Abstract
Purpose :
The regulatory lipid, phosphatidylinositol (4,5) bisphosphate (PI(4,5)P2) plays important roles in membrane trafficking and signal transduction. It is synthesized from its precursor, phosphatidylinositol (4) phosphate by the catalytic subunits of the α, β, and γ isoforms of phosphatidylinositolphosphate-5-kinase (PIP5K1A, PIP5K1B, PIP5K1C). The purpose of this project is to determine the functional roles of these enzymes and of PI(4,5)P2 in mammalian retinal development and in the function and health of rod cells.
Methods :
Antibodies specific for each isoform were used in immunofluorescence experiments to determine their localization in the mouse retina. Mice were bred to be homozygous for a “floxed” allele of the Pip5k1c gene and heterozygous for a Six3-driven Cre transgene to achieve knockout in early stages of retinal development. Mice with rod-specific knockout of the Pip5k1c gene were prepared using a opsin promoter (Icre-75). The phenotypes were assessed by immunofluorescence and electroetinography (ERG).
Results :
Expression of all three isoforms can be readily detected by isoform-specific antibodies in multiple retina layers, including the outer plexiform layer and the photoreceptor inner segments. The γ isoform is enriched in the pres-synaptic side of the outer plexiform layer. Six3-Cre driven knockout of the γ isoform γ isoform had no obvious effect on retinal development, but the rod-specific knockout resulted in reduced ERG b-wave amplitudes and progressive rod cell degeneration.
Conclusions :
The γ isoform of PIP-5 kinase appears dispensable for early development, possibly because of redundant roles with the other isoforms. The γ isoform of PIP-5 kinase and the PI(4,5)P2 it produces are essential for rod cell function and health.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.