18-2667015-A-C

Position:

• chr18-2667015-A-C

Variant summary

Our verdict is Uncertain significance. Variant got 5 ACMG points: 5P and 0B. PM2 PM5 PP2

The NM_015295.3(SMCHD1):​c.408A>C​(p.Glu136Asp) variant causes a missense change. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. E136G) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: SMCHD1 NM_015295.3 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter P:3 U:1
• Conservation: PhyloP100: 4.00

Genes affected

SMCHD1 (HGNC:29090): (structural maintenance of chromosomes flexible hinge domain containing 1) This gene encodes a protein which contains a hinge region domain found in members of the SMC (structural maintenance of chromosomes) protein family. [provided by RefSeq, Dec 2011]

SMCHD1 (HGNC:):

ACMG classification

Verdict is Uncertain_significance. Variant got 5 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chrnull-null-null-null is described in UniProt as null.
• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), SMCHD1. . Gene score misZ 3.6318 (greater than the threshold 3.09). Trascript score misZ 3.965 (greater than threshold 3.09). GenCC has associacion of gene with facioscapulohumeral muscular dystrophy, arhinia, choanal atresia, and microphthalmia, hyposmia-nasal and ocular hypoplasia-hypogonadotropic hypogonadism syndrome.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
SMCHD1	NM_015295.3	c.408A>C	p.Glu136Asp	missense_variant	3/48	ENST00000320876.11	NP_056110.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
SMCHD1	ENST00000320876.11	c.408A>C	p.Glu136Asp	missense_variant	3/48	5	NM_015295.3	ENSP00000326603.7
SMCHD1	ENST00000688342.1	c.408A>C	p.Glu136Asp	missense_variant	3/47			ENSP00000508422.1
SMCHD1	ENST00000684915.1	n.565A>C		non_coding_transcript_exon_variant	3/14

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Pathogenic:3 Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Arrhinia with choanal atresia and microphthalmia syndrome Pathogenic:2

Pathogenic, no assertion criteria provided	literature only	OMIM	Feb 27, 2017	- -
Pathogenic, no assertion criteria provided	research	MGH Harvard Center for Reproductive Medicine, Massachusetts General Hospital	-	- -

Facioscapulohumeral muscular dystrophy 2 Pathogenic:1 Uncertain:1

Uncertain significance, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Oct 18, 2023	This sequence change replaces glutamic acid, which is acidic and polar, with aspartic acid, which is acidic and polar, at codon 136 of the SMCHD1 protein (p.Glu136Asp). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with clinical features of SMCHD1-related conditions (PMID: 28067909). ClinVar contains an entry for this variant (Variation ID: 375764). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) has been performed at Invitae for this missense variant, however the output from this modeling did not meet the statistical confidence thresholds required to predict the impact of this variant on SMCHD1 protein function. 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. -
Pathogenic, no assertion criteria provided	research	MGH Harvard Center for Reproductive Medicine, Massachusetts General Hospital	-	- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.96
BayesDel_addAF	Benign	-0.071	T
BayesDel_noAF	Benign	-0.34
CADD	Uncertain	25
DANN	Uncertain	1.0
DEOGEN2	Benign	0.32	T
Eigen	Uncertain	0.55
Eigen_PC	Uncertain	0.57
FATHMM_MKL	Uncertain	0.93	D
LIST_S2	Uncertain	0.87	D
M_CAP	Benign	0.044	D
MetaRNN	Uncertain	0.71	D
MetaSVM	Benign	-0.99	T
MutationAssessor	Uncertain	2.2	M
PrimateAI	Pathogenic	0.83	D
PROVEAN	Benign	-1.4	N
REVEL	Benign	0.13
Sift	Benign	0.17	T
Sift4G	Benign	0.061	T
Polyphen		1.0	D
Vest4		0.84
MutPred		0.24		Gain of sheet (P = 0.0266);
MVP		0.28
MPC		1.6
ClinPred		0.93	D
GERP RS		5.6
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.28
gMVP		0.71

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: rs1057519643; hg19: chr18-2667014;