EFHC2 (EF-hand domain containing 2) is an X-linked gene encoding a protein with calcium-binding EF-hand motifs and DM10 domains that functions as a microtubule inner protein in ciliary axonemes. The protein is required for motile cilia beating and flagellar motility [UniProt]. In zebrafish development, EFHC2 plays a crucial role in pronephros segmentation, specifically regulating distal nephron development and multi-ciliated cell formation 1. The gene has been investigated as a candidate for several neurological conditions. A tentative association was found between EFHC2 polymorphisms and juvenile myoclonic epilepsy in German males, particularly the S430Y variant in classical JME cases 2. However, a subsequent Turkish study found no association between the S430Y polymorphism and idiopathic generalized epilepsy 3. EFHC2 variants have also been associated with fear recognition and harm avoidance traits, with one intronic SNP accounting for over 3% of variance in harm avoidance behavior 4. Contiguous deletions involving EFHC2 may contribute to syndromic features, though one case study showed that EFHC2 deletion alone may not cause epilepsy 5. The gene remains a candidate for various neurological and developmental disorders requiring further investigation.