X-24699423-A-G

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 3P and 1B. PVS1_Moderate PP3 BS1_Supporting

The NM_001330360.2(POLA1):c.44-2A>G variant causes a splice acceptor change. The variant allele was found at a frequency of 0.00000875 in 1,142,712 control chromosomes in the GnomAD database, with no homozygous occurrence. There are 5 hemizygotes in GnomAD. In-silico tool predicts a benign outcome for this variant. 2/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: 𝑓 0.000036 (0 hom., 1 hem., cov: 22)
  • Exomes 𝑓: 0.0000058 (0 hom. 4 hem.)
• Consequence: POLA1 NM_001330360.2 splice_acceptor
• Scores: Splicing: ADA: 0.9970
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 3.80

Genes affected

POLA1 (HGNC:9173): (DNA polymerase alpha 1, catalytic subunit) This gene encodes the catalytic subunit of DNA polymerase, which together with a regulatory and two primase subunits, forms the DNA polymerase alpha complex. The catalytic subunit plays an essential role in the initiation of DNA replication. [provided by RefSeq, Mar 2010]

ACMG classification

Verdict is Uncertain_significance. Variant got 2 ACMG points.

• PVS1: Splicing variant, NOT destroyed by nmd, known LOF gene, truncates exone, which is 0.028137054 fraction of the gene. Cryptic splice site detected, with MaxEntScore 7.7, offset of 9, new splice context is: tcttttttcggctctgtcAGatt. Cryptic site results in inframe change. If cryptic site found is not functional and variant results in exon loss, it results in frameshift change.
• PP3: Splicing scoreres supports a deletorius effect: Scorers claiming Pathogenic: dbscSNV1_ADA, max_spliceai. No scorers claiming Uncertain. Scorers claiming Benign: dbscSNV1_RF.
• BS1: Variant frequency is greater than expected in population afr. gnomad4 allele frequency = 0.0000359 (4/111339) while in subpopulation AFR AF= 0.000131 (4/30607). AF 95% confidence interval is 0.0000444. There are 0 homozygotes in gnomad4. There are 1 alleles in male gnomad4 subpopulation. Median coverage is 22. This position pass quality control queck. Existence of Clinvar submissions makes me limit the strength of this signal to Supporting

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
POLA1	NM_001330360.2	c.44-2A>G		splice_acceptor_variant		ENST00000379068.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
POLA1	ENST00000379068.8	c.44-2A>G		splice_acceptor_variant		5	NM_001330360.2	A1

Frequencies

GnomAD3 genomes AF: 0.0000359 AC: 4 AN: 111339 Hom.: 0 Cov.: 22 AF XY: 0.0000298 AC XY: 1 AN XY: 33555

Gnomad AFR AF: 0.000131

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: 0.00

Gnomad OTH AF: 0.00

GnomAD4 exome AF: 0.00000582 AC: 6 AN: 1031373 Hom.: 0 Cov.: 25 AF XY: 0.0000125 AC XY: 4 AN XY: 321189

Gnomad4 AFR exome AF: 0.000250

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: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.0000359 AC: 4 AN: 111339 Hom.: 0 Cov.: 22 AF XY: 0.0000298 AC XY: 1 AN XY: 33555

Gnomad4 AFR AF: 0.000131

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: 0.00

Gnomad4 OTH AF: 0.00

Bravo AF: 0.0000529

ExAC AF: 0.0000249 AC: 3

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Dec 06, 2022

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. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. ClinVar contains an entry for this variant (Variation ID: 1397392). This variant has not been reported in the literature in individuals affected with POLA1-related conditions. The frequency data for this variant in the population databases is considered unreliable, as metrics indicate poor data quality at this position in the gnomAD database. This sequence change affects an acceptor splice site in intron 1 of the POLA1 gene. It is expected to disrupt RNA splicing. Variants that disrupt the donor or acceptor splice site typically lead to a loss of protein function (PMID: 16199547), however the current clinical and genetic evidence is not sufficient to establish whether loss-of-function variants in POLA1 cause disease. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Benign	-0.44	T
BayesDel_noAF	Benign	-0.87
Cadd	Pathogenic	26
Dann	Benign	0.44
FATHMM_MKL	Benign	0.73	D
MutationTaster	Benign	1.0	N;N
GERP RS		1.4

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Benign	0.47
SpliceAI score (max)		1.0		Details are displayed if max score is > 0.2
DS_AG_spliceai		0.98		Position offset: 11
DS_AL_spliceai		1.0		Position offset: 2

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

Publications

LitVar

Other links and lift over

dbSNP: rs757360400; hg19: chrX-24717540;