Pathogenicity: Alzheimer's Disease : Pathogenic
ACMG/AMP Pathogenicity Criteria: PS3, PS4, PM1, PM2, PM5, PP1, PP2, PP3
Clinical Phenotype: Alzheimer's Disease
Reference Assembly: GRCh37/hg19
Position: Chr21:27264096 G>C
dbSNP ID: rs63750264
Coding/Non-Coding: Coding
Mutation Type: Point, Missense
Codon Change: GTC to CTC
Reference Isoform: APP Isoform APP770 (770 aa)
Genomic Region: Exon 17


This was the fourth AD-associated mutation discovered involving codon 717 in APP. It was first reported in an American family in which the proband was diagnosed with Alzheimer's disease at age 38. Her presentation was typical for her family, with short-term memory problems appearing in the mid- to late 30s and gradual deterioration over approximately 10 years. The mean age of onset in this family was 38 years (range: 35 to 39 years) based on data from four affected family members. While three affected members carried the mutation, five unaffected members who were older than the mean age at onset, did not, indicating cosegregation of the mutation with disease (Murrell et al., 2000).

Another kindred, known as "Family 171," was also found to carry this mutation. This Caucasian family of English ancestry had a later age of onset. The mean age of onset for the seven affected family members was 50 years (range: 48 to 57 years). The mean age at death was 61 years (range: 57 to 68 years). In addition to the progressive memory impairment typical of AD, some members of this family also experienced seizures and hallucinations (Godbolt et al., 2006).

Two additional unrelated patients of German origin were also found to carry this mutation. One patient, identified as P. 43, had dementia onset at age 50 and a family history of dementia. The other, identified as P. 83, had dementia onset at age 43 and a family history of dementia (Finckh et al., 2005).

This mutation was detected in a Japanese family affected by early onset Alzheimer’s disease. The reported pedigree shows nine affected family members over three generations. The average age at onset in this family was 47.1 ± 3.1 years (range: 42 to 52 years). Typical of his family, the proband developed short-term memory loss and concentration deficits at age 45. Other symptoms in this family included psychiatric symptoms (e.g., depression, irritability, emotional lability), seizures, myoclonus, gait disturbance, and pyramidal signs. The mutation was detected in three affected family members, but not in the proband's unaffected mother, indicating the mutation cosegregates with disease. The mutation was also absent from 50 unrelated controls. MRI showed relatively minor atrophic changes in the bilateral hippocampus and cerebral cortices (Abe et al., 2012).

Additional reports of mutation carriers include another kindred (Ghetti et al., 2008) and an individual Caucasian patient affected by early onset AD (onset at age 59) whose diagnosis was confirmed by autopsy (Sassi et al., 2014).

This mutation was absent from the gnomAD variant database (v2.1.1, Oct 2021).


MRIs of affected members of the Japanese family showed relatively minor atrophic changes in the bilateral hippocampus and cerebral cortices (Abe et al., 2012).

Biological Effect

In primary mouse neurons this mutation increases the Aβ42/Aβ40 ratio by increasing levels of Aβ42 and decreasing levels of Aβ40 (De Jonghe et al., 2001). It has been predicted to be "possibly damaging" in silico (Sassi et al., 2014). Consistently, V717L's PHRED-scaled CADD score, which integrates diverse information in silico, was above 20, suggesting a deleterious effect (CADD v.1.6, Oct 2021).

A cryo-electron microscopy study of an APP fragment bound to PSEN1 revealed that V717 is nestled in a shallow hydrophobic pocket formed by PSEN1 F237, I387, and F388 (Zhou et al., 2019; Jan 2019 news).


Alzheimer's Disease : Pathogenic

This variant fulfilled the following criteria based on the ACMG/AMP guidelines. See a full list of the criteria in the Methods page.


Well-established in vitro or in vivo functional studies supportive of a damaging effect on the gene or gene product.


The prevalence of the variant in affected individuals is significantly increased compared to the prevalence in controls. V717L : The variant was reported in 3 or more unrelated patients with the same phenotype, and absent from controls.


Located in a mutational hot spot and/or critical and well-established functional domain (e.g. active site of an enzyme) without benign variation. V717L : Variant is in a mutational hot spot and cryo-EM data suggest residue is of functional importance.


Absent from controls (or at extremely low frequency if recessive) in Exome Sequencing Project, 1000 Genomes Project, or Exome Aggregation Consortium. *Alzforum uses the gnomAD variant database.


Novel missense change at an amino acid residue where a different missense change determined to be pathogenic has been seen before.


Co-segregation with disease in multiple affected family members in a gene definitively known to cause the disease: *Alzforum requires at least one affected carrier and one unaffected non-carrier from the same family to fulfill this criterion. V717L : At least one family with >=3 affected carriers and >=1 unaffected noncarriers.


Missense variant in a gene that has a low rate of benign missense variation and where missense variants are a common mechanism of disease.


Multiple lines of computational evidence support a deleterious effect on the gene or gene product (conservation, evolutionary, splicing impact, etc.). *In most cases, Alzforum applies this criterion when the variant’s PHRED-scaled CADD score is greater than or equal to 20.

Pathogenic (PS, PM, PP) Benign (BA, BS, BP)
Criteria Weighting Strong (-S) Moderate (-M) Supporting (-P) Supporting (-P) Strong (-S) Strongest (BA)

Last Updated: 22 Feb 2022


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News Citations

  1. CryoEM γ-Secretase Structures Nail APP, Notch Binding

Paper Citations

  1. . Early-onset Alzheimer disease caused by a new mutation (V717L) in the amyloid precursor protein gene. Arch Neurol. 2000 Jun;57(6):885-7. PubMed.
  2. . A second family with familial AD and the V717L APP mutation has a later age at onset. Neurology. 2006 Feb 28;66(4):611-2. PubMed.
  3. . Novel mutations and repeated findings of mutations in familial Alzheimer disease. Neurogenetics. 2005 May;6(2):85-9. Epub 2005 Mar 18 PubMed.
  4. . Phenotypical difference of Amyloid Precursor Protein (APP) V717L mutation in Japanese family. BMC Neurol. 2012 Jun 15;12(1):38. PubMed.
  5. . Familial Alzheimer disease associated with the V717L amyloid precursor protein gene mutation: Neuropathological characterization. Alzheimers Dement. 2008 Jul;4(4 Suppl):T585.
  6. . Exome sequencing identifies 2 novel presenilin 1 mutations (p.L166V and p.S230R) in British early-onset Alzheimer's disease. Neurobiol Aging. 2014 Oct;35(10):2422.e13-6. Epub 2014 May 2 PubMed.
  7. . Pathogenic APP mutations near the gamma-secretase cleavage site differentially affect Abeta secretion and APP C-terminal fragment stability. Hum Mol Genet. 2001 Aug 1;10(16):1665-71. PubMed.
  8. . Recognition of the amyloid precursor protein by human γ-secretase. Science. 2019 Feb 15;363(6428) Epub 2019 Jan 10 PubMed.

Further Reading


  1. . Presymptomatic Genetic Testing with an APP Mutation in Early-Onset Alzheimer Disease: A Descriptive Study of Sibship Dynamics. J Genet Couns. 2000 Aug;9(4):327-41. PubMed.

Protein Diagram

Primary Papers

  1. . Early-onset Alzheimer disease caused by a new mutation (V717L) in the amyloid precursor protein gene. Arch Neurol. 2000 Jun;57(6):885-7. PubMed.

Other mutations at this position


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