthetic biologists have an increasingly large library of naturally derived and synthetic parts at their disposal to design and build living systems. These parts are the words of a DNA language and the "grammar" a set of design rules governing the language.

GenoCAD is an open-source computer-assisted-design (CAD) application for synthetic biology. The foundation of GenoCAD is to consider DNA as a language to program synthetic biological systems. GenoCAD includes a large database of annotated genetic parts which are the words of the language. GenoCAD also includes design rules describing how parts should be combined in genetic constructs. These rules are used to build a wizard that guides users through the process of designing complex genetic constructs and artificial gene networks. The same rules are used by the GenoCAD compiler to maintain the integrity of existing constructs. GenoCAD provides users with data import and export capabilities using standard formats (FASTA, GenBank, and tab-delimited text) so that users' personal workspaces can be customized to meet their specific needs. It has to be expressive enough to allow scientists to generate a broad range of constructs, but it has to be focused enough to limit the possibilities of designing faulty constructs.

"Just like software engineers need different languages like HTML, SQL, or Java to develop different kinds of software applications, synthetic biologists need languages for different biological applications," said Jean Peccoud, investigator of the GenoCAD project. "From its inception, we envisioned GenoCAD as a framework allowing users to capture their expertise of a particular domain in languages that they could use themselves or share with others."

The researchers said encapsulating current knowledge by defining standards will become increasingly important as the number and complexity of components engineered by synthetic biologists increases.

They propose that grammars are a first step toward the standardization of a broad range of synthetic genetic parts that could be combined to develop innovative products.

"Developing a grammar in GenoCAD is a little like writing a review paper," Purcell said. "You start with the headings and you progressively dig deeper in the details. At the end of the process, you have a much better appreciation for what you know and what you don't know about a particular domain."

Posted By:-

Bioinformatics Department

New way to turn genes on discovered: Technique allows rapid, large-scale studies of gene function (CRISPR)

Using a gene-editing system originally developed to delete specific genes, researchers have now shown that they can reliably turn on any gene of their choosing in living cells. The findings are expected to help researchers refine and further engineer the tool to accelerate genomic research and bring the technology closer to use in the treatment of human genetic disease. Using a gene-editing system originally developed to delete specific genes, MIT researchers have now shown that they can reliably turn on any gene of their choosing in living cells.

This new application for the CRISPR/Cas9 gene-editing system should allow scientists to more easily determine the function of individual genes. This approach also enables rapid functional screens of the entire genome, allowing scientists to identify genes involved in particular diseases. 

A new function for CRISPR

The CRISPR system relies on cellular machinery that bacteria use to defend themselves from viral infection. Researchers have previously harnessed this cellular system to create gene-editing complexes that include a DNA-cutting enzyme called Cas9 bound to a short RNA guide strand that is programmed to bind to a specific genome sequence, telling Cas9 where to make its cut.

Scientists have tried to do this before using proteins that are individually engineered to target DNA at specific sites. However, these proteins are difficult to work with. There have also been attempts to use CRISPR to turn on genes by inactivating the part of the Cas9 enzyme that cuts DNA and linking Cas9 to pieces of proteins called activation domains. These domains recruit the cellular machinery necessary to begin reading copying RNA from DNA, a process known as transcription.

However, these efforts have been unable to consistently turn on gene transcription. In previous efforts, scientists had tried to attach the activation domains to either end of the Cas9 protein, with limited success. From their structural studies, the MIT team realized that two small loops of the RNA guide poke out from the Cas9 complex and could be better points of attachment because they allow the activation domains to have more flexibility in recruiting transcription machinery.

Using their revamped system, the researchers activated about a dozen genes that had proven difficult or impossible to turn on using the previous generation of Cas9 activators. Each gene showed at least a twofold boost in transcription, and for many genes, the researchers found multiple orders of magnitude increase in activation.

In new research, scientists have shown that they can reliably turn on any gene of their choosing in living cells.

Genome-scale activation screening

Once the researchers had shown that the system was effective at activating genes, they created a library of 70,290 guide RNAs targeting all of the more than 20,000 genes in the human genome.

They screened this library to identify genes that confer resistance to a melanoma drug called PLX-4720. This drug works Drugs of this type work well in patients whose melanoma cells have a mutation in the BRAF gene, but cancer cells that survive the treatment can grow into new tumors, allowing the cancer to recur.

To discover the genes that help cells become resistant, the researchers delivered CRISPR components to a large population of melanoma cells grown in the lab, with each cell receiving a different guide RNA targeting a different gene. After treating the cells with PLX-4720, they identified several genes that helped the cells to survive -- some previously known to be involved in drug resistance, as well as several novel targets.

Studies like this could help researchers discover new cancer drugs that prevent tumors from becoming resistant.

Scientists have tried to do large-scale screens like this by delivering single genes carried by viruses, but that does not work with all genes.

Posted By;-

Biotechnology Department