On the trail of anxiety

With the advances in genome wide screening arrays and sequencing
techniques scientists were enabled to examine genetic variations
and their effects on behavioral phenotypes. While single nucleotide
polymorphisms (SNPs) are the most widely studied form of genomic
variations to date, another type of variants has become
increasingly important in recent research, the copy number variants
(CNVs). These large segments of DNA that can comprise up to several
megabasepairs and differ in copy number with respect to a reference
genome have been associated with several disorders and behavioral
phenotypes before. This study investigated the influence of CNVs on
anxiety related behavior. The detection of these variants turned
out to be a major challenge since all methods available are biased
by limitations of the design of the approach and the subsequent
computational analyses. Therefore, three different techniques (next
generation sequencing and two distinct whole genome genotyping
arrays) were employed to identify CNVs in a CD 1 derived mouse
model consisting of two mouse strains showing high (HAB) and low
(LAB) anxiety related behavior, respectively. By comparing CNVs in
HAB vs. LAB mice with expression data of four distinct brain
regions of high relevance to the limbic system (central and
basolateral amygdala, cingulate cortex and the hypothalamic
paraventricular nucleus), it was shown that CNVs can influence the
expression of protein coding genes by the alteration of the genes’
copy number per se. Therefore, the genes mapping into regions where
CNVs were detected in HAB vs. LAB mice (by all three detection
methods) were suggested to be possible effectors of anxiety related
behavior. Amongst these candidate genes those were considered to be
the most interesting ones that were additionally found to map into
regions of CNVs associated with anxiety related behavior in CD 1
mice. CNVs in these mice were detected by means of a whole genome
genotyping array and subsequent processing of the raw data with a
novel computational approach that was adapted from existing
analysis methods. Furthermore, to test the effect of a specific CNV
on anxiety related behavior in vivo, a breeding approach was used
to generate animals with a full genetic background of HAB mice
except for one LAB derived locus harboring a CNV that included the
Glo1 gene. No direct effect on the phenotype could be observed,
however, the respective CNV might be involved in the manipulation
of anxiety related behavior taken into account the interaction with
other factors. Taken together, this study provides not only a
comprehensive catalogue of CNVs in HAB/LAB mice but also the
evidence that these variants can influence anxiety related
behavior. Furthermore, it gives a first insight into the
functionality of CNVs with respect to anxiety related behavior.
Therefore, this thesis provides a profound basis for multiple
advanced studies.