Cplx4, also known as Complexin 4, is a SNARE complex regulator. It is involved in controlling the speed and Ca(2+) sensitivity of SNARE-mediated synaptic vesicle fusion, especially at retinal ribbon synapses, which are crucial for the transmission of visual information [2,3,4]. It may also be related to the regulation of neurotransmitter release in the auditory pathway, and potentially has a role in lipid biosynthesis and fatty acid composition regulation [1,5]. Mouse models are valuable for studying its function.

In retinal studies using Cplx3/4 double-knockout (DKO) mice, the absence of Cplx4 (along with Cplx3) led to aberrant function and structure of retinal ribbon synapses. There were cooperative and additive perturbing effects on the b-wave amplitude in electroretinographic recordings, disorganization in the outer plexiform layer with spherical free-floating ribbons in photoreceptor terminals, and behavioral deficits indicating vision problems [2]. The DKO also differentially impacted the ON and OFF pathways in the retina, with diminished responses in the cone ON pathway under photopic conditions and reduced ON and OFF response rates and missing high-sensitivity OFF responses under scotopic conditions [6].

In conclusion, Cplx4 is essential for the normal function of retinal ribbon synapses, playing a role in regulating neurotransmitter release and maintaining the proper structure and function of the retina. The study of Cplx4 using gene-knockout mouse models has provided important insights into its role in vision-related biological processes, potentially guiding research in vision-related disease areas.