Transthyretin amyloidosis (ATTR) is a progressive disease characterised by the accumulation of misfolded transthyretin (TTR) protein. In ocular manifestations of ATTR, the mutant TTR protein aggregates in the vitreous humor and around the optic nerve, causing demyelination (loss of the myelin sheath) of the retinal ganglion cell axons.
A clinical trial investigated a novel gene-silencing therapy consisting of short, single-stranded DNA molecules (antisense oligonucleotides) designed to target the TTRTTRTTR gene transcript. The therapeutic agent was administered via intravitreal injection directly into the vitreous humor of the eye.
Answer the following questions based on this information:
Explain how damage to the myelin sheath of the optic nerve can lead to a delay or failure in visual signals reaching the brain.
Suggest and explain how this single-stranded DNA drug causes a reduction in the concentration of the mutant TTR protein.
Suggest two reasons why the DNA drug is administered via intravitreal injection rather than taken orally as a pill.
