Postnatal development of the ciliary body and iris in β-catenin knockout

Abstract

Purpose : Previous studies have shown that β-catenin is critical for the specification of mammalian ciliary margin at the embryonic stage. However, its role in the postnatal stage remains unclear. Using β-catenin knockout mice, we investigated the impact of β-catenin signaling on the postnatal development of the ciliary body (CB) and iris.

Methods : Cre-mediated inactivation of β-catenin signaling (βcat^null) in the peripheral retina was used for this study. tdTomato (Td) was incorporated as a reporter. Eyes from both Postnatal Day 0 (P0) and Postnatal 1 Month (P1M) stages were harvested, fixed, cryo-sectioned, and inspected with immunohistochemistry (IHC). Wildtype (WT) samples from the same litters and stages were used as controls.

Results : Morphologically, the CB and iris remained intact at both the P0 and P1M stages, but the peripheral retina exhibited extensive neural retina rosettes positive for the Td reporter expression. Surprisingly, although β-catenin were absent in the peripheral retina, they were detected in the CB and iris, which were mostly devoid of Td expression. As a result, markers including CDO (pan-CM), P-cadherin (pigmented CB), Otx2 (distal CM), and αSMA (iris muscle) were all expressed in the similar locations as the WT counterparts (n=3 for each marker).

Conclusions : At the postnatal stage, βcat^null animals retain the normal structures of the CB and iris, but these structures are exclusively composed of β-catenin positive cells. In contrast, the neural retina contains both β-catenin positive and negative cells. These results show that wild type cells can coexist with βcat^null cells in the neural retina, but they outcompete βcat^null cells in the CB and iris.

This is a 2020 ARVO Annual Meeting abstract.