ANALYSIS OF PYRUVATE-DEHYDROGENASE EXPRESSION IN EMBRYONIC MOUSE-BRAIN - LOCALIZATION AND DEVELOPMENTAL REGULATION

Brain malformations and neurological dysfunctions are often seen in py ruvate dehydrogenase (PDH) deficient patients. To understand these cli nical presentations, we have analyzed the localization and development al expression of PDH in the embryonic mouse nervous system. Immunostai ning was performed to localize PDH E1alpha protein. PDH activities wer e measured before and after activation. PDH E1alpha mRNA levels were q uantitated by reverse transcriptase-polymerase chain reaction. Abundan t PDH E1alpha protein was localized in the central nervous system and other neural tissues in embryos at embryonic day (E) 11 onwards. The P DH activity was very low in E9 brain and it increased continuously unt il the end of gestation. The proportion of active form of PDH increase d significantly in E15 brain. Analysis of the PDH E1alpha mRNA showed that only the X-linked form of the gene was transcribed. The overall m RNA level of E9 brain was approximately 93% of the adult value. It dec reased gradually during embryogenesis. A large increase took place at the end of gestation. The mRNA level of PDH was approximately 100 time s higher than that of the acetoacetyl-CoA thiolase gene. These results suggest that PDH E1alpha transcripts of E9 brain are not translated a t a high level. The appearance of PDH activity and its increase during E11 and E15 are mainly due to increased levels of translation and act ivation of PDH. Increased PDH activity at the end of gestation is attr ibuted to an increase in transcription. Our data to a large extent exp lain pathological presentations in PDH E1alpha deficient patients with congenital brain disorders.