12-106357931-G-T

Position:

• chr12-106357931-G-T

Variant summary

Our verdict is Uncertain significance. Variant got 1 ACMG points: 3P and 2B. PM2 PP2 BP4_Moderate

The NM_018082.6(POLR3B):​c.52G>T​(p.Ala18Ser) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. 12/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency: Genomes: not found (cov: 33)
• Consequence: POLR3B NM_018082.6 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 8.19

Genes affected

POLR3B (HGNC:30348): (RNA polymerase III subunit B) This gene encodes the second largest subunit of RNA polymerase III, the polymerase responsible for synthesizing transfer and small ribosomal RNAs in eukaryotes. The largest subunit and the encoded protein form the catalytic center of RNA polymerase III. Mutations in this gene are a cause of hypomyelinating leukodystrophy. Alternatively spliced transcript variants encoding multiple isoforms have been observed for this gene. [provided by RefSeq, Dec 2011]

ACMG classification

Verdict is Uncertain_significance. Variant got 1 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), POLR3B. . Gene score misZ 3.1978 (greater than the threshold 3.09). Trascript score misZ 3.4842 (greater than threshold 3.09). GenCC has associacion of gene with hypomyelination-hypogonadotropic hypogonadism-hypodontia syndrome, Charcot-Marie-Tooth disease, demyelinating, IIA 1I, hypomyelinating leukodystrophy 8 with or without oligodontia and-or hypogonadotropic hypogonadism, endosteal sclerosis-cerebellar hypoplasia syndrome.
• BP4: Computational evidence support a benign effect (MetaRNN=0.17566791).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
POLR3B	NM_018082.6	c.52G>T	p.Ala18Ser	missense_variant	1/28	ENST00000228347.9	NP_060552.4
POLR3B	XM_017019621.3	c.52G>T	p.Ala18Ser	missense_variant	1/26		XP_016875110.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
POLR3B	ENST00000228347.9	c.52G>T	p.Ala18Ser	missense_variant	1/28	1	NM_018082.6	ENSP00000228347.4

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 33

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

Labcorp Genetics (formerly Invitae), Labcorp

Dec 07, 2023

This sequence change replaces alanine, which is neutral and non-polar, with serine, which is neutral and polar, at codon 18 of the POLR3B protein (p.Ala18Ser). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with POLR3B-related conditions. ClinVar contains an entry for this variant (Variation ID: 1939723). An algorithm developed to predict the effect of missense changes on protein structure and function (PolyPhen-2) suggests 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	0.11
BayesDel_addAF	Uncertain	0.038	T
BayesDel_noAF	Benign	-0.18
CADD	Benign	22
DANN	Uncertain	0.99
DEOGEN2	Benign	0.023	T
Eigen	Benign	-0.078
Eigen_PC	Benign	0.16
FATHMM_MKL	Uncertain	0.95	D
LIST_S2	Uncertain	0.88	D
M_CAP	Benign	0.032	D
MetaRNN	Benign	0.18	T
MetaSVM	Benign	-0.80	T
MutationAssessor	Benign	0.41	N
PrimateAI	Uncertain	0.55	T
PROVEAN	Benign	0.13	N
REVEL	Benign	0.21
Sift	Benign	0.35	T
Sift4G	Benign	0.66	T
Polyphen		0.0050	B
Vest4		0.35
MutPred		0.30		Gain of glycosylation at A18 (P = 0.0225);
MVP		0.61
MPC		0.56
ClinPred		0.90	D
GERP RS		5.2
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		2.7
Varity_R		0.16
gMVP		0.45

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: rs2036409168; hg19: chr12-106751709;