Blue-green algae linked to motor neuron disease

The discovery that the misincorporation of a toxin from blue-green algae (cyanobacteria) into human neuroproteins helps explain how this bacteria is linked to neurodegenerative diseases.

Blue green algae has long been suspected to be linked with an increased risk of motor neuron disease in some people, but it was not known how this toxicity occurred.

University of Technology, Sydney (UTS) researchers led by Dr Ken Rodgers, in collaboration with leading ethno botanist Dr Paul Cox and researchers from the Institute of EthnoMedicine in the US, recently worked this out by identifying a link between a toxic amino acid found in blue-green algae and several motor neuron diseases.

Blue-green algae, most often associated with nutrient runoff in coastal waters, produce a neurotoxic amino acid called β-methylamino-L-alanine, or BMAA.

Australian waterways regularly succumb to toxic algal blooms. The Barwon-Darling River System in NSW underwent one of the world’s largest in the summer of 1991-92 when a bloom spread for over 1000 kilometres.

The researchers discovered that BMAA mimics the amino acid serine that is used to make human proteins. BMAA is mistakenly incorporated into human proteins in place of serine, resulting in damaged proteins which, over time, build up to toxic levels and kill the cells.

UTS researcher Dr Rachael Dunlop said for many years people had linked BMAA with an increased risk of motor neuron disease.

“The missing piece of the puzzle was how this might occur. Finally, we have that piece,” said Dunlop.

“Common amongst all neurodegenerative diseases is the problem of clumps of proteins overloading cells and forcing them to ‘commit suicide’. This research reveals that BMAA can also trigger this process,” said Dunlop.

BMAA was originally identified in Guam after the indigenous Chamorros people were found to suffer motor neuron disease up to 100 times more often than other people. The Chamorros used seeds from cycad palms to make flour and regularly ate fruit bats, which also ate the seeds. Both these foodstuffs contained BMAA.

Since then, research has revealed increased incidences of motor neuron disease in people who lived near lakes subject to frequent cyanobacterial blooms, among consumers of contaminated shellfish and in soldiers deployed to the Gulf War between 1990-1991.

Over 90% of motor neuron diseases have no known cause or cure. The diseases kill motor neurons in the brain and spinal cord, progressively paralysing the body.

Although motor neuron disease is relatively rare, it is relatively well known because of a number of high-profile people being affected, including Professor Stephen Hawking.

The research has been published in the journal PLOS ONE.