Mutations

PSEN1 c.869-22_869-23ins18 (ΔE9)

Other Names: ΔE9, Δ9, deltaE9

Overview

Pathogenicity: Alzheimer's Disease : Not Classified
ACMG/AMP Pathogenicity Criteria: PS3, PM1, PM2, PM4, BP4
Clinical Phenotype: Alzheimer's Disease, Spastic Paraparesis
Reference Assembly: GRCh37/hg19
Position: Chr14:73673071_73673072 ->TGGAATTTTGTGCTGTTG
dbSNP ID: NA
Coding/Non-Coding: Both
DNA Change: Insertion
Expected RNA Consequence: Splicing Alteration
Expected Protein Consequence: Deletion
Genomic Region: Intron 8, Exon 9

Findings

This mutation involves the insertion of 18 nucleotides in intron 8 (c.869-22_869-23insTGGAATTTTGTGCTGTTG) and results in the in-frame skipping of exon 9. It is one of several mutations in PSEN1 that are notable for exclusion of exon 9, which are variously referred to as ΔE9, Δ9, delE9, or deltaE9. This particular mutation was identified in a French patient whose family had a history of dementia (three affected family members in two generations). Onset ranged from 42 to 47 years, and two of the affected individuals also developed nearly concurrent symptoms of spasticity (Dumanchin et al., 2006).

This variant was absent from the gnomAD variant database (gnomAD v2.1.1).

Neuropathology

Neuropathological examination of two brains revealed widespread neurofibrillary tangles and numerous plaques, including both large, non-neuritic cotton-wool plaques and neuritic plaques more typical of AD. Marked cerebral amyloid angiopathy was also observed (Dumanchin et al., 2006).

Biological Effect

Analysis of patient mRNA extracted from peripheral blood cells and analyzed by RT-PCR followed by ethidium bromide gel separation showed transcripts lacking exon 9. Ex vivo splicing assays confirmed these results in HeLa cells and in the neuroblastoma cell line SH-SY5Y (Dumanchin et al., 2006). Although several in silico algorithms predicted this variant is damaging (Xiao et al., 2021), its PHRED-scaled CADD score, which integrates diverse information, was only 7.7 (CADD v.1.6, Sep 2021).

The following summary refers to studies of PSEN1 mutants that result in the exclusion of exon 9 (denoted here as PSEN1ΔE9). Multiple in vitro and in vivo assays have shown that PSEN1ΔE9 impairs endoproteolytic processing of PSEN1 (Thinakaran et al., 1996, Lee et al., 1997) and alters the production of Aβ42 and Aβ40 peptides resulting in an increased Aβ42/Aβ40 ratio (Borchelt et al., 1996, Steiner et al., 1999, Dumanchin et al., 2006; Kumar-Singh et al., 2006, Bentahir et al., 2006, Woodruff et al., 2013, Cacquevel et al., 2012, Sun et al., 2017). Moreover, studies surveying the production of Aβ peptides of different lengths have indicated that these mutations result in increased levels of longer Aβ peptides, and decreased levels of shorter peptides (Chávez-Gutiérrez et al., 2012; Svedružić et al., 2012; Kakuda et al., 2021). Chávez-Gutiérrez and colleagues proposed this is the result of impairment of the fourth γ-secretase cleavage in the two Aβ production lines that sequentially digest Aβ49 and Aβ48 into shorter peptides (Chávez-Gutiérrez et al., 2012).

Consistent with these findings, three more recent studies revealed PSEN1ΔE9 mutants decrease the Aβ (37 + 38 + 40) / (42 + 43) ratio and the Aβ37/Aβ42 ratio, both of which reflect γ-processivity, compared with cells expressing wildtype PSEN1 (Apr 2022 news; Petit et al., 2022; Liu et al., 2022). The two ratios were reported to outperform the Aβ42/Aβ40 ratio as indicators of AD pathogenicity, with the former correlating with AD age at onset. Moreover, a follow-up study reported in a preprint, combined the Aβ (37 + 38 + 40) / (42 + 43) ratio with the commonly used Aβ42/Aβ40 ratio (a measure of the relative production of aggregation-prone Aβ) to yield a composite measure which reflects γ-secretase function as a percentage of wildtype activity (Schulz et al., 2023). This composite score (36.87 for PSEN1ΔE9) was strongly associated, not only with age at onset, but with biomarker and cognitive trajectories.

Exon 9 deletion mutations may also affect PSEN1 transcription. In a bacterial artificial chromosome (BAC)-based expression model, PSEN1ΔE9-expressing cells exhibited reduced PSEN1 gene expression and partial loss of function relative to cells expressing wild-type PSEN1 (Ahmadi et al., 2014).

The absence of exon 9 may impair Notch processing as well. Although one study found no effect of the mutation on this substrate (Chávez-Gutiérrez et al., 2012), others have reported impaired Notch S3 cleavage and corresponding alterations in the differentiation and self-renewal of neural progenitor cells in the adult mouse brain (Bentahir et al., 2006; Veeraraghavalu et al., 2010; May 2010 news).

PSEN1ΔE9 mutations have also been implicated in the disruption of several intracellular functions. For example, by lowering PIP2 levels, PSEN1ΔE9 appears to block a cation channel that mediates capacitive calcium entry (Landman et al., 2006; Dec 2006 news). In addition, impairments in endocytosis, cholesterol homeostasis, autophagy, and APP intracellular localization have been reported (Woodruff et al., 2016; Oct 2016 news; Cho et al., 2019; Oh and Chung, 2017). In addition, alterations in tight and adherens junction protein expression, as well as in efflux properties, were found in iPSC-derived brain endothelial cells, a model of blood-brain barrier function (Oikari et al., 2020).

Interestingly, PSEN1 was reported to play a key role in ApoE secretion and cytoplasmic localization. In experiments with PSEN-deficient fibroblasts, PSEN1ΔE9 transfection was less able to rescue these functions compared with transfection of wildtype PSEN1 (Islam et al., 2022).

PSEN1ΔE9 had little effect on microglia, a cell type that normally expresses very low levels of PSEN1, although it appeared to weaken the cells’ inflammatory response (Konttinen et al., 2019, Sep 2019 news).

Pathogenicity

Alzheimer's Disease : Not Classified*

*This variant fulfilled some ACMG-AMP criteria, but it is not classified by Alzforum because only one affected carrier has been reported, and the variant is absent from the gnomAD database. Note that multiple mutations resulting in the same consequence (deletion of exon 9) are pathogenic.

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

PS3-S

Well-established in vitro or in vivo functional studies supportive of a damaging effect on the gene or gene product. c.869-22_869-23ins18: Functional data derive from assays involving exon 9 deletion mutants, not necessarily this specific variant.

PM1-M

Located in a mutational hot spot and/or critical and well-established functional domain (e.g. active site of an enzyme) without benign variation.

PM2-M

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.

PM4-M

Protein length changes due to in-frame deletions/insertions in a non-repeat region or stop-loss variants.

BP4-P

Multiple lines of computational evidence suggest no impact on 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 less than 20.

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

Research Models

Transgenic mice expressing PSEN1 lacking exon 9 have beeen generated, such as line S-9 (Lee et al., 1997), which was subsequently bred to an APP transgenic mouse to generate APPSwe/PSEN1dE9, which has more extensive pathology than either of the parental lines. Another double transgenic model was made by coinjecting vectors expressing PSEN1ΔE9 and APP with the Swedish mutation (APPswe/PSEN1dE9 (Borchelt mice)). Although cotton wool plaques are sometimes prominent in the brains of AD patients with ΔE9 mutations, this pathology has not been observed in ΔE9 mouse models.

In addition, induced pluripotent stem cell lines derived from patients have been used to generate neurons (Woodruff et al., 2013), astrocytes (Oksanen et al., 2017), and brain endothelial cells (Oikari et al., 2020) which display several features of AD pathology.

Last Updated: 14 Oct 2023

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References

News Citations

  1. Ratio of Short to Long Aβ Peptides: Better Handle on Alzheimer's than Aβ42/40?
  2. Notch Your Average Joe—Grounds for PS1 Neurogenesis Inhibition?
  3. Beyond γ-Secretase: FAD Mutations Affect Calcium Channel via Lipid Messenger
  4. Cholesterol Trafficking Takes a Hit in Alzheimer’s Neurons
  5. Among AD Mutations, Only ApoE4 Seems to Hobble Microglia

Paper Citations

  1. . Hyperaccumulation of FAD-linked presenilin 1 variants in vivo. Nat Med. 1997 Jul;3(7):756-60. PubMed.
  2. . Defective Transcytosis of APP and Lipoproteins in Human iPSC-Derived Neurons with Familial Alzheimer's Disease Mutations. Cell Rep. 2016 Oct 11;17(3):759-773. PubMed.
  3. . PSEN1 Mutant iPSC-Derived Model Reveals Severe Astrocyte Pathology in Alzheimer's Disease. Stem Cell Reports. 2017 Dec 12;9(6):1885-1897. Epub 2017 Nov 16 PubMed.
  4. . Altered Brain Endothelial Cell Phenotype from a Familial Alzheimer Mutation and Its Potential Implications for Amyloid Clearance and Drug Delivery. Stem Cell Reports. 2020 May 12;14(5):924-939. Epub 2020 Apr 9 PubMed.
  5. . Biological effects of four PSEN1 gene mutations causing Alzheimer disease with spastic paraparesis and cotton wool plaques. Hum Mutat. 2006 Oct;27(10):1063. PubMed.
  6. . APP, PSEN1, and PSEN2 Variants in Alzheimer's Disease: Systematic Re-evaluation According to ACMG Guidelines. Front Aging Neurosci. 2021;13:695808. Epub 2021 Jun 18 PubMed.
  7. . Endoproteolysis of presenilin 1 and accumulation of processed derivatives in vivo. Neuron. 1996 Jul;17(1):181-90. PubMed.
  8. . Familial Alzheimer's disease-linked presenilin 1 variants elevate Abeta1-42/1-40 ratio in vitro and in vivo. Neuron. 1996 Nov;17(5):1005-13. PubMed.
  9. . The biological and pathological function of the presenilin-1 Deltaexon 9 mutation is independent of its defect to undergo proteolytic processing. J Biol Chem. 1999 Mar 19;274(12):7615-8. PubMed.
  10. . Mean age-of-onset of familial alzheimer disease caused by presenilin mutations correlates with both increased Abeta42 and decreased Abeta40. Hum Mutat. 2006 Jul;27(7):686-95. PubMed.
  11. . Presenilin clinical mutations can affect gamma-secretase activity by different mechanisms. J Neurochem. 2006 Feb;96(3):732-42. PubMed.
  12. . The presenilin-1 ΔE9 mutation results in reduced γ-secretase activity, but not total loss of PS1 function, in isogenic human stem cells. Cell Rep. 2013 Nov 27;5(4):974-85. Epub 2013 Nov 14 PubMed.
  13. . Alzheimer's disease-linked mutations in presenilin-1 result in a drastic loss of activity in purified γ-secretase complexes. PLoS One. 2012;7(4):e35133. PubMed.
  14. . Analysis of 138 pathogenic mutations in presenilin-1 on the in vitro production of Aβ42 and Aβ40 peptides by γ-secretase. Proc Natl Acad Sci U S A. 2017 Jan 24;114(4):E476-E485. Epub 2016 Dec 5 PubMed.
  15. . The mechanism of γ-Secretase dysfunction in familial Alzheimer disease. EMBO J. 2012 May 16;31(10):2261-74. Epub 2012 Apr 13 PubMed.
  16. . Modulation of γ-secretase activity by multiple enzyme-substrate interactions: implications in pathogenesis of Alzheimer's disease. PLoS One. 2012;7(3):e32293. PubMed.
  17. . Switched Aβ43 generation in familial Alzheimer's disease with presenilin 1 mutation. Transl Psychiatry. 2021 Nov 3;11(1):558. PubMed.
  18. . Aβ profiles generated by Alzheimer's disease causing PSEN1 variants determine the pathogenicity of the mutation and predict age at disease onset. Mol Psychiatry. 2022 Jun;27(6):2821-2832. Epub 2022 Apr 1 PubMed.
  19. . Identification of the Aβ37/42 peptide ratio in CSF as an improved Aβ biomarker for Alzheimer's disease. Alzheimers Dement. 2022 Mar 12; PubMed.
  20. . Functional variations in gamma-secretase activity are critical determinants of the clinical, biomarker, and cognitive progression of autosomal dominant Alzheimer's disease. 2023 Jul 25 10.1101/2023.07.04.547688 (version 2) bioRxiv.
  21. . Familial Alzheimer's disease coding mutations reduce Presenilin-1 expression in a novel genomic locus reporter model. Neurobiol Aging. 2014 Feb;35(2):443.e5-443.e16. PubMed.
  22. . Presenilin 1 mutants impair the self-renewal and differentiation of adult murine subventricular zone-neuronal progenitors via cell-autonomous mechanisms involving notch signaling. J Neurosci. 2010 May 19;30(20):6903-15. PubMed.
  23. . Presenilin mutations linked to familial Alzheimer's disease cause an imbalance in phosphatidylinositol 4,5-bisphosphate metabolism. Proc Natl Acad Sci U S A. 2006 Dec 19;103(51):19524-9. PubMed.
  24. . Elevated cellular cholesterol in Familial Alzheimer's presenilin 1 mutation is associated with lipid raft localization of β-amyloid precursor protein. PLoS One. 2019;14(1):e0210535. Epub 2019 Jan 25 PubMed.
  25. . Activation of transient receptor potential melastatin 7 (TRPM7) channel increases basal autophagy and reduces amyloid β-peptide. Biochem Biophys Res Commun. 2017 Nov 4;493(1):494-499. Epub 2017 Sep 1 PubMed.
  26. . Presenilin Is Essential for ApoE Secretion, a Novel Role of Presenilin Involved in Alzheimer's Disease Pathogenesis. J Neurosci. 2022 Feb 23;42(8):1574-1586. Epub 2022 Jan 5 PubMed.
  27. . PSEN1ΔE9, APPswe, and APOE4 Confer Disparate Phenotypes in Human iPSC-Derived Microglia. Stem Cell Reports. 2019 Oct 8;13(4):669-683. Epub 2019 Sep 12 PubMed.

Other Citations

  1. APPSwe/PSEN1dE9

External Citations

  1. gnomAD v2.1.1
  2. CADD v.1.6

Further Reading

No Available Further Reading

Protein Diagram

Primary Papers

  1. . Biological effects of four PSEN1 gene mutations causing Alzheimer disease with spastic paraparesis and cotton wool plaques. Hum Mutat. 2006 Oct;27(10):1063. PubMed.

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