Abstract
Purpose: :
A transmembrane protein, TMEM16A, also called anoctamin 1(ANO1), is a bona fide calcium (Ca2+)-activated chloride (Cl-) channel. It has been known that TMEM16A is mainly expressed in various secretory epithelia and also abundantly expressed in nervous tissues such as retina and dorsal root ganglia. However, information on the TMEM16A/ANO1 expression pattern in the retina at cellular level has not been available. Thus, we examined the expression pattern of TMEM16A/ANO1 and further characterized TMEM16A/ANO1-expressing cells in the mouse retina.
Methods: :
The retinas were isolated from ten-week-old male C57BL/6 mice. Immunohistochemistry with a specific antibody against TMEM16A/ANO1 and double-label immunofluoresence with various retinal neuronal markers were conducted.
Results: :
In the mouse retina, TMEM16A/ANO1 immunoreactivities was found in numerous bipolar and amacrine cells in the inner nuclear layer and some cells in the ganglion cell layer (GCL). Both plexiform layers, the outer plexiform layer (OPL) and the inner plexiform layer (IPL) contained strong immunoreactive puncta. The large amount of immunoreactive puncta in the OPL also showed synaptophysin immunoreactivities and numerous puncta in the IPL were VGLUT1- or PKC-immunoreactive. Some amacrine cells and the cells in the GCL showed GABA immunoreactivities.
Conclusions: :
TMEM16B, a member of the TMEM16 family of transmembrane proteins, is confined to be present in photoreceptor terminals, while TMEM16A/ANO1 is expressed in various retinal neurons of mouse. Especially, strong immunoreactivities were present in two synaptic layers of the retina. This diverse expression pattern of TMEM16A/ANO1 suggests various potential roles including specific synaptic transmission in the retina.
Keywords: retina: distal (photoreceptors, horizontal cells, bipolar cells) • ion channels • retina: proximal (bipolar, amacrine, and ganglion cells)