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NIPAL4
NIPA like domain containing 4
NIPAL4 is located on the long (q) arm of chromosome 5, at band 5q33.3. Arm ratio per GRCh38 - banding schematic.
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Overview
NIPAL4 (NIPA like domain containing 4) is a gene located on chromosome 5 that encodes a transmembrane protein involved in magnesium transport. This protein belongs to a family of transporters that regulate the movement of magnesium ions, which are essential for numerous cellular processes including enzyme function and membrane stability.
Pathogenic variants in NIPAL4 are associated with autosomal recessive congenital ichthyosis, a group of inherited skin disorders characterised by abnormal skin scaling and barrier dysfunction. The gene was identified through research into families with unexplained ichthyosis, revealing that disrupted magnesium homeostasis in skin cells contributes to the characteristic features of the condition. Understanding NIPAL4 function has provided insights into the molecular mechanisms underlying skin barrier formation and maintenance.
What the gene does
The NIPAL4 protein functions as a magnesium transporter, facilitating the movement of magnesium ions across cellular membranes. Magnesium is the second most abundant intracellular cation and serves as a cofactor for hundreds of enzymes, including those involved in DNA synthesis, protein production, and energy metabolism.
In skin tissue, NIPAL4-mediated magnesium transport appears particularly important for keratinocyte differentiation and the formation of the epidermal barrier. Keratinocytes are the predominant cell type in the outer layer of skin, and their proper maturation requires coordinated regulation of ion gradients and enzymatic processes. The protein localises to cellular membranes where it maintains appropriate magnesium concentrations necessary for normal skin cell function.
When NIPAL4 function is compromised, altered magnesium homeostasis disrupts the complex biochemical processes required for normal skin development. This disruption affects the formation of lipid barriers and structural proteins in the stratum corneum, the outermost protective layer of skin, leading to the scaling and barrier defects characteristic of ichthyosis.
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Chromosome location
NIPAL4 is located on the long arm of chromosome 5 at position 5q33.3. This chromosomal region contains numerous genes involved in diverse cellular functions. The precise genomic structure of NIPAL4, including its exon organisation, contributes to the production of a 404-amino-acid protein through standard transcription and translation processes.
Protein structure
Domain architecture has not been experimentally characterised in detail for this protein. The NIPAL4 protein comprises 404 amino acids and is predicted to contain multiple transmembrane segments that enable its function as a membrane-embedded ion transporter. These transmembrane regions allow the protein to span cellular membranes and create a channel or carrier mechanism for magnesium ion passage. Structural predictions suggest the protein adopts a conformation typical of cation transporters, though detailed three-dimensional structural data remain limited.
Key variants
Pathogenic variants in NIPAL4 follow an autosomal recessive inheritance pattern, meaning that affected individuals typically carry two altered copies of the gene, one inherited from each parent. These variants generally disrupt the protein's ability to transport magnesium effectively, either by affecting the transmembrane structure or by altering regions critical for ion binding and translocation. The variant spectrum includes missense changes, nonsense mutations, and small insertions or deletions that result in loss of normal protein function.
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.247C>T | p.Arg83Ter | Pathogenic | ★★☆☆ | NIPAL4-related disorders |
c.341C>A | p.Ala114Asp | Pathogenic/Likely pathogenic | ★★☆☆ | Fetal anomalies with a likely genetic cause |
c.421del | p.Leu140_Ile141insTer | Pathogenic/Likely pathogenic | ★★☆☆ | Autosomal recessive congenital ichthyosis 6 |
c.502G>A | p.Gly168Arg | Pathogenic | ★★☆☆ | Lamellar ichthyosis |
c.703G>A | p.Gly235Arg | Pathogenic | ★★☆☆ | Autosomal recessive congenital ichthyosis 6 |
c.703G>C | p.Gly235Arg | Pathogenic | ★★☆☆ | NIPAL4-related disorders |
g.(?_156887143)_(156899968_?)del | - | Pathogenic | ★☆☆☆ | not provided |
c.139C>T | p.Gln47Ter | Pathogenic | ★☆☆☆ | not provided |
c.318G>A | p.Trp106Ter | Pathogenic | ★☆☆☆ | not provided |
c.586G>A | p.Gly196Arg | Pathogenic | ★☆☆☆ | Autosomal recessive congenital ichthyosis 6 |
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
Pathogenic variants in NIPAL4 cause autosomal recessive congenital ichthyosis, a heterogeneous group of inherited disorders affecting skin cornification. Affected individuals typically present at birth or in early infancy with generalised dry, scaly skin that persists throughout life. The severity can vary depending on the specific variants involved and other genetic or environmental modifying factors. The condition primarily affects skin barrier function, though quality of life can be significantly impacted by the visible skin changes and associated discomfort.
No disease links recorded for this gene in our reference set.
Inheritance pattern
Conditions caused by pathogenic NIPAL4 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
NIPAL4 appears on several NHS Genomic Medicine Service gene panels relevant to inherited skin conditions. The gene holds green (high evidence) classification on the Autosomal recessive congenital ichthyosis panel, the Ichthyosis and erythrokeratoderma panel (R165), and the Palmoplantar keratodermas panel (R166). NIPAL4 is also included on the Fetal anomalies panel (R21) with green status, reflecting its role in conditions that may be detected prenatally or perinatally. These panel inclusions indicate that NIPAL4 testing is considered clinically appropriate within NHS pathways for individuals with relevant clinical presentations.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What inheritance pattern does NIPAL4 follow?
NIPAL4-related conditions follow an autosomal recessive pattern, meaning an individual must inherit two pathogenic variants (one from each parent) to develop the associated ichthyosis. Parents who each carry one variant are typically unaffected carriers.
How does NIPAL4 affect skin health?
NIPAL4 encodes a magnesium transporter important for maintaining proper ion balance in skin cells. When the protein is non-functional, disrupted magnesium homeostasis impairs the normal development and maintenance of the skin barrier, leading to the dry, scaly skin characteristic of ichthyosis.
Is NIPAL4 testing available through the NHS?
Yes, NIPAL4 is included on multiple NHS Genomic Medicine Service panels with high-evidence (green) status, including panels for autosomal recessive congenital ichthyosis and related skin conditions. Testing may be offered to individuals meeting specific clinical criteria through NHS genetics services.