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One of the most significant risk variants for Parkinson’s disease (PD), rs356182, is located at the PD-associated locus near the alpha-synuclein (α-syn) encoding gene, SNCA. SNCA-proximal variants, including rs356182, are thought to function in PD risk through enhancers via allele-specific regulatory effects on SNCA expression. However, this interpretation discounts the complex activity of genetic enhancers and possible non-conical functions of α-syn. Here we investigated a novel risk mechanism for rs356182. We use CRISPR-Cas9 in LUHMES cells, a model for dopaminergic midbrain neurons, to generate precise hemizygous lesions at rs356182. The PD-protective (A/−), PD-risk (G/−) and wild-type (A/G) clones were neuronally differentiated and then compared transcriptionally and morphologically. Among the affected genes was SNCA, whose expression was promoted by the PD-protective allele (A) and repressed in its absence. In addition to SNCA, hundreds of genes were differentially expressed and associated with neurogenesis and axonogenesis—an effect not typically ascribed to α-syn. We also found that the transcription factor FOXO3 specifically binds to the rs356182 A-allele in differentiated LUHMES cells. Finally, we compared the results from the rs356182-edited cells to our previously published knockouts of SNCA and found only minimal overlap between the sets of significant differentially expressed genes. Together, the data implicate a risk mechanism for rs356182 in which the risk-allele (G) is associated with abnormal neuron development, independent of SNCA expression. We speculate that these pathological effects manifest as a diminished population of dopaminergic neurons during development leading to the predisposition for PD later in life.

Normal polymorphic size variation of the exon 1 CAG microsatellite of the androgen receptor (AR) is associated with prostate cancer, benign prostatic hyperplasia and male infertility. Furthermore, abnormal expansion of the satellite leads to Kennedy's disease. We have shown recently that the AR N-terminal domain (NTD), which contains the polyglutamine (polyQ) stretch (encoded by the CAG repeat), functionally interacts with the C-termini of p160 coactivators. In the present study we explored possible AR CAG size effects on the p160 coactivator-mediated transactivation activity of the receptor. First, we mapped the p160 coactivator interaction on the AR NTD and found an interaction surface between amino acids 351 and 537. Although this region is 'downstream' from the polyQ stretch, it is still within the AR NTD, is implicated in constitutive transactivation activity of the receptor, and thus might be subject to polyQ size modulation. Indeed, cotrans- fection experiments in cultured prostate epithelial cells, using AR constructs of varying CAG sizes and p160 coactivator expression vectors, revealed that increased polyQ length, up to a size of 42 repeats, inhibited both basal and coactivator-mediated AR transactivation activity. AR expression in these cells, on the other hand, was unaffected by the same increased CAG repeat size range. We conclude that the AR NTD contributes to AR transactivation activity via functional interactions with p160 coactivators and that increasing polyQ length negatively affects p160-mediated coactivation of the AR. This molecular mechanism thus might explain, at least in part, the observed phenotypic effects of the AR CAG size polymorphism.

Background: Prostate cancer is an increasingly common disease for which there are few well-established risk factors. Family history data suggest a genetic component; however, the majority of prostate cancer cases cannot be explained by a single-gene model. Prostate cell division is influenced by two steroid hormones, testosterone and vitamin D, the action of each being mediated by its respective receptor. The genes for the two receptors are candidates in a multigenic model for prostate cancer susceptibility. Purpose: We examined genetic polymorphisms in two steroid receptors, the androgen receptor (AR) and the vitamin D receptor (VDR), in a case-control pilot study of prostate cancer. Methods: Fifty-seven non-Hispanic white case patients with prostate cancer and 169 non-Hispanic white control subjects were genotyped for a previously described microsatel-lite (CAG repeats) in the AR gene and for a newly discovered poly-A micro-satellite in the 3'-untranslated region (3'UTR) of the VDR gene. To compare genotypes with respect to prostate cancer risk, we estimated odds ratios (ORs) by using logistic regression. ORs were also estimated separately for advanced and localized cases of disease. All P values resulted from two-sided tests. Results: Both the AR and the VDR polymorphisms were associated, individually and after mutual adjustment, with prostate cancer. Adjusted ORs (95% confidence intervals [CIs]) for prostate cancer were 2.10 (95% CI = 1.11-3.99) for individuals carrying an AR CAG allele with fewer than 20 repeats versus an allele with 20 or more repeats and 4.61 (95% CI = 1.34-15.82) for individuals carrying at least one long (A 18 to A 22 ) VDR poly-A allele versus two short (A 14 to A 17 ) poly-A alleles. For both the AR and VDR genes, the at-risk genotypes were more strongly associated with advanced disease than with localized disease. Conclusions : In this pilot study, genetic variation in both the VDR and the AR genes was associated with prostate cancer, and both genes appear to preferentially confer risk for advanced disease. These two genetic risk factors, if confirmed, are among the strongest risk factors yet identified for prostate cancer. Implications: These results are consistent with a multigenic model of prostate cancer susceptibility. On the basis of the joint effect of several genetic loci, one might ultimately be able to construct a risk profile to predict advanced disease, so that men whose disease is unlikely to progress to an advanced stage can possibly be spared aggressive treatment.

A subgroup of trinucleotide repeat diseases result from abnormal expansions of CAG repeats which are translated into polyglutamine stretches. As yet there is little understanding of how the polyglutamines function either normally, or when expanded. We have investigated these sequences in the Machado-Joseph disease, androgen receptor and spinocerebellar ataxia type 1 genes in humans and other primates. None of the 748 normal chromosomes that were examined had more than 34 uninterrupted glutamine codons in the Machado-Joseph disease gene. Similarly, no normal alleles with more than 39 uninterrupted glutamine codons have been reported for the other disease genes associated with polyglutamine expansions. Sequence analyses of the repeats in primates revealed shorter polyglutamine stretches in some of the non-human primates at all three loci and marked diversions from the expected polyglutamines in the orang-utan Machado-Joseph gene and in the marmoset spinocerebellar ataxia type 1 gene. These data suggest that conservation of these polyglutamine stretches may not always be necessary for normal gene function.