Abstract
Purpose: :
The goal of this project was to determine the temporal and spatial expression of an unconventional class III myosin in the mouse retina. Class III myosins are characterized by a kinase domain at their N-terminus and are expressed in the retinas of both invertebrates and vertebrates including horseshoe crabs, flies, fish, mouse and humans. Two different genes encoding class III myosins have been cloned from vertebrates: myo3A and myo3B. Mutations in the human myo3A gene are implicated in the progressive nonsyndromic hearing loss DFNB30 (Walsh et al., 2002); however, the functions of Myo3B are not known. Myo3B is the focus of this study.
Methods: :
To detect the protein in the mouse retina we used an antibody raised against the tail domain of mouse myosin3B located towards the C-terminus of the protein. To investigate protein expression during development, western blots were performed using retinal homogenates from mice of various ages (postnatal day zero [P0] to adult). The protein was localized in the adult mouse retina by immunocytochemistry (ICC) performed in paraformaldehyde-fixed frozen sections that were boiled in sodium citrate for epitope unmasking
Results: :
Our antibody specifically recognizes a 130 kDa band in mouse retinal homogenates. Myosin3B is present in the retina at P0 and its expression is maintained through adulthood. The levels of myosin3B relative to total protein in the retina peak at ages P7-P14. ICC using the same antibody revealed staining of some cells in the ganglion and amacrine cell layers, and the inner segments of rods and cones. Intense myosin3B staining was observed in the outer segments of blue cones.
Conclusions: :
Myosin3B protein is present in the mouse retina as early as P0; its concentration relative to total retinal protein peaks at ages P7-P14. Myosin3B is present in some cells in the ganglion and amacrine cell layers, in the inner segments of rods and cones, and in the outer segments of blue cones.
Keywords: retina • photoreceptors • immunohistochemistry