Loss of Sip1 leads to migration defects and retention of ectodermal markers during lens development

Abstract

SIP1 encodes a DNA-binding transcription factor that regulates multiple developmental processes, as highlighted by the pleiotropic defects observed in Mowat-Wilson Syndrome, which results from mutations in this gene. Further, in adults, dysregulated SIP1 expression has been implicated in both cancer and fibrotic diseases, where it functionally links TGFβ signaling to the loss of epithelial cell characteristics and gene expression. In the ocular lens, an epithelial tissue important for vision, Sip1 is co-expressed with epithelial markers, such as E-cadherin, and is required for the complete separation of the lens vesicle from the head ectoderm during early ocular morphogenesis. However, the function of Sip1 after early lens morphogenesis is still unknown. Here, we conditionally deleted Sip1 from the developing mouse lens shortly after lens vesicle closure, leading to defects in coordinated fiber cell tip migration, defective suture formation, and cataract. Interestingly, RNA-Sequencing analysis on Sip1 knockout lenses identified 190 differentially expressed genes, all of which are distinct from previously described Sip1 target genes. Furthermore, 34% of the genes with increased expression in the Sip1 knockout lenses are normally downregulated as the lens transitions from the lens vesicle to early lens, while 49% of the genes with decreased expression in the Sip1 knockout lenses are normally upregulated during early lens development. Overall, these data imply that Sip1 plays a major role in reprogramming the lens vesicle away from a surface ectoderm cell fate towards that necessary for the development of a transparent lens and demonstrate that Sip1 regulates distinctly different sets of genes in different cellular contexts.

Novel phenotypes and loci identified through clinical genomics approaches to pediatric cataract

“…It has been shown that enriched expression in developing lens tissue can be used as a criterion to evaluate potential function in lens development (Lachke et al 2011, 2012a, b; Anand and Lachke 2016; Anand et al 2015; Agrawal et al 2015; Kasaikina et al 2011; Wolf et al 2013; Manthey et al 2014; Dash et al 2015; Audette et al 2016). Consistent with those data, we find that all six candidates are significantly expressed in mouse lens development, and five exhibit lens-enrichment.…”

Beta-1 integrin is important for the structural maintenance and homeostasis of differentiating fiber cells

“…It is also possible that the β1-integrin cKO phenotype is influenced by the concomitant downregulation of β5- and β8-integrin expression in these lenses. However, removal of αV-integrin from the developing lens (which is the obligate α-integrin partner for both β5 and β8-integrin) did not result in lens fiber cell structural defects (Mamuya, Wang, 2014) while β1-integrin was found to be the most abundant β-integrin message detected in the E15.5 embryonic mouse lens by RNA-seq (Manthey et al, 2014). …”

Prox1 and fibroblast growth factor receptors form a novel regulatory loop controlling lens fiber differentiation and gene expression

“…Mice were genotyped for the Prox1 flox allele and MLR10Cre as described in Table S1. Histology was performed as described previously (Manthey et al, 2014a). No lens defects were observed in mice homozygous or heterozygous for either the MLR10Cre transgene or the Prox1 flox allele alone.…”