Abstract
Purpose :
Brain-derived neurotrophic factor (BDNF) and its high affinity receptor TrkB (also referred as BDNF/NT-3 growth factor receptor) is a major neurotrophic pathway in various tissues. The purpose of this study was to determine whether or not TrkB expresses in the mouse cornea for BDNF based corneal neuron regeneration.
Methods :
Mouse cornea, retina, limbus and choroid/sclera were harvested from C57BL/6J mice for protein lysate and total RNA. Anti-mouse TrkB antibody (AF1494, R&D systems), which recognizes extracellular domains, was used for TrkB detection by western blot. To determine alternative splicing products, 3`RACE (rapid amplification of cDNA ends) was performed using mouse corneal total RNA. Moreover, RT-PCR (reverse transcription polymerase chain reaction) was used to determine respective TrkB mRNA expression.
Results :
While retina showed ~110kDa band of TrkB by western blot, cornea, limbus and choroid/sclera showed ~80kDa band of TrkB, which is less than the calculated molecular weight of full-length TrkB (92kDa). 3`RACE from corneal total RNA reveals an alternative splicing product which terminates translation before transmembrane and tyrosine kinase domains, but still possesses the BDNF binding domain. In this study, we named it soluble form TrkB. RT-PCR confirmed that mouse cornea express only soluble form TrkB mRNA.
Conclusions :
In this study, we found mouse cornea expresses only soluble form TrkB, but not full-length TrkB. Since soluble TrkB lacks a transmembrane domain and tyrosine kinase domains but still possess BDNF binding domains, it is expected to work as an antagonist of BDNF. Therefore, our data suggests BDNF may not be functional in corneal neuron regeneration or soluble TrkB may interfere with it. We will confirm the inhibitory function of the soluble form of TrkB to BDNF and determine if the soluble form of TrkB expresses in human cornea.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.