RNA: DNA's lesser-known companion

DNA, RNA and proteins are the three key macromolecules for all known life. While science has recognised the importance of DNA for more than 100 years, it has not fully appreciated the diverse roles of RNA (ribonucleic acid) until quite recently. During her first six months at the Australian Regenerative Medicine Institute, Dr Edwina McGlinn has made great progress working with short pieces of RNA, known as microRNAs.

RNA is similar to DNA in the sense that it consists of a chain of components called nucleotides. RNA's nucleotide sequence allows it to encode genetic information, while some RNA molecules can link amino acids to form proteins. MicroRNAs are common in many human cell types and can play a role in target degradation and gene silencing. Edwina says her focus has shifted to microRNAs in recent years, partly due to their involvement in gene silencing.

'It is well established that certain RNAs are a key intermediate step between DNA and proteins, but it turns out that some RNAs never make protein and actually regulate gene expression directly,' Edwina explains. 'It was a big shift in the central dogma. Now the challenge is to work out what microRNAs are doing in the body.

'The same 25,000 genes are present in the DNA of each cell. However, our liver cell is very different from a brain cell. This is because not all genes are active in every cell. Each cell knows what to be because the genes it turns on and off leads to a unique protein output. It gives cells their identity and makes them functional in the right area.

'If this unique 'code' of gene expression within a cell is altered, things can go wrong and may lead to disease. It is therefore very important to understand all factors that regulate gene expression, and this now includes microRNAs.

'We didn't know anything about microRNAs 20 years ago but this field of research has exploded, particularly over the last 10 years. Our lab has developed technologies to assess microRNA function in vivo, in a developmental context. Nobody had really done it in this way before,' she says.

Edwina is also trying to develop a better understanding of the genetic networks that control limb formation. She says the limb is a great basis for this research.

'The limb is a classic model for understanding how cells interact with each other and how genetic systems interact in a three-dimensional space. We can add or remove a gene and see what happens to the whole genetic network, and importantly, the consequences later in development.

'The limb model has been used for decades, and we're now using more modern genetic techniques to look at classic developmental experiments.

'We hope that the basic developmental questions we are asking will also shed light on genetic pathways that may be involved in disease later in life,' Edwina says.

Understanding how a limb grows in the first place is also likely to help other researchers investigating limb regrowth techniques in humans, but Edwina concedes this is a long-term goal.

'It's not going to happen tomorrow, but a lot of great work is happening in that area.'