rs121918014

chr1-21576582-A-G

Variant summary

Our verdict is Pathogenic. Variant got 14 ACMG points: 14P and 0B. PM1 PP3_Strong PP5_Very_Strong

The NM_000478.6(ALPL):c.1250A>G(p.Asn417Ser) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000031 in 1,613,808 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 (★★). Synonymous variant affecting the same amino acid position (i.e. N417N) has been classified as Likely benign.

• Frequency:
  • Genomes: 𝑓 0.000053 (0 hom., cov: 32)
  • Exomes 𝑓: 0.000029 (0 hom.)
• Consequence: ALPL NM_000478.6 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:12 O:1
• Conservation: PhyloP100: 8.60

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 Pathogenic. Variant got 14 ACMG points.

• PM1: In a hotspot region, there are 9 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 5 uncertain in NM_000478.6
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.954
• PP5: Variant 1-21576582-A-G is Pathogenic according to our data. Variant chr1-21576582-A-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 13679.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr1-21576582-A-G is described in Lovd as [Likely_pathogenic]. Variant chr1-21576582-A-G is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
ALPL	NM_000478.6	c.1250A>G	p.Asn417Ser	missense_variant	11/12	ENST00000374840.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
ALPL	ENST00000374840.8	c.1250A>G	p.Asn417Ser	missense_variant	11/12	1	NM_000478.6	P1

Frequencies

GnomAD3 genomes AF: 0.0000526 AC: 8 AN: 152044 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000242

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: 0.000103

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.0000199 AC: 5 AN: 251442 Hom.: 0 AF XY: 0.0000294 AC XY: 4 AN XY: 135898

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

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: 0.0000440

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000287 AC: 42 AN: 1461764 Hom.: 0 Cov.: 31 AF XY: 0.0000316 AC XY: 23 AN XY: 727196

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.0000252

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000369

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.0000526 AC: 8 AN: 152044 Hom.: 0 Cov.: 32 AF XY: 0.0000404 AC XY: 3 AN XY: 74264

Gnomad4 AFR AF: 0.0000242

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.000103

Gnomad4 OTH AF: 0.00

Bravo AF: 0.0000340

ESP6500AA AF: 0.00 AC: 0

ESP6500EA AF: 0.000116 AC: 1

ExAC AF: 0.0000494 AC: 6

EpiCase AF: 0.0000545

EpiControl AF: 0.0000593

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:12 Other:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:6

Likely pathogenic, criteria provided, single submitter	clinical testing	Athena Diagnostics	Jul 17, 2018	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Eurofins Ntd Llc (ga)	Jul 16, 2015	- -
Pathogenic, criteria provided, single submitter	clinical testing	Invitae	Jan 25, 2024	This sequence change replaces asparagine, which is neutral and polar, with serine, which is neutral and polar, at codon 417 of the ALPL protein (p.Asn417Ser). This variant is present in population databases (rs121918014, gnomAD 0.006%). This missense change has been observed in individual(s) with hypophosphatasia (PMID: 11745997, 25731960, 27998428). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. It has also been observed to segregate with disease in related individuals. This variant is also known as p.Asn400Ser. ClinVar contains an entry for this variant (Variation ID: 13679). 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 ALPL protein function with a positive predictive value of 95%. Experimental studies have shown that this missense change affects ALPL function (PMID: 19500388, 23688511). For these reasons, this variant has been classified as Pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	Feb 23, 2021	- -
Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Apr 13, 2022	Published functional studies demonstrate that N417S exhibits a dominant effect on the ALPL protein (Fauvert et al., 2009); In silico analysis, which includes protein predictors and evolutionary conservation, supports a deleterious effect; This variant is associated with the following publications: (PMID: 21956185, 29405932, 34258332, 34662886, 19500388, 23688511, 11745997, 27998428, 19232125, 28401263, 28939177, 29236161, 28000043, 29160013, 32160374, 28436937, 33069919, 33549410) -
Pathogenic, criteria provided, single submitter	clinical testing	ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories	Jun 20, 2023	The ALPL c.1250A>G; p.Asn417Ser variant (rs121918014) is reported in the literature in numerous heterozygous individuals affected with hypophosphatasia (Durrough 2021, Fauvert 2009, Hepp 2021, Taillandier 2018), and in one compound heterozygous case affected with perinatal hypophosphatasia (Sergi 2001). This variant is also reported in ClinVar (Variation ID: 13679), and is found in the non-Finnish European population with an allele frequency of 0.006% (8/129126 alleles) in the Genome Aggregation Database. In vitro functional analyses demonstrate reduced ALP enzymatic activity and exhibits a dominant negative effect on wild-type enzymatic activity (Del Angel 2020, Fauvert 2009, Sultana 2013). Computational analyses also predict that this variant is deleterious (REVEL: 0.81). Based on available information, this variant is considered to be pathogenic. References: Del Angel G et al. Large-scale in vitro functional testing and novel variant scoring via protein modeling provide insights into alkaline phosphatase activity in hypophosphatasia. Hum Mutat. 2020 Jul;41(7):1250-1262. PMID: 32160374. Durrough C et al. Characterization of physical, functional, and cognitive performance in 15 adults with hypophosphatasia. Bone. 2021 Jan;142:115695. PMID: 33069919. Fauvert D et al. Mild forms of hypophosphatasia mostly result from dominant negative effect of severe alleles or from compound heterozygosity for severe and moderate alleles. BMC Med Genet. 2009 Jun 6;10:51. PMID: 19500388. Hepp N et al. Biochemical, clinical and genetic characteristics in adults with persistent hypophosphatasaemia; Data from an endocrinological outpatient clinic in Denmark. Bone Rep. 2021 Jun 28;15:101101. PMID: 34258332. Sergi C et al. Perinatal hypophosphatasia: radiology, pathology and molecular biology studies in a family harboring a splicing mutation (648+1A) and a novel missense mutation (N400S) in the tissue-nonspecific alkaline phosphatase (TNSALP) gene. Am J Med Genet. 2001 Oct 15;103(3):235-40. PMID: 11745997. Sultana S et al. An asparagine at position 417 of tissue-nonspecific alkaline phosphatase is essential for its structure and function as revealed by analysis of the N417S mutation associated with severe hypophosphatasia. Mol Genet Metab. 2013 Jul;109(3):282-8. PMID: 23688511. Taillandier A et al. Genetic analysis of adults heterozygous for ALPL mutations. J Bone Miner Metab. 2018 Nov;36(6):723-733. PMID: 29236161. -

Adult hypophosphatasia Pathogenic:3

Pathogenic, criteria provided, single submitter	clinical testing	Johns Hopkins Genomics, Johns Hopkins University	May 25, 2021	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Institute of Human Genetics, University of Leipzig Medical Center	Nov 30, 2020	- -
Pathogenic, criteria provided, single submitter	clinical testing	Baylor Genetics	Sep 21, 2023	- -

Hypophosphatasia Pathogenic:1 Other:1

not provided, no classification provided	phenotyping only	GenomeConnect - Invitae Patient Insights Network	-	Variant interpreted as Pathogenic and reported on 11-16-2020 by Invitae. GenomeConnect-Invitae Patient Insights Network assertions are reported exactly as they appear on the patient-provided report from the testing laboratory. Registry team members make no attempt to reinterpret the clinical significance of the variant. Phenotypic details are available under supporting information. -
Pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Aug 05, 2019	Variant summary: ALPL c.1250A>G (p.Asn417Ser) results in a conservative amino acid change located in the Crown domain (Simon-Bouy_2008) of the encoded protein sequence. Four of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 2e-05 in 251442 control chromosomes (gnomAD). c.1250A>G has been reported in the literature as a single heterozygous variant (i.e. no other variants detected) in multiple individuals with features of mild HPP (odontohypophosphatasia, adult and childhood hypophosphatasia) but also in at least 2 parents that were carriers of the variant without any reported symptoms (Fauvert_2009, Reibel_2009, Whyte_2015). It has also been reported in compound heterozygous state with other pathogenic variants in patients affected with severe perinatal or severe childhood hypophosphatasia (Sergi_2001, Whyte_2015). These data indicate that the variant is very likely to be associated with disease. Using a cell system Fauvert et al reported that this variant has a dominant negative effect (Fauvert_2009) on wild-type enzymatic activity. In addition, Sultana et al performed several functional experiments using an in vitro system and concluded that a complete loss of ALP enzymatic activity resulting from the disruption of its functional dimer structure may represent the molecular basis of HPP associated with ALPL N417S (Sultana_2013). Three ClinVar submitters (evaluation after 2014) cite the variant as likely pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic. -

Infantile hypophosphatasia Pathogenic:1

Pathogenic, no assertion criteria provided

clinical testing

Counsyl

Oct 03, 2018

- -

Perinatal lethal hypophosphatasia Pathogenic:1

Pathogenic, no assertion criteria provided

literature only

OMIM

Oct 15, 2001

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.34
BayesDel_addAF	Uncertain	0.077	D
BayesDel_noAF	Uncertain	0.0
Cadd	Pathogenic	26
Dann	Uncertain	1.0
DEOGEN2	Pathogenic	0.96	D;.;.;D
Eigen	Pathogenic	0.84
Eigen_PC	Pathogenic	0.77
FATHMM_MKL	Pathogenic	1.0	D
M_CAP	Pathogenic	0.79	D
MetaRNN	Pathogenic	0.95	D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.0	M;.;.;M
MutationTaster	Benign	1.0	A;A;A;A;A;A;A
PrimateAI	Uncertain	0.61	T
PROVEAN	Pathogenic	-4.7	D;D;D;D
REVEL	Pathogenic	0.81
Sift	Uncertain	0.018	D;D;D;D
Sift4G	Uncertain	0.020	D;D;D;D
Polyphen		1.0	D;.;.;D
Vest4		0.93
MVP		0.98
MPC		1.1
ClinPred		0.92	D
GERP RS		5.1
Varity_R		0.64
gMVP		0.92

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: rs121918014; hg19: chr1-21903075;