Applying Imaging Genetics to ADHD: the Promises and the Challenges

Attention deficit/hyperactivity disorder (ADHD) is one of the most prevalent childhood psychiatric disorders. During the past decades, studies have focused on its genetic background and the abnormality of the brain structure and function. Recently, an advanced technique linking these two areas, namely, the imaging genetics emerged and kept growing. Imaging genetics primarily identifies genes that influence the brain variations. There are three main strategies of doing an imaging genetic study: using neuroimaging as endophenotypes to find the associated DNA variants, finding neuroimaging effects of risk genes, and hypothesis-free whole-brain voxelwise genome-wide association study. In this review, we begin with demonstrating the basic principles of imaging genetics precisely, with examples from other psychiatric conditions, and then go on to synthesize the existing imaging genetic studies in ADHD. Finally, we elaborate the challenges of applying imaging genetics to ADHD. We conclude that imaging genetics has somewhat showed its potential to provide a more precise understanding of how the genes shape the brain variations and further the clinical features of ADHD.     

Variation,Sex, and Social Cooperation: Molecular Population Genetics of the Social Amoeba Dictyostelium discoideum

Dictyostelium discoideum is a eukaryotic microbial model system for multicellular development, cell–cell signaling, and social behavior. Key models of social evolution require an understanding of genetic relationships between individuals across the genome or possibly at specific genes, but the nature of variation within D. discoideum is largely unknown. We re-sequenced 137 gene fragments in wild North American strains of D. discoideum and examined the levels and patterns of nucleotide variation in this social microbial species. We observe surprisingly low levels of nucleotide variation in D. discoideum across these strains, with a mean nucleotide diversity (π) of 0.08%, and no strong population stratification among North American strains. We also do not find any clear relationship between nucleotide divergence between strains and levels of social dominance and kin discrimination. Kin discrimination experiments, however, show that strains collected from the same location show greater ability to distinguish self from non-self than do strains from different geographic areas. This suggests that a greater ability to recognize self versus non-self may arise among strains that are more likely to encounter each other in nature, which would lead to preferential formation of fruiting bodies with clonemates and may prevent the evolution of cheating behaviors within D. discoideum populations. Finally, despite the fact that sex has rarely been observed in this species, we document a rapid decay of linkage disequilibrium between SNPs, the presence of recombinant genotypes among natural strains, and high estimates of the population recombination parameter ρ. The SNP data indicate that recombination is widespread within D. discoideum and that sex as a form of social interaction is likely to be an important aspect of the life cycle.     

遗传学、优生学与伦理学试探A

遗传学、优生学与伦理学试探邱仁宗（中国社会科学院哲学研究所,北京１００７３２）ＡＰｒｅｌｉｍｉｎａｒｙＡｐｐｒｏａｃｈｔｏＧｅｎｅｔｉｃｓ,ＥｕｇｅｎｉｃｓａｎｄＥｔｈｉｃｓＱｉｕＲｅｎｚｏｎｇ（ＩｎｓｔｉｔｕｔｅｏｆＰｈｉｌｏｓｏｐｈｙ,Ｃｈｉｎｅ...     

Psychiatric and Social Factors in the Abortion Decision

A total of 132 consecutive referrals for psychiatric opinion on termination of pregnancy were examined and followed up at nine months. Of these, 48 (36%) were refused and 44 of the 84 terminated were sterilized. Those recommended for abortion tended to be older, married, and to have children. They had used contraception more often and they showed more clinical psychiatric abnormalities. The group had numerous social problems, but these did not distinguish those terminated from those refused, nor were there differences in religious affiliation or duration of pregnancy. Most of those refused obtained an abortion elsewhere and only 25 of the original 132 had a live child. General practitioners were more likely to disagree with a refusal decision than with termination. Psychiatric, physical, and social sequelae were infrequent in both groups. Contraception before and after was inadequate in most patients.     

花形态形成的分子遗传学

花由茎顶分生组织的少数细胞分化而来。花的分生组织进行活跃的细胞分裂,并逐步分化形成萼片、花瓣、雄蕊和雌蕊4个器官。这些器官的性质由花的“同源异型基因”决定,决定花的器官数和对称性等的基因族也在起作用。就目前对这些基因族的研究进展做些探讨。     

The Psychiatric Team and the Social Definition of Schizophrenia

The Psychiatric Team and the Social Definition of Schizophrenia. Rob Barrett. Cambridge: Cambridge University Press, 1996.337 pp.