Genetic heterogeneity of propionic acidemia: Analysis of 15 Japanese patients

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Abstract
Summary Propionic acidemia is an autosomal recessive metabolic disease resulting from a deficiency of propionyl CoA carboxylase (PCC) activity. We have analyzed the molecular heterogeneity of Japanese propionic acidemia patients using anti-human PCC antiserum and cDNA clones coding for the two protein subunits (α and β) of the enzyme. The steady state levels of both α and β subunits of PCC from 15 Japanese patients were determined by Western blot. Three patients had neither α nor β subunits, and the amounts of both α and β subunits were low in 3 other patients. According to our previous data, we classified these 6 patients as having α subunit deficiency. In the remaining 8 patients, α subunits were normal, but the β subunits were aberrant. Two patients had low levels of normal-sized β subunits and 6 had β subunits smaller than normal in size and greatly reduced in quantity. These 8 patients were assigned to the β subunit deficiency category. One patient had apparently normal α and β subunits. We could not determine this patient's primary defect. These data reveal the genetic heterogeneity of molecular defects causing propionic acidemia in the Japanese. Southern blot analysis did not reveal any gross alteration in gene structure when DNA was digested withHindIII,EcoRI andTaqI. However, DNA from 3 β-subunit-deficient patients, when digested withMspI and probed with β PCC cDNA, revealed a unique 2.7-kb band not observed in blots of DNA from any other patient or 15 normal controls. We conclude that this alteredMspI restriction map is the result of a mutation in the β subunit gene of these patients.