PAX6 Regulates Melanogenesis in the Retinal Pigmented Epithelium through Feed-Forward Regulatory Interactions with MITF

Abstract

During organogenesis, PAX6 is required for establishment of various progenitor subtypes within the central nervous system, eye and pancreas. PAX6 expression is maintained in a variety of cell types within each organ, although its role in each lineage and how it acquires cell-specific activity remain elusive. Herein, we aimed to determine the roles and the hierarchical organization of the PAX6-dependent gene regulatory network during the differentiation of the retinal pigmented epithelium (RPE). Somatic mutagenesis of Pax6 in the differentiating RPE revealed that PAX6 functions in a feed-forward regulatory loop with MITF during onset of melanogenesis. PAX6 both controls the expression of an RPE isoform of Mitf and synergizes with MITF to activate expression of genes involved in pigment biogenesis. This study exemplifies how one kernel gene pivotal in organ formation accomplishes a lineage-specific role during terminal differentiation of a single lineage.

Pax6 is essential for the generation of late-born retinal neurons and for inhibition of photoreceptor-fate during late stages of retinogenesis

“…Retinas were analyzed at P14, when cell specification is complete (Young, 1985). Pax6 deletion in Cre-GFP-expressing cells was verified by co-immunostaining with an antibody against GFP and a monoclonal antibody against the N-terminus of Pax6 protein, which includes the region of Pax6 that is deleted following Cre activation (Ashery-Padan et al, 2000; Raviv et al, 2014). GFP + cells were detected in the INL and the ONL, but not in the GCL of both Pax6 +/+ ;Cre late (Fig.…”

Identification and profiling of microRNAs associated with white and black plumage pigmentation in the white and black feather bulbs of ducks by RNA sequencing

“…At the start of melanogenesis, PAX6 functions in a feed-forward regulatory loop with MITF. PAX6 not only regulates the expression of a retinal pigment epithelium isoform of MITF, but also synergises with MITF to activate the expression of genes involved in pigment biogenesis (Raviv et al 2014). Previous studies have established that PAX3, a transcription factor and member of the PAX gene family, is involved in melanocyte propagation, resistance to apoptosis, migration, lineage specificity and differentiation (Kubic et al 2008).…”

Sip1 regulates the generation of the inner nuclear layer retinal cell lineages in mammals

“…qPCR analysis was performed as described previously (Raviv et al, 2014). Results were calibrated relative to expression levels of Actb.…”

“…Reporter assays were performed in HeLa cells as described previously (Raviv et al, 2014). Cells were transfected with 1 μg luciferase reporter vector with either the 5′ or 3′ Ptf1a enhancer, 50 ng of an expression vector carrying the Sip1 ORF or empty vector, and 10 ng normalizing vector ( pRL-TK).…”