22-42619849-G-A

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM1 PM2 PP3_Moderate

The NM_000398.7(CYB5R3):c.830C>T(p.Pro277Leu) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000275 in 1,453,022 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: 0.0000028 (0 hom.)
• Consequence: CYB5R3 NM_000398.7 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 9.90

Genes affected

CYB5R3 (HGNC:2873): (cytochrome b5 reductase 3) This gene encodes cytochrome b5 reductase, which includes a membrane-bound form in somatic cells (anchored in the endoplasmic reticulum, mitochondrial and other membranes) and a soluble form in erythrocytes. The membrane-bound form exists mainly on the cytoplasmic side of the endoplasmic reticulum and functions in desaturation and elongation of fatty acids, in cholesterol biosynthesis, and in drug metabolism. The erythrocyte form is located in a soluble fraction of circulating erythrocytes and is involved in methemoglobin reduction. The membrane-bound form has both membrane-binding and catalytic domains, while the soluble form has only the catalytic domain. Alternate splicing results in multiple transcript variants. Mutations in this gene cause methemoglobinemias. [provided by RefSeq, Jan 2010]

ACMG classification

Verdict is Likely_pathogenic. Variant got 6 ACMG points.

• PM1: In a chain NADH-cytochrome b5 reductase 3 (size 299) in uniprot entity NB5R3_HUMAN there are 70 pathogenic changes around while only 8 benign (90%) in NM_000398.7
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.886

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
CYB5R3	NM_000398.7	c.830C>T	p.Pro277Leu	missense_variant	9/9	ENST00000352397.10

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
CYB5R3	ENST00000352397.10	c.830C>T	p.Pro277Leu	missense_variant	9/9	1	NM_000398.7	P3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 0.00000275 AC: 4 AN: 1453022 Hom.: 0 Cov.: 32 AF XY: 0.00000139 AC XY: 1 AN XY: 722006

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: 0.00

Gnomad4 NFE exome AF: 0.00000180

Gnomad4 OTH exome AF: 0.0000333

GnomAD4 genome Cov.: 33

ExAC AF: 0.00000825 AC: 1

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

May 19, 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. This sequence change replaces proline, which is neutral and non-polar, with leucine, which is neutral and non-polar, at codon 277 of the CYB5R3 protein (p.Pro277Leu). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with CYB5R3-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 disruptive. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.40
BayesDel_addAF	Pathogenic	0.18	D
BayesDel_noAF	Uncertain	0.020
Cadd	Pathogenic	26
Dann	Uncertain	1.0
Eigen	Pathogenic	0.69
Eigen_PC	Uncertain	0.59
FATHMM_MKL	Uncertain	0.95	D
LIST_S2	Uncertain	0.97	D;D;.;.;D
M_CAP	Pathogenic	0.41	D
MetaRNN	Pathogenic	0.89	D;D;D;D;D
MetaSVM	Uncertain	0.65	D
MutationTaster	Benign	1.0	D;D;D;D;D;D
PrimateAI	Uncertain	0.70	T
PROVEAN	Pathogenic	-8.8	D;D;D;D;D
REVEL	Pathogenic	0.66
Sift	Uncertain	0.021	D;D;D;D;D
Sift4G	Uncertain	0.021	D;D;D;D;D
Polyphen		0.99	.;D;.;.;.
Vest4		0.70
MutPred		0.67		.;Loss of glycosylation at P277 (P = 0.0063);.;.;.;
MVP		0.99
MPC		0.28
ClinPred		1.0	D
GERP RS		3.4
Varity_R		0.73
gMVP		0.83

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: rs752824154; hg19: chr22-43015855;