CLDN9: Claudin-9 in Hearing and Cancer
Tight junction protein with roles in cochlear function and tumorigenesis
Gene Information Card
| Symbol | CLDN9 |
|---|---|
| Full Name | Claudin 9 |
| Gene Type | protein-coding |
| Chromosomal Location | 16p13.3 |
| NCBI Gene ID | 9080 ncbi.nlm.nih.gov/gene/9080 |
| Ensembl ID | ENSG00000113924 |
| UniProt ID | O95484 |
| OMIM ID | 615799 |
| HGNC ID | 2050 |
| Aliases | claudin-9 |
Description
CLDN9 encodes claudin-9, a member of the claudin family of tight junction proteins. Claudin-9 is essential for the maintenance of the paracellular barrier in epithelial cells, particularly in the inner ear where it is required for normal hearing. Mutations in CLDN9 cause autosomal recessive deafness. The protein also plays roles in cell adhesion and signaling, and its dysregulation is implicated in various cancers.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Deafness, autosomal recessive 116 (DFNB116) | Loss-of-function mutations disrupt tight junctions in cochlear hair cells, impairing ion homeostasis and sound transduction. | OMIM, ClinVar |
| Gastric cancer | CLDN9 overexpression promotes cell proliferation and invasion through modulation of tight junction integrity. | NCBI, COSMIC |
| Hepatocellular carcinoma | Upregulation of CLDN9 correlates with poor prognosis and increased metastatic potential. | NCBI, COSMIC |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Liver | 12.3 | Medium |
| Kidney | 8.7 | Medium |
| Inner ear (cochlea) | 5.2 | Low |
| Stomach | 4.1 | Low |
| Lung | 3.5 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HepG2 | 15.6 | Hepatocellular carcinoma cell line |
| MKN45 | 9.8 | Gastric cancer cell line |
| HEK293 | 2.1 | Embryonic kidney cells |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.101C>T (p.Thr34Met) | Missense | Rare | Loss of function; associated with DFNB116 |
| c.167G>A (p.Arg56His) | Missense | Rare | Likely pathogenic; hearing loss |
| c.200_201del (p.Leu67fs) | Frameshift | Rare | Loss of function; deafness |
Mutation functional classification
Loss of Function (LOF)
Missense and frameshift mutations in CLDN9 cause autosomal recessive deafness by disrupting tight junction assembly in the inner ear.
Gain of Function (GOF)
Not well documented; overexpression in cancers may act as a gain-of-function through increased cell proliferation.
Dominant Negative (DN)
No dominant-negative mutations reported for CLDN9.
View complete mutation data：
Gene Ontology (GO)
Pathways
• Tight junction (KEGG: hsa04530)
• Cell adhesion molecules (CAMs) (KEGG: hsa04514)
Protein Summary
Claudin-9 is a 23 kDa transmembrane protein with four helical domains, two extracellular loops, and intracellular N- and C-termini. It polymerizes with other claudins to form tight junction strands that regulate paracellular permeability. In the inner ear, claudin-9 is critical for maintaining the ionic composition of endolymph. In cancer, altered expression disrupts cell polarity and promotes invasion.
Related Services
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| CLDN9 Knockout HEK293 Cell Line | EDJ-KQ3825 | Human | 9080 | Details Get a Quote |
| CLDN9 Knockout HeLa Cell Line | EDJ-KQ55076 | Human | 9080 | Details Get a Quote |
| CLDN9 Knockout A-549 Cell Line | EDJ-KQ63556 | Human | 9080 | Details Get a Quote |
| CLDN9 Knockout HCT 116 Cell Line | EDJ-KQ72025 | Human | 9080 | Details Get a Quote |
