20-44621103-G-A

Variant names:

• chr20-44621103-G-A
• rs121908718
• NM_000022.4:c.890C>T

Variant summary

Our verdict is Likely pathogenic. The variant received 6 ACMG points: 6P and 0B. PM3 PS3_Supporting PP4_Moderate PM2_Supporting

This summary comes from the ClinGen Evidence Repository: The c.890C>T (NM_000022.4) variant in ADA is a missense variant predicted to cause the substitution of Proline by Leucine at amino acid 297 (p.Pro297Leu).The highest population minor allele frequency in gnomAD v4 is 0.000008350 (2/44896 alleles) in the East Asian population, which is lower than the ClinGen SCID VCEP threshold (<0.0001742) for PM2_Supporting, meeting this criterion (PM2_Supporting). No homozygous was reported.This variant was described in at least one patient in the literature, who presents *Reduced ADA enzyme activity in patient cells (1pt); *Reported also reported "a definite increase in intracellular metabolites" (dAdo nucleotides), (2 pts); *SCID gene panel or exome/genome sequencing conducted (0.5pt). Total 3.5 points, PP4_Moderate (PMID:34975878).The variant expression in E. Coli falls into our activity Group III (Dr. Hershfield - internal communication). PS3 is met at the Supporting level of evidence.In summary, this variant is classified as Likely Pathogenic for autosomal recessive SCID based on ACMG/AMP criteria applied, as specified by the ClinGen SCID VCEP (specification version 1.0): PM2_Supporting, PP4_Moderate, PM3_Moderate, and PS3_Supporting. LINK:https://erepo.genome.network/evrepo/ui/classification/CA9871472/MONDO:0007064/114

• Frequency:
  • Genomes: 𝑓 0.0000066 (0 hom., cov: 32)
  • Exomes 𝑓: 0.0000048 (0 hom.)
• Consequence: ADA NM_000022.4 missense
• Clinical Significance: Likely pathogenic reviewed by expert panel P:3
• Conservation: PhyloP100: 6.50
• 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]

PKIG (HGNC:9019): (cAMP-dependent protein kinase inhibitor gamma) This gene encodes a member of the protein kinase inhibitor family. Studies of a similar protein in mice suggest that this protein acts as a potent competitive cAMP-dependent protein kinase inhibitor, and is a predominant form of inhibitor in various tissues. The encoded protein may be involved in osteogenesis. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Jul 2013]

ACMG classification

Our verdict: Likely_pathogenic. The variant received 6 ACMG points.

• PS3: For more information check the summary or visit ClinGen Evidence Repository.
• PM2: For more information check the summary or visit ClinGen Evidence Repository.
• PM3: For more information check the summary or visit ClinGen Evidence Repository.
• PP4: For more information check the summary or visit ClinGen Evidence Repository.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000022.4. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	ADA	NM_000022.4	MANE Select	c.890C>T	p.Pro297Leu	missense	Exon 10 of 12	NP_000013.2
	ADA	NM_001322051.2		c.818C>T	p.Pro273Leu	missense	Exon 9 of 11	NP_001308980.1
	ADA	NM_001322050.2		c.485C>T	p.Pro162Leu	missense	Exon 9 of 11	NP_001308979.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	ADA	ENST00000372874.9	TSL:1 MANE Select	c.890C>T	p.Pro297Leu	missense	Exon 10 of 12	ENSP00000361965.4
	ADA	ENST00000537820.2	TSL:1	c.818C>T	p.Pro273Leu	missense	Exon 9 of 11	ENSP00000441818.1
	ADA	ENST00000695995.1		c.500C>T	p.Pro167Leu	missense	Exon 7 of 9	ENSP00000512318.1

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152144 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000147

Gnomad OTH AF: 0.00

GnomAD2 exomes AF: 0.00000795 AC: 2 AN: 251492 AF XY: 0.0000147

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.0000544

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000879

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000479 AC: 7 AN: 1461878 Hom.: 0 Cov.: 31 AF XY: 0.00000413 AC XY: 3 AN XY: 727238

African (AFR) AF: 0.00 AC: 0 AN: 33480

American (AMR) AF: 0.00 AC: 0 AN: 44724

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

East Asian (EAS) AF: 0.0000504 AC: 2 AN: 39700

South Asian (SAS) AF: 0.00 AC: 0 AN: 86258

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53418

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 0.00000450 AC: 5 AN: 1111998

Other (OTH) AF: 0.00 AC: 0 AN: 60396

GnomAD4 genome AF: 0.00000657 AC: 1 AN: 152144 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 74314

African (AFR) AF: 0.00 AC: 0 AN: 41422

American (AMR) AF: 0.00 AC: 0 AN: 15272

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3470

East Asian (EAS) AF: 0.00 AC: 0 AN: 5196

South Asian (SAS) AF: 0.00 AC: 0 AN: 4824

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10594

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 316

European-Non Finnish (NFE) AF: 0.0000147 AC: 1 AN: 68046

Other (OTH) AF: 0.00 AC: 0 AN: 2092

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.00000378

ExAC AF: 0.00000824 AC: 1

EpiCase AF: 0.0000545

EpiControl AF: 0.00

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:3

Revision: reviewed by expert panel

Submissions by phenotype

Severe combined immunodeficiency, autosomal recessive, T cell-negative, B cell-negative, NK cell-negative, due to adenosine deaminase deficiency Pathogenic:3

Mar 18, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces proline, which is neutral and non-polar, with leucine, which is neutral and non-polar, at codon 297 of the ADA protein (p.Pro297Leu). This variant is present in population databases (rs121908718, gnomAD 0.006%). This missense change has been observed in individual(s) with clinical features of ADA-related conditions (PMID: 34975878). ClinVar contains an entry for this variant (Variation ID: 1505857). 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 not expected to disrupt ADA protein function with a negative predictive value of 80%. This variant disrupts the p.Pro297 amino acid residue in ADA. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 2166947, 2783588). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. 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.

Jan 23, 2024

ClinGen Severe Combined Immunodeficiency Variant Curation Expert Panel, ClinGen

Significance: Likely pathogenic

Review Status: reviewed by expert panel

Collection Method: curation

The c.890C>T (NM_000022.4) variant in ADA is a missense variant predicted to cause the substitution of Proline by Leucine at amino acid 297 (p.Pro297Leu). The highest population minor allele frequency in gnomAD v4 is 0.000008350 (2/44896 alleles) in the East Asian population, which is lower than the ClinGen SCID VCEP threshold (<0.0001742) for PM2_Supporting, meeting this criterion (PM2_Supporting). No homozygous was reported. This variant was described in at least one patient in the literature, who presents *Reduced ADA enzyme activity in patient cells (1pt); *Reported also reported "a definite increase in intracellular metabolites" (dAdo nucleotides), (2 pts); *SCID gene panel or exome/genome sequencing conducted (0.5pt). Total 3.5 points, PP4_Moderate (PMID: 34975878). The variant expression in E. Coli falls into our activity Group III (Dr. Hershfield - internal communication). PS3 is met at the Supporting level of evidence. In summary, this variant is classified as Likely Pathogenic for autosomal recessive SCID based on ACMG/AMP criteria applied, as specified by the ClinGen SCID VCEP (specification version 1.0): PM2_Supporting, PP4_Moderate, PM3_Moderate, and PS3_Supporting.

Mar 18, 2024

Baylor Genetics

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.73
BayesDel_addAF	Pathogenic	0.44	D
BayesDel_noAF	Pathogenic	0.56
CADD	Pathogenic	28
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.95	D
Eigen	Pathogenic	0.82
Eigen_PC	Pathogenic	0.74
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Uncertain	0.97	D
M_CAP	Pathogenic	0.39	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.9	H
PhyloP100		6.5
PrimateAI	Uncertain	0.61	T
PROVEAN	Pathogenic	-7.4	D
REVEL	Pathogenic	0.96
Sift	Uncertain	0.0020	D
Sift4G	Uncertain	0.0050	D
Polyphen		1.0	D
Vest4		0.89
MutPred		0.92		Loss of phosphorylation at T294 (P = 0.1147)
MVP		0.97
MPC		0.61
ClinPred		1.0	D
GERP RS		5.0
Varity_R		0.90
gMVP		0.97
Mutation Taster		=20/80	disease causing

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

Other links and lift over

dbSNP: rs121908718; hg19: chr20-43249744;