rs60627726

Positions:

• chr12-52447788-C-T

Variant summary

Our verdict is Pathogenic. Variant got 14 ACMG points: 14P and 0B. PM2 PP3_Strong PP5_Very_Strong

The NM_005555.4(KRT6B):​c.1414G>A​(p.Glu472Lys) variant causes a missense change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: KRT6B NM_005555.4 missense
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:4 O:1
• Conservation: PhyloP100: 3.86

Genes affected

KRT6B (HGNC:6444): (keratin 6B) The protein encoded by this gene is a member of the keratin gene family. The type II cytokeratins consist of basic or neutral proteins which are arranged in pairs of heterotypic keratin chains coexpressed during differentiation of simple and stratified epithelial tissues. As many as six of this type II cytokeratin (KRT6) have been identified; the multiplicity of the genes is attributed to successive gene duplication events. The genes are expressed with family members KRT16 and/or KRT17 in the filiform papillae of the tongue, the stratified epithelial lining of oral mucosa and esophagus, the outer root sheath of hair follicles, and the glandular epithelia. Mutations in these genes have been associated with pachyonychia congenita. The type II cytokeratins are clustered in a region of chromosome 12q12-q13. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Pathogenic. Variant got 14 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.973
• PP5: Variant 12-52447788-C-T is Pathogenic according to our data. Variant chr12-52447788-C-T is described in ClinVar as [Pathogenic]. Clinvar id is 14633.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr12-52447788-C-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
KRT6B	NM_005555.4	c.1414G>A	p.Glu472Lys	missense_variant	7/9	ENST00000252252.4	NP_005546.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
KRT6B	ENST00000252252.4	c.1414G>A	p.Glu472Lys	missense_variant	7/9	1	NM_005555.4	ENSP00000252252	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:4 Other:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:2 Other:1

not provided, no classification provided	literature only	Epithelial Biology; Institute of Medical Biology, Singapore	-	- -
Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Apr 12, 2022	This sequence change replaces glutamic acid, which is acidic and polar, with lysine, which is basic and polar, at codon 472 of the KRT6B protein (p.Glu472Lys). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individuals with pachyonychia congenita (PMID: 9618173, 33301203). It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 14633). Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Possibly Damaging"; Align-GVGD: "Class C0"). For these reasons, this variant has been classified as Pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Jun 17, 2016	The E472K variant in the KRT6B gene has been previously reported in patients with pachyonychia congenita (Smith et al., 1998; Wilson et al., 2014). It was not observed in approximately 6,500 individuals of European and African American ancestry in the NHLBI Exome Sequencing Project, indicating it is not a common benign variant in these populations. E472K is a non-conservative amino acid substitution, which is likely to impact secondary protein structure as these residues differ in polarity, charge, size and/or other properties. This substitution occurs within a known mutational hotspot region (helix termination motif) that is highly conserved across all species and among all members of the keratin family. Many other pathogenic variants in patients with pachyonychia congenita have been reported in nearby residues (L469R) according to the Human Gene Mutation Database (Stenson et al., 2014). It is well established that keratin gene mutations affecting the residues at the ends of the central rod domains of the keratin proteins (helix initiation and termination motifs) interfere with proper keratin intermediate filament assembly and function, resulting in hyperkeratosis (Chamcheu et al., 2011). Additionally, the KRT6B gene has a low rate of benign missense variant with missense variants being a common mechanism of disease. Therefore, we consider E472K to be pathogenic. -

Pachyonychia congenita 4 Pathogenic:2

Pathogenic, no assertion criteria provided	literature only	OMIM	Oct 01, 2005	- -
Pathogenic, criteria provided, single submitter	clinical testing	Fulgent Genetics, Fulgent Genetics	Mar 07, 2022	- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.96
BayesDel_addAF	Pathogenic	0.33	D
BayesDel_noAF	Pathogenic	0.24
CADD	Uncertain	26
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.93	D
Eigen	Uncertain	0.36
Eigen_PC	Benign	0.14
FATHMM_MKL	Uncertain	0.94	D
LIST_S2	Uncertain	0.90	D
M_CAP	Benign	0.071	D
MetaRNN	Pathogenic	0.97	D
MetaSVM	Pathogenic	0.96	D
MutationAssessor	Pathogenic	3.3	M
MutationTaster	Benign	0.98	A
PrimateAI	Uncertain	0.68	T
PROVEAN	Uncertain	-3.7	D
REVEL	Pathogenic	0.77
Sift	Pathogenic	0.0	D
Sift4G	Uncertain	0.051	T
Polyphen		1.0	D
Vest4		0.90
MutPred		0.87		Gain of catalytic residue at L476 (P = 0.0072);
MVP		0.93
MPC		0.65
ClinPred		1.0	D
GERP RS		0.88
Varity_R		0.82
gMVP		0.95

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: rs60627726; hg19: chr12-52841572; COSMIC: COSV52882395;