Page 35 - Mouse Molecular Genetics

Full Abstracts
Program number is above title. Author in bold is the presenter.
35
changes in orientation when quantified. In addition, the protein encoded by the
Looptail
mutation (Vangl2
S464N
)
disrupts Vangl1
and Vangl2 delivery to the surface of cells in vitro due to oligomer formation between Vangl1 and Vangl2 coupled with the
intracellular retention of Vangl2
S464N
.
As a result, Vangl1 protein is missing from the apical cell surface of vestibular hair cells
in
Looptail
mutants, but is retained at the cell surface in
vangl2
knockouts. Similarly the distribution of Prickle-like2, a putative
Vangl2 interacting protein, is differentially affected in the two lines. We propose that altered Vangl2
S464N
trafficking prevents the
delivery of multiple polarity proteins to the cell surface and that this net effect underlies the dominant phenotypic traits associated
with the
Looptail
mutation. One interpretation is that prior genetic interactions with
Looptail
may be indirect and reflect a
permissive enhancement of this semi-dominant phenotype.
4
Host Resistance To A Gastrointestinal Parasite Regulated By A SNP Modulating SMAD3 Binding To A TGFb-
Responsive Transcriptional Enhancer Of Mina. Mark Bix
1,3
,
Meenu Pillai
1,3
,
Shangli Lian
1
,
Peter Vogel
1
,
Mathew Coleman
2
,
Peter Ratcliffe
2
. 1)
Immunology, St. Jude Children's Research Hospital, Memphis, TN; 2) Oxford University, Oxford, UK; 3)
Equal contribution.
Th1 immune responses, characterized by IFN production, promote clearance of intracellular microbes while Th2 responses,
characterized by IL4 production, promote control of helminthic parasites. The genetic predisposition of certain inbred mouse
strains toward developing T helper 2 (Th2) as opposed to Th1 type immune responses (Th2-bias) has long been associated with
differential susceptibility to a wide range of diseases, ranging from cancer, autoimmunity and allergy/asthma to chronic microbial
infection. However, the molecular genetic basis of Th2-bias and thus causal relationship to specific disease states has remained
poorly understood. We initiated an investigation into the nature of this relationship by mapping a Th2-bias-regulatory
quantitative trait locus (
Dice
)
to distal chromosome 16. Subsequent interval-specific congenic fine-mapping and gene expression
analysis led to the physical isolation of the
Dice1.2
locus and the identification of
Mina
,
a
Dice1.2
-
resident gene with apparent
Th2-bias regulatory activity. Th2-bias phenotype across a representative panel of inbred mouse strains correlated inversely with
Mina expression level that in turn was in perfect concordance with two distinct
Mina
haplotypes defined by 21 promoter/exon
1/
intron 1-spanning SNPs. These data suggested that a naturally occurring regulatory polymorphism controlling Mina expression
level conferred dose-dependent negative regulation of Th2-bias. To study how natural variation at the
Mina
locus affects
susceptibility to chronic infectious disease, we selected the gastrointestinal whipworm parasite
Trichuris muris
(
Tm, a close
relative of the human pathogen
Trichuris trichiura
)
because chronic versus acute infection outcomes in this model, respectively,
require Th1 versus Th2 host responses. Using a KO mouse model, we found that Mina promoted expression of the resistin-like
molecule Relm in intestinal epithelial cells that in turn promoted Th1 development and the secretion of IFN that exacerbated
helminthiasis. Further, the allele of an intronic SNP carried by BALB/c but not C57BL/6 mice prevented the binding of SMAD3
to a TGF activated
Mina
enhancer, providing an explanation for the differential susceptibility of BALB/c and C57BL/6 mice to
Tm disease.
5
Discovering genes and pathways involved in naevus and melanoma development using the Collaborative Cross. Graeme
Walker
1
,
Ramesh Ram
2
,
Blake Ferguson
1
,
Herlina Handoko
1
,
Peter Soyer
3
,
Grant Morahan
2
. 1)
Skin Carcinogenesis Lab,
QIMR, Brisbane, Qld, Australia; 2) Centre for Diabetes Research, WAIMR, The University of Western Australia, Perth,
Australia; 3) Dermatology Research Centre, UQ School of Medicine, Brisbane QLD.
Upon metastatic conversion malignant melanoma (MM) is very difficult to treat. The most successful drug treatments target
somatic BRAF mutation, but resistance soon develops and new drugs are needed. Genes are critical determinants of how MMs
develop and grow, and are arguably more important than sun exposure. The presence of above average numbers of nevi is the
strongest phenotypic risk factor. GWAS have revealed many MM susceptibility genes that have improved risk prediction, but
none have yet been functionally validated as potential drug targets. We have developed genetically modified mice
(
Cdk4R24C::Tyr-Nras) which model MM progression via a benign nevus phase, evaluated the evolution of lesions, and
developed a tumor staging schema for murine MM. We have combined this model with the Collaborative Cross (CC) as a novel
approach to find genes which strongly influence MM development. We find major differences in various MM-related phenotypes
when crossed onto the CC strains. We have mapped these phenotypes to small chromosomal regions, containing either just one or
a small number of genes, and are testing more strains to enable fine mapping. We have used these data to define a molecular
pathway for MM progression, as follows: 1. Nevus histological phenotype (scattered subepidermal vs pagetoid dermal):
controlled by a chr 7 locus. 2. Nevus age of onset: one locus is on chr 2, which contains a candidate gene that is frequently
mutated in human MM and associated with MM risk. We also found loci on chr 1 (which is associated with MM in published
GWAS), chr 8, and chr 14. 3. MM age of onset: controlled by loci that map to chromosomes 1 and 19. The latter is associated
with human MM in our cohort, but was not reported previously, hence is a novel finding. 4. Time for conversion of nevus to
MM: loci map to regions containing genes known to be involved in MM biology. The strong congruence of our data with human
MM genetics highlights the power of our approach. Our findings confirm that MM progression appears to be controlled not only
by stochastic events occurring over time, but also by different inherited factors at each stage. The discovery of genes that explain
why nevi develop so frequently and rapidly, and often convert to MM, will lead to a much fuller understanding of MM
progression. Especially attractive as potential therapeutic targets are protective genes that are dominant over the oncogenic
mutations known to generate MM in both mice and humans.