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PLCB1
phospholipase C beta 1
PLCB1 encodes phospholipase C beta 1, an enzyme critical for cellular signalling pathways in the brain and nervous system. The PLCB1 gene provides instructions for making phospholipase C beta 1, a signalling enzyme particularly important in brain development and function.
PLCB1 is located on the short (p) arm of chromosome 20, at band 20p12.3. Arm ratio per GRCh38 - banding schematic.
Explore chromosome 20 in the library →Overview
PLCB1 is located on chromosome 20 and encodes phospholipase C beta 1, an enzyme that plays a fundamental role in transmitting signals within cells. The protein is particularly abundant in the brain, where it helps convert chemical messages received at the cell surface into internal responses that regulate neuronal activity and development.
Pathogenic variants in PLCB1 follow an autosomal recessive inheritance pattern, meaning affected individuals carry two altered copies of the gene. These variants impair the enzyme's ability to process cellular signals effectively, leading to disrupted brain function. The gene is included in UK clinical genomics panels for epilepsy and intellectual disability, reflecting its importance in neurodevelopmental conditions.
What the gene does
Phospholipase C beta 1 functions as a signal transduction enzyme that breaks down phosphatidylinositol 4,5-bisphosphate (PIP2), a lipid molecule embedded in cell membranes. When certain receptors on the cell surface are activated by external signals, they trigger PLCB1 to cleave PIP2 into two important messenger molecules: inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG).
These messenger molecules then activate distinct downstream pathways. IP3 prompts the release of calcium ions from internal cellular stores, whilst DAG activates protein kinase C enzymes that modify other proteins through phosphorylation. Together, these cascades regulate fundamental cellular processes including gene expression, neuronal excitability, and synaptic plasticity. In the developing and mature nervous system, PLCB1-mediated signalling is essential for establishing proper neuronal connections and maintaining balanced brain activity.
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Chromosome location
PLCB1 is positioned on the short arm of chromosome 20 at band p12.3. The gene spans multiple exons that encode a 1,216-amino-acid protein. This chromosomal region contains several genes involved in developmental processes, though PLCB1 itself is the primary contributor to neurological phenotypes mapped to this locus.
Protein structure
The PLCB1 protein comprises 1,216 amino acids organised into several functional domains. The PI-PLC X-box domain (amino acids 316-467) and PI-PLC Y-box domain (amino acids 540-656) together form the catalytic core responsible for cleaving PIP2. Between these two catalytic domains lies a disordered region (amino acids 469-534) that may provide structural flexibility.
The C2 domain (amino acids 656-786) mediates calcium-dependent membrane binding, positioning the enzyme at the cell membrane where its substrate resides. Additional disordered regions are found at amino acids 834-891, 963-994, 1071-1095, and 1173-1216. These intrinsically disordered segments likely contribute to regulatory interactions with other signalling proteins, allowing the enzyme to respond dynamically to cellular conditions.
Key variants
Pathogenic variants in PLCB1 are typically loss-of-function changes that reduce or eliminate enzyme activity. Most reported variants are missense substitutions affecting critical residues within the catalytic domains, though nonsense and frameshift variants have also been identified. Because the condition follows autosomal recessive inheritance, affected individuals carry pathogenic variants in both copies of the gene, whilst parents who carry a single variant typically show no symptoms.
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.2443C>T | p.Arg815Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Developmental and epileptic encephalopathy, 12 |
c.664C>T | p.Arg222Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Developmental and epileptic encephalopathy, 12 |
GRCh37/hg19 20p12.3(chr20:8097725-8586513)x1 | - | Pathogenic | ★☆☆☆ | not specified |
g.(?_8113299)_(8352117_?)del | - | Pathogenic | ★☆☆☆ | Developmental and epileptic encephalopathy, 12 |
g.(?_8696891)_(8698515_?)del | - | Pathogenic | ★☆☆☆ | Developmental and epileptic encephalopathy, 12 |
c.1087del | p.Asp363fs | Pathogenic | ★☆☆☆ | Developmental and epileptic encephalopathy, 12 |
c.1332T>A | p.Tyr444Ter | Pathogenic | ★☆☆☆ | not provided |
c.1612G>T | p.Glu538Ter | Pathogenic | ★☆☆☆ | Developmental and epileptic encephalopathy, 12 |
c.1678dup | p.Arg561fs | Pathogenic | ★☆☆☆ | Developmental and epileptic encephalopathy, 12 |
c.1888+2T>C | - | Pathogenic | ★☆☆☆ | not provided |
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
Two altered copies of pathogenic variants in PLCB1 cause a neurodevelopmental disorder characterised by early-onset epilepsy and intellectual disability. Affected individuals typically present with seizures beginning in infancy or early childhood, often including multiple seizure types that may be difficult to control with standard medications. Developmental delay and intellectual disability are consistent features, with severity varying among individuals.
Additional neurological features can include abnormalities in muscle tone, movement difficulties, and behavioural challenges. Brain imaging may reveal structural changes such as malformations of cortical development or progressive brain volume loss in some cases. The severity and specific combination of features can differ between families and even between affected siblings.
No disease links recorded for this gene in our reference set.
Inheritance pattern
Conditions caused by pathogenic PLCB1 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
PLCB1 holds green classification status on the NHS Genomic Medicine Service Developmental Disorders Genotype-to-Phenotype (DDG2P) panel, indicating strong evidence linking the gene to neurodevelopmental conditions. It also appears with green status on the Early Onset or Syndromic Epilepsy panel (R59) and the Intellectual Disability panel (R29), reflecting its established role in these clinical presentations. Inclusion on these panels means that PLCB1 is routinely analysed when individuals with early-onset epilepsy or unexplained intellectual disability undergo genomic testing through NHS services.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Diet & lifestyle considerations
No specific lifestyle modifications have been shown to modify PLCB1-related conditions. Management focuses on seizure control through appropriate antiepileptic medications and supportive therapies tailored to individual developmental needs.
Supplement considerations
No specific supplements have been shown to modify PLCB1-related conditions. Management focuses on seizure control and supportive therapies rather than nutritional supplementation.
Frequently asked questions
What does PLCB1 do in the brain?
PLCB1 produces an enzyme that helps brain cells respond to chemical signals by generating internal messenger molecules. These messengers regulate calcium release and protein activation, processes essential for normal neuronal communication and development.
How is PLCB1-related epilepsy inherited?
PLCB1-related conditions follow autosomal recessive inheritance, meaning a child must inherit a pathogenic variant from both parents to be affected. Parents who carry one variant alongside one working copy typically do not have symptoms.
Is PLCB1 tested on the NHS?
Yes, PLCB1 is included on NHS Genomic Medicine Service panels for early-onset epilepsy, intellectual disability, and developmental disorders. Clinicians may order genomic testing that includes PLCB1 when an individual's symptoms match these clinical presentations.