Mettl3 Regulates Lens Development by Promoting the Differentiation Processes of Secondary Fiber Cells.

Purpose: Lens development requires tight regulation of cell proliferation and differentiation processes, the disruption of which might lead to congenital cataract formation. N6-methyladenosine (m6A) is the most prevalent mRNA internal modification and has been shown to play important roles in regulating the development, physiology, and pathology of various organs and tissues. However, the function of m6A during lens development remains unknown. The purpose of this study was to investigate the function of Mettl3, the core catalytic component of the m6A-writer complex, during lens development.

Methods: Lens-specific Mettl3 conditional knockout (Mettl3-CKO) mice were used as a model to investigate the function of Mettl3 during lens development. Hematoxylin and eosin staining was used to examine lens histology. Immunofluorescence (IF) staining was used to examine the expression of genes in the lenses. RNA sequencing (RNA-seq) was used to characterize the transcriptome of the lenses. Modified m6A sequencing was used to characterize the m6A epitranscriptome of the lenses.

Results: Mettl3-CKO mice developed cataracts; histologic and IF examination revealed that Mettl3-CKO lenses presented defects in several secondary fiber differentiation processes, including delayed cell cycle exit, mislocalization, and failed cell body elongation. RNA-seq revealed that the expression of genes regulating actin-cytoskeleton dynamics and cell cycle progression was altered in Mettl3-CKO lenses. m6A-seq characterized the lens m6A epitranscriptome and suggested its potential role in regulating fiber cell differentiation processes.

Conclusions: Mettl3 regulates lens development by promoting the cell cycle exit and cell morphological changes during secondary lens fiber differentiation.