STRC Research

ARBITER — Deciphering Enhancers of Hearing Loss Genes — Zhao et al. 2025

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ARBITER — Deciphering Enhancers of Hearing Loss Genes — Zhao et al. 2025

Citation: Zhao, S. et al. (2025). Deciphering enhancers of hearing loss genes for efficient and targeted gene therapy of hereditary deafness. Neuron. DOI: 10.1016/j.neuron.2025.03.023

Authors: Simeng Zhao, Guisheng Zhong (co-corresponding) — iHuman Institute, ShanghaiTech University.

Key Claims

  1. ARBITER workflow: AAV-reporter-based in vivo transcriptional enhancer reconstruction. Delivers synthetic regulatory elements via round window injection into neonatal mouse cochleae, reads out specificity and efficiency by fluorescence imaging. Generalizable to any hearing loss gene.

  2. Slc26a5 (prestin) enhancers: Two conserved non-coding elements (CNEs) in intron 1 and 2 of Slc26a5 — E1 (247 bp) and E2 (525 bp) — collaboratively control OHC-specific prestin expression. Identified by cross-species conservation analysis (9 species).

  3. E1 is a facilitator, not a classic enhancer: E1 alone does not drive expression. It amplifies E2 activity. This is a novel class — “facilitator” elements that boost nearby enhancers without independent activity.

  4. E1 KO: Progressive prestin reduction from P30 onward, worst in basal/middle turns. Hearing loss is progressive, high-frequency first.

  5. E1+E2 double KO: Completely abolishes prestin expression at all ages. OHC structural damage (stereocilia fusion, cell loss) at P30. Profound deafness.

  6. Native E1+E2 in gene therapy is insufficient: OHC-specific but too weak. High dose (5e10 gc) showed only partial rescue in 3/12 mice. Failed to restore ABR thresholds.

  7. B8 synthetic enhancer: Engineered by reassembling the most conserved modules — E1P3×2 + E2P2×2 + E2P3×2. Achieves ~100% OHC transduction in apical, middle, and basal turns. Expression levels match wild-type.

  8. B8 gene therapy result: High-dose AAV-ie-B8-Slc26a5 (5e10 gc) restored hearing in 8/11 Slc26a5−/− mice to wild-type levels. ABR thresholds and DPOAE fully rescued at 16 kHz. ABR wave 1 amplitudes and latencies completely normalized.

  9. Safety: B8 shows no off-target expression in IHCs, vestibular HCs, brain, heart, or liver. No stereocilia morphology changes.

  10. Works in adults: AAV2-B8 drives OHC-specific expression in P30 mice. Clinically relevant since human cochleae are mature at birth.

Methodology

  • Mouse model: Slc26a5 KO via CRISPR base editing. RWI at P3, analysis at P30.
  • AAV-ie vector for neonatal; AAV2 for adult.
  • Readouts: immunofluorescence (prestin, Myo7a), ABR, DPOAE, SEM stereocilia imaging.
  • Module conservation scored by average sequence identity across 9 species; correlated linearly with transduction efficiency.

Key Numbers

  • Native E1+E2: insufficient; only ~3/12 partial rescues at high dose
  • B8 at 5e10 gc: 8/11 ABR rescue, 6/11 DPOAE recovery
  • B8 transduction: ~100% OHC, all cochlear turns
  • AAV-ie CAG: ectopic IHC + vestibular HC expression; no hearing rescue despite prestin protein present

Relevance to STRC

STRC is expressed specifically in OHCs, like prestin. The ARBITER method directly applies to finding STRC enhancers for targeted gene therapy. The lesson here: native regulatory elements can be too weak; engineered synthetic enhancers built from conserved modules can be dramatically more effective. B8-level efficiency in STRC delivery would be the difference between partial and full hearing rescue.

Connections

  • [source] Deciphering enhancers (self) (self)
  • [about] Cochlear Enhancer Engineering
  • [about] OHC-Specific Gene Delivery
  • [about] ARBITER Workflow
  • [see-also] STRC Gene Therapy sphere
  • [see-also] Acoustics sphere

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