Measuring Consequences of Protein Misfolding and Cellular Stress Using OMICS Techniques - Protein Misfolding and Cellular Stress in Disease and Aging - page 119

polygenic diseases (see, e.g., ( 6, 7 )). If many very rare variations
account for the phenotypes, these are overlooked when screening
for common variations only.

2.2. Full Genome
Sequencing

Full sequencing of individual genomes would get around many of
the limitations pertinent to GWAS experiments. Although cur-
rently still a quite futuristic prospect due to still immense costs
and technical challenges, sequencing of the first three individuals
has shown that personal genome sequencing is feasible ( 8-10 ).
The first of these personal genomes was performed by “classical”
Sanger sequencing, whereas the other two have been determined
by new technologies. These novel techniques referred to as “Next
Generation Sequencing” (NGS), “Deep Sequencing,” or with
the more descriptive term “Massively parallel sequencing” allow
to sequence in the range of 10 8 -10 9 bases in a single experiment.
A number of commercial platforms exist and we will not go into
details with the different technologies, but just briefly sketch basic
characteristics of these methods. For a more thorough discussion
of the technical background, the interested reader is referred to
the following reviews ( 11, 12 ). NGS is based on the sequencing
of fragments from complex DNA mixtures like a whole genome
or a full cDNA population. Each fragment is sequenced at a cer-
tain spot in an analysis cell and the sequence of bases is recorded
for each of these spots. This setup allows to both sequence
extremely large numbers of bases simultaneously (in parallel) and
to get a quantitative record of the relative abundance of the
sequences. The latter is especially relevant if cDNA produced from
messenger RNA is sequenced as pointed out in Subheading 3.2
for a special application of these technologies termed “RNA-seq”.
Like all the other OMICS techniques, NGS also depends strongly
on powerful bioinformatics tools to build large coherent contigs
of the sequenced DNA fragments and extract all the information
contained in it. These new technologies have a great potential
and will likely be further developed ( 13 ) so that the price will fall
in the near future.
Besides the technicalities, many challenges regarding the
uses of such full genome sequence information have to be solved
( 14 ) before “personal genomics” holds its entrance into routine
diagnostics. Likely the biggest challenge is to interpret the huge
amount of variations present in different individuals, most of
which are in no way characterized and, for those that are, there is
in most cases only very limited information available. If only the
variations in coding regions and promoter sequences discovered
so far and to be discovered should be analyzed experimentally,
this would engage scientists for a very long time. One possible
solution to this may be the availability of thousands to millions of
personal sequences tied to certain phenotypes and ethnic groups,
which - with the use of smart bioinformatics - may enable scientists