Masaki et al. 2009 — Col11a2 deletion reveals the molecular basis for TM mechanical anisotropy
CORRECTION NOTE: The STRC topic file originally cited “Masaki K et al. 2009 PLOS One 4:e4877” for TM Young’s modulus 24–210 kPa. That DOI (10.1371/journal.pone.0004877) and journal (PLoS One) belong to Gavara & Chadwick 2009, a different paper measuring TM fiber modulus using AFM + modeling. The actual Masaki 2009 paper is this one (Biophys J, PMID 19486694) on Col11a2 knockout TM mechanics. The 24–210 kPa Young’s modulus values attributed to “Masaki 2009” require re-sourcing — they may originate from Gavara & Chadwick 2009 or another measurement.
TL;DR. Masaki et al. used Col11a2-knockout mice (lacking collagen XI, which organizes radial TM fibrils) to show collagen XI is responsible for TM mechanical anisotropy: KO reduces radial shear impedance 5.5 ± 0.8 dB, longitudinal 3.3 ± 0.3 dB; anisotropy ratio (radial:longitudinal) drops from 1.8 to 1.0. Hearing thresholds elevated 30–50 dB.
Key finding. Collagen XI organizes radial fibrils which confer direction-dependent stiffness: radial direction is ~1.8× stiffer than longitudinal in wild-type. This is the molecular origin of the anisotropy that Ghaffari 2007 and Gueta 2008 measured mechanically.
Numbers that matter
| Parameter | Value | Units | Source location | Conditions |
|---|---|---|---|---|
| Radial shear impedance reduction (KO vs WT) | 5.5 ± 0.8 | dB | Abstract | Col11a2−/− vs wild-type mouse TM |
| Longitudinal shear impedance reduction (KO vs WT) | 3.3 ± 0.3 | dB | Abstract | Col11a2−/− vs wild-type |
| Radial:longitudinal shear impedance ratio (WT) | 1.8 ± 0.7 | dimensionless | Abstract | Wild-type mouse TM |
| Radial:longitudinal shear impedance ratio (KO) | 1.0 ± 0.1 | dimensionless | Abstract | Col11a2−/− TM (isotropic) |
| Hearing threshold elevation in KO | 30–50 | dB | Abstract | Auditory thresholds |
| Absolute G′ or Young’s modulus | NOT reported | — | — | Only relative changes; no absolute kPa in abstract |
Data not in this paper. The values 24 kPa (apical) and 210 kPa (basal) attributed to “Masaki 2009” in the h02 topic file are NOT from this paper. Those values originate from Gavara & Chadwick 2009 (PLoS One 4:e4877, PMID 19293929), which measured TM fiber modulus by AFM. The topic file citation must be corrected.
Limitations
- Only relative impedance changes reported; no absolute stiffness values in kPa from this paper alone.
- Col11a2 KO may have systemic effects on collagen network; TM changes are the most specific outcome.
- Shear impedance is a different measurement than Young’s modulus; comparing across papers requires care.
Connections
[source]tectorial-membrane — corrects citation error: “Masaki 2009 PLoS One 4:e4877” was wrong journal/paper[see-also]2026-04-25-gavara-2009-tm-collagen-anisotropy-afm — actual source of 24 kPa / fiber modulus values[see-also]2026-04-25-ghaffari-2007-tm-traveling-wave-pnas — G′ measurements these collagen fibers explain[applies]STRC Piezoelectric TM Bioelectronic Amplifier