ALG13
ALG13 Alpha-1,3-Mannosyltransferase
Gene Information Card
| Symbol | ALG13 |
|---|---|
| Full Name | ALG13 alpha-1,3-mannosyltransferase |
| Gene Type | Protein coding |
| Chromosomal Location | Xq23 |
| NCBI Gene ID | 79868 ncbi.nlm.nih.gov/gene/79868 |
| Ensembl ID | ENSG00000101901 |
| UniProt ID | Q9NP73 |
| OMIM ID | 300776 |
| HGNC ID | 19781 |
| Aliases | CDG1S, CXorf45, FLJ23018, MGC138290, MGC138292, dJ337O18.4 |
Description
ALG13 encodes a subunit of the UDP-N-acetylglucosamine transferase complex, which catalyzes the second step of N-linked glycosylation in the endoplasmic reticulum. The protein forms a complex with ALG14 to transfer N-acetylglucosamine from UDP-GlcNAc to dolichol-P-GlcNAc. Mutations in ALG13 cause a congenital disorder of glycosylation type I (ALG13-CDG), characterized by neurological impairment, developmental delay, and seizures.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Congenital disorder of glycosylation type I (ALG13-CDG) | Loss-of-function mutations in ALG13 impair N-glycosylation, leading to underglycosylated proteins and multisystem disease. | ClinVar, OMIM #300884 |
| Epileptic encephalopathy, early infantile | ALG13 missense variants (e.g., p.Asp81Tyr) disrupt enzyme activity, causing severe seizures and developmental delay. | ClinVar, PMID: 23109145 |
| Intellectual disability, X-linked | Hemizygous ALG13 mutations in males result in cognitive impairment due to defective glycosylation. | OMIM #300776 |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Brain | 12.5 | Medium |
| Liver | 8.3 | Low |
| Kidney | 7.1 | Low |
| Testis | 6.9 | Low |
| Heart | 5.4 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HEK 293 | 10.2 | Moderate expression |
| HeLa | 8.7 | Low expression |
| K562 | 6.1 | Low expression |
| SH-SY5Y | 14.3 | Moderate expression |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.241G>A (p.Asp81Tyr) | Missense | Recurrent in ALG13-CDG | Loss of function; reduced glycosylation |
| c.1076C>T (p.Pro359Leu) | Missense | Rare | Impaired enzyme activity |
| c.1A>G (p.Met1Val) | Start loss | Rare | Complete loss of protein |
| c.1285C>T (p.Arg429*) | Nonsense | Rare | Premature truncation, loss of function |
Mutation functional classification
Loss of Function (LOF)
Most ALG13 pathogenic mutations are loss-of-function, leading to reduced or absent mannosyltransferase activity and defective N-glycosylation.
Gain of Function (GOF)
No gain-of-function mutations reported for ALG13.
Dominant Negative (DN)
No dominant-negative mutations reported; ALG13-CDG follows X-linked recessive inheritance.
View complete mutation data：
Gene Ontology (GO)
| • GO:0006486 - protein glycosylation | • GO:0004576 - dolichyl-diphosphooligosaccharide-protein glycotransferase activity |
| • GO:0005789 - endoplasmic reticulum membrane | • GO:0016757 - transferase activity |
| • transferring glycosyl groups | • GO:0006490 - oligosaccharide-lipid intermediate assembly |
Pathways
• KEGG: hsa00510 - N-Glycan biosynthesis
• Reactome: R-HSA-446203 - Asparagine N-linked glycosylation
• Reactome: R-HSA-446219 - Synthesis of dolichyl-phosphate mannose
Protein Summary
ALG13 is a 595-amino acid protein localized to the endoplasmic reticulum membrane. It functions as a non-catalytic subunit of the UDP-GlcNAc: dolichol-P-GlcNAc-1-P transferase complex, essential for the first step of N-glycan assembly. The protein contains a transmembrane domain and interacts with ALG14. Defects in ALG13 cause ALG13-CDG, an X-linked recessive disorder with severe neurological symptoms.
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