Seroatlas · Human Serome Atlas

SPAG8

Sperm-associated antigen 8

Also known as: BS-84, CT142, HSD-1, hSMP-1, SPAG3, SPAG8_HUMAN

Cross-references: UniProt · Ensembl · Human Protein Atlas · GeneCards · NCBI Gene

Protein identityUniProt · HPA

UniProt accession
Q99932
Gene
SPAG8
Ensembl
ENSG00000137098
Chromosome
9
Canonical length
485 aa
Protein class
Predicted intracellular proteins
Subcellular location
Nucleoplasm,Primary cilium,Cytosol,Acrosome,Equatorial segment,Principal piece,End piece

OverviewNCBI Gene

The correlation of anti-sperm antibodies with cases of unexplained infertility implicates a role for these antibodies in blocking fertilization. Improved diagnosis and treatment of immunologic infertility, as well as identification of proteins for targeted contraception, are dependent on the identification and characterization of relevant sperm antigens. The protein encoded by this gene is recognized by sperm agglutinating antibodies from an infertile woman. This protein is localized in germ cells of the testis at all stages of spermatogenesis and is localized to the acrosomal region of mature spermatozoa. This protein interacts with ACT (activator of CREM in testis) and may play a role in CREM (cAMP response element modulator)-ACT-mediated gene transcription during spermatogenesis. This protein may also play a role in spermatogenesis by regulating microtubule formation and cell division. Alternatively spliced variants that encode different protein isoforms have been described but the full-length sequences of only two have been determined. [provided by RefSeq, Jul 2012]

Canonical amino-acid sequenceUniProt

485 residues, UniProt reviewed canonical sequence.

>Q99932|SPAG8
     1  METNESTEGS RSRSRSLDIQ PSSEGLGPTS EPFPSSDDSP RSALAAATAA AAAAASAAAA
    61  TAAFTTAKAA ALSTKTPAPC SEFMEPSSDP SLLGEPCAGP GFTHNIAHGS LGFEPVYVSC
   121  IAQDTCTTTD HSSNPGPVPG SSSGPVLGSS SGAGHGSGSG SGPGCGSVPG SGSGPGPGSG
   181  PGSGPGHGSG SHPGPASGPG PDTGPDSELS PCIPPGFRNL VADRVPNYTS WSQHCPWEPQ
   241  KQPPWEFLQV LEPGARGLWK PPDIKGKLMV CYETLPRGQC LLYNWEEERA TNHLDQVPSM
   301  QDGSESFFFR HGHRGLLTMQ LKSPMPSSTT QKDSYQPPGN VYWPLRGKRE AMLEMLLQHQ
   361  ICKEVQAEQE PTRKLFEVES VTHHDYRMEL AQAGTPAPTK PHDYRQEQPE TFWIQRAPQL
   421  PGVSNIRTLD TPFRKNCSFS TPVPLSLGKL LPYEPENYPY QLGEISSLPC PGGRLGGGGG
   481  RMTPF

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against SPAG8 can act on the native protein depends on physical access: surface and secreted proteins are reachable by circulating antibodies, intracellular proteins usually are not.

Antibody reachability
Intracellular
Secreted
No
Transmembrane segments
0
Mean surface accessibility (rSASA)
0.65
Highest tissue expression
13 nTPM

Expression across tissuesHPA

Tissue

  • fallopian tube: 13 nTPM
  • choroid plexus: 11 nTPM
  • testis: 8.2 nTPM
  • pituitary gland: 1.7 nTPM
  • heart muscle: 1.6 nTPM
  • hippocampal formation: 1.4 nTPM

Single-cell type

  • ependymal cells: 323 nCPM
  • fallopian tube ciliated cells: 181 nCPM
  • respiratory ciliated cells: 172 nCPM
  • late primary spermatocytes: 138 nCPM
  • epididymal efferent duct ciliated cells: 133 nCPM
  • choroid plexus epithelial cells: 103 nCPM

Immune cell

  • basophil: 1.5 nTPM
  • myeloid DC: 1.1 nTPM
  • T-reg: 1 nTPM
  • NK-cell: 0.9 nTPM
  • naive CD8 T-cell: 0.8 nTPM
  • classical monocyte: 0.7 nTPM

Brain region

  • choroid plexus: 33 nTPM
  • midbrain: 11 nTPM
  • medulla oblongata: 7.9 nTPM
  • pons: 4.6 nTPM
  • spinal cord: 4 nTPM
  • hippocampal formation: 2.9 nTPM

Genetic constraint and essentialitygnomAD · DepMap

Does the body need this protein intact? Low LOEUF or a strong DepMap dependency means loss or blockade of the protein is likely to be felt.

gnomAD LOEUF (loss-of-function intolerance)
1.25
gnomAD pLI
0
gnomAD missense Z
0.57
DepMap mean gene effect
-0.16
DepMap dependency class
selective

Cancer expressionTCGA

Across TCGA tumor cohorts, this protein is over-expressed in roughly 4% of surveyed tumor types (aggregate summary; per-cohort expression, alteration, and survival load in the interactive view).

OntologyGO

Biological processes

Molecular functions

Cellular components

Protein domainsUniProt · Pfam · InterPro

  • Sperm-associated antigen 8
  • Cilia- and flagella-associated protein 143

KeywordsUniProt

InteractionsUniProt · HPA

Protein binding partners of SPAG8 in the human serome: UniProt-annotated complex subunits plus reported interactors. Each links to its own Seroatlas record.

Antibody and autoantibody relevanceSeroatlas analysis

Seroatlas reads SPAG8 as an antibody target. Whether an autoantibody or antibody against SPAG8 could matter depends on whether native SPAG8 is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

SPAG8 is annotated as predominantly intracellular. Intracellular proteins are common autoantibody markers, becoming visible to the immune system after cell injury or altered processing, but are usually markers of disease rather than direct drivers.

Source-annotated serology context

The source annotations explicitly mention antibody, autoantibody, autoantigen, or autoimmune context. This is biological context, not study-specific reactivity.

  • The correlation of anti-sperm antibodies with cases of unexplained infertility implicates a role for these antibodies in blocking fertilization.
  • The protein encoded by this gene is recognized by sperm agglutinating antibodies from an infertile woman.

Canonical record: https://seroatlas.com/gene/SPAG8. Study-independent annotations aggregated from UniProt, Human Protein Atlas, PubMed, IEDB, Pfam, InterPro, Gene Ontology, AlphaFold, gnomAD, DepMap, ClinVar, TCGA. Catalog release seroatlas-reviewed-human-uniprot-20260313.

Seroatlas is the reference for exploring autoantibody and antibody serology at the human-protein level: the autoreactome and human serome, multiplex serology (HuProt, HuScan, VirScan, PhIP-Seq).

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