ATP1A4 encodes the alpha-4 catalytic subunit of the Na+/K+-ATPase, responsible for maintaining electrochemical gradients of sodium and potassium across the plasma membrane through ATP hydrolysis 1. This testis-specific isoform exhibits the most restricted expression pattern among four Na,K-ATPase alpha subunits, being produced almost exclusively in male germ cells 2. ATP1A4 is essential for sperm function, particularly sperm motility and hyperactivation 3. The gene comprises 22 exons and 21 introns, encoding a 1029-1032 amino acid polypeptide that is structurally divergent from other isoforms, especially at the N-terminus 1. Functionally, ATP1A4 maintains proper sperm flagellar morphology through osmotic regulation and structural mechanisms 4. ATP1A4 expression is transcriptionally regulated by cAMP and CREMtau, a testis-specific transcription factor 5. Mutations in ATP1A4 cause male infertility phenotypes including spermatogenic failure and azoospermia. The protein's restricted expression and crucial role in male fertility make ATP1A4 an attractive pharmacological target for non-hormonal male contraception 6.