Developmental expression of α- and β- synuclein in the mouse retina.

The synuclein family comprises three presynaptic proteins-alpha-synuclein (α-Syn), beta-synuclein (β-Syn), and gamma-synuclein (γ-Syn)-which are crucial for synaptic transmission. Our previous studies have detailed the precise cellular and subcellular localization of α- and β-Syn in the adult mouse retina, revealing distinct expression patterns in excitatory and inhibitory synaptic elements. The balance between excitatory and inhibitory neurotransmitters in the inner plexiform layer (IPL) is critical for neural development in the mouse retina. Here, we employed light-microscopic immunocytochemistry to investigate the expression of α- and β-Syn in the developing mouse retina, examining from embryonic day 13.5 to postnatal day 21 (E13.5, E16.5, E19.5, P1, P7, P10, P14, and P21). We revealed distinct developmental expression patterns across these stages. We found that α-Syn was first detected at E13.5, whereas β-Syn expression appeared later at E16.5. After E16.5, β-Syn exhibited a broader expression profile compared to α-Syn. Consistent with findings in the adult retina, α-Syn was confined to inhibitory synapses, while β-Syn was present in both excitatory and inhibitory synapses during development. These unique expression patterns of α- and β-Syn in the developing retina suggest potential roles in modulating excitatory and inhibitory inputs during retinal maturation. Furthermore, this research may contribute to understanding the broader role of α- and β-Syn in neural development within the central nervous system.