Changes in mRNA Expression of Class 3 Semaphorins and Their Receptors in the Adult Rat Retino-Collicular System after Unilateral Optic Nerve Injury

Abstract

Increasing interest in the role of Class 3 Semaphorins (Sema3s) in plasticity and repair in the injured mammalian central nervous system prompted us to characterize changes in Sema3 expression after optic nerve (ON) injury. We used unilateral ON transection (ONT) and ON crush (ONC) models in conjunction with quantitative polymerase chain reaction (qPCR), and in situ hybridization (ISH) to characterize postinjury changes in the expression of the Sema3s and their receptors in the rat retina, optic nerve, and superior colliculus (SC). We observed no changes in mRNA expression in axotomized retinas at 1 or 14 days after ONT, but there was a transient increase for Sema3b, Sema3f, L1cam, and Plxna3 at 3 days postinjury. There was no change in transcript expression in the deafferented contralateral SC 1 day following ONT, but there was a transient increase in Plxna2 at 3 days, and a decrease in Sema3e, L1cam, and Plxna4a mRNA levels by 14 days. There were also several changes in transcript expression in the unlesioned contralateral retina and ipsilateral SC that differed from those seen in axotomized retina and contralateral SC. At the injury site after ONC, there was a reduction in Sema3b and Sema3f mRNA at 6 hours, returning to control levels by 1 day, and a transient increase in SEMA3A immunoreactivity at 6 hours. These new data on Class 3 Semaphorins and their receptors provide more information about the complex reactive events that occur bilaterally in the retino-collicular system following unilateral adult ON injury.