What is a genetic cause? The example of Alzheimer's Disease

Polymorphisms within ASTN2 gene are associated with age at onset of Alzheimer's disease

Alzheimer's disease (AD) is a multifactorial neurological condition associated with genetic profiles that are still not completely understood. We performed a family-based low-density genome-wide association analysis of age at onset (AAO) in AD (244 patients and their relatives) using Illumina 6 K single-nucleotide polymorphisms (SNPs) panel and the FBAT-logrank statistic. We observed 10 SNPs associated with AAO in AD with p < 2 × 10(-3). The most significant hit within a known gene, the neuronal protein astrotactin 2 (ASTN2), was SNP rs1334071 (p = 8.74 × 10(-4)). ASTN2 has been implicated in several neuropsychiatric disorders, including cognitive disorders, autism and schizophrenia. We then conducted a replication study focusing on ASTN2 gene in a Canadian sample of 791 AD patients and 782 controls using the logrank test. Five ASTN2 SNPs (highest association is rs16933774 with p = 0.0053) showed associations with AAO in this Canadian sample (p < 0.05). Furthermore, Kaplan-Meier survival analysis of SNP rs16933774 showed that the AAO of AD in individuals heterozygous for AG genotype of rs16933774 (median of AAO = 68.5 years) was approximately 4.5 years earlier than those individuals having the AA genotype (median of AAO = 73 years). In conclusion, a significant association of ASTN2 genetic variants with AAO of AD in two independent samples demonstrates a role for ASTN2 in the pathogenesis of AD. Future functional studies of this gene may help to characterize the genetic architecture of the AAO of AD. Genetic factors in AAO may be a critical factor for early AD intervention and prevention efforts.

Explanatory pluralism in the medical sciences: theory and practice

Explanatory pluralism is the view that the best form and level of explanation depends on the kind of question one seeks to answer by the explanation, and that in order to answer all questions in the best way possible, we need more than one form and level of explanation. In the first part of this article, we argue that explanatory pluralism holds for the medical sciences, at least in theory. However, in the second part of the article we show that medical research and practice is actually not fully and truly explanatory pluralist yet. Although the literature demonstrates a slowly growing interest in non-reductive explanations in medicine, the dominant approach in medicine is still methodologically reductionist. This implies that non-reductive explanations often do not get the attention they deserve. We argue that the field of medicine could benefit greatly by reconsidering its reductive tendencies and becoming fully and truly explanatory pluralist. Nonetheless, trying to achieve the right balance in the search for and application of reductive and non-reductive explanations will in any case be a difficult exercise.

Genetic research into Alzheimer's disease: a European focus group study on ethical issues

BACKGROUND

Nowadays, there is an increasing interest in the heritable aspects of Alzheimer's Disease (AD). The ethical implications of this kind of research are also attracting attention. However, relatively few open-ended qualitative studies have been carried out to study these aspects.

OBJECTIVE

To explore and analyse ethical issues raised by genetic research into AD.

METHODS

A modified focus group technique.

RESULTS

Participants stressed the importance of relatives in genetic research and suggested a family consent procedure. The consent procedure ought to be more uniform within Europe and should allow for variation in the types of research being done. The long-term results of genetic research into AD are expected to be positive while the short-term results seem likely to be negative. The perception of AD as a disease could be changed by the results from genetic research into AD, and this could have effects at the individual level (feelings of guilt and responsibility for one's own health).

CONCLUSIONS

(1) The role of the family in genetic AD research differs from its role in other biomedical research into AD. The development of a family consent procedure might solve some informed consent problems. (2) Negative social consequences of genetic AD research are expected in the short term, but there are hopes of positive consequences in the long term.

Memory enhancing drugs and Alzheimer's disease: enhancing the self or preventing the loss of it?

In this paper we analyse some ethical and philosophical questions related to the development of memory enhancing drugs (MEDs) and anti-dementia drugs. The world of memory enhancement is coloured by utopian thinking and by the desire for quicker, sharper, and more reliable memories. Dementia is characterized by decline, fragility, vulnerability, a loss of the most important cognitive functions and even a loss of self. While MEDs are being developed for self-improvement, in Alzheimer's Disease (AD) the self is being lost. Despite this it is precisely those patients with AD and other forms of dementia that provide the subjects for scientific research on memory improvement. Biomedical research in the field of MEDs and anti-dementia drugs appears to provide a strong impetus for rethinking what we mean by 'memory', 'enhancement', 'therapy', and 'self'. We conclude (1) that the enhancement of memory is still in its infancy, (2) that current MEDs and anti-dementia drugs are at best partially and minimally effective under specific conditions, (3) that 'memory' and 'enhancement' are ambiguous terms, (4) that there is no clear-cut distinction between enhancement and therapy, and (5) that the research into MEDs and anti-dementia drugs encourages a reductionistic view of the human mind and of the self.