Cc2d1a, also known as Freud-1, belongs to a gene family with conserved domains including DM14, a C-terminal helix-loop-helix domain, and a C2 calcium-dependent phospholipid binding domain. It functions as a transcriptional repressor of the serotonin-1A receptor gene and is involved in regulating multiple intracellular signaling pathways, with a particularly strong effect on the NF-κB pathway [4,8]. It also regulates the degradation and signaling of transmembrane receptors like EGFR and TLR4 by interacting with components of the ESCRT-III complex [7].

In gene knockout studies, conditional deletion of Cc2d1a in glutamatergic neurons of mice led to autistic-like features, such as self-injurious repetitive grooming, aberrant social interactions, decreased complexity of apical dendritic arbors, and an increased synaptic excitation/inhibition ratio [2]. Heterozygous Cc2d1a mice showed sex-dependent changes in autophagy markers in the hippocampus and prefrontal cortex, with an overall decrease in autophagy and alterations in the Beclin-1/p62 ratio [3]. Conditional deletion from excitatory neurons of the male mouse forebrain impaired hippocampal synaptic plasticity, cognitive function, and led to anxiety-like behavior, which was related to enhanced basal Rac1 activity [5]. Cc2d1a deletion in male mice also increased irritability-like behavior, associated with reduced oxytocin-expressing neurons in the hypothalamus, and this behavior could be rescued by oxytocin-related treatments [6]. In Xenopus, Drosophila, and patient-derived fibroblasts, loss of cc2d1a led to cardiac heterotaxy, cystic kidneys, and abnormal CSF circulation via defective ciliogenesis [1].

In conclusion, Cc2d1a plays essential roles in neurodevelopment, ciliogenesis, and autophagy. Studies using Cc2d1a KO/CKO mouse models have revealed its significance in various disease conditions, including autism-related disorders, intellectual disability, and ciliopathies. These models have provided valuable insights into the molecular mechanisms underlying these diseases, highlighting the potential of Cc2d1a as a therapeutic target.