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PQBP1
polyglutamine binding protein 1
PQBP1 is located on the short (p) arm of chromosome X, at band Xp11.23. Arm ratio per GRCh38 - banding schematic.
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Overview
PQBP1 (polyglutamine binding protein 1) is located on the X chromosome and encodes a 265-amino acid protein that participates in RNA metabolism within nerve cells. The protein binds to polyglutamine stretches in other proteins and is thought to regulate gene expression during brain development. Pathogenic changes in PQBP1 typically result in X-linked neurodevelopmental disorders, predominantly affecting males due to the gene's chromosomal location. The protein's role in RNA granule function makes it critical for proper neuronal signalling and development.
What the gene does
Polyglutamine-binding protein 1 functions primarily in the processing and cellular transport of RNA molecules. Within neurons, the protein localises to RNA granules, which are specialised structures that store and move RNA throughout the cell. These granules hold RNA molecules until cellular signals determine whether the genetic information should be translated into proteins or degraded. Through this mechanism, PQBP1 helps control gene expression patterns essential for normal brain development. The protein's ability to bind polyglutamine-rich sequences allows it to interact with specific partner proteins, though the complete catalogue of its molecular interactions remains under investigation. Current evidence suggests the protein coordinates multiple steps in RNA metabolism, from nuclear processing to cytoplasmic localisation.
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Chromosome location
PQBP1 is located at chromosomal band Xp11.23 on the short arm of the X chromosome. This X-linked location explains the inheritance pattern observed in associated conditions, where males carrying pathogenic variants typically show more severe manifestations than heterozygous females. The gene's position within a region containing multiple genes involved in neurodevelopment may contribute to the clinical overlap seen among various X-linked intellectual disability syndromes.
Protein structure
The PQBP1 protein contains a WW domain spanning amino acids 46-80, which mediates protein-protein interactions by recognising proline-rich sequences. The protein also features an extensive disordered region from amino acids 94-265, which contains multiple tandem repeat elements. Notably, there are five tandem repeats of approximately seven amino acids each (D-R-[SG]-H-D-K-S pattern) spanning amino acids 104-138. Additional shorter repeats include three tandem repeats of [DE]-R (amino acids 139-144) and seven tandem repeats of [DE]-R (amino acids 150-163). These repetitive sequences and the large intrinsically disordered region likely provide flexibility for multiple protein-protein and protein-RNA interactions.
Key variants
Pathogenic variants in PQBP1 have been identified in families with X-linked intellectual disability syndromes. Most disease-causing changes result in a truncated protein lacking critical functional domains. Frameshift and nonsense variants are common, typically eliminating the C-terminal portion of the protein. Because PQBP1 follows an X-linked pattern, males with a single pathogenic variant generally show clinical manifestations, whilst carrier females may display milder or variable features due to X-inactivation patterns.
No pathogenic or likely-pathogenic ClinVar variants recorded yet for this gene.
Associated conditions
Variants in PQBP1 are primarily associated with Renpenning syndrome, a condition characterised by intellectual disability, microcephaly, short stature, and distinctive facial features. The syndrome occurs almost exclusively in males, reflecting the X-linked inheritance pattern. Additional neurodevelopmental features may include delayed speech development and behavioural challenges. The severity and specific clinical presentation can vary among affected individuals, even within the same family, though intellectual disability remains a consistent feature across cases.
- Renpenning syndrome Dedicated page coming soon
UK clinical status
Within the NHS Genomic Medicine Service, PQBP1 appears on multiple clinical gene panels with green (high evidence) classification. The gene is included in the DDG2P panel for developmental disorders, the Fetal anomalies panel (R21), the Intellectual disability panel (R29), and the Severe microcephaly panel (R88). These panel memberships reflect the gene's established role in neurodevelopmental conditions and support its use in diagnostic genomic testing for individuals presenting with intellectual disability and associated features.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
Why do PQBP1 variants primarily affect males?
PQBP1 is located on the X chromosome. Males have only one X chromosome, so a single pathogenic variant results in complete loss of functional protein. Females have two X chromosomes and typically retain one functional copy, which often provides substantial protection against severe symptoms.
What is the role of RNA granules in neurons?
RNA granules are cellular structures that package and transport RNA molecules within nerve cells. They regulate where and when specific proteins are produced, allowing neurons to respond rapidly to signals by controlling local protein synthesis at synapses and other specialised compartments.
Can PQBP1 variants be detected through standard genetic testing?
Yes, PQBP1 variants can be identified through gene panel testing, exome sequencing, or genome sequencing approaches offered within the NHS for individuals with unexplained intellectual disability or neurodevelopmental concerns. Targeted testing may be recommended based on clinical features and family history.