rs1555647170

Variant names:

• chr18-2750086-G-A
• rs1555647170
• NM_015295.3:c.3971G>A

Variant summary

Our verdict is Uncertain significance. Variant got 1 ACMG points: 3P and 2B. PM2 PP2 BP4_Moderate

The NM_015295.3(SMCHD1):​c.3971G>A​(p.Arg1324Lys) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. 15/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: SMCHD1 NM_015295.3 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 2.32

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]

ENSG00000266049 (HGNC:):

ACMG classification

Verdict is Uncertain_significance. Variant got 1 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant in the SMCHD1 gene, where missense mutations are typically associated with disease (based on misZ statistic). The gene has 23 curated pathogenic missense variants (we use a threshold of 10). The gene has 10 curated benign missense variants. Gene score misZ: 3.6318 (above the threshold of 3.09). Trascript score misZ: 3.965 (above the threshold of 3.09). GenCC associations: The gene is linked to facioscapulohumeral muscular dystrophy, arhinia, choanal atresia, and microphthalmia, hyposmia-nasal and ocular hypoplasia-hypogonadotropic hypogonadism syndrome.
• BP4: Computational evidence support a benign effect (MetaRNN=0.07403067).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SMCHD1	NM_015295.3	c.3971G>A	p.Arg1324Lys	missense_variant	Exon 31 of 48	ENST00000320876.11	NP_056110.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SMCHD1	ENST00000320876.11	c.3971G>A	p.Arg1324Lys	missense_variant	Exon 31 of 48	5	NM_015295.3	ENSP00000326603.7

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

Facioscapulohumeral muscular dystrophy 2 Uncertain:1

Nov 27, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces arginine, which is basic and polar, with lysine, which is basic and polar, at codon 1324 of the SMCHD1 protein (p.Arg1324Lys). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with SMCHD1-related conditions. ClinVar contains an entry for this variant (Variation ID: 532804). Invitae Evidence Modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) indicates that this missense variant is not expected to disrupt SMCHD1 protein function with a negative predictive value of 80%. 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.10
BayesDel_addAF	Benign	-0.18	T
BayesDel_noAF	Benign	-0.49
CADD	Benign	17
DANN	Benign	0.97
DEOGEN2	Benign	0.066	T
Eigen	Benign	-0.21
Eigen_PC	Benign	-0.022
FATHMM_MKL	Uncertain	0.85	D
LIST_S2	Benign	0.58	T
M_CAP	Benign	0.0086	T
MetaRNN	Benign	0.074	T
MetaSVM	Benign	-1.0	T
MutationAssessor	Benign	1.5	L
PrimateAI	Benign	0.40	T
PROVEAN	Benign	-0.32	N
REVEL	Benign	0.052
Sift	Benign	0.49	T
Sift4G	Benign	0.37	T
Polyphen		0.0	B
Vest4		0.16
MutPred		0.30		Gain of ubiquitination at R1324 (P = 0.0109);
MVP		0.043
MPC		0.23
ClinPred		0.31	T
GERP RS		4.1
Varity_R		0.078
gMVP		0.56

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs1555647170; hg19: chr18-2750084;