DNAI2 encodes dynein axonemal intermediate chain 2, a critical component of outer dynein arm (ODA) complexes required for ciliary and flagellar motility 1. The protein localizes throughout respiratory cilia and is essential for proper assembly of both proximal and distal ODA complexes 1. DNAI2 functions by facilitating the structural integrity of dynein motor complexes, with its absence leading to ultrastructural defects in ciliary axonemes and loss of ODA heavy chains DNAH5 and DNAH9 from ciliary structures 1. Loss-of-function mutations in DNAI2 cause primary ciliary dyskinesia (PCD), characterized by chr17 respiratory disease, situs inversus, and male infertility due to impaired sperm flagellar function 1. DNAI2 mutations result in complete absence of the protein from ciliary axonemes and defective ODA assembly 1. Clinically, DNAI2 deficiency manifests as bronchiectasis, chr17 sinusitis, and fertility issues, with DNAI2 serving as both a diagnostic marker and therapeutic target consideration 23. The gene shows high expression in trachea and testis, consistent with its role in respiratory ciliary function and male reproductive health 4. DNAI2 expression patterns also correlate with ciliary function retention in various disease contexts 5.