Open Access Research article

MAOA haplotypes associated with thrombocyte-MAO activity

Mårten Jansson15, Shane McCarthy2, Patrick F Sullivan3, Paul Dickman1, Björn Andersson2, Lars Oreland4, Martin Schalling5 and Nancy L Pedersen16*

Author Affiliations

1 Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden

2 Center for Genomics and Bioinformatics, Karolinska Institutet, Stockholm, Sweden

3 Departments of Genetics, Psychiatry & Epidemiology, University of North Carolina at Chapel Hill, NC, USA

4 Department of Neuroscience, Uppsala University, Uppsala, Sweden

5 Department of Molecular Medicine, Karolinska Institutet, Stockholm, Sweden

6 Department of Psychology, University of Southern California, Los Angeles, USA

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BMC Genetics 2005, 6:46  doi:10.1186/1471-2156-6-46

Published: 20 September 2005



The aim was to ascertain whether thrombocyte MAO (trbc-MAO) activity and depressed state are genetically associated with the MAO locus on chromosome X (Xp11.3 – 11.4). We performed novel sequencing of the MAO locus and validated genetic variants found in public databases prior to constructing haplotypes of the MAO locus in a Swedish sample (N = 573 individuals).


Our results reveal a profound SNP desert in the MAOB gene. Both the MAOA and MAOB genes segregate as two distinct LD blocks. We found a significant association between two MAOA gene haplotypes and reduced trbc-MAO activity, but no association with depressed state.


The MAO locus seems to have an effect on trbc-MAO activity in the study population. The findings suggest incomplete X-chromosome inactivation at this locus. It is plausible that a gene-dosage effect can provide some insight into the greater prevalence of depressed state in females than males.