ehaviors related to self-regulation, such as substance use disorders or antisocial behaviors, have far-reaching consequences for affected individuals, their families, communities and society at large 1,2 . Collectively, this group of correlated traits are classified as externalizing 3 . Twin studies have demonstrated that externalizing liability is highly heritable (~80%) 4,5 . To date, however, no large-scale molecular genetic studies have utilized the extensive degree of genetic overlap among externalizing traits to aid gene discovery, as most studies have focused on individual disorders 6 . For many high-cost, high-risk behaviors with an externalizing component-opioid use disorder and suicide attempts 7 being salient examples-there are limited genotyped cases available for gene discovery 8,9 .A complementary strategy to the single-disease approach is to study the shared genetic architecture across traits in multivariate analyses, which boosts statistical power by pooling data across

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Background: The PARK2 gene at 6q26 encodes parkin, whose inactivation is implicated in an early-onset autosomal recessive form of Parkinson disease (PD). Objective: To evaluate the influence of heterozygosity for parkin mutation on onset age in a sample of families with at least 2 PD-affected members. Design: Clinical and genetic study. Setting: Twenty collaborative clinical sites. Patients: Patients with familial PD collected in the GenePD study. Studied families were selected for (1) affected sibling pairs sharing 2 alleles identical by state at PARK2 (D6S305) or (2) 1 or more family members with onset age younger than 54 years, regardless of D6S305 status. At least 1 member from each of 183 families underwent comprehensive screening for deletion/insertion variants and point mutations in PARK2. Main Outcome Measures: Mutations in the parkin gene were screened by means of single-stranded conformation polymorphism and sequencing in all 12 coding exons and flanking intronic sequences for point mutations and duplex quantitative polymerase chain reaction in all exons for rearrangement, duplication, and deletion. Results: Mutations were found in 23 families (12.6% of those screened). Among the mutation-positive families, 10 (43%) contained compound heterozygotes; 3 (13%), homozygotes; and 10 (43%), heterozygotes. The onset age in patients with parkin gene mutations ranged from 20 to 76 years. Patients with 1 parkin mutation had an 11.7-year age at onset than did patients with none (P=.04), and patients with 2 or more parkin mutations had a 13.2year decrease in age at onset compared with patients with 1 mutation (P =.04). Conclusions: These data indicate that parkin mutations are not rare in multiply affected sibships, and that heterozygous mutation carrier status in PARK2 significantly influences age at onset of PD.

A screening questionnaire with high sensitivity for detection of Parkinson's disease would make it easier to identify undiagnosed, yet affected, family members for genetic research. We assessed the validity of a screening questionnaire developed by Duarte et al. [1995: Mov Disord 10:643-649] with reported high specificity and sensitivity for Parkinson's disease (PD). We applied the questionnaire to 78 asymptomatic members of families that had at least two people diagnosed with PD. These families were participating in a linkage study of Parkinson's disease. Examination of these 78 revealed that 53 were normal (normal controls) and 25 were classified ("undiagnosed" PD defined) as possible, probable, or clinically definite PD based on standardized criteria. We compared these results with 123 patients with clinically definite PD ("diagnosed" PD). There were significant differences among the mean scores on the questionnaire for normal controls (4.4), subjects with undiagnosed PD (9.8), and patients with diagnosed PD (42.1; p<0.000001) and a significant difference between undiagnosed PD and normals (p<0.01). The questionnaire had only 4% sensitivity for detection of parkinsonism in undiagnosed PD using the original criteria [Duarte et al., 1995]. Revising the criteria increased the sensitivity from 4 to 48% in the undiagnosed group. The positive predictive value was 39% and the negative predictive value was 72%. Prospective application of these revised criteria is necessary to confirm the improved sensitivity. However, we conclude that this screening questionnaire has inadequate sensitivity for detection of mild parkinsonism and direct examination is still critical for accurate classification for genetic studies.

The Fawn-Hooded (FH/Wjd) rat is an inbred strain of rat that has been reported to exhibit both high immobility in the forced swim test and high voluntary ethanol intake, measures that have been periodically linked with depression and alcoholism in humans. The present paper will first present a survey of the literature and previously unpublished findings that bear on the question of whether FH/Wjd rats should be considered genetic animal models of depression and alcoholism. Subsequently, behavioral studies of the FH/Wjd rats, the non-drinking ACI/N strain, and their F1 and F2 intercrosses will be described. Under free choice conditions, the FH/Wjd rat drinks up to 6 g/kg 10% ethanol per day. This intake was sufficient to render the rats tolerant to the hypothermic effects of injected ethanol (2.5 g/kg). Rats that had been voluntarily drinking for at least 6 weeks also exhibited withdrawal-induced anxiety in the social interaction, elevated plus maze, and ultrasonic vocalization tasks. The FH/Wjd rat exhibits a 25-30% increase in alcohol intake when the alcohol is returned after a 24-h period of deprivation. It responds to drugs that are effective in humans with a reduction in alcohol intake. Therefore, the FH/Wjd rat meets most of the criteria for an animal model of alcoholism. Chronic antidepressant treatments correct several of the abnormalities exhibited by the FH/Wjd rats, including the exaggerated immobility in the forced swim test. Therefore, the FH/Wjd rats also fulfill some of the criteria for an animal model of depression. On the contrary, inbred ACI/N rats do not drink much alcohol voluntarily and are quite active in the forced swim test. The FH/Wjd and ACI/N rats were intercrossed to obtain the F1 and F2 progenies, which were then tested for alcohol intake and immobility. Alcohol intake and immobility were distributed in different patterns in the F1 and F2 progenies. Alcohol intake was intermediate in the F1 progeny, while immobility was closer to the FH/Wjd parents. In the F2 progeny, chi-square analyses indicated that the distributions were significantly different. In addition, there were no significant litter effects, indicating that maternal effects did not appear to occur. There were also no significant differences among rats with different coat colors, suggesting that the Fawn-Hooded phenotype can be separated from the measures of alcohol intake and immobility. We conclude that the FH/Wjd rat is a genetic animal model of depression and alcoholism, but that the two measures reflective of these states are under separate genetic controls.