A newly identified AMSH-family protein is specifically expressed in haploid stages of testicular germ cells

Abstract

Associated Molecule with SH3 domain of STAM (AMSH) plays a critical role in the cytokine-mediated intracellular signal transduction downstream of the Jak2/Jak3-STAM complex. We newly identified a family molecule of AMSH, AMSH-FP ( AMSH-Family Protein) in the mouse brain. AMSH-FP encodes the intracellular protein and has a highly conserved JAB1 Subdomain Homologous (JSH) region, suggesting that AMSH-FP may act as adaptor of gene transcription and/or regulation system. AMSH-FP has two splicing forms, one is expressed in various tissues, whereas the other one is restricted to expression in testis. We named the abundant type AMSH-FPα and the testis type AMSH-FPβ. AMSH-FPβ is a variant lacking N-terminal 166 amino acid residues of AMSH-FPα. Analysis of the 5 ′-untranslated regions in AMSH-FPα and AMSH-FPβ mRNAs and exon–intron structure of AMSH-FP gene suggests that testis-specific transcripts are generated due to alternative promoter usage and/or alternative splicing. Importantly, AMSH-FPβ mRNA was not detected in juvenile and infertile mouse testis but was restrictively expressed in the haploid stage of testicular germ cells in the normal mature testis. We suggested that AMSH-FPβ had a functional role in the spermiogenesis.