期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2021
卷号：118
期号：47
DOI：10.1073/pnas.2112749118
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance
Cuticulosomes are subcellular structures located within the inner ear hair cells of a variety of avian species with potential relevance to magnetoreception. Here we apply quantum magnetic microscopy to image the magnetic properties of individual iron cuticulosomes within tissue samples. The magnetic susceptibility of the cuticulosomes was determined by characterizing the stray magnetic field strength as a function of applied magnetic field in two distinct locations of the pigeon inner ear. The measured susceptibilities do not support the particle model of magnetoreception, suggesting the physiological relevance of cuticulosomes lies in iron storage or stabilization of stereocilia. The quantum magnetic imaging method can be applied across a variety of biological systems providing an effective tool to screen for magnetic particle–based magnetoreceptors.
The ability of pigeons to sense geomagnetic fields has been conclusively established despite a notable lack of determination of the underlying biophysical mechanisms. Quasi-spherical iron organelles previously termed “cuticulosomes” in the cochlea of pigeons have potential relevance to magnetoreception due to their location and iron composition; however, data regarding the magnetic susceptibility of these structures are currently limited. Here quantum magnetic imaging techniques are applied to characterize the magnetic properties of individual iron cuticulosomes in situ. The stray magnetic fields emanating from cuticulosomes are mapped and compared to a detailed analytical model to provide an estimate of the magnetic susceptibility of the individual particles. The images reveal the presence of superparamagnetic and ferrimagnetic domains within individual cuticulosomes and magnetic susceptibilities within the range 0.029 to 0.22. These results provide insights into the elusive physiological roles of cuticulosomes. The susceptibilities measured are not consistent with a torque-based model of magnetoreception, placing iron storage and stereocilia stabilization as the two leading putative cuticulosome functions. This work establishes quantum magnetic imaging as an important tool to complement the existing array of techniques used to screen for potential magnetic particle–based magnetoreceptor candidates.
