Identification and Phylogenetic Characterization
of Cytochrome p450 IA (CYP1A) in Little Skate, Raja
erinacea Danielle
Gilbert Department of
Biology,Massachusetts Institute of Technology, Cambridge, MA 02139
Work conducted with Dr. Rebeka Merson in the laboratory of Dr.Mark
Hahn,Woods Hole Oceanographic Institution,Woods Hole, MA 02543
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Non-Scientific
Abstract Phylogenetics is the study of evolutionary
relationships.Historically, this field utilized morphological
studies,which analyze the physical characteristics of organisms to
classify relationships.Recent advances in molecular biology allow
researchers to organize evolutionary relationships through the
examination of DNA. By characterizing one gene in number of species,
researchers can construct the same ³trees of life² as those from
morphological studies. Sometimes molecular techniques reveal surprising
results, changing the trees to show a more correct relationship. In this
study, we examine a gene in the little skate, Raja erinacea.We chose the
little skate as our model organism for several reasons: (1) it is
representative of the earliest jawed vertebrates, cartilaginous fish;
(2) among cartilaginous fish, skates and rays are one of the oldest
groups, second only to chimeras; and (3) the little skate is small,
easily handled, and was readily available for study. The gene we
selected is cytochrome p450 1A (CYP1A).The CYP1A protein metabolizes
common pollutants, including TCDD.This metabolic process may release
carcinogens.We hope to find and sequence the CYP1A gene in the little
skate, and then compare its sequence to those of CYP1A genes in other
animals to place the little skate CYP1A in a phylogenetic tree.
Abstract Cytochrome p450 IA (CYPIA) is a xenobiotic
metabolizing enzyme involved in the hydrolysis of numerous environmental
toxins, including halogenated and polynuclear aromatic hydrocarbons.
This biotransformation releases free radicals and other mutagenic
metabolites, resulting in most of the deleterious effects observed with
these pollutants.CYP1A is induced by toxic compounds through a
ligand-activated transcription factor, the aryl hydrocarbon receptor
(AHR). A significant inducer of AHR is
2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a common contaminant that
results from chemical bleaching and the manufacture of organochlorine
compounds. The AHR/CYP1A regulatory system is well-known in many
vertebrate taxa from mammals to bony fish, though the natural
physiologic function has yet to be determined. Studies of the
evolutionary history of AHR and CYP1A may reveal this function and its
significance.Here we report cDNA cloning of CYP1A in an elasmobranch,
the little skate Raja erinacea. The presence of a CYP1A ortholog in this
ancient lineage suggests that CYP1A arose before the divergence of bony
and cartilaginous fish. |