Rare and Common Variants Conferring Risk of Tooth Agenesis.

We present association results from a large genome-wide association study of tooth agenesis (TA) as well as selective TA, including 1,944 subjects with congenitally missing teeth, excluding third molars, and 338,554 controls, all of European ancestry. We also tested the association of previously identified risk variants, for timing of tooth eruption and orofacial clefts, with TA. We report associations between TA and 9 novel risk variants. Five of these variants associate with selective TA, including a variant conferring risk of orofacial clefts. These results contribute to a deeper understanding of the genetic architecture of tooth development and disease. The few variants previously associated with TA were uncovered through candidate gene studies guided by mouse knockouts. Knowing the etiology and clinical features of TA is important for planning oral rehabilitation that often involves an interdisciplinary approach.

15q11.2 CNV affects cognitive, structural and functional correlates of dyslexia and dyscalculia.

Several copy number variants have been associated with neuropsychiatric disorders and these variants have been shown to also influence cognitive abilities in carriers unaffected by psychiatric disorders. Previously, we associated the 15q11.2(BP1-BP2) deletion with specific learning disabilities and a larger corpus callosum. Here we investigate, in a much larger sample, the effect of the 15q11.2(BP1-BP2) deletion on cognitive, structural and functional correlates of dyslexia and dyscalculia. We report that the deletion confers greatest risk of the combined phenotype of dyslexia and dyscalculia. We also show that the deletion associates with a smaller left fusiform gyrus. Moreover, tailored functional magnetic resonance imaging experiments using phonological lexical decision and multiplication verification tasks demonstrate altered activation in the left fusiform and the left angular gyri in carriers. Thus, by using convergent evidence from neuropsychological testing, and structural and functional neuroimaging, we show that the 15q11.2(BP1-BP2) deletion affects cognitive, structural and functional correlates of both dyslexia and dyscalculia.

A common biological basis of obesity and nicotine addiction.

Smoking influences body weight such that smokers weigh less than non-smokers and smoking cessation often leads to weight increase. The relationship between body weight and smoking is partly explained by the effect of nicotine on appetite and metabolism. However, the brain reward system is involved in the control of the intake of both food and tobacco. We evaluated the effect of single-nucleotide polymorphisms (SNPs) affecting body mass index (BMI) on smoking behavior, and tested the 32 SNPs identified in a meta-analysis for association with two smoking phenotypes, smoking initiation (SI) and the number of cigarettes smoked per day (CPD) in an Icelandic sample (N=34,216 smokers). Combined according to their effect on BMI, the SNPs correlate with both SI (r=0.019, P=0.00054) and CPD (r=0.032, P=8.0 × 10(-7)). These findings replicate in a second large data set (N=127,274, thereof 76,242 smokers) for both SI (P=1.2 × 10(-5)) and CPD (P=9.3 × 10(-5)). Notably, the variant most strongly associated with BMI (rs1558902-A in FTO) did not associate with smoking behavior. The association with smoking behavior is not due to the effect of the SNPs on BMI. Our results strongly point to a common biological basis of the regulation of our appetite for tobacco and food, and thus the vulnerability to nicotine addiction and obesity.

A large Icelandic family with early osteoarthritis of the hip associated with a susceptibility locus on chromosome 16p.

OBJECTIVE: To describe a large kinship with inherited hip osteoarthritis (OA) and its associated susceptibility locus. METHODS: Four generations of a kinship with familial hip OA were identified and characterized by family history and by clinical, radiographic, and histopathologic examination. In the genome-wide search for a susceptibility locus, OA cases were defined as those who had undergone total hip replacement associated with a clinical and radiographic diagnosis of hip OA. A genome-wide scan was performed using a framework set of microsatellite markers with an average spacing of 10 cM. RESULTS: The hip OA of this family was indistinguishable from that of idiopathic, nonfamilial hip OA. There was no apparent evidence of spondyloepiphyseal dysplasia or other dysplasias usually associated with mutations in collagen genes. The genome-wide scan revealed a locus on chromosome 16p between 28 cM and 47 cM from the telomere, and this locus met the criteria for suggestive linkage (multipoint allele-sharing logarithm of odds [LOD] score 2.58, P = 1.6 x 10(-4)). Two additional regions with LOD scores of >1.5 were obtained. CONCLUSION: We have identified and described the largest kinship with familial hip OA reported to date. Evidence for linkage in this family suggests that a gene for susceptibility to hip OA exists on chromosome 16p. This represents an independent identification of a susceptibility locus previously reported for hip OA in this geographic region.

The technique of scleral indentation.

The technique of scleral indentation, or depression, shall be presented in both mechanical and clinical manners. Explanation and diagrams of several optical principles involved in indentation precede a discussion of clinical performance. Indications, cautions, and suggestions for improving skill are cited.