A comparison of HoxA13 sequences in Cypriniformes and other closely related speciesBy Emily Edenburn

Teacher, East Rock Global Magnet School, 8

7th Grade Science

Related to zebrafish

Question: How do novel characteristics arise and what changes in genes cause them to occur?

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.

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.

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.

Phenotype associated with HoxA13a knockdown in zebrafish

Normal Zebrafish larva with yolk sac extension phenotype

Loss of phenotype when HoxA13a is knocked down

Return of phenotype when HoxA13a is artificially restored

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

HoxA13 was duplicated in teleost fishes producing the A13a and A13b paralogs

Could HoxA13a or A13b may be associated with the YSE?

We sequenced A13 paralogs in six fish species to address this question.

Chanos chanos— a milk fish

Apteronotus leptorhynchus—electric knifefish

Gyrinocheilus sp.— Chinese algae

eater

Misgurnus anguilicaudatus— dojo loach

Ictalurus punctatus— channel catfish

Sampled Fish Species

Carassius auratus— common goldfish

These six species of fish were chosen because they are representative of the main

groups within the Ostariophysi.

We compared our HoxA13 sequences with the published HoxA13 sequences of the zebrafish Danio rerio- a member of the Cypriniformes

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

The Ostariophysi

We sampled six members of the Ostariophysi including 3 cypriniformes and 3 non-cypriniformes.

Yolk sac extensionYolk sac extension

Danio rerio larvae Carasius auratus larvae

Two examples of cypriniformes and their yolk sac extentions:

Conclusions:

I sequenced the Hox A13b paralogs in the milkfish (Chanos chanos) and the dojo loach (Misgurnus anguilicaudatus).

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!

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

In my classroom:

•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.

HoxA13a amino acid sequences unique to Cypriniformes

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are needed to see this picture.