Loss of Ribosomal Protein L11 Affects Zebrafish Embryonic Development through a p53-Dependent Apoptotic Response

Ribosome is responsible for protein synthesis in all organisms and ribosomal proteins (RPs) play important roles in the formation of a functional ribosome. L11 was recently shown to regulate p53 activity through a direct binding with MDM2 and abrogating the MDM2-induced p53 degradation in response to ribosomal stress. However, the studies were performed in cell lines and the significance of this tumor suppressor function of L11 has yet to be explored in animal models. To investigate the effects of the deletion of L11 and its physiological relevance to p53 activity, we knocked down the rpl11 gene in zebrafish and analyzed the p53 response. Contrary to the cell line-based results, our data indicate that an L11 deficiency in a model organism activates the p53 pathway. The L11-deficient embryos (morphants) displayed developmental abnormalities primarily in the brain, leading to embryonic lethality within 6–7 days post fertilization. Extensive apoptosis was observed in the head region of the morphants, thus correlating the morphological defects with apparent cell death. A decrease in total abundance of genes involved in neural patterning of the brain was observed in the morphants, suggesting a reduction in neural progenitor cells. Upregulation of the genes involved in the p53 pathway were observed in the morphants. Simultaneous knockdown of the p53 gene rescued the developmental defects and apoptosis in the morphants. These results suggest that ribosomal dysfunction due to the loss of L11 activates a p53-dependent checkpoint response to prevent improper embryonic development

Mutation of FOXC1 and PITX2 induces cerebral small-vessel disease

Patients with cerebral small-vessel disease (CSVD) exhibit perturbed end-artery function and have an increased risk for stroke and age-related cognitive decline. Here, we used targeted genome-wide association (GWA) analysis and defined a CSVD locus adjacent to the forkhead transcription factor FOXC1. Moreover, we determined that the linked SNPs influence FOXC1 transcript levels and demonstrated that patients as young as 1 year of age with altered FOXC1 function exhibit CSVD. MRI analysis of patients with missense and nonsense mutations as well as FOXC1-encompassing segmental duplication and deletion revealed white matter hyperintensities, dilated perivascular spaces, and lacunar infarction. In a zebrafish model, overexpression or morpholino-induced suppression of foxc1 induced cerebral hemorrhage. Inhibition of foxc1 perturbed platelet-derived growth factor (Pdgf) signaling, impairing neural crest migration and the recruitment of mural cells, which are essential for vascular stability. GWA analysis also linked the FOXC1-interacting transcription factor PITX2 to CSVD, and both patients with PITX2 mutations and murine Pitx2(-/-) mutants displayed brain vascular phenotypes. Together, these results extend the genetic etiology of stroke and demonstrate an increasing developmental basis for human cerebrovascular disease

Whole-exome sequencing of congenital glaucoma patients reveals hypermorphic variants in GPATCH3, a new gene involved in ocular and craniofacial development

Congenital glaucoma (CG) is a heterogeneous, inherited and severe optical neuropathy that originates from maldevelopment of the anterior segment of the eye. To identify new disease genes, we performed whole-exome sequencing of 26 unrelated CG patients. In one patient we identified two rare, recessive and hypermorphic coding variants in GPATCH3, a gene of unidentified function, and 5% of a second group of 170 unrelated CG patients carried rare variants in this gene. The recombinant GPATCH3 protein activated in vitro the proximal promoter of CXCR4, a gene involved in embryo neural crest cell migration. The GPATCH3 protein was detected in human tissues relevant to glaucoma (e.g., ciliary body). This gene was expressed in the dermis, skeletal muscles, periocular mesenchymal-like cells and corneal endothelium of early zebrafish embryos. Morpholino-mediated knockdown and transient overexpression of gpatch3 led to varying degrees of goniodysgenesis and ocular and craniofacial abnormalities, recapitulating some of the features of zebrafish embryos deficient in the glaucoma-related genes pitx2 and foxc1. In conclusion, our data suggest the existence of high genetic heterogeneity in CG and provide evidence for the role of GPATCH3 in this disease. We also show that GPATCH3 is a new gene involved in ocular and craniofacial development.This study has been supported by research grants from the “Instituto de Salud Carlos III/FEDER” (RD12/0034/0003, PI11/00662, PI15/01193 to JE and CP12/03256 to MC), the Ministry of Economy and Competitiveness/FEDER (MINECO, SAF2013-46943-R to MC and PT13/0001/0044 to MG), Mutua Madrileña Foundation (to MC), and the Regional Ministry of Science and Technology of the Board of the Communities of “Castilla-La Mancha” (PEII-2014-002-P to JE). Jesús-José Ferre-Fernández is the recipient of a predoctoral fellowship from the “Instituto de Salud Carlos III” (FI12/00287). Miguel Coca-Prados is “Catedrático Rafael del Pino en Oftalmología” in the “Fundación de Investigación Oftalmológica, Instituto Oftalmológico Fernández-Vega” Oviedo, Spain. Marta Corton is sponsored by the Miguel Servet Program (CP12/03256) from Instituto de Salud Carlos III/FEDER)

Ribosomes

Ribosomes are fundamental components of the cell that are essential for its growth and proliferation. It is hard to imagine that such a fundamental physiological machinery, as ribosomes, does not participate in cancer biology. However, surprisingly, there is a lack of studies towards the role of ribosomal alterations in cancer. Here, we will attempt to summarize current knowledge regarding the link between the ribosomal machinery and human cancer. Various malfunctions in ribosomal activity represented by defects in ribosome biogenesis have been associated with human disease. Recent studies performed both in yeast and in higher eukaryotes have linked various aspects of ribosome biogenesis to the control of cell growth and proliferation. It is now clear that disruption of ribosome biogenesis is a cause of several inherited genetic disorders that have been associated with an increased risk of tumor development. In this chapter we discuss some recent insights into the mechanisms by which alterations in ribosome biogenesis contribute to the biology of cancer