Seroatlas · Human Serome Atlas

FNDC9

Fibronectin type III domain-containing protein 9

Also known as: C5orf40, FNDC9_HUMAN, MGC27121

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

Protein identityUniProt · HPA

UniProt accession: Q8TBE3
Gene: FNDC9
Ensembl: ENSG00000172568
Chromosome: 5
Canonical length: 224 aa
Protein class: Predicted membrane proteins

OverviewNCBI Gene

Predicted to be located in membrane. [provided by Alliance of Genome Resources, Jul 2025]

Canonical amino-acid sequenceUniProt

224 residues, UniProt reviewed canonical sequence.

>Q8TBE3|FNDC9
     1  MNIEVGNISY TGAIISWSSS EPCLEDYYHI MYRPNWNSIF SGYLRYSFHH EEKVPRTISS
    61  VVLEHLAPST LYFLCISCKK AAFPYRHYCT MFHTLDKSPL APGSSLVDPQ ISLWVLMAIL
   121  LACFTAVLAF ICLQFWCVRC HEPRWSYRAG HMEEANGLVR WPEEAPDLGQ REEDLQGLPL
   181  VEMPRKNSRD GAELDPEANQ DAPDAGALQR GGGDPPAILP HCGE

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against FNDC9 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: Unknown
Secreted: No
Transmembrane segments: 1
Mean surface accessibility (rSASA): 0.53
Highest tissue expression: 27 nTPM

Expression across tissuesHPA

Tissue

hypothalamus: 27 nTPM
basal ganglia: 16 nTPM
cerebral cortex: 11 nTPM
pituitary gland: 11 nTPM
cerebellum: 8.3 nTPM
adrenal gland: 4.5 nTPM

Single-cell type

other brain neurons: 13 nCPM
brain inhibitory neurons: 3.9 nCPM
brain excitatory neurons: 3.2 nCPM
loop of henle epithelial cells: 1.9 nCPM
renal collecting duct principal cells: 1.3 nCPM
renal collecting duct intercalated cells: 0.7 nCPM

Immune cell

gdT-cell: 0.2 nTPM
naive CD8 T-cell: 0.2 nTPM
eosinophil: 0.1 nTPM
memory CD8 T-cell: 0.1 nTPM
basophil: 0 nTPM
classical monocyte: 0 nTPM

Brain region

hypothalamus: 84 nTPM
cerebral cortex: 23 nTPM
midbrain: 20 nTPM
medulla oblongata: 19 nTPM
cerebellum: 17 nTPM
pons: 16 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): 1.35
gnomAD pLI: 0.01
gnomAD missense Z: 0.03
DepMap mean gene effect: -0.02
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

Cellular components

membrane

Protein domainsUniProt · Pfam · InterPro

KeywordsUniProt

Antibody and autoantibody relevanceSeroatlas analysis

Seroatlas reads FNDC9 as an antibody target. Whether an autoantibody or antibody against FNDC9 could matter depends on whether native FNDC9 is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

FNDC9 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 FNDC9 as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

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