Graduate Student

(574) 631-8641
tmurphy4@nd.edu

2004	California State University, Channel Islands Camarillo, CA	B.S. Biology
Present	University of Notre Dame, Center for Zebrafish Research	Doctoral Student
	Project: Molecular and Genetic Analysis of Zebrafish Lens and Retinal Development
	under David R. Hyde

My research is focused on identifying genes crucial to the development of the zebrafish lens and retina, by the molecular genetic analysis of eye morphological mutants identified by chemical mutagenesis.  Our current characterization centers around the zebrafish lens opaque (lop) mutant.  The mutant phenotype is characterized by the macroscopic appearance of a lens cataract at 7dpf; earlier developmental time points show no phenotype.  Histological and immunohistochemical analysis revealed that lop mutants accumulate proliferating cells in the anterior ocular chamber that impede light passage through the lens.  Interestingly, lop mutants also exhibit rod and cone photoreceptor degeneration.  Mutation mapping identified the genomic region that harbors the lop mutant gene.  A variety of molecular genetic techniques including morpholino mediated knockdown, phenotype rescue experiments, as well as complementation analysis are being used in an attempt to identify the mutant gene responsible for the observed phenotype.  Future analysis will include in situ hybridization to localize lop gene transcripts as well as the generation and characterization of an antibody that is specific to the gene product of interest.  This traditional forward genetics approach will reveal genes that are critical for proper development of the zebrafish eye.

Figure 1: Panel (A) shows histological sections of a wild-type zebrafish eye 7dpf.  Note the darkly stained photoreceptor layer (PL) along the full length of the retina as well as the large lens nucleus (*) that is free of cellular organelles.  Panel (D) is a histological section of the lop mutant at 7dpf.  Arrowheads point to the only discernable rod outer segments found at the retinal margins.  The mutant lens is characterized by the accumulation of proliferative tissue found here surrounding the lens nucleus.  This tissue is not organelle-free and impedes light as it passes through the lens.

Harding, R.L., Howley, S., Baker, L.J., Murphy, T.R., Archer, W.E., Winstow, G., Hyde, D.R., Vihtelic, T.S. (2008). Lengsin expression and function during zebrafish lens formation. Exp Eye Res. 2008 May;86(5):807-818. Epub 2008 Mar 2.