Activation of silenced transgene expression in neural precursor cell lines by inhibitors of histone deacetylation

Area of Science:

• Neuroscience
• Gene Therapy
• Cell Biology

Background:

• Ex vivo gene therapy for central nervous system (CNS) disorders shows potential but struggles with long-term transgene expression in grafted cells.
• Immortalized neural progenitor cell lines (HiB5, RN33B) were used to model transgene down-regulation.
• This research addresses the critical need for stable gene expression in neural gene therapy applications.

Purpose of the Study:

• To establish an in vitro model for studying transgene down-regulation in neural progenitor cells.
• To evaluate the efficacy of this model in predicting in vivo gene expression.
• To identify mechanisms that can overcome transgene silencing for improved gene therapy vectors.

Main Methods:

• Neural cell lines were transduced with various green fluorescent protein (GFP) constructs (viral/non-viral) at 33°C.
• In vitro differentiation and cell cycle arrest were induced by culturing cells at 37°C in serum-free media.
• GFP expression was quantified using flow cytometry (FACS); validation involved grafting cells into the rat striatum.

Main Results:

• Transgene (GFP) expression significantly decreased in most cell lines within 3 days of culture at 37°C, mirroring in vivo down-regulation patterns.
• Inhibitors of histone deacetylation, but not DNA methylation inhibitors, reversed GFP silencing in quiescent neural progenitors.
• Reversal of silencing reached up to 308% of control values, indicating epigenetic regulation of transgene expression.

Conclusions:

• Mechanisms controlling host genome transcription are active in regulating transgene expression.
• Vector design for gene therapy must consider these host cell transcription control mechanisms.
• The developed in vitro assay serves as a valuable screening tool for novel gene therapy vectors.