6-41909439-G-A

Position:

• chr6-41909439-G-A

Variant summary

Our verdict is Uncertain significance. Variant got 3 ACMG points: 3P and 0B. PM2 PP3

The NM_004275.5(MED20):​c.253C>T​(p.Leu85Phe) variant causes a missense change. The variant allele was found at a frequency of 0.000000684 in 1,461,892 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: 31)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: MED20 NM_004275.5 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 6.42

Genes affected

MED20 (HGNC:16840): (mediator complex subunit 20) This gene encodes a component of the mediator complex (also known as TRAP, SMCC, DRIP, or ARC), a transcriptional coactivator complex thought to be required for the expression of almost all genes. The mediator complex is recruited by transcriptional activators or nuclear receptors to induce gene expression, by interacting with RNA polymerase II and promoting the formation of a transcriptional pre-initiation complex. A mutation in this gene has been associated with a novel infantile-onset neurodegenerative movement disorder. Alternatively spliced transcript variants have been identified. [provided by RefSeq, Mar 2015]

ENSG00000288721 (HGNC:):

BYSL (HGNC:1157): (bystin like) Bystin is expressed as a 2-kb major transcript and a 3.6-kb minor transcript in SNG-M cells and in human trophoblastic teratocarcinoma HT-H cells. Protein binding assays determined that bystin binds directly to trophinin and tastin, and that binding is enhanced when cytokeratins 8 and 18 are present. Immunocytochemistry of HT-H cells showed that bystin colocalizes with trophinin, tastin, and the cytokeratins, suggesting that these molecules form a complex in trophectoderm cells at the time of implantation. Using immunohistochemistry it was determined that trophinin and bystin are found in the placenta from the sixth week of pregnancy. Both proteins were localized in the cytoplasm of the syncytiotrophoblast in the chorionic villi and in endometrial decidual cells at the uteroplacental interface. After week 10, the levels of trophinin, tastin, and bystin decreased and then disappeared from placental villi. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Uncertain_significance. Variant got 3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.796

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MED20	NM_004275.5	c.253C>T	p.Leu85Phe	missense_variant	3/4	ENST00000265350.9	NP_004266.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MED20	ENST00000265350.9	c.253C>T	p.Leu85Phe	missense_variant	3/4	1	NM_004275.5	ENSP00000265350.4
ENSG00000288721	ENST00000684631.1	n.253C>T		non_coding_transcript_exon_variant	3/10			ENSP00000507261.1

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 251462 Hom.: 0 AF XY: 0.00000736 AC XY: 1 AN XY: 135910

Gnomad AFR exome AF: 0.0000615

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461892 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 727248

Gnomad4 AFR exome AF: 0.0000299

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: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 31

Alfa AF: 0.0000936 Hom.: 0

Bravo AF: 0.0000113

ExAC AF: 0.00000824 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

GeneDx

Jun 19, 2017

The L85F variant in the MED20 gene has not been reported previously as a pathogenic variant, nor as a benign variant, to our knowledge. The L85F variant is not observed at a significant frequency in large population cohorts (Lek et al., 2016; 1000 Genomes Consortium et al., 2015; Exome Variant Server). The L85F variant is a conservative amino acid substitution, which is not likely to impact secondary protein structure as these residues share similar properties. This substitution occurs at a position that is conserved across species. In silico analysis predicts this variant is probably damaging to the protein structure/function. We interpret L85F as a variant of uncertain significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.69
BayesDel_addAF	Benign	-0.045	T
BayesDel_noAF	Benign	-0.12
CADD	Pathogenic	26
DANN	Uncertain	1.0
DEOGEN2	Benign	0.29	T;.;T;T
Eigen	Uncertain	0.37
Eigen_PC	Uncertain	0.40
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Uncertain	0.93	D;D;D;D
M_CAP	Benign	0.024	T
MetaRNN	Pathogenic	0.80	D;D;D;D
MetaSVM	Uncertain	-0.081	T
MutationAssessor	Uncertain	2.4	M;M;.;.
PrimateAI	Uncertain	0.63	T
PROVEAN	Uncertain	-2.8	D;D;D;D
REVEL	Uncertain	0.61
Sift	Uncertain	0.021	D;D;D;D
Sift4G	Pathogenic	0.0	D;D;D;D
Polyphen		1.0	D;.;.;.
Vest4		0.79
MutPred		0.76		Loss of sheet (P = 0.1501);Loss of sheet (P = 0.1501);.;Loss of sheet (P = 0.1501);
MVP		0.44
MPC		1.1
ClinPred		0.91	D
GERP RS		5.0
Varity_R		0.33
gMVP		0.62

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: rs759721745; hg19: chr6-41877177;