This study is extremely interesting because it identifies rare functional variations that lead to mental retardation and epilepsy in genes encoding NMDA receptor subunits. Here mutations in the GRIN2B gene are identified and cause moderate to severe mental retardation and brain structure anomalies. Though this study shows a severe phenotype resulting from a single mutation, late-onset AD is commonly thought to be a multi-factorial disease, which results from carrying many risk alleles, each of which lends a small predisposition to the development of the disease. As such it is unlikely that the specific variants identified here are also related to Alzheimer's.

However, this study does demonstrate that variations in the coding sequence of the GRIN2B gene have serious consequences on the structure and function of the brain. In our work, we found that a variant in the non-coding region of the same gene between exons 2 and 3 (which is close to one of the causative mutations identified in this study) is associated with subtle differences in temporal lobe volume and slight...  Read more

This study is extremely interesting because it identifies rare functional variations that lead to mental retardation and epilepsy in genes encoding NMDA receptor subunits. Here mutations in the GRIN2B gene are identified and cause moderate to severe mental retardation and brain structure anomalies. Though this study shows a severe phenotype resulting from a single mutation, late-onset AD is commonly thought to be a multi-factorial disease, which results from carrying many risk alleles, each of which lends a small predisposition to the development of the disease. As such it is unlikely that the specific variants identified here are also related to Alzheimer's.

However, this study does demonstrate that variations in the coding sequence of the GRIN2B gene have serious consequences on the structure and function of the brain. In our work, we found that a variant in the non-coding region of the same gene between exons 2 and 3 (which is close to one of the causative mutations identified in this study) is associated with subtle differences in temporal lobe volume and slight predisposition to development of Alzheimer's disease. This suggests that more common variants in the same gene, like the one we identified, may have effects similar but more subtle than those identified in this paper. The subtle effects might lend risk to neurodegeneration and subsequent development of Alzheimer's disease.

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