PC Gene Analysis
The pyruvate carboxylase (PC) gene is a nuclear-encoded mitochondrial enzyme that catalyzes the conversion of pyruvate to oxaloacetate. It is a key regulatory enzyme in gluconeogenesis, lipogenesis, and maintenance of the tricarboxylic acid cycle through anapleurosis. Human PC is a tetramer composed of identical subunits. Mutations in this gene (PC) have been associated with pyruvate carboxylase deficiency. PC deficiency has been clinically categorized into three major phenotypic subgroups, although there are other variants: Group A (“North American”, or moderate severity) has lactic acidemia and psychomotor retardation. Group B (“European”, or severe infantile form) has a more complex biochemical phenotype, frequently presenting with hypoglycemia, lactic acidosis, ketosis, hyperammonemia, and elevated citrulline, as well as an intracellular redox disturbance. Patients in group B have decreased survival compared to group A, and usually do not survive beyond 3 months of age. Group C may have the biochemical features of pyruvate carboxylase deficiency but have a relatively benign clinical course.
For patients with suspected PC deficiency, PC gene sequence analysis is recommended as the first step in mutation identification. PC Known Familial Mutation Analysis is available for family members when a mutation is identified. PC Prenatal Diagnosis is also available for families who have had a mutation identified or by special arrangement in advance with the director.
Indications for Testing
- Confirmation of a clinical/biochemical diagnosis of pyruvate carboxylase deficiency.
- Targeted mutation analysis for known familial mutations
- Pregnancy known to be at risk for pyruvate carboxylase deficiency and known PC familial mutations.
- Infants: 2-3 mL whole blood in purple top EDTA tube
- Children (>2 years) and adults: 3-4 mL whole blood in purple top EDTA tube
- Amniotic fluid or cultured amniocytes
- Chorionic villi or cultured chorionic villi
Contact laboratory genetic counselors or molecular director for specific sample requirements in advance.
Note: Maternal blood sample is also required for maternal cell contamination studies. Send 3-4 mL purple top EDTA along with prenatal sample.
Cultured skin fibroblasts and frozen tissue remaining from a fresh liver biopsy performed for enzyme analysis may also be used for DNA analysis. Cell line build up is available as is DNA Extract and Store. Enzyme analysis may be arranged directly with the Center for Inherited Disorders of Metabolism
Blood samples stored overnight should be refrigerated or kept cold. Blood samples should never be frozen. Specimens being sent from outside facilities should be packaged with a cold pack according to standard medical safety practices. The specimen should be shipped by overnight priority (scheduled to arrive by Friday morning at the latest).
Center for Human Genetics Laboratory
10524 Euclid Avenue, Sixth Floor
Cleveland, OH 44106
For local samples, please call Client Service (216-844-5227) to arrange for sample pick-up.
PC Sequencing – three weeks
PC Known Familial Mutation analysis – one week
PC Prenatal Diagnosis – one week
PC Gene Sequencing: 81406
PC Prenatal Analysis: 81406
PC Known Familial Mutation Analysis: 81403
Please submit a completed Molecular Requisition for each sample.