Tet proteins regulate differentiation potential across retinal cell types

Tet enzymes are epigenetic modifiers that impact gene expression via 5mC to 5hmC oxidation; 5hmC generation is known to induce chromatin remodeling and promote transcriptional accessibility and therefore gene expression. Previous work demonstrated the requirement for Tet and 5hmC in early retinogenesis–revealing that Tet-null(tet2-/-;tet3-/-) zebrafish exhibit extensive retinal defects. Here, we leveraged scRNAseq technologies to better understand cell type-specific deficits and molecular signatures underlying the tet2-/-;tet3-/- phenotype across differentiation stages. Our results revealed phenotypes in developing tet2-/-;tet3-/- retinae including delayed specification of several retinal cell types, reduced maturity across late-stage tet2-/-;tet3-/- cones, expansions of immature subpopulations of both horizontal and bipolar cells, and altered biases of bipolar cell subtype fates at late differentiation stages. Together, these data support Tet proteins as regulators of cell specification, lineage fate commitment, and terminal differentiation. This study enables a better understanding of how Tet proteins impact the differentiation of many unique yet interacting cell types in a cellularly complex neuronal tissue. Embryonic and larval eye cells were collected from 36,48,72, and 120 hpf zebrafish retinae from sibling control (sibCTL) and tet2-/-tet3-/- retinae. Dissociated cells were analyzed via scRNAseq