Lens fiber cell differentiation and denucleation are disrupted through expression of the N-terminal nuclear receptor box of NCOA6 and result in p53-dependent and p53-independent apoptosis.
Nuclear receptor coactivator 6 (NCOA6) is a multifunctional protein implicated in embryonic development, cell survival, and homeostasis. An 81-amino acid fragment, dnNCOA6, containing the N-terminal nuclear receptor box (LXXLL motif) of NCOA6, acts as a dominant-negative (dn) inhibitor of NCOA6. Here, we expressed dnNCOA6 in postmitotic transgenic mouse lens fiber cells. The transgenic lenses showed reduced growth; a wide spectrum of lens fiber cell differentiation defects, including reduced expression of gamma-crystallins; and cataract formation. Those lens fiber cells entered an alternate proapoptotic pathway, and the denucleation (karyolysis) process was stalled. Activation of caspase-3 at embryonic day (E)13.5 was followed by double-strand breaks (DSBs) formation monitored via a biomarker, gamma-H2AX. Intense terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) signals were found at E16.5. Thus, a window of approximately 72 h between these events suggested prolonged though incomplete apoptosis in the lens fiber cell compartment that preserved nuclei in its cells. Genetic experiments showed that the apoptotic-like processes in the transgenic lens were both p53-dependent and p53-independent. Lens-specific deletion of Ncoa6 also resulted in disrupted lens fiber cell differentiation. Our data demonstrate a cell-autonomous role of Ncoa6 in lens fiber cell differentiation and suggest novel insights into the process of lens fiber cell denucleation and apoptosis.
Wang
Wei-Lin
WL
Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Li
Qingtian
Q
Xu
Jianming
J
Cvekl
Ales
A
D020816:Amino Acid Motifs; D000818:Animals; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D002386:Cataract / Q000150:complications / Q000473:pathology; D002454:Cell Differentiation; D004789:Enzyme Activation; D017353:Gene Deletion; D020287:In Situ Nick-End Labeling; D007908:Lens, Crystalline / Q000002:abnormalities / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D051379:Mice; D008822:Mice, Transgenic; D008850:Microphthalmos / Q000150:complications / Q000473:pathology; D008954:Models, Biological; D056918:Nuclear Receptor Coactivators / Q000737:chemistry* / Q000378:metabolism*; D009928:Organ Specificity; D051257:Proto-Oncogene Proteins c-maf / Q000378:metabolism; D013329:Structure-Activity Relationship; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D038222:gamma-Crystallins / Q000378:metabolism
C405683:Ncoa6 protein, mouse; D056918:Nuclear Receptor Coactivators; D051257:Proto-Oncogene Proteins c-maf; D016159:Tumor Suppressor Protein p53; D038222:gamma-Crystallins; D053148:Caspase 3