FAM20B: Glycosaminoglycan Xylosylkinase and Key Regulator of Proteoglycan Biosynthesis
A comprehensive biomedical resource for FAM20B gene, including genomic annotation, expression, mutations, and associated diseases.
Gene Information Card
| Symbol | FAM20B |
|---|---|
| Full Name | FAM20B, glycosaminoglycan xylosylkinase |
| Gene Type | protein-coding |
| Chromosomal Location | 1q25.2 |
| NCBI Gene ID | 9917 ncbi.nlm.nih.gov/gene/9917 |
| Ensembl ID | ENSG00000116106 |
| UniProt ID | Q9Y6C9 |
| OMIM ID | 611446 |
| HGNC ID | 23140 |
| Aliases | C1orf85, DKFZp686B20100, FLJ10761, GAGXK, GXK, XYLK |
Description
FAM20B (FAM20B, glycosaminoglycan xylosylkinase) encodes a member of the FAM20 family of secreted proteins. The encoded protein functions as a xylosylkinase that phosphorylates the xylose residue in the glycosaminoglycan-protein linkage region of proteoglycans, a critical step in proteoglycan biosynthesis. FAM20B is involved in the regulation of chondroitin sulfate and heparan sulfate chain elongation. Mutations in this gene are associated with skeletal dysplasia and other developmental disorders.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Skeletal dysplasia (e.g., Desbuquois dysplasia type 2) | Loss-of-function mutations impair xylose phosphorylation, disrupting proteoglycan synthesis and cartilage development. | ClinVar, OMIM |
| Short stature and joint laxity | Defective glycosaminoglycan elongation due to FAM20B deficiency leads to abnormal extracellular matrix. | OMIM, PubMed |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Cartilage | nTPM: 12.5 | Medium |
| Bone | nTPM: 8.3 | Medium |
| Heart | nTPM: 6.1 | Low |
| Brain | nTPM: 4.7 | Low |
| Liver | nTPM: 3.2 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| Chondrocytes | nTPM: 15.0 | High expression |
| Osteoblasts | nTPM: 10.2 | Moderate expression |
| Fibroblasts | nTPM: 7.8 | Moderate expression |
| HEK293 | nTPM: 5.5 | Low expression |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.1A>G (p.Met1?) | Missense | Rare | Loss of start codon, likely loss of function |
| c.107C>T (p.Pro36Leu) | Missense | Rare | Impaired kinase activity |
| c.442G>A (p.Gly148Arg) | Missense | Rare | Reduced protein stability |
| c.1000C>T (p.Arg334*) | Nonsense | Rare | Premature truncation, loss of function |
Mutation functional classification
Loss of Function (LOF)
Most reported FAM20B mutations are loss-of-function, leading to reduced or absent xylosylkinase activity and defective proteoglycan biosynthesis.
Gain of Function (GOF)
No gain-of-function mutations have been reported for FAM20B.
Dominant Negative (DN)
No dominant-negative mutations have been described for FAM20B.
View complete mutation data：
Gene Ontology (GO)
| • Golgi membrane (GO:0000139) | • Golgi apparatus (GO:0005794) |
| • protein phosphorylation (GO:0006468) | • phosphotransferase activity (GO:0016773) |
| • peptide cross-linking (GO:0018149) | • glycosaminoglycan metabolic process (GO:0030203) |
| • chondroitin sulfate biosynthetic process (GO:0030206) | • heparan sulfate proteoglycan biosynthetic process (GO:0030207) |
| • metal ion binding (GO:0046872) | • xylosylkinase activity (GO:0050291) |
Pathways
• Proteoglycan biosynthesis (Reactome: R-HSA-1630316)
• Chondroitin sulfate/dermatan sulfate metabolism (Reactome: R-HSA-1793185)
• Heparan sulfate/heparin metabolism (Reactome: R-HSA-1638091)
Protein Summary
FAM20B encodes a 422-amino acid protein (UniProt Q9Y6C9) localized to the Golgi apparatus. It functions as a xylosylkinase that phosphorylates the xylose residue in the tetrasaccharide linkage region of proteoglycans, a prerequisite for proper glycosaminoglycan chain elongation. The protein contains a conserved kinase domain and is essential for normal skeletal development. Loss of function leads to skeletal dysplasias such as Desbuquois dysplasia type 2.
Related Services
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| FAM20B Knockout HEK293 Cell Line | EDJ-KQ2481 | Human | 9917 | Details Get a Quote |
| FAM20B Knockout A-549 Cell Line | EDJ-KQ23053 | Human | 9917 | Details Get a Quote |
| FAM20B Knockout HCT 116 Cell Line | EDJ-KQ23054 | Human | 9917 | Details Get a Quote |
| FAM20B Knockout HeLa Cell Line | EDJ-KQ23055 | Human | 9917 | Details Get a Quote |
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