12-106457147-GT-AC

Variant names:

• chr12-106457147-GT-AC
• NM_018082.6:c.2303_2304delGTinsAC
• POLR3B p.Arg768His

Variant summary

Our verdict is Likely pathogenic. The variant received 6 ACMG points: 6P and 0B. PS1_Moderate PM5 PP2 PP3

The NM_018082.6(POLR3B):​c.2303_2304delGTinsAC​(p.Arg768His) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. It is difficult to determine the true allele frequency of this variant because it is of type MNV, and the frequency of such variant types in population databases may be underestimated and unreliable. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Another nucleotide change resulting in the same amino acid substitution has been previously reported as Likely pathogenic in ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R768C) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: POLR3B NM_018082.6 missense
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 9.96
• Publications: 0 publications found

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]

POLR3B Gene-Disease associations (from GenCC):

• hypomyelinating leukodystrophy 8 with or without oligodontia and-or hypogonadotropic hypogonadism

  Inheritance: AR Classification: DEFINITIVE, STRONG Submitted by: Illumina, Labcorp Genetics (formerly Invitae), G2P
• neurodevelopmental disorder

  Inheritance: AR, AD Classification: DEFINITIVE, STRONG Submitted by: G2P
• POLR3B-related disorder

  Inheritance: AR, AD Classification: DEFINITIVE Submitted by: ClinGen
• Charcot-Marie-Tooth disease, demyelinating, IIA 1I

  Inheritance: AD Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae)
• endosteal sclerosis-cerebellar hypoplasia syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• hypomyelination-hypogonadotropic hypogonadism-hypodontia syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Likely_pathogenic. The variant received 6 ACMG points.

• PS1: Transcript NM_018082.6 (POLR3B) is affected with MISSENSE_VARIANT having same AA change as one Pathogenic present in ClinVar.
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr12-106457146-C-T is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 973230.
• PP2: Missense variant in the POLR3B gene, where missense mutations are typically associated with disease (based on misZ statistic). The gene has 24 curated pathogenic missense variants (we use a threshold of 10). The gene has 6 curated benign missense variants. Gene score misZ: 3.1978 (above the threshold of 3.09). Trascript score misZ: 3.4842 (above the threshold of 3.09). GenCC associations: The gene is linked to POLR3B-related disorder, hypomyelinating leukodystrophy 8 with or without oligodontia and-or hypogonadotropic hypogonadism, hypomyelination-hypogonadotropic hypogonadism-hypodontia syndrome, neurodevelopmental disorder, endosteal sclerosis-cerebellar hypoplasia syndrome, Charcot-Marie-Tooth disease, demyelinating, IIA 1I.
• PP3: No computational evidence supports a deleterious effect, but strongly conserved according to phyloP

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_018082.6. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	POLR3B	NM_018082.6	MANE Select	c.2303_2304delGTinsAC	p.Arg768His	missense	N/A	NP_060552.4
	POLR3B	NM_001160708.2		c.2129_2130delGTinsAC	p.Arg710His	missense	N/A	NP_001154180.1	Q9NW08-2

Ensembl Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	POLR3B	ENST00000228347.9	TSL:1 MANE Select	c.2303_2304delGTinsAC	p.Arg768His	missense	N/A	ENSP00000228347.4	Q9NW08-1
	POLR3B	ENST00000970165.1		c.2303_2304delGTinsAC	p.Arg768His	missense	N/A	ENSP00000640224.1
	POLR3B	ENST00000887559.1		c.2315_2316delGTinsAC	p.Arg772His	missense	N/A	ENSP00000557618.1

Frequencies

GnomAD3 genomes Cov.: 32

We have no GnomAD4 exomes data on this position. Probably position not covered by the project.

GnomAD4 genome Cov.: 32

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
PhyloP100		10

Splicing

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

MaxEntScan Visualizer can be used to analyze the impact of this mutation on the neighboring sequence.

Other links and lift over

hg19: chr12-106850925;