Version history

{
  "session_id": "sess_SDA-BIOMNI-CAS13_PR-d6f415f0",
  "round_number": 1,
  "agent_persona": "persona-theorist",
  "agent_backend": "mini-max",
  "action": "propose",
  "content": "\n\n# Hypotheses: Selective 4R-Tau Silencing via Cas13 RNA Editing\n\n---\n\n## Hypothesis 1: Splice-Site-Adjacent mRNA Targeting\n\n**Title:** *Targeting the Exon 10 5' Splice Site with Cas13-dCas13 to Discriminate 4R vs 3R mRNAs*\n\n**Description:** By designing guide RNAs complementary to the 5' splice site region of exon 10 (nucleotides -6 to +20 relative to the splice junction), Cas13 can specifically bind and cleave 4R-tau mRNA while leaving 3R-tau mRNA intact. The 4R mRNA retains the complete exon 10 splice site context; the 3R mRNA skips this region entirely. This spatial distinction allows preferential 4R knockdown without affecting 3R-tau transcripts.\n\n**Target:** MAPT exon 10 5' splice site sequence (5'-GUAGGG-3' motif)\n\n**Confidence:** 0.65\n> *Basis: Splice sites are highly conserved; off-target risk mitigated by neuron-specific delivery systems. Precedent exists for splice-site targeting in other splicing disorders (e.g., SMA).*\n\n---\n\n## Hypothesis 2: Intron 10 Branch Point/Polypyrimidine Tract Disruption\n\n**Title:** *Selective Disruption of 4R-tau mRNA Stability via Intron 10 Branch Point Sequence Targeting*\n\n**Description:** The branch point adenosine and polypyrimidine tract within intron 10 are essential for the splicing reaction that retains exon 10. Targeting these sequences with Cas13 can interfere with the recognition complex on the nascent pre-mRNA. This disrupts 4R-tau processing *before* mature mRNA export, reducing 4R-tau load while preserving the 3R-tau splicing pathway, which uses different intronic elements.\n\n**Target:** MAPT intron 10 branch point region (~30-40 nucleotides upstream of 3' splice site)\n\n**Confidence:** 0.45\n> *Basis: Mechanistically plausible but indirect; may affect splicing efficiency rather than direct cleavage. Requires high-efficiency Cas13 delivery to nuclear-nascent RNA complexes.*\n\n---\n\n## Hypothesis 3: Alternative Polyadenylation Site Redirected Degradation\n\n**Title:** *Exploiting 4R-Tau-Specific Alternative Polyadenylation Signals for Targeted mRNA Decay*\n\n**Description:** 4R-tau transcripts utilize a distinct polyadenylation signal (AAUAAA variant) within intron 10 that is absent in 3R-tau. Guide RNAs designed to the pre-mRNA region flanking this polyA signal can recruit Cas13 to induce co-transcriptional cleavage and cytoplasmic decay specifically in 4R-tau mRNAs. This leverages endogenous RNA degradation machinery while maintaining splice site integrity.\n\n**Target:** MAPT intron 10 alternative polyadenylation signal (position ~150-200 nt into intron 10)\n\n**Confidence:** 0.55\n> *Basis: Alternative polyA sites in MAPT have been documented (Zhang et al., JBC 2021); targeting offers high specificity but may have variable efficiency depending on 3' end processing kinetics.*\n\n---\n\n## Hypothesis 4: Dual-Guide Cas13 Strategy for Exon 10-Excluded Transcripts\n\n**Title:** *Utilizing Cas13 to Prevent Trans-splicing Events that Generate Aberrant 4R-tau Variants*\n\n**Description:** A subset of pathogenic 4R-tau includes minor splice variants using cryptic exon 10 donor sites. Dual guide RNAs flanking the canonical exon 10 boundaries can simultaneously block cryptic splice site usage and induce RNase-mediated decay of mis-spliced transcripts. This preserves wild-type 3R-tau while eliminating pathologically altered 4R-tau isoforms.\n\n**Target:** MAPT exon 10 flanking regions (5' splice donor: chr17:44074000-44074040; 3' acceptor: chr17:44083500-44083540)\n\n**Confidence:** 0.50\n> *Basis: Cryptic splicing in MAPT has been reported in PSP/C",
  "tokens_used": "882"
}