Genetic and functional analysis of eye degeneration in natural populations of a cave-dwelling crustacean - Abstract:
An understanding of eye development is necessary to comprehend proper functioning of the
eye, capacity for regeneration, and the developmental basis of disease. Many model systems,
both vertebrate and invertebrate, have historically provided much important data about the
developmental and genetic basis of eye formation. However, hurdles exist studying eye
development in model systems such as inherent biases in mutant screens and the minimal
amount of naturally occurring variation in eye size. One novel approach allowing for a greater
understanding of the developmental and genetic bases of eye formation is to examine naturally
occurring eye size variation in non-model organisms, such as that occurs in cave animals.
We initially chose the crustacean, Asellus aquaticus, as a model for studying eye variation
because of the extreme difference in eye size between cave and surface dwelling populations.
Our work on the species has shown multiple independent mechanisms of eye reduction/ loss
within a single cave population and a large genetic component influencing eye size. Our current
grant utilized comparative transcriptome sequencing of cave and surface embryonic samples as
an unbiased method to identify genes and pathways responsible for eye degeneration in two
different cave populations. Additionally, we sequenced transcriptomes of hybrid embryos to
identify genes with allele-specific expression containing putative cis-regulatory changes. One
major next step is to obtain positional information for all three potentially different genetic
mechanisms responsible for eye loss present in two different cave populations and in a surface
intercross. Additionally, the genes identified from the previous grant showing allele-specific
expression support the idea that genetic variants responsible for eye loss could be responsible
for additional phenotypes. Therefore, an understanding of the genetic basis of eye loss could be
furthered with an understanding of the other phenotypes that might be linked. To address these
two major questions we will first utilize restriction site-associated DNA sequencing (RADseq) to
map regions responsible for eye loss in the two cave populations and the surface intercross.
Second, we will identify phenotypes that are linked to eye loss in Asellus aquaticus through the
same genetic variants or different but linked genetic variants. Finally, we will investigate two
genes from our previous allele-specific expression work, efr3 and mut-7, examining them
functionally in flies for eye phenotype and additional behaviors. Our work provides a novel
perspective on the developmental and genetic basis of eye size differences and furthers the
development of A. aquaticus as an important model for eye degeneration and disease.
