PIGB: Phosphatidylinositol Glycan Anchor Biosynthesis Class B
A key enzyme in GPI anchor biosynthesis, associated with inherited glycosylphosphatidylinositol (GPI) biosynthesis defects and neurodevelopmental disorders.
Gene Information Card
| Symbol | PIGB |
|---|---|
| Full Name | Phosphatidylinositol Glycan Anchor Biosynthesis Class B |
| Gene Type | Protein coding |
| Chromosomal Location | 15q21.3 |
| NCBI Gene ID | 9488 ncbi.nlm.nih.gov/gene/9488 |
| Ensembl ID | ENSG00000137869 |
| UniProt ID | Q92521 |
| OMIM ID | 605122 |
| HGNC ID | 8959 |
| Aliases | GPI7, MGC138290, MGC141976 |
Description
PIGB encodes a mannosyltransferase involved in the third step of glycosylphosphatidylinositol (GPI) anchor biosynthesis. The protein localizes to the endoplasmic reticulum and transfers the first mannose residue to the GPI core structure. Defects in PIGB cause autosomal recessive GPI biosynthesis deficiency, leading to intellectual disability, seizures, and dysmorphic features.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| GPI biosynthesis defect 20 (GPIBD20) | Loss-of-function mutations in PIGB impair GPI anchor attachment to cell surface proteins, disrupting signaling and adhesion in neural tissues. | ClinVar, OMIM #618580 |
| Neurodevelopmental disorder with seizures and dysmorphic facies | Biallelic PIGB variants reduce GPI-anchored protein expression, affecting neuronal migration and synaptic function. | PubMed, OMIM |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Brain | 12.5 | Medium |
| Testis | 10.2 | Medium |
| Kidney | 8.9 | Low |
| Liver | 6.3 | Low |
| Heart | 5.1 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HEK293 | 14.0 | High expression in embryonic kidney cells |
| SH-SY5Y | 11.5 | Neuroblastoma line, relevant for neurological studies |
| HepG2 | 7.2 | Hepatocellular carcinoma |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.1A>G (p.Met1?) | Missense/Start loss | Rare | Loss of translation initiation, complete loss of function |
| c.632G>A (p.Arg211Gln) | Missense | Rare | Impaired mannosyltransferase activity |
| c.1075C>T (p.Arg359*) | Nonsense | Rare | Premature stop, nonsense-mediated decay |
Mutation functional classification
Loss of Function (LOF)
Most reported PIGB mutations are loss-of-function, leading to reduced GPI anchor synthesis and cell surface GPI-AP deficiency.
Gain of Function (GOF)
No gain-of-function mutations have been reported for PIGB.
Dominant Negative (DN)
No dominant-negative effects described; disease is autosomal recessive.
View complete mutation data：
Gene Ontology (GO)
| • GPI anchor biosynthetic process (GO:0006506) | • mannosyltransferase activity (GO:0004575) |
| • endoplasmic reticulum membrane (GO:0005789) | • integral component of membrane (GO:0016021) |
Pathways
• GPI anchor biosynthesis (KEGG: hsa00563)
• Metabolism of GPI-anchored proteins (Reactome: R-HSA-162791)
Protein Summary
PIGB is a 578-amino acid transmembrane protein residing in the endoplasmic reticulum. It functions as a mannosyltransferase (EC 2.4.1.-) that adds the first mannose to the GPI lipid core. The protein is essential for proper GPI anchor assembly; deficiency results in incomplete anchors and reduced surface expression of GPI-linked proteins such as CD55 and CD59.
Related Services
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| PIGB Knockout HEK293 Cell Line | EDJ-KQ6606 | Human | 9488 | Details Get a Quote |
| PIGBOS1 Knockout HEK293 Cell Line | EDJ-KQ14760 | Human | 101928527 | Details Get a Quote |
| PIGB Knockout A-549 Cell Line | EDJ-KQ30838 | Human | 9488 | Details Get a Quote |
| PIGB Knockout HCT 116 Cell Line | EDJ-KQ30839 | Human | 9488 | Details Get a Quote |
| PIGB Knockout HeLa Cell Line | EDJ-KQ30840 | Human | 9488 | Details Get a Quote |
| PIGBOS1 Knockout A-549 Cell Line | EDJ-KQ45145 | Human | 101928527 | Details Get a Quote |
| PIGBOS1 Knockout HCT 116 Cell Line | EDJ-KQ45146 | Human | 101928527 | Details Get a Quote |
| PIGBOS1 Knockout HeLa Cell Line | EDJ-KQ45147 | Human | 101928527 | Details Get a Quote |
