A human isogenic iPSC-derived cell line panel identifies major regulators of aberrant astrocyte proliferation in Down syndrome.

Astrocytes exert adverse effects on the brains of individuals with Down syndrome (DS). Although a neurogenic-to-gliogenic shift in the fate-specification step has been reported, the mechanisms and key regulators underlying the accelerated proliferation of astrocyte precursor cells (APCs) in DS remain elusive. Here, we established a human isogenic cell line panel based on DS-specific induced pluripotent stem cells, the XIST-mediated transcriptional silencing system in trisomic chromosome 21, and genome/chromosome-editing technologies to eliminate phenotypic fluctuations caused by genetic variation. The transcriptional responses of genes observed upon XIST induction and/or downregulation are not uniform, and only a small subset of genes show a characteristic expression pattern, which is consistent with the proliferative phenotypes of DS APCs. Comparative analysis and experimental verification using gene modification reveal dose-dependent proliferation-promoting activity of DYRK1A and PIGP on DS APCs. Our collection of human isogenic cell lines provides a comprehensive set of cellular models for further DS investigations.

4-Phenylbutyrate ameliorates apoptotic neural cell death in Down syndrome by reducing protein aggregates.

Individuals with Down syndrome (DS) commonly show unique pathological phenotypes throughout their life span. Besides the specific effects of dosage-sensitive genes on chromosome 21, recent studies have demonstrated that the gain of a chromosome exerts an adverse impact on cell physiology, regardless of the karyotype. Although dysregulated transcription and perturbed protein homeostasis are observed in common in human fibroblasts with trisomy 21, 18, and 13, whether and how this aneuploidy-associated stress acts on other cell lineages and affects the pathophysiology are unknown. Here, we investigated cellular stress responses in human trisomy 21 and 13 neurons differentiated from patient-derived induced pluripotent stem cells. Neurons of both trisomies showed increased vulnerability to apoptotic cell death, accompanied by dysregulated protein homeostasis and upregulation of the endoplasmic reticulum stress pathway. In addition, misfolded protein aggregates, comprising various types of neurodegenerative disease-related proteins, were abnormally accumulated in trisomic neurons. Intriguingly, treatment with sodium 4-phenylbutyrate, a chemical chaperone, successfully decreased the formation of protein aggregates and prevented the progression of cell apoptosis in trisomic neurons. These results suggest that aneuploidy-associated stress might be a therapeutic target for the neurodegenerative phenotypes in DS.

Elimination of protein aggregates prevents premature senescence in human trisomy 21 fibroblasts.

Chromosome abnormalities induces profound alterations in gene expression, leading to various disease phenotypes. Recent studies on yeast and mammalian cells have demonstrated that aneuploidy exerts detrimental effects on organismal growth and development, regardless of the karyotype, suggesting that aneuploidy-associated stress plays an important role in disease pathogenesis. However, whether and how this effect alters cellular homeostasis and long-term features of human disease are not fully understood. Here, we aimed to investigate cellular stress responses in human trisomy syndromes, using fibroblasts and induced pluripotent stem cells (iPSCs). Dermal fibroblasts derived from patients with trisomy 21, 18 and 13 showed a severe impairment of cell proliferation and enhanced premature senescence. These phenomena were accompanied by perturbation of protein homeostasis, leading to the accumulation of protein aggregates. We found that treatment with sodium 4-phenylbutyrate (4-PBA), a chemical chaperone, decreased the protein aggregates in trisomy fibroblasts. Notably, 4-PBA treatment successfully prevented the progression of premature senescence in secondary fibroblasts derived from trisomy 21 iPSCs. Our study reveals aneuploidy-associated stress as a potential therapeutic target for human trisomies, including Down syndrome.

Reliability of Total Bilirubin Measurements in Whole Blood from Preterm Neonates Using a Blood Gas Analyzer.

BACKGROUND: Blood gas analyses are usually required more frequently in preterm neonates than in term neonates. If total bilirubin (TB) levels in whole blood measured using a blood gas analyzer are reliable, blood sampling for total serum bilirubin (TSB) levels alone can be reduced in preterm neonates. We investigated the reliability of measuring TB levels in whole blood from preterm neonates using the latest generation blood gas analyzer. METHODS: TB measured on an ABL90 FLEX blood gas analyzer and TSB analyzed in the hospital laboratory were simultaneously analyzed. TB and TSB levels (300 data sets in 85 preterm neonates) were compared using linear regression and Bland-Altman difference plots. RESULTS: Concordance correlation coefficient analysis showed a strong relationship between TB and TSB levels (a CCC value of 0.94) with a Pearson's coefficient of 0.97 and a bias correction of 0.97. Bland-Altman difference p lots demonstrated that, on average, TB tended to underestimate the TSB, with a mean (95% confidence interval) bias of -0.7 (-0.6 to -0.8) mg/dL. CONCLUSIONS: Whole blood TB levels measured using an ABL90 FLEX are reliable and can lead to a reduction in blood sampling for TSB in preterm neonates.