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MCOLN1
mucolipin TRP cation channel 1
The MCOLN1 gene provides instructions for mucolipin-1, a protein crucial for normal lysosomal function and cellular recycling within the body. The MCOLN1 gene is responsible for producing the mucolipin-1 protein, which plays a key role in the transport of lipids and proteins within cellular compartments called lysosomes and endosomes.
MCOLN1 is located on the short (p) arm of chromosome 19, at band 19p13.2. Arm ratio per GRCh38 - banding schematic.
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Overview
The MCOLN1 gene encodes the mucolipin-1 protein, a type of transient receptor potential (TRP) cation channel. This protein is primarily located in the membranes of lysosomes and endosomes, which are organelles vital for cellular waste processing and recycling. Understanding the function of MCOLN1 is important for comprehending the mechanisms behind certain inherited disorders.
Mutations in MCOLN1 are associated with mucolipidosis type IV, a rare inherited condition. This gene is classified as autosomal recessive, meaning a person must inherit two altered copies of the gene (one from each parent) to develop the condition.
What the gene does
The mucolipin-1 protein, encoded by the MCOLN1 gene, functions as a cation channel embedded within the membranes of lysosomes and endosomes. While the exact ions it transports are still under investigation, its role involves facilitating the movement of positively charged atoms across these membranes. This channel activity is critical for the proper trafficking of fats (lipids) and proteins between these compartments, which are essential for cellular digestion and recycling processes.
Mucolipin-1 is thought to be important for the development and maintenance of the brain and the retina, the light-sensitive tissue at the back of the eye. It also appears to be significant for the normal function of stomach cells responsible for producing digestive acids.
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Chromosome location
The MCOLN1 gene is situated on chromosome 19, specifically at position 19p13.2. This location refers to the short arm of chromosome 19, within band 13.2. Humans have two copies of chromosome 19, inheriting one from each parent.
Protein structure
The mucolipin-1 protein is composed of 580 amino acids and features several distinct functional regions and motifs. The N-terminal region, spanning amino acids 1-38, is classified as disordered. A Dileucine motif, located at amino acids 11-16, is involved in targeting the protein to lysosomes. Another region (amino acids 42-62) facilitates interaction with phosphoinositides. An extracellular/lumenal pore loop is found between amino acids 107-121, while a selectivity filter is present from amino acids 469-474. The region from amino acids 565-567 is essential for palmitoylation and membrane association. Finally, a Dileucine internalization motif, located at amino acids 573-578, mediates AP2 complex-dependent internalisation.
Key variants
Genetic variations within the MCOLN1 gene can impact the structure and function of the mucolipin-1 protein. These changes, known as pathogenic variants or mutations, can lead to the production of a non-functional protein or prevent its production entirely. The severity and specific symptoms of associated conditions can vary depending on the nature and location of these genetic alterations.
Sample of pathogenic variants
10 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.
| Variant (HGVS) | Protein change | Classification | Evidence | Associated condition |
|---|---|---|---|---|
c.1005G>A | p.Trp335Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Mucolipidosis type IV |
c.1627C>T | p.Gln543Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Mucolipidosis type IV |
c.327C>G | p.Tyr109Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Mucolipidosis type IV |
c.499C>T | p.Gln167Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Lisch epithelial corneal dystrophy |
c.608del | p.Pro203fs | Pathogenic/Likely pathogenic | ★★☆☆ | Mucolipidosis type IV |
c.777+1G>T | - | Pathogenic/Likely pathogenic | ★★☆☆ | Mucolipidosis type IV |
c.832C>T | p.Gln278Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Mucolipidosis type IV |
c.871C>T | p.Gln291Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Lisch epithelial corneal dystrophy |
c.878-2A>G | - | Pathogenic/Likely pathogenic | ★★☆☆ | Mucolipidosis type IV |
c.95dup | p.Pro33fs | Pathogenic/Likely pathogenic | ★★☆☆ | Mucolipidosis type IV |
Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.
Associated conditions
Mutations in the MCOLN1 gene are known to cause Mucolipidosis IV, an inherited lysosomal storage disorder. This condition is characterised by the accumulation of certain substances within lysosomes due to impaired cellular recycling. The disease typically affects the nervous system and eyes, leading to developmental delays, intellectual disability, and progressive vision impairment. It is inherited in an autosomal recessive pattern.
Inheritance pattern
Conditions caused by pathogenic MCOLN1 variants typically follow autosomal recessive inheritance.
When both parents are carriers, each child has a 25% chance of being affected, 50% of being a carrier, and 25% of being unaffected.
UK clinical status
The MCOLN1 gene is included in several NHS England Genomic Medicine Service national test panels, indicating its clinical significance within the UK. It is listed as 'green' on panels such as DDG2P, Foetal anomalies (R21), Inherited white matter disorders, Intellectual disability, Leukodystrophy, adult onset (R62), Likely inborn error of metabolism (R98), Lysosomal storage disorder (R276), Mucopolysaccharideosis, Gaucher, Fabry, Retinal disorders (R32), and Undiagnosed metabolic disorders, and White matter disorders and cerebral calcification - childhood onset. This indicates that MCOLN1 is a gene for which there is strong evidence of association with disease and is routinely analysed in these clinical contexts.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What is the primary function of the MCOLN1 gene?
The MCOLN1 gene provides instructions for the mucolipin-1 protein, which acts as a cation channel in the membranes of lysosomes and endosomes, crucial for cellular waste processing and material transport.
What condition is associated with mutations in MCOLN1?
Mutations in the MCOLN1 gene are associated with Mucolipidosis IV, an autosomal recessive lysosomal storage disorder affecting neurological development and vision.
How is Mucolipidosis IV inherited?
Mucolipidosis IV is inherited in an autosomal recessive pattern, meaning an individual must inherit two altered copies of the MCOLN1 gene, one from each parent, to develop the condition.
References
- Venugopal B, Mesires NT, Kennedy JC. Chaperone-mediated autophagy is defective in mucolipidosis type IV. Journal of cellular physiology. 2009. PMID: 19117012
- Ruivo R, Anne C, Sagné C. Molecular and cellular basis of lysosomal transmembrane protein dysfunction. Biochimica et biophysica acta. 2009. PMID: 19146888
- Puertollano R, Kiselyov K. TRPMLs: in sickness and in health. American journal of physiology. Renal physiology. 2009. PMID: 19158345
- Vergarajauregui S, Oberdick R, Kiselyov K. Mucolipin 1 channel activity is regulated by protein kinase A-mediated phosphorylation. The Biochemical journal. 2008. PMID: 17988215
- Miedel MT, Rbaibi Y, Guerriero CJ. Membrane traffic and turnover in TRP-ML1-deficient cells: a revised model for mucolipidosis type IV pathogenesis. The Journal of experimental medicine. 2008. PMID: 18504305
- Vergarajauregui S, Connelly PS, Daniels MP. Autophagic dysfunction in mucolipidosis type IV patients. Human molecular genetics. 2008. PMID: 18550655
- Vergarajauregui S, Puertollano R. Mucolipidosis type IV: the importance of functional lysosomes for efficient autophagy. Autophagy. 2008. PMID: 18635948
- Dong XP, Cheng X, Mills E. The type IV mucolipidosis-associated protein TRPML1 is an endolysosomal iron release channel. Nature. 2008. PMID: 18794901
- Adam MP, Bick S, Mirzaa GM. Mucolipidosis IV. 1993. PMID: 20301393