Abstract
Purpose:
Vertebrate homologs of Caenorhabditis elegans Par-3 have versatile biological functions including their prototypical role in cell polarization; such functional versatility may be partly explained by the variety of vertebrate Par-3 homologs. Thus, revealing the similarities and differences among individual Par-3 homologs is a prerequisite for a thorough understanding of their biology in vertebrates. What is lacking in particular is an understanding of just what and how Par-3 homologs regulate vertebrate eye development. Thus, we set out to clone additional zebrafish Par-3 orthologs and characterized their functions in zebrafish retinal development.
Methods:
Molecular biology techniques were used to clone the pard3c gene. Confocal microscopy and JB4 plastic histology were used to study the expression pattern of the pard3c gene and the localization of Pard3c protein. Morpholino knockdown was used to perform loss-of-function analysis. And mRNA injection was used to perform rescue analyses and gain-of-function analysis.
Results:
Pard3c is a novel zebrafish Par-3 ortholog. As one of the four zebrafish Par-3 orthologs, Pard3c is most closely related to Pard3, a zebrafish Par-3 ortholog that has been studied extensively. However, unlike the typical polarity protein Pard3, Pard3c does not restrictively localize apically nor does it regulate apicobasal polarity in epithelia; instead, Pard3c localizes more broadly to the cell membranes and is required for proper morphogenesis of the retina, lens, and some other organs by regulating cell survival, proliferation, and differentiation.
Conclusions:
As an unconventional member of the Par-3 polarity protein family, Pard3c plays essential and unique roles in the morphogenesis of zebrafish eye and other organs.