Trinucleotide repeat expansion in the beta 1 subunit of the sodium pump inmanic-depression illness: a negative study

Background: Trinucleotide repeats have become a recognized molecular abnorm ality in a variety of neuropsychiatric conditions. Bipolar illness has been purported to be a possible trinucleotide repeat-associated disease. Since abnormalities in the expression and regulation of the sodium- and potassium -activated adenosine triphosphatase (Na,K-ATPase) have been documented in b ipolar patients and since the pi subunit of this pump contains a heterogeno us GCC repeat, we decided to investigate the possibility of a repeat expans ion in beta 1 subunit of Na,K-ATPase in bipolar patients. Methods: DNA from postmortem temporal cerebral cortex tissue of five bipolar subjects and fi ve matched normal controls and five lyumphoblastoid cells lines from the Ol d Order Amish bipolar pedigrees and match normal controls were used for thi s study. The GCC rich region of beta 1 DNA was amplified by polymerase chai n reaction (PCR) and sequenced. Results: The range of GCC repeat in the bet a 1 gene is between 7 and 9 in our population. This is not different in bip olar patients from normal controls. Limitations: This study examined a smal l number of patients and examined a very limited portion of the locus. Conc lusion: It appears that there is not an expansion of the GCC repeat in the beta 1 gene in bipolar patients. (C) 2000 Elsevier Science B.V. All rights reserved.