Biology subjects

Bjorklund, T.

Publications and source records attributed to Bjorklund, T..

4 recordsLinked to original sources

bioRxiv2025

Administration of barcoded AAV capsid library to the putamen of non-human primates identifies variants with efficient retrograde transport

Adeno-associated viral vectors have become a leading choice for gene therapy in the central nervous system due to their safety profile, efficient neuronal transduction, and capacity for sustained transgene expression. We previously reported that AAV2-derived capsids developed using the BRAVE (Barcoded Rational AAV Vector Evolution) approach have enhanced retrograde transport properties in the rodent brain, compared to parental AAV2. Retrograde transport enables broader coverage of connected brain regions after a single focal intraparenchymal brain injection and is therefore a powerful tool for delivery of vectors to distant sites with potentially higher specificity, transduction efficacy and safety. Because transport properties can vary among species, we further characterized a barcoded library of 25 BRAVE-derived AAV2 capsid variants, along with the parental AAV2 serotype and benchmark AAV capsids, in brains of adult cynomolgus monkeys after intraputaminal dosing. Based on RNA and DNA amplicon sequencing, single-nucleus RNA sequencing, and histological assessment, we report here capsid variants with enhanced retrograde transport and expression compared to the parental AAV2 capsid. These properties make them potentially useful for disease indications in which broader brain coverage is desirable beyond the injection site.

neuroscience↗

bioRxiv2023

Mutant huntingtin expression in the hypothalamus promotes ventral striatal neuropathology

Huntingtons disease is a fatal neurodegenerative disorder caused by an expanded CAG triplet repeat in the huntingtin (HTT) gene. Previous research focused on neuropathology in the striatum and its association with a typical movement disorder. Direct effects of mutant HTT (mHTT) in the striatum may cause neuropathology, although non-cell autonomous effects have also been suggested. Important non-motor features of HD include psychiatric symptoms and metabolic dysfunction, which may be linked to hypothalamic neuropathology. As hypothalamic neurons project to the ventral striatum, we hypothesized that expression of mHTT in the hypothalamus leads to disrupted neurotransmission in the ventral striatum and causes pathology. The overall aim of this study was to investigate the impact of mHTT expression in the hypothalamus on ventral striatal neuropathology and its contribution to non-HD motor symptoms. We demonstrate that selective expression of mHTT in the hypothalamus leads to the loss of dopamine and cAMP-regulated phosphoprotein (DARPP-32) immunopositive neurons in the ventral striatum in mice. Contrary to the effects of direct expression of mHTT in the hypothalamus, selective overexpression of mHTT in the ventral striatum does not affect body weight. Selective expression of mHTT in the ventral striatum leads to mHTT inclusion formation and loss of DARPP-32 neurons without affecting motor activity or anxiety-like behavior. We show that DARPP-32 neuron loss in the ventral striatum is recapitulated in the R6/2 mouse model of HD. Chemogenetic activation of hypothalamic neurons projecting to the ventral striatum had a blunted response in the R6/2 mice compared to wild-type mice, indicating a disrupted hypothalamus-ventral striatal circuitry. In summary, the expression of mHTT in the hypothalamus may impact the development of ventral striatal pathology in mice. This opens the possibility that non-cell-autonomous effects in the reward circuitry play a role in HD.

neuroscience↗

bioRxiv2021

FRET-based screening in HEK293T identifies p38 MAPK and PKC inhibition as therapeutic targets for α-synuclein aggregation

Aggregation of -synuclein is associated with neurodegeneration and a hallmark pathology in synucleinopathies. These aggregates are thought to function as prion-like particles where the conformation of misfolded -synuclein determines the induced pathologys traits similar to prion diseases. Still, little is known about the molecular targets facilitating the conformation-specific biological effects, but their identification could form the basis for new therapeutic intervention. High-throughput screening (HTS) of annotated compound libraries could facilitate mechanistic investigation by identifying targets with impact on -synuclein aggregation. To this end, we developed a FRET-based cellular reporter in HEK293T cells, with sensitivity down to 6.5 nM -synuclein seeds. Using this model system, we identified GF109203X, SB202190, and SB203580 as inhibitors capable of preventing induction of - synuclein aggregation via inhibition of p38 MAPK and PKC, respectively. Our findings highlight the value HTS brings to the mechanistic investigation of -synuclein aggregation while simultaneously identifying novel therapeutic compounds.

molecular biology↗

bioRxiv2018

Barcoded Rational AAV Vector Evolution enables systematic in vivo mapping of peptide binding motifs

Engineering of Adeno-associated viral (AAV) vector capsids through directed evolution has been used to generate novel capsids with altered tropism and function1-9. This approach, however, involves a selection process that requires multiple generations of screenings to identify real functional capsids2-4. Due to the random nature of this process, it is also inherently unreproducible, and the resulting capsid variants provide little mechanistic insights into the molecular targets engaged. To overcome this, we have developed a novel method for rational capsid evolution named Barcoded Rational AAV Vector Evolution (BRAVE). The key to this method is a novel viral production approach where each virus particle displays a protein-derived peptide on the surface which is linked to a unique barcode in the packaged genome10. Through hidden Markov model-based clustering11, we were able to identify novel consensus motifs for cell-type specific retrograde transport in neurons in vivo in the brain. The BRAVE approach enables the selection of novel capsid structures using only a single-generation screening. Furthermore, it can be used to map, with high resolution, the putative binding sequences of large protein libraries.

neuroscience↗