6-16306357-A-G

Position:

• chr6-16306357-A-G

Variant summary

Our verdict is Likely benign. Variant got -2 ACMG points: 2P and 4B. PP3_Moderate BS2

The NM_001128164.2(ATXN1):​c.2420T>C​(p.Ile807Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000479 in 1,459,996 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 Uncertain significance (★).

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000048 (0 hom.)
• Consequence: ATXN1 NM_001128164.2 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 8.95

Genes affected

ATXN1 (HGNC:10548): (ataxin 1) The autosomal dominant cerebellar ataxias (ADCA) are a heterogeneous group of neurodegenerative disorders characterized by progressive degeneration of the cerebellum, brain stem and spinal cord. Clinically, ADCA has been divided into three groups: ADCA types I-III. ADCAI is genetically heterogeneous, with five genetic loci, designated spinocerebellar ataxia (SCA) 1, 2, 3, 4 and 6, being assigned to five different chromosomes. ADCAII, which always presents with retinal degeneration (SCA7), and ADCAIII often referred to as the `pure' cerebellar syndrome (SCA5), are most likely homogeneous disorders. Several SCA genes have been cloned and shown to contain CAG repeats in their coding regions. ADCA is caused by the expansion of the CAG repeats, producing an elongated polyglutamine tract in the corresponding protein. The expanded repeats are variable in size and unstable, usually increasing in size when transmitted to successive generations. The function of the ataxins is not known. This locus has been mapped to chromosome 6, and it has been determined that the diseased allele contains 40-83 CAG repeats, compared to 6-39 in the normal allele, and is associated with spinocerebellar ataxia type 1 (SCA1). Alternative splicing results in multiple transcript variants, with one variant encoding multiple distinct proteins, ATXN1 and Alt-ATXN1, due to the use of overlapping alternate reading frames. [provided by RefSeq, Nov 2017]

ACMG classification

Verdict is Likely_benign. Variant got -2 ACMG points.

• PP3: MetaRNN computational evidence supports a deleterious effect, 0.864
• BS2: High AC in GnomAdExome4 at 7 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
ATXN1	NM_001128164.2	c.2420T>C	p.Ile807Thr	missense_variant	8/8	ENST00000436367.6	NP_001121636.1
ATXN1	NM_000332.4	c.2420T>C	p.Ile807Thr	missense_variant	9/9		NP_000323.2
ATXN1	NM_001357857.2	c.*1833T>C		3_prime_UTR_variant	9/9		NP_001344786.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
ATXN1	ENST00000436367.6	c.2420T>C	p.Ile807Thr	missense_variant	8/8	1	NM_001128164.2	ENSP00000416360	P1
ATXN1	ENST00000244769.8	c.2420T>C	p.Ile807Thr	missense_variant	9/9	1		ENSP00000244769	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD3 exomes AF: 0.00000399 AC: 1 AN: 250608 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 135522

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000880

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000479 AC: 7 AN: 1459996 Hom.: 0 Cov.: 30 AF XY: 0.00000413 AC XY: 3 AN XY: 726206

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: 0.0000190

Gnomad4 NFE exome AF: 0.00000540

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

Alfa AF: 0.0000469 Hom.: 0

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Inborn genetic diseases Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Oct 04, 2022

The c.2420T>C (p.I807T) alteration is located in exon 9 (coding exon 2) of the ATXN1 gene. This alteration results from a T to C substitution at nucleotide position 2420, causing the isoleucine (I) at amino acid position 807 to be replaced by a threonine (T). Based on insufficient or conflicting evidence, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.44	D
BayesDel_noAF	Pathogenic	0.39
CADD	Pathogenic	27
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.72	D;D
Eigen	Pathogenic	0.82
Eigen_PC	Pathogenic	0.83
FATHMM_MKL	Uncertain	0.97	D
LIST_S2	Uncertain	0.96	.;D
M_CAP	Pathogenic	0.32	D
MetaRNN	Pathogenic	0.86	D;D
MetaSVM	Uncertain	0.55	D
MutationAssessor	Uncertain	2.2	M;M
MutationTaster	Benign	1.0	D;D;D
PrimateAI	Pathogenic	0.81	D
PROVEAN	Uncertain	-2.7	D;D
REVEL	Pathogenic	0.66
Sift	Pathogenic	0.0	D;D
Sift4G	Pathogenic	0.0	D;D
Polyphen		1.0	D;D
Vest4		0.95
MutPred		0.38		Loss of sheet (P = 0.007);Loss of sheet (P = 0.007);
MVP		1.0
MPC		1.4
ClinPred		0.96	D
GERP RS		6.0
Varity_R		0.59
gMVP		0.71

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs1361611293; hg19: chr6-16306588;