The solute carrier SLC7A1 may act as a protein transporter at the blood-brain barrier

Restricting lysine normalizes toxic catabolites associated with ALDH7A1 deficiency in cells and mice

Lysine metabolism converges at α-aminoadipic semialdehyde dehydrogenase (ALDH7A1). Rare loss-of-function mutations in ALDH7A1 cause a toxic accumulation of lysine catabolites, including piperideine-6-carboxylate (P6C), that are thought to cause fatal seizures in children unless strictly managed with dietary lysine reduction. In this study, we perform metabolomics and expression analysis of tissues from Aldh7a1-deficient mice, which reveal tissue-specific differences in lysine metabolism and other metabolic pathways. We also develop a fluorescent biosensor to characterize lysine transporter activity and identify competitive substrates that reduce the accumulation of lysine catabolites in ALDH7A1-deficient HEK293 cells. Lastly, we show that intravenous administration of lysine α-oxidase from Trichoderma viride reduces lysine and P6C levels by >80% in mice. Our results improve our understanding of lysine metabolism and make inroads toward improving therapeutic strategies for lysine catabolic disorders.

Different gene expression patterns between mouse and human brain pericytes revealed by single-cell/nucleus RNA sequencing

AIMS

Pericytes in the brain play important roles for microvascular physiology and pathology and are affected in neurological disorders and neurodegenerative diseases. Mouse models are often utilized for pathophysiology studies of the role of pericytes in disease; however, the translatability is unclear as brain pericytes from mouse and human have not been systematically compared. In this study, we investigate the similarities and differences of brain pericyte gene expression between mouse and human. Our analysis provides a comprehensive resource for translational studies of brain pericytes.

METHODS

We integrated and compared four mouse and human adult brain pericyte single-cell/nucleus RNA-sequencing datasets derived using two single-cell RNA sequencing platforms: Smart-seq and 10x. Gene expression abundance and specificity were analyzed. Pericyte-specific/enriched genes were assigned by comparison with endothelial cells present in the same datasets, and mouse and human pericyte transcriptomes were subsequently compared to identify species-specific genes.

RESULTS

An overall concordance between pericyte transcriptomes was found in both Smart-seq and 10x data. 206 orthologous genes were consistently differentially expressed between human and mouse from both platforms, 91 genes were specific/up-regulated in human and 115 in mouse. Gene ontology analysis revealed differences in transporter categories in mouse and human brain pericytes. Importantly, several genes implicated in human disease were expressed in human but not in mouse brain pericytes, including SLC6A1, CACNA2D3, and SLC20A2.

CONCLUSIONS

This study provides a systematic illustration of the similarities and differences between mouse and human adult brain pericytes.

Overcoming Barriers in Glioblastoma-Advances in Drug Delivery Strategies

The world of cancer treatment is evolving rapidly and has improved the prospects of many cancer patients. Yet, there are still many cancers where treatment prospects have not (or hardly) improved. Glioblastoma is the most common malignant primary brain tumor, and even though it is sensitive to many chemotherapeutics when tested under laboratory conditions, its clinical prospects are still very poor. The blood-brain barrier (BBB) is considered at least partly responsible for the high failure rate of many promising treatment strategies. We describe the workings of the BBB during healthy conditions and within the glioblastoma environment. How the BBB acts as a barrier for therapeutic options is described as well as various approaches developed and tested for passing or opening the BBB, with the ultimate aim to allow access to brain tumors and improve patient perspectives.