Whole Number And Spatial Distribution Of The Pou4f Family Of Transcription Factors In The Adult Rat Retina

Abstract

Purpose: : To quantify and characterize the spatial distribution of retinal ganglion cells (RGCs) expressing Brn3a, Brn3b and/or Brn3c, in the adult albino rat retina

Methods: : In adult albino Sprague Dawley female rats retinas were dissected as whole mounts. By using double immunodetection (Brn3a+b, Brna+c, Brn3b+c), the level of Brn3 coexpression was assessed. In addition in some retinas the 3 transcription factors were detected with the same fluorofore to quantify the total number of Brn3 expressing RGCs. Retinas were examined and photographed under an epifluorescence microscope. In all retinas the whole number of RGCs expressing either of the transcription factors was quantified using automated routines specifically developed for this purpose. With these data, isodensity maps showing the spatial distribution of these RGCs were generated

Results: : Nearly 100% of Brn3b+ or Brn3c+ RGCs coexpress Brn3a as well, while the percentage of Brn3b and Brn3c co-expression is of 47%. The total number of Brn3 positive RGCs is 84,699±2148, whereas the mean number of Brn3b positive RGCs is 52,552±8657 and of Brn3c 42,093±2979. These numbers are significantly smaller than the population of RGCs expressing Brn3a (83,449±4541, Nadal-Nicolás et al, 2009, IOVS, 50(8):3860). Isodensity maps of Brn3b+RGCs and Brn3c+RGCs show that these neurons are more abundant in the mid-central retina than in the periphery

Conclusions: : The three members of the POU4F family of transcription factors, Brn3a, b and c, are expressed by adult rat RGCs. Whilst Brn3b and Brn3c are only expressed by a subset of RGC, the vast majority of these neurons express Brn3a

Keywords: ganglion cells • retina • retina: proximal (bipolar, amacrine, and ganglion cells)