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POC1A
POC1 centriolar protein A
POC1A is located on the short (p) arm of chromosome 3, at band 3p21.2. Arm ratio per GRCh38 - banding schematic.
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Overview
POC1A (POC1 centriolar protein A) encodes a component of the centriole, the core structure within the centrosome that orchestrates the mitotic spindle during cell division. The protein is essential for maintaining centriole integrity and ensuring accurate chromosome distribution to daughter cells. Pathogenic variants in POC1A impair centrosome assembly, resulting in a spectrum of developmental abnormalities that primarily affect tissues with high rates of cell division during embryonic growth. These conditions follow an autosomal recessive inheritance pattern, meaning two altered copies of the gene are required for disease manifestation.
What the gene does
The POC1A protein localises to the centriole, where it contributes to the structural scaffold required for microtubule nucleation and organisation. During interphase and mitosis, POC1A helps maintain the cylindrical architecture of the centriole and supports its duplication cycle, ensuring each daughter cell inherits the correct number of centrosomes. The protein's WD repeat domains facilitate protein-protein interactions that anchor other centriolar components, whilst the coiled-coil region enables oligomerisation and structural stability. Research suggests that POC1A cooperates with other centriolar proteins to coordinate the timing of centrosome maturation, which is particularly critical in rapidly dividing cells of the developing brain and skeleton. Loss of POC1A function disrupts spindle pole formation, leading to chromosome segregation errors and reduced proliferative capacity in embryonic tissues.
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Chromosome location
POC1A is located on chromosome 3 at band p21.2, a region on the short arm of the chromosome. The gene spans multiple exons that encode a 407-amino-acid protein. This chromosomal region has been associated with various developmental gene clusters, though POC1A functions independently in centrosome biology.
Protein structure
The POC1A protein comprises 407 amino acids organised into distinct functional domains. Seven tandem WD repeat domains (WD 1 through WD 7) occupy the majority of the protein sequence, spanning amino acids 17 through 308. Each WD repeat typically forms a blade of a beta-propeller structure that mediates protein interactions essential for centriolar assembly. A coiled-coil region extends from amino acids 369 to 397 near the C-terminus, enabling the protein to self-associate and interact with other structural components of the centriole. This domain architecture allows POC1A to serve as a scaffold, recruiting additional proteins required for centrosome maturation and function.
Key variants
Pathogenic variants in POC1A typically result in loss of protein function, impairing the centriole's structural integrity and centrosome duplication cycle. Both missense and truncating variants have been documented, with most affecting the WD repeat domains that mediate critical protein interactions. The severity of clinical features often correlates with the degree of residual protein activity, though individual variation exists. Carrier testing for POC1A variants is relevant for families with a history of severe microcephaly or related skeletal dysplasias.
No pathogenic or likely-pathogenic ClinVar variants recorded yet for this gene.
Associated conditions
Pathogenic variants in POC1A cause autosomal recessive disorders characterised by severe microcephaly, short stature, skeletal abnormalities, and in some cases lipodystrophy. Affected individuals present with reduced head circumference evident at birth or in early infancy, reflecting impaired neuronal proliferation during brain development. Skeletal features may include short ribs, limb abnormalities, and delayed bone maturation. The clinical spectrum ranges from isolated severe microcephaly to multi-system syndromes, depending on the specific variants inherited and their impact on protein function.
No disease links recorded for this gene in our reference set.
Inheritance pattern
Conditions caused by pathogenic POC1A 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
POC1A is included on multiple NHS Genomic Medicine Service gene panels with green classification, indicating strong evidence for clinical validity. The gene appears on the Severe microcephaly panel (R88), Skeletal dysplasia panel (R104), Lipodystrophy - childhood onset panel (R158), and Fetal anomalies panel (R21), reflecting its role in diverse developmental processes. Green status on the DDG2P (Developmental Disorders Genotype-to-Phenotype) database confirms robust gene-disease associations. NHS clinical genetics services may offer diagnostic testing for POC1A when patients present with appropriate clinical features, and carrier screening is available through accredited laboratories for at-risk families.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What inheritance pattern does POC1A follow?
POC1A-related conditions follow an autosomal recessive pattern, meaning an individual must inherit two altered copies of the gene (one from each parent) to develop the associated disorder. Carriers with one altered copy typically show no symptoms.
Can POC1A variants be detected prenatally?
Yes, if pathogenic POC1A variants have been identified in a family, prenatal testing may be available through NHS clinical genetics services or accredited diagnostic laboratories. Severe microcephaly and skeletal abnormalities may also be detected on routine ultrasound scans.
Why is POC1A important for brain development?
The POC1A protein is essential for accurate cell division in the developing brain, where neural progenitor cells undergo rapid proliferation. Defective centrosomes impair chromosome segregation and reduce the number of neurons generated, resulting in severe microcephaly.