Morphologies of mouse retinal ganglion cells expressing transcription factors Brn3a, Brn3b, and Brn3c: Analysis of wild type and mutant cells using genetically-directed sparse labeling

Abstract

The mammalian retina contains more than 50 distinct neuronal types, which are broadly classified into several major classes: photoreceptor, bipolar, horizontal, amacrine, and ganglion cells. Although some of the developmental mechanisms involved in the differentiation of retinal ganglion cells (RGCs) are beginning to be understood, there is little information regarding the genetic and molecular determinants of the distinct morphologies of the 15 – 20 mammalian RGC cell types. Previous work has shown that the transcription factor Brn3b/Pou4f2 plays a major role in the development and survival of many RGCs. The roles of the closely related family members, Brn3a/Pou4f1 and Brn3c/Pou4f3 in RGC development are less clear. Using a genetically-directed method for sparse cell labeling and sparse conditional gene ablation in mice, we describe here the sets of RGC types in which each of the three Brn3/Pou4f transcription factors are expressed and the consequences of ablating these factors on the development of RGC morphologies.

Ascl1 expression defines a subpopulation of lineage-restricted progenitors in the mammalian retina

“…First, Ascl1-GFP and pan-Brn3 co-expression data suggests that this putative subtype would have to be exceedingly rare during development (one cell or fewer per retina) (binomial distribution, P<0.00001, see Table S5 in the supplementary material). Second, whereas Brn3a/b/c expression might not label all ganglion cell subtypes (Badea and Nathans, 2011), retrograde dextran uptake labels all RGCs; nonetheless, we did not observe a significant number of Brn3+ or dextran-labeled RGCs in the Ascl1 lineage.…”

Late-Onset Inner Retinal Dysfunction in Mice Lacking Sigma Receptor 1 (σR1)

“…Brn3a is a well characterized marker for RGCs [26], and cleaved caspase-3 is a marker for apoptosis [21]. Immunohistochemical detection methods were used to determine the number of RGCs in retinal cryosections, using a goat polyclonal antibody against Brn-3a (1:100; Santa Cruz Corp., Santa Cruz, CA) followed by incubation with AlexaFluor-488-conjugated donkey anti-goat immunoglobulin (IgG) secondary antibody (1:1,000; Invitrogen, Carlsbad, CA).…”

Molecular Control of Retinal Ganglion Cell Specification and Differentiation

“…In spite of the extensive overlap in expression and function, however, individual Pou4f factors have distinct roles during RGC development. For instance, conditional deletion of Pou4f1 changes dendritic morphology and stratification of RGCs, increases the ratio of bistratified to monostratified RGCs, and causes modest RGC loss (Badea et al, 2009;Badea and Nathans, 2011). Although conditional inactivation of Pou4f2 results in similar defects, it causes no alteration in RGC dendritic stratification but additionally leads to RGC transdifferentitation and central projection defects (Badea et al, 2009;Badea and Nathans, 2011).…”

“…Although conditional inactivation of Pou4f2 results in similar defects, it causes no alteration in RGC dendritic stratification but additionally leads to RGC transdifferentitation and central projection defects (Badea et al, 2009;Badea and Nathans, 2011). However, conditional Pou4f3 mutants lack any of these RGC phenotypes (Badea and Nathans, 2011). Pou4f2 is not only necessary but also sufficient to promote RGC differentiation from retinal progenitors.…”