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A comparison of HoxA13 sequences in Cypriniformes and other closely related species
By Emily Edenburn
Question: How do novel characteristics arise and what changes in
genes cause them to occur?
Teacher, East Rock Global Magnet School, 8
I focused on a novel character that is putatively specific to Cypriniformes-the yolk sac extension. I hope to identify novel sequences might be
associated with this group.
The purpose of this study was to evaluate sequence divergence in
duplicated HoxA13 genes in zebrafish and identify amino acid sites that
may be associated with the YSE.
We compared our HoxA13 sequences with
the published HoxA13 sequences of the
zebrafish Danio rerio- a member of the
Cypriniformes
Hox grenes are a family of genes that affect body plan features during
larval development. These genes show evolutionary importance
because they are highly conserved across taxa.
This specific sampling of fish will allow us to
see what sequences are novel to
cypriniformes and are not shared among the
other closely related taxa
Scientists have been able to remove and then replace Hox genes in
animals, including zebrafish. The following shows what happens when
Hox A13a is removed and then replaced in Danio rerio.
Sampled Fish Species
Chanos chanos—
a milk fish
Ictalurus punctatus—
channel catfish
Apteronotus leptorhynchus—
electric knifefish
Misgurnus
anguilicaudatus— dojo
loach
Carassius auratus—
common goldfish
Gyrinocheilus sp.—
Chinese algae eater
Conclusions:
I sequenced the Hox A13b paralogs in the milkfish (Chanos
chanos) and the dojo loach (Misgurnus anguilicaudatus).
The Ostariophysi
Phenotype associated with HoxA13a knockdown in zebrafish
When compared with sequences from the Chinese algae
eater, (Gyrinocheilus sp.) electric knifefish (Apteronotus
sp.), and goldfish (Carassius sp.), we identified >15 amino
acid sites that may be associated with a novel character in
Cypriniformes-the YSE!
Normal Zebrafish larva with yolk
sac extension phenotype
Loss of phenotype when
HoxA13a is knocked down
Return of phenotype when
HoxA13a is artificially restored
7th Grade Science
These six species of fish were chosen
because they are representative of the main
groups within the Ostariophysi.
We sampled six members of the Ostariophysi including 3 cypriniformes and 3 non-cypriniformes.
HoxA13a amino acid sequences unique to Cypriniformes
What does Hox A13 do?
HoxA13 codes for distal and posterior body development in
vertebrates. The yolk sac extension (YSE) is a distal body
feature
Related to zebrafish
HoxA13 was duplicated in teleost fishes producing the
A13a and A13b paralogs
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Could HoxA13a or A13b may be associated with the YSE?
We sequenced A13 paralogs in six fish species to address this
question.
Two examples of cypriniformes and their yolk sac extentions:
Danio rerio larvae
Carasius auratus larvae
In my classroom:
References:
Kenji Saitoh, Masaki Miya, Jun G. Inoue, Naoya B. Ishiguro, Mutsumi Nishida, “Mitochondrial
Genomics of Ostariophysan Fishes: Perspectives on Phylogeny and Biogeography, “ J of
Molecular Evolution, 56:4, 2003, p 464-472
Yolk sac extension
Yolk sac extension
•I was able to use my research experience to link what my students learned last school year
in their seventh grade life sciences course to the first unit I taught them in either grade. This
link was based on the relationship between structure and function in animal skeletons
compared to the relationship between structure and function for bridges.
•I was able to explain how one takes a question and turns it into a multi-step scientific
process when it came time for my students to do their own science fair projects.
•I am able to have an aquarium with Danio rerio species that I raised from eggs. This
aquarium is something that my students are very interested in. A number of my students
take care of the fish, from feeding them to refilling the water, I do very little maintenance, the
students take care of these fish and through that learn about them.