Applications of gene therapy for familial amyloidotic polyneuropathy

Dynamics and Thermodynamics of Transthyretin Association from Molecular Dynamics Simulations

Molecular dynamics simulations are used in this work to probe the structural stability and the dynamics of engineered mutants of transthyretin (TTR), i.e., the double mutant F87M/L110M (MT-TTR) and the triple mutant F87M/L110M/S117E (3M-TTR), in relation to wild-type. Free energy analysis from end-point simulations and statistical effective energy functions are used to analyze trajectories, revealing that mutations do not have major impact on protein structure but rather on protein association, shifting the equilibria towards dissociated species. The result is confirmed by the analysis of 3M-TTR which shows dissociation within the first 10 ns of the simulation, indicating that contacts are lost at the dimer-dimer interface, whereas dimers (formed by monomers which pair to form two extended β-sheets) appear fairly stable. Overall the simulations provide a detailed view of the dynamics and thermodynamics of wild-type and mutant transthyretins and a rationale of the observed effects.

Familial amyloidotic polyneuropathy and transthyretin

There has been much progress in our understanding of transthyretin (TTR)-related amyloidosis including familial amyloidotic polyneuropathy (FAP), senile systemic amyloidosis and its related disorders from many clinical and experimental aspects. FAP is an inherited severe systemic amyloidosis caused by mutated TTR, and characterized by amyloid deposition mainly in the peripheral nervous system and the heart. Liver transplantation is the only available treatment for the disease. FAP is now recognized not to be a rare disease, and to have many variations based on genetical and biochemical variations of TTR. This chapter covers the recent advances in the clinical and pathological aspects of, and therapeutic approaches to FAP, and the trend as to the molecular pathogenesis of TTR.

Les amyloses à transthyrétine

PURPOSE

Transthyretin amyloidoses are the most common form of amyloidosis. Two different types of transthyretin amyloidoses are described, one is rare, familial, its precursor is the mutated transthyretin, this type is called transthyretin amyloid, the other is more common, its precursor is wild transthyretin, this second type is called senile amyloid. The review describes the molecular, clinical and evolutives features of both types.

CURRENT KNOWLEDGE AND KEY POINTS

Transthyretin is a naturally beta-pleated protein. Reported mutations increase its proteolysis resistance and its ability to form amyloid deposits. While transthyretin amyloid is clinically aggressive (neuropathy, cardiomyopathy, nephropathy, and vitreous deposits), senile amyloid is slightly symptomatic (rarely congestive heart failure). The differential diagnosis is essentially based on molecular biology.

FUTURE PROSPECTS AND PROJECTS

Liver transplantation is an effective treatment of transthyretin amyloid because it switches the mutated protein synthesis to the wild protein synthesis. Liver transplantation is sometimes associated with cardiac or kidney transplantation depending of the clinical presentation. Concerning a specific treatment, P component analogous are developed for inhibiting amyloid deposits formation. Tetrameric transthyretin structure stabilisators are in development.

Iatrogenic amyloid neuropathy in a Japanese patient after sequential liver transplantation

A 57-year-old woman in Japan, the first recipient of part of a liver from a 58-year-old man with familial amyloidotic polyneuropathy (FAP) amyloidogenic transthyretin Val30Met who had had sensorimotor polyneuropathy in the lower limbs for 3 years, started to develop sensory neuropathy 7 years after transplantation. Before the July 1998 sequential transplantation, she had been in a hepatic coma at the terminal stage of primary biliary cirrhosis and waiting for deceased donor liver transplantation. In September 2004, biopsy samples of her duodenum first showed amyloid deposition. Although biopsy materials in 2005 and 2006 showed no changes in amyloid deposition, decreased temperature sensation and pain in fingertips and toes were detected at a neurologic examination in March 2006. Thus, clinical symptoms of FAP appeared about 2 years after amyloid deposition started. Nerve conduction velocity studies revealed mild to moderate axonal sensory polyneuropathy without demyelination. Our findings confirmed iatrogenic sensory neuropathy induced by amyloid deposition 7 years after sequential liver transplantation.