Could a hereditary illness ever spread by contamination? Researchers at the CNRS Laboratoire d’enzymologie et biochimie structurales, studying Huntington’s disease in collaboration with Professor Ron Kopito’s team at Stanford University, have shown that the normal form of huntingtin protein can acquire an abnormal form without any modification of its genetic code. These researchers observed that clumps of abnormal huntingtin protein, characteristic of Huntington’s disease, could induce clumping in the normal form of the protein.

Huntington’s disease is a genetic neurological disorder causing neuron degeneration, which in turn affects motor and cognitive functions. The illness arises due to an alteration in the gene sequence coding for huntingtin protein. When Huntington’s disease develops, huntingtin protein forms clumps that hinder normal functions and are closely linked to neurodegeneration.

Researchers at the CNRS Laboratoire d’enzymologie et biochimie structurales, in collaboration with researchers at Stanford University, have shown that huntingtin protein clumps are released from the cells where they develop and can propagate to healthy cells. Once cells are infected, the normal form of huntingtin then starts to clump and the illness spreads. The researchers noticed that the clumps persisted over several generations of cells expressing normal huntingtin following their temporary exposure to protein clumps from Huntington’s disease. This contamination by proximity is similar to the development of illnesses caused by prions (encephalopathies associated with "abnormal" prions).

These results suggest that huntingtin protein clumps are transmissible and that their propagation from one cell to another could be a generic vector of neurodegenerative illnesses.

Article: Cytoplasmic penetration and persistent infection of mammalian cells by polyglutamine aggregates, Pei-Hsien Ren, Jane E. Lauckner, Loulia Kachirskaia, John E. Heuser, Ronald Melki and Ron R. Kopito, Nature cell biology, February 2009