NM_000478.6:c.620A>C

Variant names:

• chr1-21564188-A-C
• rs121918004
• NM_000478.6:c.620A>C

Variant summary

Our verdict is Likely pathogenic. Variant got 7 ACMG points: 7P and 0B. PM1 PP3_Strong PP5

The NM_000478.6(ALPL):​c.620A>C​(p.Gln207Pro) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.0000041 in 1,461,712 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: not found (cov: 32)
  • Exomes 𝑓: 0.0000041 (0 hom.)
• Consequence: ALPL NM_000478.6 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:4 U:1
• Conservation: PhyloP100: 8.83

Genes affected

ALPL (HGNC:438): (alkaline phosphatase, biomineralization associated) This gene encodes a member of the alkaline phosphatase family of proteins. There are at least four distinct but related alkaline phosphatases: intestinal, placental, placental-like, and liver/bone/kidney (tissue non-specific). The first three are located together on chromosome 2, while the tissue non-specific form is located on chromosome 1. The product of this gene is a membrane bound glycosylated enzyme that is not expressed in any particular tissue and is, therefore, referred to as the tissue-nonspecific form of the enzyme. Alternative splicing results in multiple transcript variants, at least one of which encodes a preproprotein that is proteolytically processed to generate the mature enzyme. This enzyme may play a role in bone mineralization. Mutations in this gene have been linked to hypophosphatasia, a disorder that is characterized by hypercalcemia and skeletal defects. [provided by RefSeq, Oct 2015]

ACMG classification

Verdict is Likely_pathogenic. Variant got 7 ACMG points.

• PM1: In a hotspot region, there are 5 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 8 uncertain in NM_000478.6
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.991
• PP5: Variant 1-21564188-A-C is Pathogenic according to our data. Variant chr1-21564188-A-C is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 13666.We mark this variant Likely_pathogenic, oryginal submissions are: {Likely_pathogenic=1, Uncertain_significance=1, Pathogenic=2}. Variant chr1-21564188-A-C is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
ALPL	NM_000478.6	c.620A>C	p.Gln207Pro	missense_variant	Exon 6 of 12	ENST00000374840.8	NP_000469.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
ALPL	ENST00000374840.8	c.620A>C	p.Gln207Pro	missense_variant	Exon 6 of 12	1	NM_000478.6	ENSP00000363973.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000410 AC: 6 AN: 1461712 Hom.: 0 Cov.: 32 AF XY: 0.00000550 AC XY: 4 AN XY: 727162

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: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000540

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:4 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Infantile hypophosphatasia Pathogenic:2

Oct 15, 1992

OMIM

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: literature only

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-

Neuberg Centre For Genomic Medicine, NCGM

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The missense variant p.Q207P in ALPL (NM_000478.6) ha been previously reported with autosomal recessive infantile hypophosphatasia (Henthron P et al). It has been submitted to ClinVar as Pathogenic. The p.Q207P variant is novel (not in any individuals) in gnomAD Exomes and is novel (not in any individuals) in 1000 Genomes. The p.Q207P missense variant is predicted to be damaging by both SIFT and PolyPhen2. The glutamine residue at codon 207 of ALPL is conserved in all mammalian species. The nucleotide c.620 in ALPL is predicted conserved by GERP++ and PhyloP across 100 vertebrates -

not provided Pathogenic:2

Dec 07, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces glutamine, which is neutral and polar, with proline, which is neutral and non-polar, at codon 207 of the ALPL protein (p.Gln207Pro). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with clinical features of hypophosphatasia (PMID: 1409720; internal data). This variant is also known as p.Gln190Pro. ClinVar contains an entry for this variant (Variation ID: 13666). 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 expected to disrupt ALPL protein function with a positive predictive value of 95%. This variant disrupts the p.Gln207 amino acid residue in ALPL. Other variant(s) that disrupt this residue have been observed in individuals with ALPL-related conditions (PMID: 32066479), which suggests that this may be a clinically significant amino acid residue. 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. -

May 06, 2016

Center for Pediatric Genomic Medicine, Children's Mercy Hospital and Clinics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

not specified Uncertain:1

Apr 26, 2023

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: ALPL c.620A>C (p.Gln207Pro) results in a non-conservative amino acid change in the encoded protein sequence. Four of five in-silico tools predict a damaging effect of the variant on protein function. The variant was absent in 251116 control chromosomes. c.620A>C has been reported in the literature in a compound heterozygous individual affected with Perinatal Hypophosphatasia, Autosomal Recessive (Henthorn_1992) carrying an additional variant scored as VUS-possibly pathogenic by our lab. This patient had enzyme activity of <10% in fibroblasts (Fedde_1996). The following publications have been ascertained in the context of this evaluation (PMID: 8675582, 1409720). Four clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation, classifying the variant as pathogenic (n=3) or likely pathogenic (n=1). Based on the evidence outlined above, the variant was classified as VUS-possibly pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.58	D
BayesDel_noAF	Pathogenic	0.59
CADD	Pathogenic	29
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.99	D;.;.;D
Eigen	Pathogenic	0.85
Eigen_PC	Pathogenic	0.79
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.94	.;D;D;D
M_CAP	Pathogenic	0.89	D
MetaRNN	Pathogenic	0.99	D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	4.3	H;.;.;H
PrimateAI	Uncertain	0.57	T
PROVEAN	Pathogenic	-5.6	D;D;D;D
REVEL	Pathogenic	0.98
Sift	Uncertain	0.0010	D;D;D;D
Sift4G	Uncertain	0.0030	D;D;D;D
Polyphen		0.29	B;.;.;B
Vest4		0.94
MutPred		0.90		Loss of catalytic residue at Q207 (P = 0.027);.;.;Loss of catalytic residue at Q207 (P = 0.027);
MVP		0.99
MPC		0.79
ClinPred		1.0	D
GERP RS		5.4
Varity_R		0.99
gMVP		1.0

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

Publications

LitVar

Other links and lift over

dbSNP: rs121918004; hg19: chr1-21890681;