17-44915253-G-T

Variant names:

• chr17-44915253-G-T
• rs121909720
• NM_002055.5:c.234C>A

Variant summary

Our verdict is Pathogenic. The variant received 12 ACMG points: 12P and 0B. PM1 PM2 PM5 PP3_Strong PP5_Moderate

The NM_002055.5(GFAP):​c.234C>A​(p.Asp78Glu) variant causes a missense change. The variant allele was found at a frequency of 0.000000684 in 1,461,850 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. D78N) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: GFAP NM_002055.5 missense
• Clinical Significance: Pathogenic criteria provided, single submitter P:2 O:1
• Conservation: PhyloP100: 5.86
• Publications: 8 publications found

Genes affected

GFAP (HGNC:4235): (glial fibrillary acidic protein) This gene encodes one of the major intermediate filament proteins of mature astrocytes. It is used as a marker to distinguish astrocytes from other glial cells during development. Mutations in this gene cause Alexander disease, a rare disorder of astrocytes in the central nervous system. Alternative splicing results in multiple transcript variants encoding distinct isoforms. [provided by RefSeq, Oct 2008]

GFAP Gene-Disease associations (from GenCC):

• Alexander disease

  Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: ClinGen, Genomics England PanelApp, Labcorp Genetics (formerly Invitae), G2P
• Alexander disease type II

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Pathogenic. The variant received 12 ACMG points.

• PM1: In a hotspot region, there are 17 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 20 uncertain in NM_002055.5
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr17-44915255-C-A is described in ClinVar as Pathogenic. ClinVar VariationId is 2138058.Status of the report is criteria_provided_single_submitter, 1 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.977
• PP5: Variant 17-44915253-G-T is Pathogenic according to our data. Variant chr17-44915253-G-T is described in ClinVar as Pathogenic. ClinVar VariationId is 16179.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
GFAP	NM_002055.5	c.234C>A	p.Asp78Glu	missense_variant	Exon 1 of 9	ENST00000588735.3	NP_002046.1
GFAP	NM_001363846.2	c.234C>A	p.Asp78Glu	missense_variant	Exon 1 of 10		NP_001350775.1
GFAP	NM_001242376.3	c.234C>A	p.Asp78Glu	missense_variant	Exon 1 of 7		NP_001229305.1
GFAP	NM_001131019.3	c.234C>A	p.Asp78Glu	missense_variant	Exon 1 of 8		NP_001124491.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
GFAP	ENST00000588735.3	c.234C>A	p.Asp78Glu	missense_variant	Exon 1 of 9	1	NM_002055.5	ENSP00000466598.2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461850 Hom.: 0 Cov.: 31 AF XY: 0.00 AC XY: 0 AN XY: 727230

African (AFR) AF: 0.00 AC: 0 AN: 33480

American (AMR) AF: 0.00 AC: 0 AN: 44724

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39700

South Asian (SAS) AF: 0.00 AC: 0 AN: 86258

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53384

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 8.99e-7 AC: 1 AN: 1112004

Other (OTH) AF: 0.00 AC: 0 AN: 60396

GnomAD4 genome Cov.: 32

Alfa AF: 0.00 Hom.: 0

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:2 Other:1

Revision: criteria provided, single submitter

Submissions by phenotype

Alexander disease Pathogenic:1 Other:1

Sep 01, 2003

OMIM

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: literature only

- -

-

GeneReviews

Significance: not provided

Review Status: no classification provided

Collection Method: literature only

- -

not provided Pathogenic:1

Jul 28, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

For these reasons, this variant has been classified as Pathogenic. This variant disrupts the p.Asp78 amino acid residue in GFAP. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 26743065). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) has been performed at Invitae for this missense variant, however the output from this modeling did not meet the statistical confidence thresholds required to predict the impact of this variant on GFAP protein function. ClinVar contains an entry for this variant (Variation ID: 16179). This missense change has been observed in individual(s) with Alexander disease (PMID: 12975300). It has also been observed to segregate with disease in related individuals. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces aspartic acid, which is acidic and polar, with glutamic acid, which is acidic and polar, at codon 78 of the GFAP protein (p.Asp78Glu). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.91
BayesDel_addAF	Pathogenic	0.42	D
BayesDel_noAF	Pathogenic	0.36
CADD	Uncertain	25
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.82	.;D;.;.;.;D;.;.;.
Eigen	Uncertain	0.68
Eigen_PC	Uncertain	0.61
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.96	D;D;D;D;D;D;D;D;D
M_CAP	Pathogenic	0.37	D
MetaRNN	Pathogenic	0.98	D;D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	1.0	D
MutationAssessor	Pathogenic	3.0	.;M;.;M;M;.;.;.;.
PhyloP100		5.9
PrimateAI	Pathogenic	0.84	D
PROVEAN	Uncertain	-3.5	.;.;D;D;.;.;.;.;.
REVEL	Pathogenic	0.90
Sift	Uncertain	0.0010	.;.;D;D;.;.;.;.;.
Sift4G	Uncertain	0.0020	.;.;D;D;.;D;D;.;.
Polyphen		0.98	.;D;.;.;.;.;.;.;.
Vest4		0.84, 0.84, 0.85
MutPred		0.92		Gain of disorder (P = 0.0378);Gain of disorder (P = 0.0378);Gain of disorder (P = 0.0378);Gain of disorder (P = 0.0378);Gain of disorder (P = 0.0378);Gain of disorder (P = 0.0378);Gain of disorder (P = 0.0378);Gain of disorder (P = 0.0378);Gain of disorder (P = 0.0378);
MVP		1.0
MPC		1.0
ClinPred		0.99	D
GERP RS		3.9
PromoterAI		-0.032	Neutral
Varity_R		0.82
gMVP		0.90
Mutation Taster		=9/91	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Other links and lift over

dbSNP: rs121909720; hg19: chr17-42992621;