rs201676105

Positions:

• chr16-81354755-G-C

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PM1 PM2

The NM_022041.4(GAN):​c.633G>C​(p.Lys211Asn) variant causes a missense, splice region change. The variant allele was found at a frequency of 0.000000723 in 1,382,544 control chromosomes in the GnomAD database, with no homozygous occurrence. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 7.2e-7 (0 hom.)
• Consequence: GAN NM_022041.4 missense, splice_region
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 6.37

Genes affected

GAN (HGNC:4137): (gigaxonin) This gene encodes a member of the cytoskeletal BTB/kelch (Broad-Complex, Tramtrack and Bric a brac) repeat family. The encoded protein plays a role in neurofilament architecture and is involved in mediating the ubiquitination and degradation of some proteins. Defects in this gene are a cause of giant axonal neuropathy (GAN). [provided by RefSeq, Oct 2008]

ACMG classification

Verdict is Uncertain_significance. Variant got 4 ACMG points.

• PM1: In a domain BACK (size 102) in uniprot entity GAN_HUMAN there are 4 pathogenic changes around while only 0 benign (100%) in NM_022041.4
• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
GAN	NM_022041.4	c.633G>C	p.Lys211Asn	missense_variant, splice_region_variant	3/11	ENST00000648994.2	NP_071324.1
GAN	NM_001377486.1	c.-7G>C		splice_region_variant, 5_prime_UTR_variant	2/10		NP_001364415.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
GAN	ENST00000648994.2	c.633G>C	p.Lys211Asn	missense_variant, splice_region_variant	3/11		NM_022041.4	ENSP00000497351	P1
GAN	ENST00000674788.1	n.758G>C		non_coding_transcript_exon_variant	3/3
GAN	ENST00000648349.2	c.*341G>C		splice_region_variant, 3_prime_UTR_variant, NMD_transcript_variant	2/10			ENSP00000498114
GAN	ENST00000650388.1	c.168-2030G>C		intron_variant, NMD_transcript_variant				ENSP00000498081

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 7.23e-7 AC: 1 AN: 1382544 Hom.: 0 Cov.: 23 AF XY: 0.00 AC XY: 0 AN XY: 692344

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 9.62e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Giant axonal neuropathy 1 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

May 03, 2018

This sequence change replaces lysine with asparagine at codon 211 of the GAN protein (p.Lys211Asn). The lysine residue is highly conserved and there is a moderate physicochemical difference between lysine and asparagine. This variant also falls at the last nucleotide of exon 3 of the GAN coding sequence, which is part of the consensus splice site for this exon. This variant is not present in population databases (ExAC no frequency). This variant has not been reported in the literature in individuals with GAN-related disease. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive, but these predictions have not been confirmed by published functional studies and their clinical significance is uncertain. Nucleotide substitutions within the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site, but this prediction has not been confirmed by published transcriptional studies. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.78
BayesDel_addAF	Benign	-0.085	T
BayesDel_noAF	Benign	-0.36
CADD	Pathogenic	34
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.46	T;T
Eigen	Uncertain	0.55
Eigen_PC	Uncertain	0.63
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.86	.;D
M_CAP	Benign	0.011	T
MetaRNN	Uncertain	0.59	D;D
MetaSVM	Benign	-0.59	T
MutationAssessor	Uncertain	2.2	M;M
MutationTaster	Benign	1.0	D
PrimateAI	Uncertain	0.77	T
Sift4G	Uncertain	0.032	D;.
Polyphen		0.85	P;P
Vest4		0.55
MutPred		0.65		Loss of methylation at K211 (P = 0.0143);Loss of methylation at K211 (P = 0.0143);
MVP		0.92
MPC		0.47
ClinPred		0.93	D
GERP RS		5.8
Varity_R		0.70
gMVP		0.40

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.99
SpliceAI score (max)		0.80		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.80		Position offset: 0

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

Publications

LitVar

Other links and lift over

dbSNP: rs201676105; hg19: chr16-81388360;