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

Abstract

The transcription factor Sip1 (Zeb2) plays multiple roles during CNS development from early acquisition of neural fate to cortical neurogenesis and gliogenesis. In humans, SIP1 (ZEB2) haploinsufficiency leads to Mowat-Wilson syndrome, a complex congenital anomaly including intellectual disability, epilepsy and Hirschsprung disease. Here we uncover the role of Sip1 in retinogenesis. Somatic deletion of Sip1 from mouse retinal progenitors primarily affects the generation of inner nuclear layer cell types, resulting in complete loss of horizontal cells and reduced numbers of amacrine and bipolar cells, while the number of Muller glia is increased. Molecular analysis places Sip1 downstream of the eye field transcription factor Pax6 and upstream of Ptf1a in the gene network required for generating the horizontal and amacrine lineages. Intriguingly, characterization of differentiation dynamics reveals that Sip1 has a role in promoting the timely differentiation of retinal interneurons, assuring generation of the proper number of the diverse neuronal and glial cell subtypes that constitute the functional retina in mammals.

Single-Cell RNA Sequencing of hESC-Derived 3D Retinal Organoids Reveals Novel Genes Regulating RPC Commitment in Early Human Retinogenesis

“…For example, TFs belonging to transcriptional repressors, such as ZEB2 , ZBTB20 , and ID4 (Figure 5D), exhibited upregulated expression. Zeb2 was reported to promote the timely differentiation of retinal interneurons, possibly through the repression of the TGFβ/Smad pathway, while Zbtb20 and Id4 determined the balance between neurogenic and gliogenic output by preventing premature neurogenesis (Bedford et al., 2005, Menuchin-Lasowski et al., 2016, Nagao et al., 2016). Another family of TFs, which contains the high-mobility group (HMG) box that maintains proliferative progenitors in the neurogenic region and controls the temporal regulation of neurogenesis, such as TOX , SOX2 , and SOX9 , was also upregulated in the RPC lineage (Artegiani et al., 2015, Poche et al., 2008).…”

Functional characterization of theZEB2regulatory landscape

“…After 24 h, enhancer activity was measured by the dual luciferase reporter assay (Promega) on a SPARK microplate reader (Tecan). In HEK293 cells, enhancer vectors were co-transfected with 25 ng of the expression constructs pCAG–ZEB2–GFP (a gift from Ruth Ashery-Padan) (47), SP(RSV)-TFAP2α (a gift from Williams Trevor) (48) and CMX-TFAP2γ (a gift from Hubert Schorle) (37) or pß-act-DLX1/2 (a gift from Shigeo Okabe) (49) to measure the effect of each construct on enhancer activity. It should be noted that TFAP2α and TFAP2γ each had an effect on enhancer activity but when introduced together caused the effect to be significantly higher.…”

ZEB2, the Mowat-Wilson Syndrome Transcription Factor: Confirmations, Novel Functions, and Continuing Surprises

“…Collectively, the homozygous Zeb2 -cKO mouse models provided explanations for multiple defective cellular and developmental aspects of MOWS in humans. This was the case for CNS deficiencies, such as brain neuro/gliogenesis and guided migration of forebrain interneurons [ 47 , 64 ], as well as for eye lens malformation and for the resulting imbalance between cell types in the early and late retina [ 77 , 79 , 86 ], neurocristopathies resulting from aberrant craniofacial and ENS, as well as trunk NCCs [ 8 , 59 , 87 ], and reduced pain sensitivity [ 73 , 74 ].…”

“…The retina is a multi-layered sensorineural epithelium and contains different types of neuron and glial cells over three layers; the photoreceptor layer, the ganglion cell layer (containing retinal ganglion cells which extend into the brain), and the inner nuclear layer (containing interneurons, i.e., horizontal, bipolar and amacrine cells, and Müller glia cells). In a screen for changed genes in Pax6-deficient retinal precursors (RPCs) [ 203 ], Zeb2 was identified and validated as downregulated gene, and its expression in various cell types during mouse retinal development was documented in detail [ 79 ]. α -Cre; Zeb2 -cKOs were used to study ZEB2’s role from E12.5 onwards, i.e., in early retinogenesis, including documentation of the phenotype till P14.…”