Gsg1, Trnp1, and Tmem215 Mark Subpopulations of Bipolar Interneurons in the Mouse Retina

Abstract

PurposeHow retinal bipolar cell interneurons are specified and assigned to specialized subtypes is only partially understood. In part, this is due to a lack of early pan- and subtype-specific bipolar cell markers. To discover these factors, we identified genes that were upregulated in Blimp1 (Prdm1) mutant retinas, which exhibit precocious bipolar cell development.MethodsPostnatal day (P)2 retinas from Blimp1 conditional knock-out (CKO) mice and controls were processed for RNA sequencing. Genes that increased at least 45% and were statistically different between conditions were considered candidate bipolar-specific factors. Candidates were further evaluated by RT-PCR, in situ hybridization, and immunohistochemistry. Knock-in Tmem215-LacZ mice were used to better trace retinal expression.ResultsA comparison between Blimp1 CKO and control RNA-seq datasets revealed approximately 40 significantly upregulated genes. We characterized the expression of three genes that have no known function in the retina, Gsg1 (germ cell associated gene), Trnp1 (TMF-regulated nuclear protein), and Tmem215 (a predicted transmembrane protein). Germ cell associated gene appeared restricted to a small subset of cone bipolars while Trnp1 was seen in all ON type bipolar cells. Using Tmem215-LacZ heterozygous knock-in mice, we observed that β-galactosidase expression started early in bipolar cell development. In adults, Tmem215 was expressed by a subset of ON and OFF cone bipolar cells.ConclusionsWe have identified Gsg1, Tmem215, and Trnp1 as novel bipolar subtype-specific genes. The spatial and temporal pattern of their expression is consistent with a role in controlling bipolar subtype fate choice, differentiation, or physiology.

Combinatorial regulation of a Blimp1 (Prdm1) enhancer in the mouse retina

“…We used the core vertebrata matrix and set the relative profile score threshold to 90% ( S2 Table ). Using previously generated RNA-seq data from the P2 retina [ 29 ], we excluded those genes that showed no expression in the retina. JASPAR predicted the Otx2 binding site and the sequence upstream matched an ROR response element (AGGTCA with 5bp of A/T rich upstream sequence) [ 45 ] ( Fig 6C ).…”

“…JASPAR predicted the Otx2 binding site and the sequence upstream matched an ROR response element (AGGTCA with 5bp of A/T rich upstream sequence) [ 45 ] ( Fig 6C ). All three ROR genes ( Rora , Rorb , and Rorc ) are made in the P2 retina, but Rorb is expressed at the highest levels [ 29 ]. Thus, we attempted ChIP with multiple RORβ antibodies, but none of them gave reproducible results (data not shown).…”

“…The output is listed in the supporting information ( S2 Table ). We compared the predictions made by JASPAR to our previously generated RNA-seq data for whole P2 retina [ 29 ]. Transcription factors that were not expressed in the P2 retina, such as Hox and Gata genes, were eliminated from consideration.…”

Region- and Cell-Specific Expression of Transmembrane Collagens in Mouse Brain

“…ISH revealed that col23a1 mRNA was distributed in the central-most region of INL, in a region between syt1+ and gad1+ amacrine cells and synaptotagmin 2 (Syt2)-expressing OFF-bipolar cells (Fox and Sanes, 2007 ; Figure 3C ). While additional studies are needed to determine the exact cellular origin of col23a1 in the retina, these results suggest it may be generated by ON-bipolar cells, a population of neurons that lie between inhibitory amacrine cells and OFF-bipolar cells (Figure 3C ; Park et al, 2017 ).…”

Transcriptomic Analysis of Young and Old Erythrocytes of Fish

“…Currently little is known about the transmembrane protein 215 (XM_014194795) and its function. It is conserved among vertebrate species and is expressed in mouse bipolar cells (Park et al, 2017). An attractive speculation is, because of the increase of its transcription in old cells, that it is involved in the age-dependent removal of cells from circulation.…”