cDNA cloning and characterization of a human sperm antigen (SPAG6) with homology to the product of the Chlamydomonas PF16 locus

Genomics. 1999 Sep 15;60(3):272-80. doi: 10.1006/geno.1999.5914.


Serum from an infertile male with high-titer anti-sperm antibodies was used to identify a novel human sperm antigen by screening of a testis expression library. The clone, initially designated Repro-SA-1 (HUGO-approved symbol SPAG6), was found to encode a sequence highly enriched in testis. The deduced amino acid sequence of the full-length cDNA revealed striking homology to the product of the Chlamydomonas reinhardtii PF16 locus, which encodes a protein localized to the central pair of the flagellar axoneme. The human gene encodes 1.8- and 2.8-kb mRNAs highly expressed in testis but not in prostate, ovary, spleen, thymus, small intestine, colon, peripheral blood leukocytes, heart, brain, placenta, liver, muscle, kidney, and pancreas. The gene was mapped to chromosome 10p11.2-p12. Antibodies raised against SPAG6 sequences localized the protein to the tails of permeabilized human sperm. Both the Chlamydomonas protein and SPAG6 contain eight contiguous armadillo repeats, which place them in a family of proteins known to mediate protein-protein interactions. The cloning of the human homologue of the Chlamydomonas PF16 locus provides a new avenue to explore the role of the axoneme central pair in human sperm function.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Algal Proteins*
  • Amino Acid Sequence
  • Animals
  • Antibodies / blood
  • Antigens / chemistry
  • Antigens / genetics
  • Antigens / immunology
  • Chlamydomonas / genetics
  • Chlamydomonas reinhardtii / genetics
  • Clone Cells
  • Cloning, Molecular
  • Conserved Sequence
  • DNA / biosynthesis
  • Databases, Factual
  • Gene Expression
  • Gene Library
  • Humans
  • Immune Sera
  • Immunohistochemistry
  • In Situ Hybridization, Fluorescence
  • Infertility, Male / blood
  • Infertility, Male / genetics
  • Infertility, Male / immunology
  • Male
  • Microtubule Proteins / chemistry
  • Microtubule Proteins / genetics*
  • Microtubule Proteins / immunology
  • Molecular Sequence Data
  • Phylogeny
  • RNA / analysis
  • Recombinant Proteins / immunology
  • Sequence Homology, Amino Acid
  • Spermatozoa / chemistry*
  • Spermatozoa / immunology*
  • Testis / chemistry
  • Tissue Distribution


  • Algal Proteins
  • Antibodies
  • Antigens
  • Immune Sera
  • Microtubule Proteins
  • Recombinant Proteins
  • SPAG6 protein, human
  • RNA
  • DNA

Associated data

  • GENBANK/AF079363