Seroatlas · Human Serome Atlas

TMEM121

Transmembrane protein 121

Also known as: hole, MGC4659, TM121_HUMAN, TMEM121A

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

Protein identityUniProt · HPA

UniProt accession: Q9BTD3
Gene: TMEM121
Ensembl: ENSG00000184986
Chromosome: 14
Canonical length: 319 aa
Protein class: Predicted membrane proteins
Subcellular location: Cytosol

OverviewNCBI Gene

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

Canonical amino-acid sequenceUniProt

319 residues, UniProt reviewed canonical sequence.

>Q9BTD3|TMEM121
     1  MVLPPPDRRH VCLTTLVIMG SMAVMDAYLV EQNQGPRKIG VCIIVLVGDV CFLLVLRYVA
    61  VWVGAEVRTA KRGYAMILWF LYIFVLEIKL YFIFQNYKAA RRGAADPVAR KALTLLLSVC
   121  VPGLFLLLVA LDRMEYVRTF RKREDLRGRL FWVALDLLDL LDMQASLWEP PRSGLPLWAE
   181  GLTFFYCYML LLVLPCVALS EVSMQGEHIA PQKMMLYPVL SLATVNVVAV LARAANMALF
   241  RDSRVSAIFV GKNVVALATK ACTFLEYRRQ VRDFPPPALS LELQPPPPQR NSVPPPPPPL
   301  HGPPGRPHMS SPTRDPLDT

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against TMEM121 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: 7
Mean surface accessibility (rSASA): 0.38
Highest tissue expression: 12 nTPM

Expression across tissuesHPA

Tissue

cerebral cortex: 12 nTPM
basal ganglia: 11 nTPM
hippocampal formation: 10 nTPM
amygdala: 9.7 nTPM
hypothalamus: 8.1 nTPM
midbrain: 6.9 nTPM

Single-cell type

respiratory ciliated cells: 35 nCPM
fallopian tube ciliated cells: 27 nCPM
oligodendrocyte progenitor cells: 25 nCPM
epididymal principal cells: 24 nCPM
epididymal efferent duct ciliated cells: 23 nCPM
ependymal cells: 18 nCPM

Immune cell

memory B-cell: 2.1 nTPM
memory CD4 T-cell: 1.2 nTPM
MAIT T-cell: 1 nTPM
NK-cell: 0.8 nTPM
naive CD4 T-cell: 0.7 nTPM
gdT-cell: 0.6 nTPM

Brain region

medulla oblongata: 20 nTPM
cerebral cortex: 19 nTPM
midbrain: 18 nTPM
basal ganglia: 18 nTPM
amygdala: 17 nTPM
hippocampal formation: 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): 0.67
gnomAD pLI: 0.59
gnomAD missense Z: 2.73
DepMap mean gene effect: -0.03
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

CECR6/TMEM121 family
CECR6/TMEM121 family
Transmembrane protein 121

KeywordsUniProt

Antibody and autoantibody relevanceSeroatlas analysis

Seroatlas reads TMEM121 as an antibody target. Whether an autoantibody or antibody against TMEM121 could matter depends on whether native TMEM121 is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

TMEM121 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 TMEM121 as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

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