Abstract
Purpose :
Prolactin (PRL) hormone has a protective role in the retina and is expressed by various retinal cell populations. Our recent RNAseq analysis comparing the retinal transcriptome of normal dogs to that of mutant rcd1 (PDE6B) and xlpra2 (RPGR) dogs at advanced stages of retinal degeneration showed, respectively, a greater than 50- and 150-fold induction of PRL mRNA. In this study, we have further examined the expression and function of PRL in diseased retinas.
Methods :
Retinas from normal controls and rcd1 and xlpra2 dogs at disease stages with ≥ 50% photoreceptor loss were used in this study. Expression of PRL and its receptor (PRLR) in total retinas of diseased dogs was analyzed by qPCR assay. Retinal cell layers (outer nuclear layer with inner segments, ONL/IS; inner nuclear layer, INL; and ganglion cell layer, GCL) were collected individually by laser capture microdissection (LCM) from unfixed OCT embedded retinal cryosections. RNA from each of the layers was isolated and mRNA was amplified using a linear RNA amplification protocol. Purity of each layer was confirmed by testing the expression of known layer-specific genes. qPCR analysis was performed to analyze PRL expression in each of the retinal cellular layers. RNA in situ hybridization (RNA-ISH, RNAscope, ACDBio) with canine PRL-specific probes was performed on OCT embedded retinal sections from normal and mutant dogs.
Results :
By qPCR assay, we confirmed our earlier RNAseq results and found an upregulation of expression of PRL mRNA in rcd1 and xlpra2 retinas at advanced stages of degeneration but no increased expression of PRLR. qPCR analysis performed on mRNA amplified from each of the retinal layers revealed that the PRL mRNA is expressed exclusively in the ONL of the diseased retinas. In addition, ONL-specific expression was confirmed by RNA-ISH. Canine-specific PRL oligonucleotide probes specifically labeled the photoreceptor cells in the ONL of diseased retinas, whereas no labeling was detected in the retinas of normal dogs.
Conclusions :
We confirmed that PRL mRNA expression is induced in diseased rcd1 and xlpra2 canine retinas and now show that PRL is expressed specifically in the photoreceptors. We have recently developed an antibody that can recognizes the canine PRL protein to test for its expression in retinas. Additional experiments are underway to examine the temporal regulation of PRL expression and its role in diseased retinas.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.