WELLINGTON - New Zealand scientists said Thursday they had made a global breakthrough in converting human skin cells directly into immature brain cells, also know as neural precursor cells.

The University of Auckland's centre for Brain Research announced it had led the world in developing a fast and efficient process for the conversion without having to go through the intermediate stage of conversion into embryonic stem cells.

"This is an advance of huge significance to stem cell research on a global level," principal investigator Associate Professor Bronwen Connor said in a statement.

"It has the potential to lead to a new understanding of neurodegenerative diseases such as Huntington's, Parkinson's and Alzheimer's."

It enabled researchers to take skin cells from patients with genetically-linked neurological diseases and use them to create brain cells which would be affected by the disease.

"This helps in gaining understanding of the mechanisms causing the disease. It will allow us to test potential treatments on actual brain tissue," said Connor.

"It also takes us further towards the possibility of replacing damaged brain cells."

The University of Auckland team claimed to be the only group conducting such research to have reprogrammed adult human skin cells as other groups using the technique were working with cells taken from animals' skin.

The Auckland team used just two genes for the process of reprogramming from skin cells to neural precursor cells, while other international groups were using between five and 11 genes, said the statement.

The conversion from skin cells to embryonic stem cells and then to neural precursor cells took four months, but it took just 20 days to convert the skin cells directly to neural precursors.

The direct conversion also overcame a problem of tumor formation, which could arise when embryonic stem cells were used.

Connor said the reason for using embryonic stem cells ?their capacity for making any type of cell in the human body - also brought a problem that had to be overcome before cell replacement could be considered.

"When creating brain cells from embryonic stem cells you have to make sure that all of them are converted. Otherwise the ones that remain can convert to other types of cells, typically cancer cells."

The elimination of this risk through direct conversion from skin cells to neural precursor cells strongly boosted the prospect of cell replacement therapy in the future.