20-44621103-G-T

Variant names:

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

Variant summary

Our verdict is Likely pathogenic. Variant got 7 ACMG points: 7P and 0B. PM2 PP3_Strong PP5

The NM_000022.4(ADA):​c.890C>A​(p.Pro297Gln) variant causes a missense change. The variant allele was found at a frequency of 0.0000242 in 1,614,020 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 Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: 𝑓 0.00012 (0 hom., cov: 32)
  • Exomes 𝑓: 0.000014 (0 hom.)
• Consequence: ADA NM_000022.4 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:5 U:2 O:1
• Conservation: PhyloP100: 6.50

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

Verdict is Likely_pathogenic. Variant got 7 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.985
• PP5: Variant 20-44621103-G-T is Pathogenic according to our data. Variant chr20-44621103-G-T is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 1961.We mark this variant Likely_pathogenic, oryginal submissions are: {Likely_pathogenic=1, Uncertain_significance=2, Pathogenic=2, not_provided=1}. Variant chr20-44621103-G-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
ADA	NM_000022.4	c.890C>A	p.Pro297Gln	missense_variant	Exon 10 of 12	ENST00000372874.9	NP_000013.2
ADA	NM_001322051.2	c.818C>A	p.Pro273Gln	missense_variant	Exon 9 of 11		NP_001308980.1
ADA	NM_001322050.2	c.485C>A	p.Pro162Gln	missense_variant	Exon 9 of 11		NP_001308979.1
ADA	NR_136160.2	n.917C>A		non_coding_transcript_exon_variant	Exon 9 of 11

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
ADA	ENST00000372874.9	c.890C>A	p.Pro297Gln	missense_variant	Exon 10 of 12	1	NM_000022.4	ENSP00000361965.4
ADA	ENST00000695995.1	c.500C>A	p.Pro167Gln	missense_variant	Exon 7 of 9			ENSP00000512318.1
ADA	ENST00000695991.1	c.428C>A	p.Pro143Gln	missense_variant	Exon 6 of 8			ENSP00000512314.1
ADA	ENST00000695956.1	c.44C>A	p.Pro15Gln	missense_variant	Exon 1 of 3			ENSP00000512285.1
ADA	ENST00000696038.1	n.*647C>A		non_coding_transcript_exon_variant	Exon 8 of 9			ENSP00000512344.1
ADA	ENST00000696038.1	n.*647C>A		3_prime_UTR_variant	Exon 8 of 9			ENSP00000512344.1

Frequencies

GnomAD3 genomes AF: 0.000125 AC: 19 AN: 152144 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000241

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00118

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: 0.00

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.0000278 AC: 7 AN: 251492 Hom.: 0 AF XY: 0.0000368 AC XY: 5 AN XY: 135918

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.000173

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.000163

GnomAD4 exome AF: 0.0000137 AC: 20 AN: 1461876 Hom.: 0 Cov.: 31 AF XY: 0.0000179 AC XY: 13 AN XY: 727236

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.000358

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.0000662

GnomAD4 genome AF: 0.000125 AC: 19 AN: 152144 Hom.: 0 Cov.: 32 AF XY: 0.000175 AC XY: 13 AN XY: 74314

Gnomad4 AFR AF: 0.0000241

Gnomad4 AMR AF: 0.00118

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.00

Gnomad4 OTH AF: 0.00

Alfa AF: 0.0000557 Hom.: 0

Bravo AF: 0.000189

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:5 Uncertain:2 Other:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Severe combined immunodeficiency, autosomal recessive, T cell-negative, B cell-negative, NK cell-negative, due to adenosine deaminase deficiency Pathogenic:2 Other:1

Oct 28, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces proline, which is neutral and non-polar, with glutamine, which is neutral and polar, at codon 297 of the ADA protein (p.Pro297Gln). This variant is present in population databases (rs121908718, gnomAD 0.02%). This missense change has been observed in individual(s) with partial adenosine deaminase (ADA) deficiency (PMID: 2166947, 2783588). ClinVar contains an entry for this variant (Variation ID: 1961). 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 ADA protein function with a negative predictive value of 80%. Experimental studies are conflicting or provide insufficient evidence to determine the effect of this variant on ADA function (PMID: 2166947). This variant disrupts the p.Pro297 amino acid residue in ADA. Other variant(s) that disrupt this residue have been determined to be pathogenic (internal data). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. For these reasons, this variant has been classified as Pathogenic. -

-

UniProtKB/Swiss-Prot

Significance: not provided

Review Status: no classification provided

Collection Method: literature only

- -

Mar 25, 2024

Baylor Genetics

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

not provided Pathogenic:1 Uncertain:1

Sep 01, 2021

Mayo Clinic Laboratories, Mayo Clinic

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

May 09, 2023

GeneDx

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; Published functional studies demonstrate a damaging effect as transfection of the mutant cDNA into heterologous cells resulted in expression of a heat-labile ADA of normal electrophoretic mobility, properties exhibited by the ADA in the patients' cells (Hirschhorn et al., 1989); Not observed at a significant frequency in large population cohorts (gnomAD); This variant is associated with the following publications: (PMID: 9225964, 2783588, 21898656, 24772956, 20493397, 2166947, 31589614, 34975878, 23645737) -

Partial adenosine deaminase deficiency Pathogenic:1

Feb 01, 1989

OMIM

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: literature only

- -

ADA-related disorder Pathogenic:1

Sep 04, 2024

PreventionGenetics, part of Exact Sciences

Significance: Likely pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

The ADA c.890C>A variant is predicted to result in the amino acid substitution p.Pro297Gln. This variant has been reported in the homozygous and compound heterozygous states in individuals with partial adenosine deaminase (ADA) deficiency (Hirschhorn et al. 1989. PubMed ID: 2783588; Hirschhorn et al. 1990. PubMed ID: 2166947). Functional studies suggest that this variant impacts ADA function (Hirschhorn et al. 1989. PubMed ID: 2783588; Hirschhorn et al. 1990. PubMed ID: 2166947). Of note, another variant impacting the same amino acid [c.890C>T (p.Pro297Leu)] was reported in the compound heterozygous state in an individual with predominantly antibody deficiency (Patient P221, Rojas-Restrepo. 2021. PubMed ID: 34975878). The c.890C>A (p.Pro297Gln) variant is reported in 0.020% of alleles in individuals of Latino descent in gnomAD and has conflicting interpretations in ClinVar regarding its pathogenicity, ranging from pathogenic to likely pathogenic to uncertain significance (https://www.ncbi.nlm.nih.gov/clinvar/variation/1961/). Taken together, this variant is interpreted as likely pathogenic. -

not specified Uncertain:1

Oct 12, 2022

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: ADA c.890C>A (p.Pro297Gln) results in a non-conservative amino acid change located in the Adenosine deaminase domain (IPR001365) of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 2.8e-05 in 251492 control chromosomes (gnomAD). c.890C>A has been reported in the literature in the homozygous and compound heterozygous states in two partially ADA deficient children, identified through Newborn Screening (Hirschhorn_1989, Hirschhorn_1990). A later report by the same authors (Hirschhorn_1995) stated that up to that date, the children had not presented with immunodeficiency. GeneReviews defines partial ADA deficiency as a benign condition which is compatible with normal immune function (PMID 20301656). These report(s) do not provide unequivocal conclusions about association of the variant with Severe Combined Immunodeficiency. Experimental evidence evaluating an impact on protein function demonstrated the variant to have normal electrophoretic mobility and abnormal heat stability, with ADA activity measured at 56% in homozygous lymphoid cells (Hirschhorn_1989, Hirschhorn_1990). A ClinVar submitter (evaluation after 2014) cites the variant as likely pathogenic, while another ClinVar submitter (evaluation after 2014) cites it as uncertain significance. Based on the evidence outlined above, the variant was classified as uncertain significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.78
BayesDel_addAF	Pathogenic	0.37	D
BayesDel_noAF	Pathogenic	0.56
CADD	Pathogenic	26
DANN	Uncertain	0.99
DEOGEN2	Pathogenic	0.97	D;D
Eigen	Pathogenic	0.82
Eigen_PC	Pathogenic	0.74
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.94	D;D
M_CAP	Pathogenic	0.37	D
MetaRNN	Pathogenic	0.98	D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.9	H;.
PrimateAI	Uncertain	0.55	T
PROVEAN	Pathogenic	-5.5	D;D
REVEL	Pathogenic	0.95
Sift	Uncertain	0.0020	D;D
Sift4G	Uncertain	0.0080	D;D
Polyphen		1.0	D;.
Vest4		0.80
MutPred		0.97		Gain of ubiquitination at K301 (P = 0.0843);.;
MVP		0.97
MPC		0.54
ClinPred		0.98	D
GERP RS		5.0
Varity_R		0.92
gMVP		0.96

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: rs121908718; hg19: chr20-43249744;