Team:Hong Kong HKU

Introduction

Our project this year continues the work of last year’s HKU iGEM 2016 Team. By focusing on the intriguing world of diagnostic probes, we aim to improve on last year’s design and increase the effectiveness of disease detection. Contrary to last year’s design, we have come up with an alternative tetrahedron structure, in which the 3D tetrahedron is only formed upon binding to the target sequence. Our ultimate goal is to enable our functional DNA nanostructure to be synthesized and self-assembled inside E. coli. They will detect specific biomarkers expressed in the diseased cells. This website will guide you on our journey throughout the iGEM Competition 2017. Click to explore and enjoy!

Inspiration

Early Diagnosis of Huntington’s Disease

Huntington’s disease (HD) is an inherited neurodegenerative disorder that results in the death of brain cells. Though the disease is incurable, early diagnosis can help to better relieve symptoms by allowing treatments to start sooner. In the early stages of HD, only subtle changes in personality, cognitive and physical abilities can be identified. Diagnosis of HD (in cases where the parents do not have HD) is usually carried out only after symptoms are identified and the patient approaches the medical professionals. As the early symptoms are generally not severe enough to be recognized as HD symptoms on their own, the treatment is usually delayed. We hope to allow prompt treatment with our non-invasive and highly accessible diagnostic method. Genetic mutations, namely the trinucleotide repeats in the Huntingtin gene (HTT) located on Chromosome 4, lead to the development of HD.

Early Diagnosis of Cancer

Cancer has always been a devastating disease. In 2012, there were 14.1 million new cancer cases worldwide. Early diagnosis of cancer may help to reduce the mortality rate and extend the life expectancy of patients. For instance, in the U. K., nearly 90% of patients diagnosed with stage I lung cancer lived for more than a year while only 19% of patients diagnosed at stage IV do so. Early diagnosis of cancer is also believed to be vital for successful treatment and recovery.

DNA nanostructures and miRNAs as biomarkers

Compared to its antibody based counterparts, DNA based diagnostic device are more stable and do not require cold-chain processing. Furthermore, the specificity and the programmability DNA allows for the generation of a wide range of shapes to be produced that are highly specific to its target.

DNA has emerged as a promising material that allows researchers to construct novel designs as its structure could be predicted easily and accurately. Examples of DNA nanostructures include nano-tweezers to detect norovirus and a DNA ‘Nano-Claw’ to detect membrane markers of cancer cells.

DNA Boolean logic gates have been constructed to produce signals in the presence of multiple targets, such as OR-gate and AND-gate DNA tetrahedra that generate fluorescence resonance energy transfer (FRET) signal when multiple inputs hybridize with the probe. As for the targets to be detected, different microRNAs (miRNAs) have been identified to be associated with cancers. For example, miR-15b-5p, miR-338-5p, and miR-764 found in plasma are potential biomarkers for detecting hepatocellular carcinoma cancer (HCC), a common type of liver cancer. It has already been reported that it is promising to use these biomarkers - miRNAs to detect cancers. For Huntington’s disease, Hsa-miR-34b can be used as a biomarker. This miRNA is stable in the plasma, allowing diagnosis to be carried out just by extracting small amounts of the patient’s blood. The miRNA is also elevated in pre-manifest Huntington’s Disease, which allows HD to be detected at the earliest stage possible, before the surfacing of symptoms.