Linkage studies in bipolar affective disorder with markers on chromosome 21

Association study of astrocyte-derived protein S100B gene polymorphisms with major depressive disorder in Chinese people

OBJECTIVE

Astroglial-derived protein S100B is known to play important roles in axonal growth, neural plasticity, and energy regulation. Disturbance of these neurodevelopmental processes is proposed as one possible etiology for mood disorder. Therefore, we performed a genetic analysis of S100B in patients with major depressive disorder (MDD).

METHOD

The polymorphisms of S100B were determined by polymerase chain reaction-restriction fragment length polymorphism in patients (n = 152) with MDD and healthy control subjects (n = 150). The genotypic and allelic distributions of 2 variants were analyzed in Chinese patients.

RESULTS

Two single nucleotide polymorphisms did not display significant associations with MDD. However, there were significant differences in age of onset in 3 genotypes of S100B rs9722. Significant differences in the subgroup depression (first-episode and recurrent depression) were also shown in 3 genotypes of S100B rs9722 and rs11911834 in patients and control subjects (P < 0.05).

CONCLUSIONS

Our findings did not suggest association of S100B gene polymorphisms in patients with MDD in China. We found there were differences in depressive episodes among different genotypes of S100B gene.

No association of the rs9722 C >T in the S100B gene and susceptibility to major depression in a Chinese population

OBJECTIVE

Astroglial-derived protein S100B is known to play important roles in axonal growth, neural plasticity, and energy regulation. Disturbance of these neurodevelopmental processes is proposed as one of the etiologies for mood disorder, and genetic polymorphisms of S100B have a possibility to be in susceptibility to major depressive disorder (MDD).

METHOD

We first investigated the association of the rs9722 C > T polymorphism of the S100B gene and susceptibility to MDD by comparing 152 major depressive patients with 150 healthy individuals in a Chinese population.

RESULTS

The genotype frequencies of the S100B rs9722 C > T polymorphism were 30% (C/C), 56% (C/T), and 14% (T/T) in depressed patients, 32% (C/C), 53% (C/T), and 15% (T/T) in healthy volunteers, respectively. The allele frequencies of the S100B rs9722 C > T polymorphism were 58% (C allele) and 42% (T allele) in depressed patients, and 59% (C allele) and 41% (T allele) in healthy volunteers, respectively.

CONCLUSION

There were no significant differences in the genotype distribution and allele frequencies between major depressive patients and healthy individuals. S100B rs9722 C > T polymorphism appears not to be an important factor in susceptibility to MDD in a Chinese population.

The genetics of bipolar disorder: genome 'hot regions,' genes, new potential candidates and future directions

Bipolar disorder (BP) is a complex disorder caused by a number of liability genes interacting with the environment. In recent years, a large number of linkage and association studies have been conducted producing an extremely large number of findings often not replicated or partially replicated. Further, results from linkage and association studies are not always easily comparable. Unfortunately, at present a comprehensive coverage of available evidence is still lacking. In the present paper, we summarized results obtained from both linkage and association studies in BP. Further, we indicated new potential interesting genes, located in genome 'hot regions' for BP and being expressed in the brain. We reviewed published studies on the subject till December 2007. We precisely localized regions where positive linkage has been found, by the NCBI Map viewer (http://www.ncbi.nlm.nih.gov/mapview/); further, we identified genes located in interesting areas and expressed in the brain, by the Entrez gene, Unigene databases (http://www.ncbi.nlm.nih.gov/entrez/) and Human Protein Reference Database (http://www.hprd.org); these genes could be of interest in future investigations. The review of association studies gave interesting results, as a number of genes seem to be definitively involved in BP, such as SLC6A4, TPH2, DRD4, SLC6A3, DAOA, DTNBP1, NRG1, DISC1 and BDNF. A number of promising genes, which received independent confirmations, and genes that have to be further investigated in BP, have been also systematically listed. In conclusion, the combination of linkage and association approaches provided a number of liability genes. Nevertheless, other approaches are required to disentangle conflicting findings, such as gene interaction analyses, interaction with psychosocial and environmental factors and, finally, endophenotype investigations.

Fine mapping of a susceptibility locus for bipolar and genetically related unipolar affective disorders, to a region containing the C21ORF29 and TRPM2 genes on chromosome 21q22.3

Linkage analyses of bipolar families have confirmed that there is a susceptibility locus near the telomere on chromosome 21q. To fine map this locus we carried out tests of allelic association using 30 genetic markers near the telomere at 21q22.3 in 600 bipolar research subjects and 450 ancestrally matched supernormal control subjects. We found significant allelic association with the microsatellite markers D21S171 (P=0.016) and two closely linked single-nucleotide polymorphisms, rs1556314 (P=0.008) and rs1785467 (P=0.025). A test of association with a three locus haplotype across the susceptibility region was significant with a permutation test of P=0.011. A two SNP haplotype was also significantly associated with bipolar disorder (P=0.01). Only two brain expressed genes, TRPM2 and C21ORF29 (TSPEAR), are present in the associated region. TRPM2 encodes a calcium channel receptor and TSPEAR encodes a peptide with repeats associated with epilepsy in the mouse. DNA from subjects who had inherited the associated marker alleles was sequenced. A base pair change (rs1556314) in exon 11 of TRPM2, which caused a change from an aspartic acid to a glutamic acid at peptide position 543 was found. This SNP showed the strongest association with bipolar disorder (P=0.008). Deletion of exon 11 of TRPM2 is known to cause dysregulation of cellular calcium homeostasis in response to oxidative stress. A second nonconservative change from arginine to cysteine at position 755 in TRPM2 (ss48297761) was also detected. A third nonconservative change from histidine to glutamic acid was found in exon 8 of TSPEAR. These changes need further investigation to establish any aetiological role in bipolar disorder.

Genética do transtorno bipolar

O Transtorno bipolar (TB) possui alta prevalência na população mundial e causa perdas significativas na vida dos portadores. É uma doença cuja herança genética se caracteriza por mecanismos complexos de transmissão envolvendo múltiplos genes. Na tentativa de identificar genes de vulnerabilidade para o TB, várias estratégias de investigação genética têm sido utilizadas. Estudos de ligação apontam diversas regiões cromossômicas potencialmente associadas ao TB, cujos marcadores ou genes podem ser candidatos para os estudos de associação. Genes associados aos sistemas monoaminérgicos e vias de sinalização intracelulares são candidatos para investigação da etiologia genética do TB. Novas técnicas de mapeamento de expressão gênica em tecidos especializados apontam para novos genes cujas mutações possam ser responsáveis pelo aparecimento da doença. Em virtude da complexidade do modo de transmissão do TB e de sua heterogeneidade fenotípica, muitas dificuldades são encontradas na determinação desses genes de vulnerabilidade. Até o momento, há apenas resultados preliminares identificando alguns genes associados à vulnerabilidade para desenvolver o TB. Entretanto, a compreensão crescente dos mecanismos epigenéticos de controle da expressão gênica e a abordagem dimensional dos transtornos mentais podem colaborar nas investigações futuras em genética psiquiátrica.

Sequence analysis of ADARB1 gene in patients with familial bipolar disorder

BACKGROUND

The ADARB1 gene is located in 21q22.3 region, previously linked to familial bipolar disorder, and its product has a documented action in the editing of the pre-mRNA of glutamate receptor B subunit. Dysfunction of glutamatergic neurotransmission could play an important role in the pathophysiology of bipolar disorder (BD). Glutamate excitatory neurotransmission regulation is a possible mechanism of the initial effect of anticonvulsants in regulating mood.

METHODS

To investigate the hypothesis of an involvement of ADARB1 gene in the BD, the ADARB1 cDNA has been cloned and sequenced in seven selected bipolar I disorder patients with evidence of familiarity of mood disorders. A detailed investigation of the gene nucleotide sequence in the open reading frame has been performed.

RESULTS

No alteration in the sequence of the ADARB1 gene cDNA was found in any patient, except a common neutral polymorphism in three out of seven patients.

CONCLUSIONS

Mutations in ADARB1 gene are not commonly associated with bipolar I disorder, therefore other genes in the 21q22 region could be associated with bipolar illness in some families, likely in the context of a multifactorial transmission model.

An overview of the genetics of psychotic mood disorders

This article presents a conceptual review of the genetic underpinnings of psychotic mood disorders. Both unipolar and bipolar forms of mood disorder sometimes feature psychotic symptoms. Some evidence from epidemiological research suggests that psychotic forms of mood disorder specifically might be heritable. Linkage studies of mood disorders in general have also provided some support for that notion, as have associated studies involving serotonin and dopamine genes and psychotic mood disorder. Some research suggests there might be a genetic connection between schizophrenia and bipolar disorder, undermining the Kraepelinian dichotomous classification of the psychoses. Future research should continue to examine psychotic forms of mood disorder using both epidemiological and molecular approaches.

Molecular genetic and family studies in affective disorders: state of the art

The identification of genes responsible for mood disorders will contribute to significant advances in the awareness of diagnosis (diagnostic process and early recognition), pathophysiology, epidemiology and treatment issues. During the past two decades, the search for genes for mood disorders has mainly contributed to better understand and confirm the genetic complexities inherent to these disorders. The large amount of results available and the difficulty to digest them corroborate this observation. The major contribution of these findings should be integrated in the context of the world-wide efforts to identify the thousands of genes of the human genome. Some of these genes may be identified within the next decade. Several consistent hypotheses are currently being tested and will, hopefully, speed up the process of narrowing the important regions when the complete genome map will be available. The most promising chromosomal regions have been localized on chromosomes 4, 5, 11, 12, 18, 21 and X. A number of candidate genes have also been investigated, some of these are directly linked to neurobiological hypotheses of the aetiology of affective disorders. In parallel, specific hypotheses have been implicated, such as anticipation and dynamic mutations. Further research should concentrate on these hypotheses and confirm positive findings through interdisciplinary and multicenter projects.

Cloning of a novel human putative type Ia integral membrane protein mapping to 21q22.3

The distal part of human chromosome 21q22.3 is exceptionally gene rich and contains several loci that have been linked to hereditary disorders. In the course of constructing an extensive transcript map for chromosome 21, we have isolated numerous coding segments in 21q22.3 that represent potential candidate genes in this region. Following this approach, we have cloned a novel single-copy gene (C21orf3) (HGMW-approved symbol C21orf1) expressed as a unique 2.69-kb mRNA in a wide range of tissues. We have precisely mapped C21orf3 by fiber FISH distal to marker D21S171. The C21orf3 gene encodes a predicted protein of 180 residues that does not share any sequence homology with other known proteins. C21orf3 harbors predicted structural features of a type Ia integral membrane protein and contains a tetrapeptide motif (YXRF) observed in several cell surface proteins involved in signal transduction. Although the function of C21orf3 is still unknown, this novel gene may play an important role in a cell trafficking mechanism.