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PPP2R1A
protein phosphatase 2 scaffold subunit Aalpha
PPP2R1A encodes the alpha isoform of the scaffolding subunit for protein phosphatase 2A, a critical enzyme complex regulating cellular signalling and development. The PPP2R1A gene provides instructions for making a structural component of the PP2A enzyme, one of the most abundant phosphatases in human cells.
PPP2R1A is located on the long (q) arm of chromosome 19, at band 19q13.41. Arm ratio per GRCh38 - banding schematic.
Explore chromosome 19 in the library →Overview
PPP2R1A encodes the alpha isoform of the regulatory A subunit of protein phosphatase 2A (PP2A), a major serine/threonine phosphatase that reverses the action of protein kinases throughout the cell. The protein functions as a scaffold, bringing together catalytic and regulatory components to form functional PP2A complexes that control cell cycle progression, signal transduction, and neuronal development.
The gene is located on chromosome 19 and provides instructions for a 589 amino acid protein that assembles into heterotrimeric complexes with diverse regulatory subunits. Pathogenic variants in PPP2R1A follow an autosomal dominant inheritance pattern and impair the formation or stability of PP2A complexes, leading to dysregulated phosphorylation signalling during brain development. Clinical recognition of PPP2R1A-related conditions has emerged from exome sequencing studies identifying de novo variants in individuals with intellectual disability and characteristic features.
What the gene does
The PPP2R1A protein serves as the primary structural platform for PP2A enzyme assembly, coordinating the interaction between catalytic and regulatory subunits to create functional phosphatase complexes. PP2A accounts for a substantial proportion of total phosphatase activity in mammalian cells and regulates fundamental processes including cell growth, division, metabolism, and differentiation.
The scaffold subunit binds the catalytic C subunit through its C-terminal region while simultaneously interacting with one of dozens of possible regulatory B subunits through its N-terminal and middle regions. This combinatorial assembly allows cells to generate PP2A complexes with distinct substrate specificities and subcellular localisations, enabling precise control of phosphorylation-dependent signalling networks. In the developing brain, PP2A complexes regulate neuronal migration, axon guidance, and synapse formation through dephosphorylation of cytoskeletal proteins, receptor tyrosine kinases, and components of major signalling pathways including MAPK and mTOR cascades.
The protein's scaffolding function is essential for maintaining appropriate phosphorylation balance during neurodevelopment, with disrupted complex assembly leading to aberrant activation or suppression of developmental signalling pathways.
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Chromosome location
PPP2R1A is located on the long arm of chromosome 19 at position q13.41, a gene-dense region containing numerous genes involved in cellular regulation and metabolism. The gene spans approximately 85 kilobases of genomic DNA and comprises 15 exons that encode the 589 amino acid scaffold protein. This chromosomal region shows high recombination rates and contains several other genes implicated in neurological function.
Protein structure
The PPP2R1A protein is organised into a distinctive elongated structure composed of fifteen tandem HEAT repeats (HEAT 1 through HEAT 15), each consisting of paired antiparallel alpha helices that stack to form a horseshoe-shaped solenoid structure. The N-terminal region encompassing HEAT 1 through HEAT 10 provides the PP2A subunit B binding interface (amino acids 8-399), allowing association with diverse regulatory subunits that determine substrate specificity.
The C-terminal section provides the PP2A subunit C binding region (amino acids 400-589), encompassing HEAT 11 through HEAT 15 to create a stable association with the catalytic subunit. This modular architecture allows the scaffold to simultaneously coordinate multiple protein-protein interactions required for functional enzyme assembly. The HEAT repeat structure is conserved across species and has been studied extensively using structural biology approaches that have included analysis of how viral proteins interact with the scaffold in laboratory settings-these viral binding studies helped researchers understand the architecture of the protein but are not relevant to human genetic disease mechanisms.
Key variants
Pathogenic variants in PPP2R1A typically arise de novo and cluster in specific regions critical for scaffold function or protein stability. Most disease-causing variants are missense changes that disrupt the HEAT repeat structure or interfere with binding interfaces for catalytic or regulatory subunits, impairing PP2A complex assembly. Loss-of-function variants are also recognised, consistent with haploinsufficiency as a disease mechanism alongside dominant-negative effects from missense variants that disrupt complex assembly. The variant spectrum reflects the dominant negative or haploinsufficient effects of disrupted scaffold function during neurodevelopment.
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.533C>A | p.Thr178Asn | Pathogenic | ★★☆☆ | Houge-Janssens syndrome 2 |
c.536C>A | p.Pro179His | Pathogenic/Likely pathogenic | ★★☆☆ | Houge-Janssens syndrome 2 |
c.536C>T | p.Pro179Leu | Pathogenic | ★★☆☆ | PPP2R1A-related neurodevelopmental disorders |
c.538A>G | p.Met180Val | Pathogenic | ★★☆☆ | Houge-Janssens syndrome 2 |
c.539T>C | p.Met180Thr | Pathogenic/Likely pathogenic | ★★☆☆ | Houge-Janssens syndrome 2 |
c.544C>T | p.Arg182Trp | Pathogenic/Likely pathogenic | ★★☆☆ | Houge-Janssens syndrome 2 |
c.545G>A | p.Arg182Gln | Pathogenic/Likely pathogenic | ★★☆☆ | Houge-Janssens syndrome 2 |
c.547C>T | p.Arg183Trp | Pathogenic/Likely pathogenic | ★★☆☆ | Houge-Janssens syndrome 2 |
c.548G>A | p.Arg183Gln | Pathogenic/Likely pathogenic | ★★☆☆ | Houge-Janssens syndrome 2 |
c.656C>T | p.Ser219Leu | Pathogenic/Likely pathogenic | ★★☆☆ | Inborn genetic diseases |
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 PPP2R1A cause a neurodevelopmental disorder characterised by intellectual disability, developmental delay, and variable additional features including epilepsy, behavioural difficulties, and distinctive facial characteristics. Affected individuals typically present in early childhood with global developmental delay and hypotonia, with the degree of intellectual impairment ranging from mild to profound. The condition follows an autosomal dominant pattern, with nearly all cases resulting from de novo variants in the affected individual rather than inheritance from parents. Neurodevelopmental features arise from disrupted PP2A-mediated regulation of signalling pathways essential for normal brain development and synaptic function.
No disease links recorded for this gene in our reference set.
Inheritance pattern
Conditions caused by pathogenic PPP2R1A variants typically follow autosomal dominant inheritance.
Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.
UK clinical status
PPP2R1A appears on multiple NHS Genomic Medicine Service gene panels reflecting its established role in neurodevelopmental conditions. The gene holds a high-confidence classification on the Developmental Disorders Genotype-to-Phenotype (DDG2P) panel with definitive evidence linking variants to developmental phenotypes. It is also included on the Fetal anomalies panel and the Intellectual disability panel, supporting its use in clinical diagnostic testing for individuals presenting with neurodevelopmental concerns or prenatally identified abnormalities. This panel representation reflects consensus among UK clinical genetics professionals regarding the gene's diagnostic utility.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Diet & lifestyle considerations
There are no specific lifestyle modifications known to modify PPP2R1A-related conditions. Management focuses on supportive therapies and educational interventions tailored to individual needs.
Supplement considerations
There are no dietary supplements known to modify PPP2R1A-related conditions. Any supplement use should be discussed with the clinical team managing the individual's care.
Frequently asked questions
How is PPP2R1A inherited?
PPP2R1A-related conditions follow an autosomal dominant pattern, meaning one altered copy of the gene is sufficient to cause the condition. Nearly all affected individuals have a de novo (new) variant that occurred spontaneously, rather than inheriting the variant from a parent.
What does the PPP2R1A protein do?
The PPP2R1A protein functions as a scaffold that assembles the PP2A enzyme complex by bringing together catalytic and regulatory components. This enzyme removes phosphate groups from proteins to control cell signalling, growth, and development, particularly in the developing brain.
Why are PPP2R1A variants associated with intellectual disability?
Pathogenic PPP2R1A variants disrupt the assembly or function of PP2A enzyme complexes, leading to dysregulated phosphorylation signalling during brain development. This disruption affects neuronal migration, synapse formation, and other critical processes required for normal cognitive development.