SMIM8 (Q96KF7) review notes

2026-10-03 Tier 2 microprotein review

Identity

• UniProt Q96KF7 SMIM8_HUMAN, 97 aa, PE1; aliases C6orf162, DC18. Disordered, basic/acidic
  N-terminal region (1-24), single predicted helical TM segment (48-70), short C-terminal tail.
  Membrane / single-pass is curator inference (ECO:0000305).
• Family: "Belongs to the SMIM8 family"; Pfam PF14937 DUF4500, InterPro IPR026686 UPF0708,
  PANTHER PTHR14274. No characterized member.
• Expression: HPA "Low tissue specificity" in human (UniProt DR line). In mouse, Smim8 was chosen as a
  testis-enriched gene PMID:34290169. HPA antibody IF (proteinatlas.org JSON, fetched 2026-10-03):
  "Vesicles". Not in GOA, not used.

Literature search

• PubMed SMIM8[tiab] OR C6orf162[tiab] -> 3 hits.
• PMID:34290169 (Asian J Androl 2022): CRISPR knockout of 12 testis-enriched mouse genes including
  Smim8. All were dispensable for male fertility PMID:34290169. The Smim8 line was mated under a different
  caging scheme PMID:34290169. The paper also notes
  PMID:34290169.
• PMID:29986096 (NAR 2018): SMIM8 skeletal muscle mRNA is among 16 "CORE-IS" genes positively
  correlated with improvement in insulin sensitivity PMID:29986096.
  Correlative only. Most of the co-clustering genes are mitochondrial enzymes, which is at least
  consistent with the MitoCoP localization, but this is not evidence of function.
• PMID:38658807 (pig myofiber ceRNA network node): expression-network mention only; not cached.

GOA rows

• mitochondrion (HTP, PMID:34800366 MitoCoP): SMIM8 is in the high-confidence mitochondrial proteome
  defined by quantitative proteomics of purified mitochondria. The only experimental localization in
  GOA. Sub-mitochondrial location unknown. -> ACCEPT.
• membrane (IEA) -> ACCEPT.

Conclusion

Mitochondrial single-pass membrane protein of unknown function. Knockout mice are fertile. No MF/BP,
no NEW terms. core_functions left empty because there is no function to describe; location-only
"core function" would be padding.