May regulate the number of excitatory synapses that are formed on hippocampus neurons. Has no effect on inhibitory synapses (By similarity). May inhibit adipocyte differentiation at an early stage of the process (By similarity). Forms homooligomers, predominantly dimers or trimers. Forms heterooligomers with C1QL1, C1QL2 and C1QL3, when proteins are coexpressed; this interaction does not occur after secretion. Interacts with ADGRB3. Highest expression levels in testis and adipose tissue, lower levels in skeletal muscle and kidney.