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SLC45A2
solute carrier family 45 member 2
SLC45A2 is located on the short (p) arm of chromosome 5, at band 5p13.2. Arm ratio per GRCh38 - banding schematic.
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Overview
The SLC45A2 gene, located on chromosome 5, encodes a membrane-associated transporter protein expressed primarily in melanocytes. These pigment-producing cells synthesise melanin, the molecule that determines the colouration of skin, hair, and eyes, and which also contributes to normal visual development through its presence in the retina. The SLC45A2 protein is thought to play a critical role in maintaining the proper function of melanosomes, the intracellular compartments where melanin is assembled.
Pathogenic variants in SLC45A2 are inherited in an autosomal recessive pattern, meaning that two altered copies of the gene must be present for an individual to develop oculocutaneous albinism type 4. This form of albinism is characterised by reduced pigmentation and associated vision problems. Common variations in the SLC45A2 gene sequence are also associated with normal differences in pigmentation across populations, highlighting the gene's central role in determining human colouration.
What the gene does
The SLC45A2 protein functions as a transmembrane transporter within melanocytes, where it localises to melanosomes. Although the exact function of the SLC45A2 protein is unknown, research suggests the protein facilitates the movement of substrates required for melanin biosynthesis. Melanosomes are lysosome-related organelles that provide the specialised environment for melanin polymerisation, and SLC45A2 appears essential for maintaining the chemical conditions necessary for this process.
The protein is thought to regulate the availability of key metabolites or cofactors that enzymes such as tyrosinase require to convert tyrosine into melanin precursors. By controlling the internal chemistry of melanosomes, SLC45A2 indirectly influences both the quantity and type of melanin produced. Eumelanin, which provides brown and black pigmentation, and pheomelanin, which produces red and yellow tones, both depend on properly functioning melanosomal transport systems. Disruption of SLC45A2 function therefore impairs the entire melanin synthesis pathway, resulting in the hypopigmentation observed in oculocutaneous albinism type 4.
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Chromosome location
SLC45A2 is located on the short arm of chromosome 5 at position 13.2, designated 5p13.2. This chromosomal region contains a cluster of genes involved in various cellular transport and metabolic functions. The genomic locus spans several kilobases and contains multiple exons that are transcribed and spliced to produce the mature messenger RNA template for the SLC45A2 protein.
Protein structure
The SLC45A2 protein comprises 530 amino acids and is predicted to contain multiple transmembrane segments characteristic of solute carrier family members. These membrane-spanning regions enable the protein to integrate into melanosomal membranes and form a transporter complex, allowing it to facilitate the movement of molecules across these biological barriers.
Key variants
More than twenty pathogenic variants in SLC45A2 have been identified in individuals with oculocutaneous albinism type 4. The variant spectrum includes missense changes, nonsense mutations, and small insertions or deletions that disrupt protein function. One particularly common pathogenic variant in Japanese populations involves the substitution of a single amino acid in the protein sequence. Different populations show distinct variant profiles, reflecting both founder effects and the gene's role in normal pigmentation diversity.
No pathogenic or likely-pathogenic ClinVar variants recorded yet for this gene.
Associated conditions
Pathogenic variants in SLC45A2 cause oculocutaneous albinism type 4, an autosomal recessive disorder characterised by reduced melanin production affecting the skin, hair, eyes, and visual system. Individuals with this condition typically present with decreased pigmentation compared to unaffected family members, though the severity can vary. Associated ocular findings include reduced visual acuity, nystagmus (involuntary eye movements), photophobia (light sensitivity), and altered retinal development due to insufficient melanin in ocular tissues during critical developmental periods. The degree of pigmentation can range from minimal to moderate, and some individuals may develop slight pigmentation with age.
No disease links recorded for this gene in our reference set.
Inheritance pattern
Conditions caused by pathogenic SLC45A2 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
SLC45A2 is included on several NHS Genomic Medicine Service gene panels with green (high evidence) classification. The gene appears on the Albinism or congenital nystagmus panel (R39), the Infantile nystagmus panel, the Ocular and oculo-cutaneous albinism panel, and the Pigmentary skin disorders panel (R236). These panel memberships reflect the strong clinical validity of SLC45A2 testing for individuals presenting with features of albinism or unexplained nystagmus. The gene also appears on the Inherited bleeding disorders panel. NHS laboratories use these panels to guide genetic testing strategies for patients referred through clinical genetics services.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What is the inheritance pattern for SLC45A2-related conditions?
Oculocutaneous albinism type 4 is inherited in an autosomal recessive pattern, meaning an affected individual must inherit one pathogenic variant from each parent. Parents who each carry one variant are typically unaffected carriers.
How does SLC45A2 differ from other albinism genes?
SLC45A2 encodes a transporter protein, whereas other albinism genes such as TYR encode enzymes directly involved in melanin synthesis. The clinical presentation of oculocutaneous albinism type 4 can overlap significantly with other albinism types, making genetic testing important for definitive diagnosis.
Can SLC45A2 variants affect only eye pigmentation?
Pathogenic SLC45A2 variants typically affect both cutaneous and ocular pigmentation, as the protein functions in melanocytes throughout the body. However, the degree of pigmentation reduction can vary, and some individuals may have more prominent ocular features than skin involvement.