To identify the functional domains of BNIP3L required for elimination of MT, ER and GA to form mature lens fiber cells

The structure and transparency of the eye lens are vital for focusing light onto the retina for vision. Lens fiber cells undergo a cellular remodeling program that removes mitochondria (MT), endoplasmic reticulum (ER), and Golgi apparatus (GA) to form mature transparent lens fiber cells. Previous studies established a requirement for the mitochondrial outer membrane protein BNIP3L for the elimination of these non-nuclear organelles in the lens; however, the precise molecular pathways for BNIP3L function remain to be elucidated. BNIP3L contains multiple functional domains whose analysis may illuminate its lens mechanisms including the LIR, BH3, and TM domains. These domains each play an important role in regulation of autophagosome formation and initiation of autophagy. To test each domain’s functionality for BNIP3L-dependent organelle elimination, we designed site-directed mutagenesis studies to delete each domain and test the resulting mutants in initiating the degradation of organelles in ex vivo cultured embryonic chick lenses.