Seroatlas · Human Serome Atlas

SPACA9

Sperm acrosome-associated protein 9

Also known as: C9orf9, Mast, SACA9_HUMAN

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

Protein identityUniProt · HPA

UniProt accession: Q96E40
Gene: SPACA9
Ensembl: ENSG00000165698
Chromosome: 9
Canonical length: 222 aa
Protein class: Predicted intracellular proteins
Subcellular location: Vesicles,Cytosol,End piece

OverviewNCBI Gene

Enables microtubule binding activity. Involved in axoneme assembly. Located in axonemal microtubule. [provided by Alliance of Genome Resources, Jul 2025]

Canonical amino-acid sequenceUniProt

222 residues, UniProt reviewed canonical sequence.

>Q96E40|SPACA9
     1  MNEVKESLRS IEQKYKLFQQ QQLTFTAALE HCRENAHDKI RPISSIGQVQ SYMEHYCNSS
    61  TDRRVLLMFL DICSELNKLC QHFEAVHSGT PVTNNLLEKC KTLVSQSNDL SSLRAKYPHD
   121  VVNHLSCDEA RNHYGGVVSL IPLILDLMKE WIAHSEKLPR KVLQHVSEPQ AHQESTRGAA
   181  RPAQAIGTQP RATKHKCRQL TKASLKPRGC SKPPWRPPGG KL

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against SPACA9 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): 0.41
Highest tissue expression: 125 nTPM

Expression across tissuesHPA

Tissue

testis: 125 nTPM
epididymis: 70 nTPM
fallopian tube: 37 nTPM
choroid plexus: 18 nTPM
hypothalamus: 18 nTPM
basal ganglia: 17 nTPM

Single-cell type

late spermatids: 2,904 nCPM
early spermatids: 2,419 nCPM
late primary spermatocytes: 637 nCPM
epididymal principal cells: 258 nCPM
respiratory ciliated cells: 227 nCPM
fallopian tube ciliated cells: 130 nCPM

Immune cell

NK-cell: 4.4 nTPM
basophil: 4 nTPM
memory B-cell: 3 nTPM
naive B-cell: 2.6 nTPM
T-reg: 2 nTPM
eosinophil: 1.9 nTPM

Brain region

midbrain: 29 nTPM
spinal cord: 27 nTPM
medulla oblongata: 25 nTPM
hypothalamus: 22 nTPM
white matter: 21 nTPM
choroid plexus: 20 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): 1.62
gnomAD pLI: 0
DepMap mean gene effect: -0.08
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 acrosome-associated protein 9
Sperm acrosome-associated protein 9

KeywordsUniProt

InteractionsUniProt · HPA

Protein binding partners of SPACA9 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 SPACA9 as an antibody target. Whether an autoantibody or antibody against SPACA9 could matter depends on whether native SPACA9 is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

SPACA9 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.

Annotation status

The present source text does not explicitly label SPACA9 as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

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