No association between oxytocin or prolactin gene variants and childhood-onset mood disorders.

BACKGROUND: Oxytocin (OXT) and prolactin (PRL) are neuropeptide hormones that interact with the serotonin system and are involved in the stress response and social affiliation. In human studies, serum OXT and PRL levels have been associated with depression and related phenotypes. Our purpose was to determine if single nucleotide polymorphisms (SNPs) at the loci for OXT, PRL and their receptors, OXTR and PRLR, were associated with childhood-onset mood disorders (COMD). METHODS: Using 678 families in a family-based association design, we genotyped 16 SNPs at OXT, PRL, OXTR and PRLR to test for association with COMD. RESULTS: No significant associations were found for SNPs in the OXTR, PRL, or PRLR genes. Two of three SNPs 3' of the OXT gene were associated with COMD (p≤0.02), significant after spectral decomposition, but were not significant after additionally correcting for the number of genes tested. Supplementary analyses of parent-of-origin and proband sex effects for OXT SNPs by Fisher's Exact test were not significant after Bonferroni correction. CONCLUSIONS: We have examined 16 OXT and PRL system gene variants, with no evidence of statistically significant association after correction for multiple tests.

No evidence of an association between two genes, EDN1 and ACE, and childhood-onset mood disorders.

Recent evidence supports a pathological link between heart disease and depressive symptoms, suggesting that depression is both etiologic and prognostic to heart disease. Thus, biological molecules which are at the interface between heart and mind are plausible candidate genes for depressive disorders. To investigate this line of enquiry we have investigated two genes, Endothelin 1 (EDN1) and Angiotensin-converting enzyme (ACE) in a family-based sample with childhood-onset mood disorders (COMDs). EDN1 is highly expressed in endothelium where it acts as a potent vasoconstrictor, and is also expressed in the brain where it exhibits neurotransmitter characteristics. ACE acts as a potent vasopressor, and interacts with the hypothalamic-pituitary-adrenocortical (HPA) system, which is often dysregulated in mood disorders. Furthermore, ACE has recently been found to be associated with major depression. Polymorphisms were selected to best capture the genetic variation at the two loci, and to replicate previous associations. The markers were genotyped across EDN1 and ACE in a sample comprised of 382 Hungarian nuclear families ascertained through affected probands diagnosed with a mood disorders before the age of 15. We found no evidence of association between either of these genes and COMD. Consequently, we were unable to support our hypothesis that these two genes, which are involved in both vascular and brain functions are contributing to the susceptibility to mood disorders of children/adolescents.

G72/G30 (DAOA) and juvenile-onset mood disorders.

The chromosome 13q region has been linked to bipolar disorder in a number of genome scans as well as focused linkage studies. Previously we identified linkage to the 13q32 region in a genome scan of 146 affected sibling pair families from Hungary with juvenile-onset mood disorders. Within this region are the overlapping genes G72/G30, with G72 now officially named as D-amino-acid oxidase activator (DAOA). This locus has been associated with panic disorder, schizophrenia, and bipolar disorder. In this study, we tested for association to 11 markers in these genes and mood disorders in a sample of 646 nuclear families identified with a proband with onset of a mood disorder before 14.9 years of age. We identified evidence for association to three markers within the gene (rs2391191, rs3918341, rs1935062), two of which had been associated with bipolar disorder in previous studies. When corrected for the number of markers tested, the results were no longer significant, however the prior evidence for association of this gene in multiple studies points to this gene as a potential contributor to juvenile-onset mood disorders.

Genome scan in sibling pairs with juvenile-onset mood disorders: Evidence for linkage to 13q and Xq.

Mood disorders (bipolar and depressive disorders) in children and adolescents are associated with significant morbidity and mortality. Twin and family studies, for the most part, indicate higher familiality and heritability for mood disorders that onset in childhood/adolescence than those that onset in adulthood. To identify the genetic contribution to mood disorders that onset in childhood/adolescence, we performed a genome scan on 146 nuclear families from Hungary containing an affected proband and affected siblings. In total, the pedigrees contained 303 affected children: 146 probands, 137 siblings with a first episode of mood disorder before 14.9 years of age, and 20 siblings with onset of their first episode after 14.9 years of age but before the age of 18. The results of the genome scan using 405 microsatellite markers did not provide evidence for linkage at the recommended genome wide significance level for any novel loci. However, markers on two chromosomes, 13q and Xq, provided evidence for linkage in regions previously identified as linked to bipolar disorder in multiple studies. For the marker on chromosome 13q the peak non-parametric multipoint LOD score was at the marker D13S779 (LOD = 1.5, P = 0.004). On chromosome Xq, evidence for linkage was observed across a large region spanning two regions previously linked to bipolar disorder; Xq24 to Xq28, with a peak at marker TTTA062 (LOD 2.10, P = 0.0009) in Xq28. Results for these regions exceed the recommended P-value for a replication study of P < 0.01 and thus provide evidence for these two loci as contributing to mood disorders with juvenile onset.

Tagging SNP association study of the IL-1beta gene (IL1B) and childhood-onset mood disorders.

Given substantial evidence for IL-1beta involvement in the etiology of depression, the IL1B gene is a strong candidate for involvement in susceptibility to depressive disorders. However, association studies investigating this, to date, have been limited to just two polymorphisms (rs1143627[-31T/C] and rs16944[-511C/T]) that constitute only a fraction of the genetic variation that is actually present across this gene in the population. Here, in a family-based association study of childhood-onset mood disorders (COMD), characterized by onset of depression before the age of 15, we have used a gene-wide approach, employing a panel of five tagging SNPs spanning the entire gene. Based on TDT analyses of both individual alleles and haplotypes, in a study sample of 646 families (with 782 affected children), none of the SNPs, including those implicated in transcriptional regulation of the gene, showed evidence for association with COMD. This is the largest and most comprehensive study of IL1B in relation to mood disorders that has been carried out, to date. The results do not support the involvement of IL1B as a major factor in genetic risk for early-onset mood disorders.

Association of the neurotrophic tyrosine kinase receptor 3 (NTRK3) gene and childhood-onset mood disorders.

OBJECTIVE: Genome scans have revealed significant evidence for linkage of depression to chromosome 15q25.3-q26.2. The gene for neurotrophic tyrosine kinase receptor 3 (NTRK3), the receptor for neurotrophin-3 (trkC) and a key gene in neurotrophin signaling, is located within this region and, given evidence for synaptic plasticity as a mechanism in mood disorders, was considered a prime candidate. The authors investigated NTRK3 as a susceptibility gene for childhood-onset mood disorders. METHOD: The study sample consisted of 603 families with 723 affected children and adolescents diagnosed with a mood disorder with onset of the first episode by age 15. The authors genotyped 18 polymorphic markers across the NTRK3 gene in this sample and tested for association. RESULTS: Results identified significant evidence for association for five of the markers using the transmission disequilibrium test. Four of the five markers were located in a region of strong linkage disequilibrium and were highly correlated. Haplotype results provided significant evidence for association to haplotypes composed of markers located in two haplotype blocks. CONCLUSIONS: The results for NTRK3 as well as the authors' previous finding for association to brain-derived neurotrophic factor in this sample support synaptic plasticity as a mechanism contributing to mood disorders that begin during childhood and adolescence and specifically implicate the NTRK3 gene as a contributing factor in the 15q-linked region.