Abstract
Purpose :
To unlock the full potential of regenerative medicine requires a more complete understanding of the molecular determinants that influence cellular migration, proliferation, identity, and fate. The factors that determine dopaminergic amacrine cell (DACs) diversity are of a particular importance given their function as the primary source of retinal dopamine. The degeneration of these cells and the resulting disruptions in visual function, circadian rhythms, and neurophysiology occurs in multiple diseases including Parkinson’s and diabetic retinopathy. The focus of our investigation was to identify factors that influence DAC diversity. Through this screen we uncovered a candidate signaling pathway controlled by the serine-threonine kinase LKB1 that is critical for DAC fate.
Methods :
We leveraged Cre recombinase technology to selectively knock out LKB1 from either retinal neurons or amacrine cell precursors. In concert with transgenic mice that allow for visualization of DACs by the expression of GFP driven by the promoter for tyrosine hydroxylase we were able to analyze the effects of the absence of LKB1 on the fate of the dopaminergic amacrine cells. Using cross sections and whole flat-mounted retinas we analyzed DACs in the first, second, and third post-natal weeks.
Results :
In LKB1 KO retinas the DACs population doubled. DACs were observed in the ganglion cell layer (GCL) in addition to their endogenous location in the Inner Nuclear Layer (INL). These cells retained expression of the amacrine cell marker Ap2 but projected their neurites to the Inner Plexiform Layer (IPL) from the opposite side from their inner nuclear layer counterparts. We also observed DAC stratification in layers S2 and S4 of the IPL in addition to layers S1 and S3 observed in controls. These results were recapitulated in mice that had LKB1 selectively deleted from amacrine cell precursors.
Conclusions :
These results indicate that LKB1 signaling is required cell intrinsically within amacrine cell precursors to restrict the total population of DACS, migration of DACS to the INL, and stratification of DAC processes to S1 and S3 layers of the IPL. These findings contribute to our understanding of signaling pathways that influence important attributes of DAC fate in murine retina. Manipulation of LKB1 signaling may potentially be utilized therapeutically in diseases like Parkinson's to maintain endogenous dopaminergic signaling pathways.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.