chr22-19759556-A-G

Position:

• chr22-19759556-A-G

Variant summary

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

The NM_080647.1(TBX1):​c.-86-2A>G variant causes a splice acceptor, intron change. The variant allele was found at a frequency of 0.00000282 in 1,420,776 control chromosomes in the GnomAD database, with no homozygous occurrence. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: not found (cov: 35)
  • Exomes 𝑓: 0.0000028 (0 hom.)
• Consequence: TBX1 NM_080647.1 splice_acceptor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 6.45

Genes affected

TBX1 (HGNC:11592): (T-box transcription factor 1) This gene is a member of a phylogenetically conserved family of genes that share a common DNA-binding domain, the T-box. T-box genes encode transcription factors involved in the regulation of developmental processes. This gene product shares 98% amino acid sequence identity with the mouse ortholog. DiGeorge syndrome (DGS)/velocardiofacial syndrome (VCFS), a common congenital disorder characterized by neural-crest-related developmental defects, has been associated with deletions of chromosome 22q11.2, where this gene has been mapped. Studies using mouse models of DiGeorge syndrome suggest a major role for this gene in the molecular etiology of DGS/VCFS. Several alternatively spliced transcript variants encoding different isoforms have been described for this gene. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Uncertain_significance. Variant got 4 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.07997312 fraction of the gene. Cryptic splice site detected, with MaxEntScore 3.5, offset of 29, new splice context is: cggagcgcaccgcccaccAGggc. Cryptic site results in frameshift change. If cryptic site found is not functional and variant results in exon loss, it results in inframe change.
• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TBX1	NM_080647.1	c.-86-2A>G		splice_acceptor_variant, intron_variant			NP_542378.1
TBX1	NM_080646.2	c.-86-2A>G		splice_acceptor_variant, intron_variant			NP_542377.1
TBX1	NM_005992.1	c.-86-2A>G		splice_acceptor_variant, intron_variant			NP_005983.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TBX1	ENST00000332710.8	c.-86-2A>G		splice_acceptor_variant, intron_variant		1		ENSP00000331791.4
TBX1	ENST00000329705.11	c.-86-2A>G		splice_acceptor_variant, intron_variant		1		ENSP00000331176.7
TBX1	ENST00000359500.7	c.-86-2A>G		splice_acceptor_variant, intron_variant		1		ENSP00000352483.3

Frequencies

GnomAD3 genomes Cov.: 35

GnomAD4 exome AF: 0.00000282 AC: 4 AN: 1420776 Hom.: 0 Cov.: 29 AF XY: 0.00000568 AC XY: 4 AN XY: 704228

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.0000367

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 9.13e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 35

Bravo AF: 0.00000378

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

Jul 19, 2023

Canonical splice site variant predicted to result in a null allele in a gene for which loss of function is a known mechanism of disease; Has not been previously published as pathogenic or benign to our knowledge; No data available from control populations to assess the frequency of this variant -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Uncertain	0.0
CADD	Benign	15
DANN	Uncertain	0.99

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.93
SpliceAI score (max)		0.90		Details are displayed if max score is > 0.2
DS_AL_spliceai		0.90		Position offset: 2

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

Publications

LitVar

Other links and lift over

dbSNP: rs1936571734; hg19: chr22-19747079;