Further RFLPs at the human tyrosine hydroxylase locus

Close linkage of bipolar disorder to chromosome 11 markers is excluded in two large Australian pedigrees

The relationship between bipolar disorder and chromosome 11 markers remains uncertain. Whilst re-analysis of the Amish pedigree weakened previous evidence for close linkage (but could not exclude the possibility of genetic heterogeneity), a recent French study has found a significant association between this condition and tyrosine hydroxylase polymorphisms. We aimed to determine if bipolar disorder in two large Australian pedigrees (of Irish and English extraction respectively) was linked to these markers. Of the 84 family members available for testing, nine were diagnosed as bipolar I, one as bipolar II and six had recurrent unipolar depression. Linkage of bipolar disorder and recurrent depression to the chromosome 11p15 markers c-Harvey ras, insulin and tyrosine hydroxylase was tested using a series of genetic models with varying penetrance levels. Additionally, linkage was examined using a series of levels of definitions of affective status (ranging from bipolar I alone to all affective illnesses). Close linkage to these markers was strongly excluded using each model and definition. The findings also persisted when a wide range of rates of 'sporadic' (non-genetic) presentations of illness were incorporated in the analysis. These results are consistent with other recent studies indicating that bipolar disorder is not linked to chromosomal region 11p15.

RFLP alleles at the tyrosine hydroxylase locus: no association found to affective disorders

Affective disorders are usually referred to as being inherited multifactorially. The contribution of a gene locus in illnesses displaying multifactorial inheritance may be assessed by searching for associations of alleles to the illness. The tyrosine hydroxylase gene encodes the rate-limiting enzyme in the synthesis of catecholamines and might be a candidate for causing the manic-depressive phenotype. Therefore, we tested 88 patients with affective disorders and 99 healthy control persons for association of restriction fragment length polymorphism (RFLP) alleles at the tyrosine hydroxylase locus. The comparison of allele or genotype frequencies did not reveal any significant differences between the two groups.