Biallelic loss of function variants in PPP1R21 cause a neurodevelopmental syndrome with impaired endocytic function.

Next-generation sequencing (NGS) has been instrumental in solving the genetic basis of rare inherited diseases, especially neurodevelopmental syndromes. However, functional workup is essential for precise phenotype definition and to understand the underlying disease mechanisms. Using whole exome (WES) and whole genome sequencing (WGS) in four independent families with hypotonia, neurodevelopmental delay, facial dysmorphism, loss of white matter, and thinning of the corpus callosum, we identified four previously unreported homozygous truncating PPP1R21 alleles: c.347delT p.(Ile116Lysfs*25), c.2170_2171insGGTA p.(Ile724Argfs*8), c.1607dupT p.(Leu536Phefs*7), c.2063delA p.(Lys688Serfs*26) and found that PPP1R21 was absent in fibroblasts of an affected individual, supporting the allele's loss of function effect. PPP1R21 function had not been studied except that a large scale affinity proteomics approach suggested an interaction with PIBF1 defective in Joubert syndrome. Our co-immunoprecipitation studies did not confirm this but in contrast defined the localization of PPP1R21 to the early endosome. Consistent with the subcellular expression pattern and the clinical phenotype exhibiting features of storage diseases, we found patient fibroblasts exhibited a delay in clearance of transferrin-488 while uptake was normal. In summary, we delineate a novel neurodevelopmental syndrome caused by biallelic PPP1R21 loss of function variants, and suggest a role of PPP1R21 within the endosomal sorting process or endosome maturation pathway.

Predicting the Correlation of EZH2 and Cancer Stem Cell Markers in Esophageal Squamous Cell Carcinoma.

BACKGROUND: Enhancer of zeste homolog 2 (EZH2), a stemness factor, plays roles in regulation of cell differentiation and embryonic development as well as cancer progression. Deregulation of EZH2 in cancers is correlated with tumor cell invasiveness, metastasis, and the patients' poor outcome. However, the mechanistic role of EZH2 in cancer is ambiguous. In this study, we aimed to inhibit the expression of EZH2 in a cancer cell line, and evaluate consequence changes in gene expression pattern. MATERIALS AND METHODS: Using specific retroviral shRNA-EZH2, EZH2 gene was silenced in the KYSE30 cell line. Relative comparative real-time PCR was used to confirm silencing of EZH2 and evaluate expression pattern of selected markers. RESULTS: Inhibition of EZH2 expression in KYSE30 cells caused significant changes in different genes. Indeed, HIWI and HEY1 genes were over- and underexpressed in KYSE30 cells, respectively, following EZH2 silencing. Other selected cancer stem cell markers were not changed significantly. CONCLUSION: To the best our knowledge, there are variety of small molecule inhibitors to target EZH2 in cancer cells as a treatment candidate; therefore, our data in this study helps the researchers to select EZH2 for cancer therapy based on its mechanism and correlation with other markers.