RECK AAV Vector (Human)

• AAV9/AAVrh10: commonly used for CNS and systemic delivery (AAV9 can cross the BBB under some conditions)
• AAV8: strong performance in liver-directed expression
• AAV1/AAV6: commonly used for muscle and some lung/immune-related applications
• AAV2: widely used, especially for CNS/retina, but performance depends heavily on cell type and receptor availability

• AAV: low immunogenicity, long-term expression in many systems; limited packaging capacity (~4.7 kb)
• Lentivirus: stable long-term expression due to integration; risk of insertional mutagenesis; generally better for dividing cells
• Adenovirus: high transduction efficiency and larger payload; typically transient expression and higher immune response
• Retrovirus: stable integration but usually limited to dividing cells

• Target cells/tissue: certain systems perform better in specific targets (e.g., AAV commonly used for neurons/CNS, lentivirus often preferred for stable cell line generation)
• Duration of expression:
• Long-term: AAV or lentivirus
• Short-term / transient: adenovirus
• Payload size:
• AAV works best for smaller payloads (≤4.7 kb total genome size)
• larger genes may require alternative strategies (dual AAV, lentivirus, etc.)
• Integration preference: lentivirus integrates; AAV typically remains episomal

• Verify plasmid quality: Confirm the plasmid is intact, at sufficient concentration, and free of contaminants (e.g., salts, ethanol, nucleases).

• Check the host strain: Use a suitable cloning strain (e.g., recA⁻/endA⁻ such as DH5α) and confirm cells are competent and not expired.

• Confirm selection conditions: Make sure the correct antibiotic is used at the proper concentration and that plates/media are fresh.

• Review transformation conditions: Ensure the transformation method (chemical or electrocompetent) and recovery time are appropriate.

• Assess plasmid compatibility: Large, low-copy, toxic, or unstable plasmids may require specialized strains or growth conditions.

• Inspect growth conditions: Verify incubation temperature, shaking speed, and culture time.

• Check plasmid sequence/features: Look for toxic genes, strong promoters, or repeats that may reduce stability.

• Confirm vector delivery: Verify successful transfection or transduction using a reporter, marker, or control vector.

• Check expression at multiple levels: Confirm expression at the RNA level (e.g., transcript detection) as well as protein level, since post-transcriptional regulation may occur.

• Consider cell type effects: CMV promoter activity can vary between cell lines and may be weak or silenced in certain cells.

• Evaluate gene-specific factors: Some genes are toxic, unstable, or tightly regulated, which can reduce detectable overexpression.

• Review culture and timing: Expression levels may depend on cell health, passage number, and time post-delivery.

• Validate construct design: Ensure the insert is in the correct orientation, reading frame, and matches the expected sequence.

Differences between the observed and expected molecular weight are relatively common and can result from several factors, including alternative splicing, post-translational modifications, proteolytic processing, or the presence of fusion tags. In some cases, the antibody may also recognize non-specific proteins.

Basic troubleshooting steps include:

• Confirming the predicted protein size, including any tags or signal peptides.

• Verifying antibody specificity and reviewing the datasheet for known cross-reactivity.

• Checking whether the protein undergoes cleavage or modification in your cell type.

• Comparing expression to a positive control or reference sample.

• Confirming construct sequence and reading frame.

Lack of GFP expression can occur even when delivery appears successful. Expression levels may be influenced by cell type, promoter activity, transduction efficiency, or cellular stress. In some cells, CMV or other strong promoters may be silenced, and high MOI can negatively impact cell health.

Basic troubleshooting steps include:

• Confirming successful delivery using an alternative marker or control construct.

• Assessing cell viability and morphology after transduction.

• Allowing sufficient time post-delivery for expression.

• Evaluating whether the promoter is active in your specific cell line.

• Verifying construct integrity and GFP coding sequence.

Because expression outcomes are highly system-dependent, optimization may be required for each experimental setup.