• SUN5 is a novel regulator of mRNA export in male germ cells, interacting with Nxf1 and Nup93 to facilitate mRNP translocation through the nuclear pore complex.
• Loss of SUN5 leads to nuclear accumulation of poly(A)+ RNA and hnRNPs, causing reduced sperm count, motility, and head-to-tail junction defects, linking SUN5 dysfunction to acephalic spermatozoa syndrome.
• SUN5 functions via the Nxf1-dependent pathway, not the CRM1 pathway, as demonstrated by leptomycin B treatment and knockout studies.
• This study reveals a testis-specific mRNA export mechanism, providing potential therapeutic targets for male infertility and a deeper understanding of spermatogenesis.