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SELENOI
selenoprotein I
SELENOI is located on the short (p) arm of chromosome 2, at band 2p23.3. Arm ratio per GRCh38 - banding schematic.
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Overview
SELENOI belongs to the selenoprotein gene family, a group of approximately 25 human genes that encode proteins containing the rare amino acid selenocysteine. Selenocysteine is sometimes called the 21st amino acid because it is incorporated into proteins through a specialised translation mechanism rather than being added after protein synthesis.
Selenoproteins collectively contribute to antioxidant defence, thyroid hormone metabolism, immune function, and other cellular processes. Whilst some selenoproteins such as glutathione peroxidases and thioredoxin reductases have well-characterised functions, the specific biological role of selenoprotein I is not yet fully understood. Research into this protein continues as scientists work to elucidate the complete functional repertoire of the selenoprotein family.
What the gene does
Selenoprotein I is expressed in various human tissues, suggesting it may perform a housekeeping function in cellular metabolism. The presence of selenocysteine in its sequence indicates that the protein likely participates in redox reactions, as selenium-containing active sites are particularly suited to catalysing oxidation-reduction processes.
The exact substrates and binding partners of selenoprotein I have not been definitively established. Some evidence suggests potential involvement in lipid metabolism or membrane-associated processes, but these hypotheses require further experimental validation. Like other selenoproteins, the activity of selenoprotein I may depend on adequate dietary selenium intake, as selenium deficiency can impair selenoprotein synthesis. The protein's expression levels may be regulated in response to cellular selenium status, a common feature among selenoprotein family members.
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Chromosome location
SELENOI is located on the short arm of chromosome 2 at position 2p23.3. This chromosomal region contains numerous genes involved in diverse cellular functions. The genomic structure of SELENOI, including its exon count and total span, has not been comprehensively detailed in standard reference databases. Like all selenoprotein-encoding genes, SELENOI contains a UGA codon that is normally a stop signal but is recoded to incorporate selenocysteine through a specialised mechanism involving a stem-loop structure in the 3' untranslated region of the mRNA.
Protein structure
Domain architecture has not been experimentally characterised in detail for this protein. The defining structural feature of selenoprotein I is the presence of at least one selenocysteine residue, which distinguishes it from the more common cysteine-containing proteins. Selenocysteine incorporation occurs co-translationally and requires specialised machinery including SECIS-binding protein 2 and selenocysteine-specific elongation factor. The three-dimensional structure of selenoprotein I has not been resolved experimentally, limiting detailed knowledge of its active site configuration and substrate-binding regions.
Key variants
Genetic variation in SELENOI has not been extensively studied in the context of human disease. As with other genes, single nucleotide changes, small insertions or deletions, and larger structural variants can occur throughout the gene. The clinical significance of most SELENOI variants remains uncertain due to limited functional studies and disease association data. Variants affecting the selenocysteine codon or the SECIS element required for selenocysteine incorporation would be expected to disrupt protein function, though specific examples have not been widely reported in clinical genetics literature.
Sample of pathogenic variants
4 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.
| Variant (HGVS) | Protein change | Classification | Evidence | Associated condition |
|---|---|---|---|---|
c.126G>A | p.Lys42= | Pathogenic | - | Spastic paraplegia 81, autosomal recessive |
c.134C>T | p.Pro45Leu | Pathogenic | - | Spastic paraplegia 81, autosomal recessive |
c.335G>C | p.Arg112Pro | Pathogenic | - | Spastic paraplegia 81, autosomal recessive |
c.732-2A>G | - | Pathogenic | - | Spastic paraplegia 81, autosomal recessive |
Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.
Associated conditions
SELENOI is not currently associated with any well-defined inherited conditions in major clinical genetics databases. Unlike some other selenoprotein genes where loss of function causes recognisable syndromes, pathogenic variants in SELENOI have not been conclusively linked to human disease phenotypes. This may reflect genuine tolerance to reduced selenoprotein I levels, functional redundancy with other proteins, or simply insufficient research into rare variants in this gene. As genomic sequencing becomes more widespread, the relationship between SELENOI variation and human health may become clearer.
No disease links recorded for this gene in our reference set.
UK clinical status
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What makes selenoproteins different from other proteins?
Selenoproteins contain the amino acid selenocysteine, which incorporates selenium into the protein structure. This rare amino acid is inserted during protein synthesis through a specialised mechanism that recodes a stop codon, distinguishing selenoproteins from the vast majority of human proteins.
Is SELENOI tested in clinical genetic screening?
SELENOI is not currently included in standard clinical genetic screening panels in the UK or elsewhere. The gene has not been associated with recognised inherited conditions that would warrant routine testing in clinical practice.
How does dietary selenium affect selenoprotein function?
Adequate dietary selenium is required for selenoprotein synthesis, as selenium must be obtained from the diet. Severe selenium deficiency can impair the production of selenoproteins, though the human body prioritises synthesis of certain selenoproteins over others when selenium is limited.