rs1556890626

Variant names:

• chrX-53412246-CCTT-C
• rs1556890626
• NM_006306.4:c.859_861delAAG

Variant summary

Our verdict is Uncertain significance. The variant received 3 ACMG points: 3P and 0B. PM2 PM4_Supporting

The NM_006306.4(SMC1A):​c.859_861delAAG​(p.Lys287del) variant causes a conservative inframe deletion change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Uncertain significance (★). Synonymous variant affecting the same amino acid position (i.e. K287K) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 22)
• Consequence: SMC1A NM_006306.4 conservative_inframe_deletion
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 7.50
• Publications: 0 publications found

Genes affected

SMC1A (HGNC:11111): (structural maintenance of chromosomes 1A) Proper cohesion of sister chromatids is a prerequisite for the correct segregation of chromosomes during cell division. The cohesin multiprotein complex is required for sister chromatid cohesion. This complex is composed partly of two structural maintenance of chromosomes (SMC) proteins, SMC3 and either SMC1B or the protein encoded by this gene. Most of the cohesin complexes dissociate from the chromosomes before mitosis, although those complexes at the kinetochore remain. Therefore, the encoded protein is thought to be an important part of functional kinetochores. In addition, this protein interacts with BRCA1 and is phosphorylated by ATM, indicating a potential role for this protein in DNA repair. This gene, which belongs to the SMC gene family, is located in an area of the X-chromosome that escapes X inactivation. Mutations in this gene result in Cornelia de Lange syndrome. Alternative splicing results in multiple transcript variants encoding different isoforms. [provided by RefSeq, Jul 2013]

SMC1A Gene-Disease associations (from GenCC):

• Cornelia de Lange syndrome 2

  Inheritance: XL Classification: DEFINITIVE, STRONG Submitted by: G2P, Labcorp Genetics (formerly Invitae)
• developmental and epileptic encephalopathy, 85, with or without midline brain defects

  Inheritance: XL Classification: DEFINITIVE, STRONG Submitted by: Labcorp Genetics (formerly Invitae), G2P
• X-linked complex neurodevelopmental disorder

  Inheritance: XL Classification: DEFINITIVE Submitted by: ClinGen
• atypical Rett syndrome

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• Cornelia de Lange syndrome

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Uncertain_significance. The variant received 3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PM4: Nonframeshift variant in NON repetitive region in NM_006306.4. Strenght limited to Supporting due to length of the change: 1aa.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SMC1A	NM_006306.4	c.859_861delAAG	p.Lys287del	conservative_inframe_deletion	Exon 6 of 25	ENST00000322213.9	NP_006297.2
SMC1A	NM_001281463.1	c.793_795delAAG	p.Lys265del	conservative_inframe_deletion	Exon 7 of 26		NP_001268392.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SMC1A	ENST00000322213.9	c.859_861delAAG	p.Lys287del	conservative_inframe_deletion	Exon 6 of 25	1	NM_006306.4	ENSP00000323421.3

Frequencies

GnomAD3 genomes Cov.: 22

We have no GnomAD4 exomes data on this position. Probably position not covered by the project.

GnomAD4 genome Cov.: 22

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Congenital muscular hypertrophy-cerebral syndrome Uncertain:1

Oct 22, 2017

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant is not present in population databases (ExAC no frequency). This variant, c.859_861delAAG, results in the deletion of 1 amino acids of the SMC1A protein (p.Lys287del), but otherwise preserves the integrity of the reading frame. This variant has not been reported in the literature in individuals with SMC1A-related disease. Experimental studies and prediction algorithms are not available for this variant, and the functional significance of the deleted amino acid is currently unknown. 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
PhyloP100		7.5

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.090		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Other links and lift over

dbSNP: rs1556890626; hg19: chrX-53439196;