Molecular dissection of cone photoreceptor-enriched genes encoding transmembrane and secretory proteins

Expression of deubiquitinating enzyme genes in the developing mammal retina

Purpose

Genes involved in the development and differentiation of the mammalian retina are also associated with inherited retinal dystrophies (IRDs) and age-related macular degeneration. Transcriptional regulation of retinal cell differentiation has been addressed by genetic and transcriptomic studies. Much less is known about the posttranslational regulation of key regulatory proteins, although mutations in some genes involved in ubiquitination and proteostasis-E3 ligases and deubiquitinating enzymes (DUBs)-cause IRDs. This study intends to provide new data on DUB gene expression during different developmental stages of mouse and human fetal retinas.

Methods

We performed a comprehensive transcriptomic analysis of all the annotated human and mouse DUBs (87) in the developing mouse retina at several embryonic and postnatal time points compared with the transcriptome of the fetal human retina. An integrated comparison of data from transcriptomics, reported chromatin immunoprecipitation sequencing (ChIP-seq) of CRX and NRL transcription factors, and the phenotypic retinal alterations in different animal models is presented.

Results

Several DUB genes are differentially expressed during the development of the mouse and human retinas in relation to proliferation or differentiation stages. Some DUB genes appear to be distinctly expressed during the differentiation stages of rod and cone photoreceptor cells, and their expression is altered in mouse knockout models of relevant photoreceptor transcription factors. We complemented this RNA-sequencing (RNA-seq) analysis with other reported expression and phenotypic data to underscore the involvement of DUBs in cell fate decision and photoreceptor differentiation.

Conclusions

The present results highlight a short list of potential DUB candidates for retinal disorders, which require further study.

Analysis of genetic networks regulating refractive eye development in collaborative cross progenitor strain mice reveals new genes and pathways underlying human myopia

BACKGROUND

Population studies suggest that genetic factors play an important role in refractive error development; however, the precise role of genetic background and the composition of the signaling pathways underlying refractive eye development remain poorly understood.

METHODS

Here, we analyzed normal refractive development and susceptibility to form-deprivation myopia in the eight progenitor mouse strains of the Collaborative Cross (CC). We used RNA-seq to analyze gene expression in the retinae of these mice and reconstruct genetic networks and signaling pathways underlying refractive eye development. We also utilized genome-wide gene-based association analysis to identify mouse genes and pathways associated with myopia in humans.

RESULTS

Genetic background strongly influenced both baseline refractive development and susceptibility to environmentally-induced myopia. Baseline refractive errors ranged from - 21.2 diopters (D) in 129S1/svlmj mice to + 22.0 D in CAST/EiJ mice and represented a continuous distribution typical of a quantitative genetic trait. The extent of induced form-deprivation myopia ranged from - 5.6 D in NZO/HILtJ mice to - 20.0 D in CAST/EiJ mice and also followed a continuous distribution. Whole-genome (RNA-seq) gene expression profiling in retinae from CC progenitor strains identified genes whose expression level correlated with either baseline refractive error or susceptibility to myopia. Expression levels of 2,302 genes correlated with the baseline refractive state of the eye, whereas 1,917 genes correlated with susceptibility to induced myopia. Genome-wide gene-based association analysis in the CREAM and UK Biobank human cohorts revealed that 985 of the above genes were associated with myopia in humans, including 847 genes which were implicated in the development of human myopia for the first time. Although the gene sets controlling baseline refractive development and those regulating susceptibility to myopia overlapped, these two processes appeared to be controlled by largely distinct sets of genes.

CONCLUSIONS

Comparison with data for other animal models of myopia revealed that the genes identified in this study comprise a well-defined set of retinal signaling pathways, which are highly conserved across different vertebrate species. These results identify major signaling pathways involved in refractive eye development and provide attractive targets for the development of anti-myopia drugs.

Methionine is a metabolic dependency of tumor-initiating cells

Understanding cellular metabolism holds immense potential for developing new classes of therapeutics that target metabolic pathways in cancer. Metabolic pathways are altered in bulk neoplastic cells in comparison to normal tissues. However, carcinoma cells within tumors are heterogeneous, and tumor-initiating cells (TICs) are important therapeutic targets that have remained metabolically uncharacterized. To understand their metabolic alterations, we performed metabolomics and metabolite tracing analyses, which revealed that TICs have highly elevated methionine cycle activity and transmethylation rates that are driven by MAT2A. High methionine cycle activity causes methionine consumption to far outstrip its regeneration, leading to addiction to exogenous methionine. Pharmacological inhibition of the methionine cycle, even transiently, is sufficient to cripple the tumor-initiating capability of these cells. Methionine cycle flux specifically influences the epigenetic state of cancer cells and drives tumor initiation. Methionine cycle enzymes are also enriched in other tumor types, and MAT2A expression impinges upon the sensitivity of certain cancer cells to therapeutic inhibition.