Nonlinkage of bipolar illness to tyrosine hydroxylase, tyrosinase, and D2 and D4 dopamine receptor genes on chromosome 11

OBJECTIVE

Previous linkage and allelic association studies using DNA polymorphisms, cosegregation of cytogenetic abnormalities with psychiatric illness, and assignment of genes involved in neutotransmitter metabolism suggested that chromosome 11 may harbor a gene predisposing to bipolar illness. The authors examined linkage in the families of 14 probands with bipolar illness, with the candidate genes tyrosine hydroxylase (TH), D4 dopamine receptor (DRD4) at 11p15, tyrosinase (TYR) at 11q14-q21, and D2 dopamine receptor (DRD2) at 11q22-q23, as well as with the c-Harvey-ras oncogene (HRAS) and insulin gene (INS), both located at 11p15, a region that previously showed linkage to bipolar illness.

METHOD

The genetic data were analyzed with both lod score analysis (parametric) and affected-sib-pair analysis (nonparametric); both narrow and broad definitions of the clinical phenotype were used. Further influences of diagnostic uncertainties were accounted for by using diagnostic probability classes weighing the stability of each phenotype.

RESULTS

Two-point linkage results excluded close linkage of bipolar illness to each candidate gene; negative results were also obtained when the narrow definition of the clinical phenotype was used. Moreover, multipoint linkage analysis of HRAS and INS excluded the 11p15 region encompassing both DRD4 and TH. In agreement with the negative linkage results, affected-sib-pair analysis did not show preferential sharing of marker alleles at any of the candidate genes.

CONCLUSIONS

The negative results obtained under different genetic models exclude a frequent role for DRD4, TH, TYR, and DRD2 in the pathogenesis of bipolar illness.

Self-esteem in recovered bipolar and unipolar out-patients

The hypothesis of a low self-esteem in depressive patients was tested using the Rosenberg Self-Esteem Scale in 24 recovered unipolar and 27 recovered bipolar patients, compared with a normal control group of 26 subjects matched for age and sex. The hypothesis was confirmed only for unipolars; bipolar patients presented a self-esteem score not significantly different from normal scores. Self-esteem was not related to clinical characteristics of the affective disorder, suggesting that low self-esteem may be a basic component of a depression-prone personality. The investigation of the relationship between self-esteem and social adjustment confirmed the presence of social conformism in bipolar patients and rigidly set low self-esteem in unipolar patients. These results should stimulate the evaluation of different psychotherapeutic treatments in the long-term psychosocial management of affectively ill patients.

Twin study of the 24-h cortisol profile: evidence for genetic control of the human circadian clock

To determine whether genetic factors control the expression of human circadian rhythmicity, we analyzed the 24-h profile of plasma cortisol in 11 monozygotic and 10 dizygotic pairs of normal male twins. Blood was sampled every 15 min, and sleep was monitored. Circadian rhythmicity was characterized by measures of amplitude, phase, and overall waveshape. Pulsatility was quantified by pulse frequency, pulse amplitude, and relative contribution of pulsatile vs. circadian variations. Data were analyzed by a procedure specifically developed for twin studies. Genetic control was demonstrated for the timing of the nocturnal nadir and for the proportion of overall temporal variability associated with pulsatility. Environmental effects were detected for the 24-h mean and the timing of the morning acrophase. The timing of the cortisol nadir is a robust marker of human circadian phase and is dependent, under entrained conditions, on the length of the endogenous period. Animal studies have shown that the endogenous period and the pattern of entrainment to exogenous 24-h periodicities are genetically controlled. Our results indicate that, despite the increased impact of social inputs, genetic factors also control human circadian rhythmicity.

Minireview: Molecular genetics in affective illness

Genetic transmission in manic depressive illness (MDI) has been explored in twins, adoption, association, and linkage studies. The X-linked transmission hypothesis has been tested by using several markers on chromosome X: Xg blood group, colour blindness, glucose-6-phosphate dehydrogenase (G6PD), factor IX (haemophilia B), and DNA probes such as DXS15, DXS52, F8C, ST14. The hypothesis of autosomal transmission has been tested by association studies with the O blood group located on chromosome 9, as well as linkage studies on chromosome 6 with the Human Leucocyte Antigens (HLA) haplotypes and on Chromosome 11 with DNA markers for the following genes: D2 dopamine receptor, tyrosinase, C-Harvey-Ras-A (HRAS) oncogene, insuline (ins), and tyrosine hydroxylase (TH). Although linkage studies support the hypothesis of a major locus for the transmission of MDI in the Xq27-28 region, several factors are limiting the results, and are discussed in the present review.

Biological and clinical features of recurrent brief depression: a comparison with major depressed and healthy subjects

Recurrent brief depression (RBD) has recently been proposed as a new subtype of affective disorder characterized by episodes of major depression which last less than two weeks. The aim of this study was to further evaluate the validity of this putative subtype by means of clinical and biological data. DST, TSH response to TRH and sleep EEG variables were compared in 25 RBD patients sex- and age-matched to 25 major depressed (MD) and 25 healthy subjects. Family history, age at onset, and psychiatric comorbidity did not discriminate RBD from MD. Recurrent unipolar depression was found to be more prevalent in MD. Although less severely depressed during the biological tests, patients with RBD did not significantly differ from those with MDD on basis of DST non-suppression, blunted TSH response and shortening of REM latency. Compared to controls, a greater sleep onset latency was observed both in RBD and MD and a lower total sleep time in MD patients only. These results suggest that RBD could be viewed as a subtype of affective disorder sharing many characteristics with MDD.

[No hypofrontality in schizophrenia demonstrated by positron emission tomography]

We studied cerebral glucose metabolism, using Positron Emission Tomography (PET) and (F-18) fluorodeoxyglucose, in 15 young schizophrenic patients compare to 15 age-matched healthy volunteers. The PET investigation was made in a quiet room with a dimly light. Each subject remained in a supine resting state with eyes closed. Results failed to demonstrate any differences in glucose utilization between schizophrenic patients and control subjects, as far as absolute or relative, left and right values are concerned. Besides, variability of metabolic values was significantly higher in schizophrenics than in controls.

5-HT2 receptor antagonism and slow-wave sleep in major depression

Specific sleep disturbances such as reduced slow-wave sleep (SWS) and decreased serotonergic (5-HT) activity have been observed in depressive disorders. Ritanserin, a specific 5-HT2 receptor antagonist, has been shown to increase SWS in healthy subjects. This study explored the effects of a single dose or ritanserin (5 mg) on sleep electroencephalography in 18 major depressed patients and in 10 control subjects. Ritanserin affected SWS differently in the two groups. Although stage 3 increased significantly in the groups, in contrast to controls, there was no significant effect of ritanserin on stage 4 in depressed patients. In the depressed group, irritability and DSM-III-R melancholic type predicted 40% or the variance of stage 4 increment after ritanserin, as assessed by stepwise multiple regression. These results are in agreement with a potential 5-HT disturbance, particularly at the 5-HT2 receptor level, in some clinical forms of depression.

Reduced clonidine rapid eye movement sleep suppression in patients with primary major affective illness

Clonidine hydrochloride, administered intravenously (2 micrograms/kg) during the second non-rapid eye movement period, was significantly less suppressant of rapid eye movement sleep in 10 depressed patients with primary major affective illness, according to Research Diagnostic Criteria, than in three groups of matched subjects (10 normal controls, 10 patients with minor depression, and 10 patients with generalized anxiety). These results suggest that depressed patients with major primary affective illness have down-regulated alpha 2-adrenergic receptors. These findings are consistent with the cholinergic-aminergic balance hypothesis of depression and support the aminergic side of the concept. Finally, the rapid eye movement sleep response to clonidine could provide a new biological marker of affective illness.

Sleep polygraphic variables in anorexia nervosa and depression: a comparative study in adolescents

Sleep EEG variables were compared in an adolescent population consisting of 11 anorectic girls, 11 young depressed patients and 11 healthy volunteers matched for age and sex. Anorectic patients differed from depressed patients in a greater number and a higher length of awakenings. In comparison with controls, anorectic patients showed less sleep efficiency, a higher length of awakenings and less REM sleep. When anorectic patients were divided in restricting and bulimic subtypes, the bulimic anorectics showed an increase in stage 3 of sleep. These results do not support a direct association between eating disorders and affective disorders. Sleep EEG variables were not significantly correlated to the Body Mass Index.

Naps and depression

In healthy subjects, napping has often been seen as an "abnormal" form of sleep, while sleep has been considered as a necessary feature of life. Social and cultural biases influence the occurrence of napping behavior. However, several observations indicate the presence in man of a two per day modulation of sleep propensity. On the other hand, alterations of nocturnal sleep have been widely described in affective disorders, but little is known about the presence of daytime sleep in depressed patients and the possible effect of daytime sleep episodes on nocturnal sleep. Some attempts to characterize daytime sleep in depression are reviewed. A recent study based on continuous polygraphic recordings indicate that napping occurrence appears to be similar in depressed patients than in control subjects. However, naps structure and organization were different in depressed patients in comparison to controls. Napping seems thus to be more prevalent in depressed patients than previously assumed. Possible effects of naps on mood, alertness in depressed patients remains to be explored.

Attributional style and depression: a controlled comparison of remitted unipolar and bipolar patients

Attributional style was investigated in remitted affective disorder patients (23 unipolars and 26 bipolars) and 26 non-psychiatric controls. We found a specific cognitive vulnerability in unipolars. Unipolars attributed negative events to causes that were more stable--but not more internal nor more global--than bipolars and controls, and did not attach more importance to these events. Attributional vulnerability seemed more apparent in patients with longer histories of depression.

Efficacy of fluvoxamine in severe depression

The therapeutic efficacy of fluvoxamine has been demonstrated in large numbers of patients participating in comparative double-blind placebo-controlled studies using imipramine as the active reference compound. Overall, patients treated with fluvoxamine for 4 to 6 weeks had significant amelioration of their depression compared with placebo-treated patients. More importantly, the response rate in patients with severe depression was greater than in patients with mild or moderate depression. However, several investigators have observed high placebo response rates, and in some studies there has been a similar response rate to imipramine and placebo treatment. While the high placebo response rate may have resulted from methodological problems, the issue does raise some questions that can only be resolved by further investigation.

Lack of association between HLA-DR antigens and sleep-onset REM periods in major depression

Narcolepsy is the disease disclosing the strongest association with the HLA system. Almost 100% of cases are associated with HLA-DR2 antigen. Moreover, narcolepsy is often characterized by the occurrence of sleep-onset REM (SOREM) periods. SOREM has also been demonstrated in major depression. To further investigate the relationship between SOREM and HLA-DR2, HLA-DR and HLA-DQ antigens were assessed in 50 research diagnostic criteria (RDC) major depressed patients. Depressed patients were elected for HLA typing on the basis of the presence of at least one SOREM period (n = 29) or three REM latencies above 50 min (n = 21) during three consecutives EEG nights recording. No significant differences were observed in the frequency of HLA-DR or HLA-DQ antigens between patients and controls. These results demonstrate a lack of association between SOREM and HLA-DR2 in major depression, and also do not confirm the presence of an association between antigens encoded by the HLA region of the chromosome 6 and major depressive illness.