The role of complement in ATTR amyloidosis: a new therapeutic avenue?

Abstract

Background Familial Amyloidotic Polyneuropathy Type I is a lethal autosomal dominant sensorimotor and autonomic neuropathy due to deposition of amyloid fibrils composed of aberrant transthyretin (TTR) protein (ATTR neuropathy). A substitution of valine for methionine at position 30 of the protein is the commonest mutation. ATTRMet30 neuropathy exhibits a great degree of variability, both in the age of onset as well as penetrance among different populations. The penetrance in Cyprus is 28% compared to 2% and 80% in north Sweden and Portugal respectively. Genetic and epigenetic factors have been implicated and although we have previously demonstrated a correlation of complement C1q polymorphisms with age of onset among the Cypriot population, the exact mechanisms remain undetermined. The complement cascade, as a whole, has long been investigated for its association with inflammation and macromolecule aggregate clean-up. In the mouse model of Alzheimer disease, C1q has been shown to modulate beta-amyloid induced complement activation and neuronal loss. C1q has also been shown to be neuroprotective against toxic concentrations of serum amyloid P and to modulate phagocytosis of soluble pre-amyloid aggregates. Thus C1q appears to be strong candidate for being a modifier in the phenotype of ATTRMet30 neuropathy.