16-81315117-G-A

Variant summary

Our verdict is Uncertain significance. Variant got 1 ACMG points: 2P and 1B. PM2 BP4

The NM_022041.4(GAN):c.4G>A(p.Ala2Thr) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000333 in 1,501,374 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Synonymous variant affecting the same amino acid position (i.e. A2A) has been classified as Likely benign.

• Frequency:
  • Genomes: 𝑓 0.0000066 (0 hom., cov: 33)
  • Exomes 𝑓: 0.0000030 (0 hom.)
• Consequence: GAN NM_022041.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 2.10

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 1 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.3799378).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GAN	NM_022041.4	c.4G>A	p.Ala2Thr	missense_variant	1/11	ENST00000648994.2
GAN	NM_001377486.1	c.-521G>A		5_prime_UTR_variant	1/10

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GAN	ENST00000648994.2	c.4G>A	p.Ala2Thr	missense_variant	1/11		NM_022041.4	P1
GAN	ENST00000674788.1	n.129G>A		non_coding_transcript_exon_variant	1/3
GAN	ENST00000648349.2	c.4G>A	p.Ala2Thr	missense_variant, NMD_transcript_variant	1/10
GAN	ENST00000650388.1	c.4G>A	p.Ala2Thr	missense_variant, NMD_transcript_variant	1/9

Frequencies

GnomAD3 genomes AF: 0.00000658 AC: 1 AN: 151904 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000147

Gnomad OTH AF: 0.00

GnomAD4 exome AF: 0.00000296 AC: 4 AN: 1349470 Hom.: 0 Cov.: 32 AF XY: 0.00000301 AC XY: 2 AN XY: 665458

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.0000335

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000189

Gnomad4 OTH exome AF: 0.0000180

GnomAD4 genome AF: 0.00000658 AC: 1 AN: 151904 Hom.: 0 Cov.: 33 AF XY: 0.00 AC XY: 0 AN XY: 74204

Gnomad4 AFR AF: 0.00

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.0000147

Gnomad4 OTH AF: 0.00

Alfa AF: 0.0000540 Hom.: 0

Bravo AF: 0.00000378

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

Invitae

Sep 02, 2021

This sequence change replaces alanine with threonine at codon 2 of the GAN protein (p.Ala2Thr). The alanine residue is weakly conserved and there is a small physicochemical difference between alanine and threonine. The frequency data for this variant in the population databases is considered unreliable, as metrics indicate insufficient coverage at this position in the ExAC database. This variant has not been reported in the literature in individuals affected with GAN-related conditions. 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 tolerated. 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	Benign	0.094
BayesDel_addAF	Benign	-0.0084	T
BayesDel_noAF	Benign	-0.25
Cadd	Pathogenic	26
Dann	Uncertain	1.0
DEOGEN2	Benign	0.22	T;T
Eigen	Benign	-0.23
Eigen_PC	Benign	-0.057
FATHMM_MKL	Benign	0.72	D
M_CAP	Pathogenic	0.96	D
MetaRNN	Benign	0.38	T;T
MetaSVM	Benign	-0.91	T
MutationAssessor	Benign	0.69	N;N
MutationTaster	Benign	0.89	N
PrimateAI	Pathogenic	0.93	D
Sift4G	Pathogenic	0.0	D;.
Polyphen		0.0	B;B
Vest4		0.12
MutPred		0.15		Gain of glycosylation at A2 (P = 0.0462);Gain of glycosylation at A2 (P = 0.0462);
MVP		0.82
MPC		0.11
ClinPred		0.62	D
GERP RS		4.2
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.6
Varity_R		0.11
gMVP		0.25

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

Publications

LitVar

Other links and lift over

dbSNP: rs1206106380; hg19: chr16-81348722;