20-44626517-G-C

Variant names:

• chr20-44626517-G-C
• rs121908717
• NM_000022.4:c.301C>G

Variant summary

Our verdict is Pathogenic. The variant received 12 ACMG points: 12P and 0B. PM1 PM2 PM5 PP3_Strong PP5_Moderate

The NM_000022.4(ADA):​c.301C>G​(p.Arg101Gly) variant causes a missense change. The variant allele was found at a frequency of 0.00000137 in 1,461,850 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 Likely pathogenic (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R101Q) has been classified as Pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: ADA NM_000022.4 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 3.69
• Publications: 7 publications found

Genes affected

ADA (HGNC:186): (adenosine deaminase) This gene encodes an enzyme that catalyzes the hydrolysis of adenosine to inosine in the purine catabolic pathway. Various mutations have been described for this gene and have been linked to human diseases related to impaired immune function such as severe combined immunodeficiency disease (SCID) which is the result of a deficiency in the ADA enzyme. In ADA-deficient individuals there is a marked depletion of T, B, and NK lymphocytes, and consequently, a lack of both humoral and cellular immunity. Conversely, elevated levels of this enzyme are associated with congenital hemolytic anemia. [provided by RefSeq, Sep 2019]

ADA Gene-Disease associations (from GenCC):

• severe combined immunodeficiency, autosomal recessive, T cell-negative, B cell-negative, NK cell-negative, due to adenosine deaminase deficiency

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: ClinGen, Labcorp Genetics (formerly Invitae), G2P, Myriad Women’s Health, Orphanet
• Omenn syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Pathogenic. The variant received 12 ACMG points.

• PM1: In a hotspot region, there are 3 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 9 uncertain in NM_000022.4
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr20-44626516-C-T is described in ClinVar as Pathogenic. ClinVar VariationId is 1956.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.993
• PP5: Variant 20-44626517-G-C is Pathogenic according to our data. Variant chr20-44626517-G-C is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 971097.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
ADA	NM_000022.4	c.301C>G	p.Arg101Gly	missense_variant	Exon 4 of 12	ENST00000372874.9	NP_000013.2
ADA	NM_001322051.2	c.301C>G	p.Arg101Gly	missense_variant	Exon 4 of 11		NP_001308980.1
ADA	NM_001322050.2	c.12C>G	p.Cys4Trp	missense_variant	Exon 4 of 11		NP_001308979.1
ADA	NR_136160.2	n.393C>G		non_coding_transcript_exon_variant	Exon 4 of 11

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
ADA	ENST00000372874.9	c.301C>G	p.Arg101Gly	missense_variant	Exon 4 of 12	1	NM_000022.4	ENSP00000361965.4
ADA	ENST00000696038.1	n.*47C>G		non_coding_transcript_exon_variant	Exon 4 of 9			ENSP00000512344.1
ADA	ENST00000696038.1	n.*47C>G		3_prime_UTR_variant	Exon 4 of 9			ENSP00000512344.1
ADA	ENST00000695995.1	c.216+2532C>G		intron_variant	Intron 3 of 8			ENSP00000512318.1
ADA	ENST00000695991.1	c.216+2532C>G		intron_variant	Intron 3 of 7			ENSP00000512314.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461850 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 AN XY: 727222

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.00 AC: 0 AN: 33478

American (AMR) AF: 0.00 AC: 0 AN: 44722

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39700

South Asian (SAS) AF: 0.00 AC: 0 AN: 86254

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53420

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5748

European-Non Finnish (NFE) AF: 0.00000180 AC: 2 AN: 1112002

Other (OTH) AF: 0.00 AC: 0 AN: 60390

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.000203), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Severe combined immunodeficiency, autosomal recessive, T cell-negative, B cell-negative, NK cell-negative, due to adenosine deaminase deficiency Pathogenic:1

Aug 31, 2022

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. This sequence change replaces arginine, which is basic and polar, with glycine, which is neutral and non-polar, at codon 101 of the ADA protein (p.Arg101Gly). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with ADA-related conditions. ClinVar contains an entry for this variant (Variation ID: 971097). 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) performed at Invitae indicates that this missense variant is expected to disrupt ADA protein function. This variant disrupts the p.Arg101 amino acid residue in ADA. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 1974554, 3182793, 9758612). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.97
BayesDel_addAF	Pathogenic	0.55	D
BayesDel_noAF	Pathogenic	0.56
CADD	Pathogenic	29
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.98	D;D
Eigen	Pathogenic	0.72
Eigen_PC	Uncertain	0.57
FATHMM_MKL	Uncertain	0.92	D
LIST_S2	Pathogenic	0.98	D;D
M_CAP	Pathogenic	0.40	D
MetaRNN	Pathogenic	0.99	D;D
MetaSVM	Pathogenic	1.1	D
PhyloP100		3.7
PrimateAI	Uncertain	0.64	T
PROVEAN	Pathogenic	-6.7	D;D
REVEL	Pathogenic	0.90
Sift	Pathogenic	0.0	D;D
Sift4G	Pathogenic	0.0	D;D
Polyphen		1.0	D;.
Vest4		0.98
MutPred		0.95		Loss of methylation at R101 (P = 0.0242);Loss of methylation at R101 (P = 0.0242);
MVP		0.94
MPC		0.71
ClinPred		1.0	D
GERP RS		4.1
Varity_R		0.99
gMVP		0.98
Mutation Taster		=5/95	disease causing

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

Other links and lift over

dbSNP: rs121908717; hg19: chr20-43255158;