Neurogenerative Diseases - 18

Biosciences Inc. has generated technological
advances sufficient to produce a number of different
monomeric, oligomeric, and fibrillar preparations of
tau, alpha-synuclein (which targets in Alzheimer's
and Parkinson's diseases, respectively), and other
proteins. The process by which this happens is
generally understood, although the number, types,
and characteristics of the oligomeric intermediate
species are unknown. A general schematic of how
these PFFs are made is shown in Figure 1.

circumstances, what is created in hours or days in
the laboratory occurs over years in humans
(however, early and rapid onsets can occur in a
minority of cases).
When viewed under an electron microscope, fibrillar
and oligomeric preparations are readily identifiable
from monomeric ones. Despite different fibril types
being available and having individualized biological
or physical properties-such as seeding or
pathology generation capabilities (measured by the
phosphorylation of serine at position 129 on alphasynuclein)-these fibrillary preparations generally
look similar under the electron microscope (EM). The
exceptions are the oligomeric ones, which have clear
morphological differences (Figure 4).

These preparations have been shown to generate
the relevant pathologies in vitro and in vivo (Figure 2),
allowing users to study these diseases in conjunction
with potential drug candidates. Furthermore, in
the cases of alpha-synuclein and tau fibrils (as well
as other proteins), these have been shown to be
active and able to "seed" their own monomers
into more complex structures-easily viewed
in vitro by a structural change (from alpha helix to
beta sheet), which occurs during aggregation that
is monitored with a fluorescent dye, Thioflavin T
(Figure 3). This means that a rapidly accelerated
process of transformation can occur-where nontoxic monomeric forms are rapidly converted into
toxic fibrils or oligomeric analogs. This is one of the
reasons why the neurological diseases themselves
are inherently progressive; although, under typical

One key element that has been referenced
repeatedly when using PFFs in in vitro or in vivo
studies is the necessity to sonicate the material prior
to application.2 Recent articles from thought leaders
have suggested that the size of the fibrils is indicative
of whether or not they will be suitable for further
work.3 This means that the role of sonication is to
reduce the size of fibrils to a point where they can
be used-often suggested to be around 30-60 nm.
Although other methods of analysis have also been
carried out in terms of characterizing sonicated fibrils,

Figure 1. Monomers aggregate to form oligomers, protofibril oligomers, and ultimately lengthen into fibrils.

Neurogenerative Diseases

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