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POMGNT1
protein O-linked mannose N-acetylglucosaminyltransferase 1 (beta 1,2-)
POMGNT1 is located on the short (p) arm of chromosome 1, at band 1p34.1. Arm ratio per GRCh38 - banding schematic.
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Overview
POMGNT1 is located on chromosome 1 and encodes an enzyme essential for a specific type of protein glycosylation. This modification process is particularly important for the protein alpha-dystroglycan, which helps maintain the structural integrity of muscle fibres and supports normal brain development. When POMGNT1 function is impaired, alpha-dystroglycan cannot be properly modified, leading to muscle weakness and neurological abnormalities.
Pathogenic variants in POMGNT1 are inherited in an autosomal recessive pattern, meaning that affected individuals carry two altered copies of the gene - one inherited from each parent. Carrier screening can identify individuals who carry one pathogenic variant and may be at risk of having affected children if their partner is also a carrier.
What the gene does
The POMGNT1 protein functions as a glycosyltransferase, an enzyme that catalyses the transfer of N-acetylglucosamine (GlcNAc) sugar molecules onto O-linked mannose residues already attached to specific proteins. This enzymatic activity is a critical step in building complex sugar chains called O-mannosyl glycans, which are essential for proper protein function.
The primary substrate for POMGNT1 is alpha-dystroglycan, a cell-surface protein that connects the inside of muscle cells to the surrounding extracellular matrix. By adding GlcNAc residues, POMGNT1 enables the subsequent extension of glycan chains that allow alpha-dystroglycan to bind properly to laminin and other matrix proteins. This glycosylation is essential for maintaining muscle cell membrane stability during contraction and for normal brain development, particularly the migration of neurons and formation of brain structures during foetal development. Without functional POMGNT1, alpha-dystroglycan remains underglycosylated and cannot perform its structural role effectively.
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Chromosome location
POMGNT1 is located on the short arm of chromosome 1 at position 34.1, designated as 1p34.1. The gene spans a genomic region that encodes a protein of 660 amino acids. The chromosomal position places POMGNT1 in a region that can be analysed through standard genetic testing approaches, including next-generation sequencing panels used in clinical diagnostic settings.
Protein structure
The POMGNT1 protein comprises 660 amino acids organised into several functional regions. The structure includes a GG-type lectin domain spanning amino acids 97-258, which is thought to contribute to substrate recognition. The catalytic region extends from amino acids 300-646 and contains the enzymatic machinery responsible for transferring N-acetylglucosamine to O-mannosylated proteins. Within this catalytic region, three specific segments interact directly with O-glycosylated substrate glycoproteins: amino acids 473-481, 506-512, and 600-605. The protein also contains disordered regions at both termini (amino acids 68-96 and 637-660), which may provide flexibility for protein-protein interactions or regulatory functions.
Key variants
Pathogenic variants in POMGNT1 have been identified throughout the gene, including missense variants that alter single amino acids, nonsense variants that introduce premature stop codons, and frameshift variants caused by small insertions or deletions. The severity of the resulting condition often correlates with the degree of residual enzyme activity - variants that completely abolish enzyme function typically lead to more severe phenotypes, while variants that permit some residual activity may result in milder presentations.
No pathogenic or likely-pathogenic ClinVar variants recorded yet for this gene.
Associated conditions
Biallelic pathogenic variants in POMGNT1 cause congenital muscular dystrophy-dystroglycanopathy, a group of conditions characterised by muscle weakness present from birth or early infancy, alongside variable neurological involvement. The phenotypic spectrum ranges from severe forms featuring significant brain and eye malformations to milder presentations with predominantly muscular symptoms. Clinical features may include hypotonia (reduced muscle tone), delayed motor milestones, intellectual disability, structural brain abnormalities such as cerebellar hypoplasia or abnormal cortical development, and eye abnormalities including myopia or retinal changes. The wide range of clinical severity reflects the variable impact of different POMGNT1 variants on enzyme function.
No disease links recorded for this gene in our reference set.
Inheritance pattern
Conditions caused by pathogenic POMGNT1 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
Within the NHS Genomic Medicine Service, POMGNT1 is included on multiple clinical gene panels reflecting its association with diverse phenotypes. The gene holds green (high evidence) classification on panels including Congenital muscular dystrophy, Congenital disorders of glycosylation, Intellectual disability, Early onset or syndromic epilepsy, and Cerebellar hypoplasia. Additional panel memberships include Malformations of cortical development, Retinal disorders, Structural eye disease, Arthrogryposis, Hydrocephalus, Fetal anomalies, and Likely inborn error of metabolism. This extensive panel representation reflects the multisystem nature of POMGNT1-related conditions and ensures that variants in this gene are assessed when patients present with relevant clinical features in NHS diagnostic pathways.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What does it mean to be a carrier of a POMGNT1 variant?
Carriers have one pathogenic variant and one normal copy of POMGNT1. Carriers typically do not have symptoms because the normal copy produces sufficient enzyme activity. However, if both partners in a couple are carriers, each pregnancy has a 25% chance of inheriting two pathogenic variants and being affected.
How is POMGNT1-related muscular dystrophy diagnosed?
Diagnosis typically involves clinical examination, blood tests showing elevated creatine kinase levels, muscle biopsy showing reduced alpha-dystroglycan glycosylation, brain imaging revealing structural abnormalities, and genetic testing to identify pathogenic variants in POMGNT1. A multidisciplinary clinical assessment guides the diagnostic approach.
Are all POMGNT1 variants equally severe?
No, the clinical severity varies depending on the specific variant and how much it reduces enzyme function. Variants that completely eliminate enzyme activity generally cause more severe phenotypes with significant brain involvement, whilst variants allowing some residual function may result in milder muscular presentations with less pronounced neurological features.