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SPINK5
serine peptidase inhibitor Kazal type 5
SPINK5 is located on the long (q) arm of chromosome 5, at band 5q32. Arm ratio per GRCh38 - banding schematic.
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Overview
SPINK5, located on chromosome 5q32, encodes a serine peptidase inhibitor known as LEKTI. This protein plays a critical role in controlling enzyme activity within the outermost layer of skin, where it regulates the natural shedding process and maintains the integrity of the protective barrier that separates the body from environmental threats. LEKTI is also expressed in the thymus, where it contributes to the development and maturation of immune cells.
Pathogenic variants in SPINK5 follow an autosomal recessive inheritance pattern and are primarily associated with Netherton syndrome, a rare condition characterised by severe skin abnormalities, hair defects, and elevated susceptibility to allergic and atopic disorders. The gene's role in epithelial barrier function has made it a focus of research into inflammatory skin conditions and immune dysregulation.
What the gene does
The LEKTI protein functions as a serine peptidase inhibitor, meaning it restrains the activity of enzymes that break down other proteins. Within the epidermis, LEKTI specifically regulates kallikrein-related peptidases, which are serine proteases responsible for degrading the connections between cells in the stratum corneum during normal skin turnover. By modulating these enzymes, LEKTI ensures that skin shedding occurs in a controlled manner, preserving the barrier that protects against water loss, infection, and irritants.
Beyond the skin, LEKTI participates in thymic development, where it influences the maturation of lymphocytes-white blood cells essential for adaptive immunity. The protein also appears to regulate peptidases involved in triggering immune responses, suggesting a broader role in controlling inflammation. Research indicates that LEKTI's inhibitory activity is crucial for preventing excessive protease activity, which can compromise tissue integrity and provoke inappropriate immune activation. Loss of functional LEKTI disrupts this delicate balance, leading to barrier dysfunction and systemic immune abnormalities.
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Chromosome location
SPINK5 is located on the long arm of chromosome 5 at position 5q32. This chromosomal region contains several genes involved in immune function and epithelial biology. The precise genomic context places SPINK5 within a cluster relevant to skin barrier formation and inflammatory response pathways.
Protein structure
The LEKTI protein comprises 1064 amino acids and features an extensive series of Kazal-type inhibitor domains, which are characteristic structural motifs for serine protease inhibitors. The protein contains 12 distinct Kazal-like domains arranged sequentially: Kazal-like 1 (atypical) spans amino acids 28-66, followed by Kazal-like 2 (amino acids 91-153), Kazal-like 3 (amino acids 155-216), Kazal-like 4 (amino acids 219-285), Kazal-like 5 (amino acids 291-352), Kazal-like 6 (amino acids 361-423), Kazal-like 7 (amino acids 431-489), Kazal-like 8 (amino acids 490-551), Kazal-like 9 (amino acids 561-622), Kazal-like 10 (amino acids 626-688), Kazal-like 11 (amino acids 701-757), and Kazal-like 12 (amino acids 768-830).
Interspersed among these structured domains are three disordered regions: amino acids 676-705, 751-775, and 818-849. These flexible segments may facilitate protein processing or interactions with target proteases. Each Kazal-like domain is capable of inhibiting specific serine peptidases, allowing LEKTI to exert broad regulatory control over multiple enzymes simultaneously.
Key variants
At least 70 pathogenic variants in SPINK5 have been identified in individuals with Netherton syndrome. These alterations typically result in a non-functional or absent LEKTI protein, preventing effective control of serine peptidase activity. Variants include missense changes, nonsense mutations, frameshift insertions or deletions, and splice-site alterations that disrupt protein production or stability.
No pathogenic or likely-pathogenic ClinVar variants recorded yet for this gene.
Associated conditions
Pathogenic variants in SPINK5 are primarily associated with Netherton syndrome, a rare autosomal recessive disorder characterised by congenital ichthyosis (scaly skin), a distinctive hair shaft abnormality called trichorrhexis invaginata (bamboo hair), and atopic manifestations including eczema, elevated immunoglobulin E levels, and increased susceptibility to allergies and asthma. The condition results from loss of LEKTI function, which allows uncontrolled protease activity to degrade the connections between skin cells, impairing barrier integrity and triggering chronic inflammation. Some research has also explored associations between SPINK5 polymorphisms and increased risk of atopic disorders in the general population, though these findings require further validation.
Inheritance pattern
Conditions caused by pathogenic SPINK5 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
SPINK5 is included on several NHS Genomic Medicine Service gene panels, reflecting its clinical relevance in the UK healthcare system. The gene appears on the Ichthyosis and erythrokeratoderma panel (R165) and the Palmoplantar keratodermas panel (R166), both with green classification indicating strong evidence for its role in these conditions. It is also listed on the Severe multi-system atopic disease with high IgE panel and the Primary immunodeficiency or monogenic inflammatory bowel disease panel (R15), acknowledging the immune-related manifestations of SPINK5-related disorders. Additionally, SPINK5 was included on the COVID-19 research panel, suggesting potential relevance to immune response and epithelial barrier function in infectious disease contexts.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What is the LEKTI protein and why is it important?
LEKTI is a serine protease inhibitor encoded by SPINK5 that controls enzymes responsible for breaking down connections between skin cells. This regulatory function is essential for maintaining the skin's protective barrier and preventing excessive inflammation. Loss of LEKTI activity leads to uncontrolled enzyme activity, resulting in barrier breakdown and immune dysregulation.
How is Netherton syndrome inherited?
Netherton syndrome follows an autosomal recessive inheritance pattern, meaning an individual must inherit two altered copies of SPINK5 (one from each parent) to develop the condition. Carriers with one pathogenic variant typically show no symptoms but can pass the variant to their children.
Is SPINK5 testing available through the NHS?
Yes, SPINK5 is included on multiple NHS Genomic Medicine Service gene panels, including those for ichthyosis, palmoplantar keratodermas, and severe atopic disease. Testing is typically arranged through specialist dermatology or clinical genetics services when clinical features suggest a SPINK5-related condition.
References
- Hovnanian A. Netherton syndrome: skin inflammation and allergy by loss of protease inhibition. Cell and tissue research. 2013. PMID: 23344365
- D'Alessio M, Fortugno P, Zambruno G. Netherton syndrome and its multifaceted defective protein LEKTI. Giornale italiano di dermatologia e venereologia : organo ufficiale, Societa italiana di dermatologia e sifilografia. 2013. PMID: 23407075
- Zhao LP, Di Z, Zhang L. Association of SPINK5 gene polymorphisms with atopic dermatitis in Northeast China. Journal of the European Academy of Dermatology and Venereology : JEADV. 2012. PMID: 21585560
- Lacroix M, Lacaze-Buzy L, Furio L. Clinical expression and new SPINK5 splicing defects in Netherton syndrome: unmasking a frequent founder synonymous mutation and unconventional intronic mutations. The Journal of investigative dermatology. 2012. PMID: 22089833
- Roelandt T, Thys B, Heughebaert C. LEKTI-1 in sickness and in health. International journal of cosmetic science. 2009. PMID: 19467033
- Liu Q, Xia Y, Zhang W. A functional polymorphism in the SPINK5 gene is associated with asthma in a Chinese Han Population. BMC medical genetics. 2009. PMID: 19534795
- Bitoun E, Chavanas S, Irvine AD. Netherton syndrome: disease expression and spectrum of SPINK5 mutations in 21 families. The Journal of investigative dermatology. 2002. PMID: 11841556
- Sprecher E, Chavanas S, DiGiovanna JJ. The spectrum of pathogenic mutations in SPINK5 in 19 families with Netherton syndrome: implications for mutation detection and first case of prenatal diagnosis. The Journal of investigative dermatology. 2001. PMID: 11511292