20-10405268-A-T

Position:

• chr20-10405268-A-T

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PVS1_Moderate PM2

The ENST00000347364.7(MKKS):​c.1692T>A​(p.Tyr564Ter) variant causes a stop gained change involving the alteration of a non-conserved nucleotide. 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 Uncertain significance (★). Synonymous variant affecting the same amino acid position (i.e. Y564Y) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 32)
• Consequence: MKKS ENST00000347364.7 stop_gained
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 1.55

Genes affected

MKKS (HGNC:7108): (MKKS centrosomal shuttling protein) This gene encodes a protein which shares sequence similarity with other members of the type II chaperonin family. The encoded protein is a centrosome-shuttling protein and plays an important role in cytokinesis. This protein also interacts with other type II chaperonin members to form a complex known as the BBSome, which involves ciliary membrane biogenesis. This protein is encoded by a downstream open reading frame (dORF). Several upstream open reading frames (uORFs) have been identified, which repress the translation of the dORF, and two of which can encode small mitochondrial membrane proteins. Mutations in this gene have been observed in patients with Bardet-Biedl syndrome type 6, also known as McKusick-Kaufman syndrome. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Feb 2023]

ACMG classification

Verdict is Uncertain_significance. Variant got 4 ACMG points.

• PVS1: Loss of function variant, product does not undergo nonsense mediated mRNA decay. Variant is located in the 3'-most exon, not predicted to undergo nonsense mediated mRNA decay. Fraction of 0.0123 CDS is truncated, and there are 0 pathogenic variants in the truncated region.
• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MKKS	NM_170784.3	c.1692T>A	p.Tyr564Ter	stop_gained	6/6	ENST00000347364.7	NP_740754.1
MKKS	NM_018848.3	c.1692T>A	p.Tyr564Ter	stop_gained	6/6		NP_061336.1
MKKS	NR_072977.2	n.1053T>A		non_coding_transcript_exon_variant	5/5

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MKKS	ENST00000347364.7	c.1692T>A	p.Tyr564Ter	stop_gained	6/6	1	NM_170784.3	ENSP00000246062	P1
MKKS	ENST00000399054.6	c.1692T>A	p.Tyr564Ter	stop_gained	6/6	1		ENSP00000382008	P1
MKKS	ENST00000651692.1	c.1692T>A	p.Tyr564Ter	stop_gained	7/7			ENSP00000498849	P1
MKKS	ENST00000652676.1	n.1336T>A		non_coding_transcript_exon_variant	7/7

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Oct 25, 2021

Variant summary: MKKS c.1692T>A (p.Tyr564X), located in the last exon (exon 6) results in a premature termination codon, predicted to cause a truncation of the encoded protein or absence of the protein due to nonsense mediated decay, which are commonly known mechanisms for disease. Truncations downstream of this position have not been classified as pathogenic by our laboratory and have not been reported in the HGMD database. The variant was absent in 249798 control chromosomes. The available data on variant occurrences in the general population are insufficient to allow any conclusion about variant significance. To our knowledge, no occurrence of c.1692T>A in individuals affected with Bardet-Biedl Syndrome and no experimental evidence demonstrating its impact on protein function have been reported. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014. Based on the evidence outlined above, the variant was classified as uncertain significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.52	D
BayesDel_noAF	Pathogenic	0.50
CADD	Pathogenic	36
DANN	Uncertain	1.0
Eigen	Uncertain	0.45
Eigen_PC	Uncertain	0.26
FATHMM_MKL	Uncertain	0.86	D
MutationTaster	Benign	1.0	D;D
Vest4		0.67
GERP RS		1.2

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

No publications associated with this variant yet.

Other links and lift over

hg19: chr20-10385916;