Date on Master's Thesis/Doctoral Dissertation

5-2015

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Anatomical Sciences and Neurobiology

Degree Program

Anatomical Sciences and Neurobiology, PhD

Committee Chair

McCall, Maureen Ann

Committee Co-Chair (if applicable)

Bickford, Martha E.

Committee Member

Borghuis, Bart

Committee Member

Gregg, Ronald

Committee Member

Krimm, Robin

Committee Member

Lei, Zhenmin

Subject

Retinal ganglion cells; Glycine--Physiological effect; Neurotransmitters

Abstract

In the retina, numerous types of neurons are wired together in a highly specific albeit complex pattern. This sophisticated retinal network allows extraction and encoding of more than 20 representations of the visual scene in its output neurons, the retinal ganglion cells (RGCs). Within the inner plexiform layer (IPL) of retina, glycine receptors (GlyRs) are expressed on different cell classes and modulate RGC visual activity to light onset (ON RGCs) and to light offset (OFF RGCs), for example, their temporal precision and gain control. There are four GlyR alpha subunits (GlyRα1-4) with differential expression patterns in IPL. Each mediates spontaneous inhibitory postsynaptic currents (sIPSCs) with different decay kinetics. Moreover, GlyR alpha subunit-specific expression was discovered across different RGC types. This evidence suggests subunit-specific roles for glycinergic inhibitory circuits to modulate the RGC visual outputs. However, the details remain largely unknown. To investigate glycinergic subunit-specific modulation, I used GlyRα subunit knockout (KO) mouse lines, which lack GlyRα2 (Glra2-/-), GlyRα3 (Glra3-/-) or both (Glra2/3-/-). I found that GlyRα2 and GlyRα3 enhance ON RGCs visual responses whereas only GlyRα2 enhances OFF RGCs visual responses. Second, I used viral tools to manipulate the expression of the GlyRα1 subunit on RGCs to examine its role in visual processing. Adeno-associated viruses (AAVs) were injected into dorsal lateral geniculate nucleus and transported retrogradely to infect RGCs and generate shRNA to selectively knockdown GlyRα1 expression. In OFFαTransient RGCs, which predominantly express GlyRα1, shRNA almost completely eliminated all glycinergic input and I showed that this input increases signal to noise ratio of OFFαTransient RGC visual responses. I expanded our understanding of subunit-specificity by surveying subunit specific expression and currents across eight identified RGCs in the PVcre mouse. By comparing co-localization of GlyR α subunit puncta on identified RGC dendrites with the decay kinetics of their sIPSCs, I showed that there is subunit-specific expression of GlyRs. My data not only support the hypothesis of subunit-specific glycinergic inhibitory modulation in retinal signaling, but provide new tools to further explore their individual roles in shaping RGC visual function.

Download

Share

COinS