MIP Gene - Major Intrinsic Protein of Lens Fiber

Aquaporin-0: Structure, Function, and Clinical Significance in Cataract Formation

Gene Information Card

Symbol MIP
Full Name Major Intrinsic Protein of Lens Fiber
Gene Type protein-coding
Chromosomal Location 12q13.3
NCBI Gene ID 4284 ncbi.nlm.nih.gov/gene/4284
Ensembl ID ENSG00000135517
UniProt ID P30301
OMIM ID 154050
HGNC ID 7103
Aliases AQP0, LIM1, MP26, MIP26

Description

The MIP gene encodes aquaporin-0 (AQP0), a water channel protein specifically expressed in lens fiber cells. It is the most abundant membrane protein in the lens and is essential for maintaining lens transparency and homeostasis. Mutations in MIP are associated with autosomal dominant congenital cataracts.

Disease Associations

Disease category Pathophysiological mechanism Genomic evidence
Congenital cataract (autosomal dominant) Missense or frameshift mutations disrupt water channel function or protein trafficking, leading to lens opacification ClinVar, OMIM: 154050
Cataract 15 multiple types MIP variants cause various cataract phenotypes including lamellar and pulverulent types OMIM: 601885
Age-related cataract Reduced AQP0 expression or function may contribute to lens aging and opacity NCBI Gene, PubMed

Expression Profile

Tissue Expression
Tissue nTPM level
Lens High High
Eye High High
Brain 0.3 Low
Kidney 0.1 Low
Liver 0.0 Not detected
Cell Line Expression
Cell Line nTPM Notes
ARPE-19 (retinal pigment epithelium) 0.0 Not detected
HUVEC (umbilical vein endothelial) 0.0 Not detected
HEK 293 (embryonic kidney) 0.0 Not detected
Lens epithelial cells (primary) High High expression
Data source：Human Protein Atlas（proteinatlas.org）

Mutations & Variants

Hotspot Mutations
Variant Type Frequency Functional Description
c.97C>T (p.Arg33Cys) Missense Rare Dominant negative; disrupts water permeability
c.413G>A (p.Gly138Asp) Missense Rare Impaired trafficking to cell membrane
c.657delC (p.Gln220Argfs*12) Frameshift Rare Truncated protein; loss of function
c.1A>G (p.Met1Val) Start loss Rare No protein synthesis
Mutation functional classification

Loss of Function (LOF)

Frameshift and start-loss mutations lead to absent or truncated AQP0, reducing water transport and lens fiber cell adhesion.

Gain of Function (GOF)

Not reported for MIP.

Dominant Negative (DN)

Missense mutations (e.g., Arg33Cys, Gly138Asp) produce defective AQP0 that interferes with wild-type channel function, causing dominant cataract.
View complete mutation data：
ClinVar：https://www.clinvar.com/gene/4284
COSMIC：https://cancer.sanger.ac.uk/cosmic/gene/analysis?ln=MIP

Gene Ontology (GO)

• water channel activity (GO:0015250) • transporter activity (GO:0005215)
• plasma membrane (GO:0005886) • integral component of membrane (GO:0016021)
• water transport (GO:0006833) • lens development in camera-type eye (GO:0002088)
• visual perception (GO:0007601)

Pathways

• REACT:14797 – Transport of small molecules
• REACT:15518 – Aquaporin-mediated transport
• KEGG:04970 – Salivary secretion
• KEGG:04976 – Bile secretion

Protein Summary

Aquaporin-0 (AQP0) is a 263-amino acid integral membrane protein with six transmembrane domains. It forms tetramers in lens fiber cell membranes and functions as a water channel, though with lower permeability than other aquaporins. AQP0 also mediates cell-cell adhesion and contributes to lens fiber cell architecture. Its N- and C-terminal domains interact with crystallins and cytoskeletal proteins. Post-translational modifications include phosphorylation and cleavage, which modulate its activity during lens development and aging.

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SPMIP6 Knockout HEK293 Cell Line EDJ-KQ10164 Human 84688 Details Get a Quote
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Displaying Records 1 To 15 Of 110 Records

Reference Databases

NCBI Gene https://www.ncbi.nlm.nih.gov/gene/4284
OMIM https://www.omim.org/entry/154050
HGNC https://www.genenames.org/data/gene-symbol-report/#!/hgnc_id/HGNC:7103
Ensembl https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000135517
UniProt https://www.uniprot.org/uniprot/P30301
ClinVar https://www.ncbi.nlm.nih.gov/clinvar/?term=MIP%5Bgene%5D
COSMIC https://cancer.sanger.ac.uk/cosmic/gene/analysis?ln=MIP
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