1-21573682-G-T

Variant names:

• chr1-21573682-G-T
• rs1553414079
• NM_000478.6:c.880G>T

Variant summary

Our verdict is Pathogenic. The variant received 13 ACMG points: 13P and 0B. PM1 PM2 PM5 PP2 PP3_Strong PP5_Moderate

The NM_000478.6(ALPL):​c.880G>T​(p.Asp294Tyr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,461,728 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. D294A) has been classified as Pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: ALPL NM_000478.6 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:1 U:1
• Conservation: PhyloP100: 9.48
• Publications: 0 publications found

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]

ALPL Gene-Disease associations (from GenCC):

• adult hypophosphatasia

  Inheritance: AD Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: ClinGen, PanelApp Australia, Labcorp Genetics (formerly Invitae), Orphanet
• childhood hypophosphatasia

  Inheritance: AR, AD Classification: DEFINITIVE, SUPPORTIVE Submitted by: Laboratory for Molecular Medicine, ClinGen, Orphanet
• hypophosphatasia

  Inheritance: AR Classification: DEFINITIVE Submitted by: Myriad Women’s Health, G2P
• infantile hypophosphatasia

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Orphanet, ClinGen, Labcorp Genetics (formerly Invitae), PanelApp Australia
• odontohypophosphatasia

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• perinatal lethal hypophosphatasia

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Pathogenic. The variant received 13 ACMG points.

• PM1: In a hotspot region, there are 18 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 7 uncertain in NM_000478.6
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr1-21573683-A-C is described in ClinVar as Pathogenic. ClinVar VariationId is 13664.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP2: Missense variant in the gene, where a lot of missense mutations are associated with disease in ClinVar. The gene has 220 curated pathogenic missense variants (we use a threshold of 10). The gene has 10 curated benign missense variants. Gene score misZ: 1.2672 (below the threshold of 3.09). Trascript score misZ: 1.9021 (below the threshold of 3.09). GenCC associations: The gene is linked to adult hypophosphatasia, infantile hypophosphatasia, odontohypophosphatasia, childhood hypophosphatasia, hypophosphatasia, perinatal lethal hypophosphatasia.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.991
• PP5: Variant 1-21573682-G-T is Pathogenic according to our data. Variant chr1-21573682-G-T is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 553092.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
ALPL	NM_000478.6	c.880G>T	p.Asp294Tyr	missense_variant	Exon 9 of 12	ENST00000374840.8	NP_000469.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
ALPL	ENST00000374840.8	c.880G>T	p.Asp294Tyr	missense_variant	Exon 9 of 12	1	NM_000478.6	ENSP00000363973.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461728 Hom.: 0 Cov.: 32 AF XY: 0.00000275 AC XY: 2 AN XY: 727162

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

American (AMR) AF: 0.00 AC: 0 AN: 44706

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26130

East Asian (EAS) AF: 0.00 AC: 0 AN: 39698

South Asian (SAS) AF: 0.00 AC: 0 AN: 86238

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53378

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

European-Non Finnish (NFE) AF: 0.00000180 AC: 2 AN: 1111944

Other (OTH) AF: 0.00 AC: 0 AN: 60388

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1 Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Hypophosphatasia Pathogenic:1

Aug 29, 2025

Genomenon, Inc, Genomenon, Inc

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: curation

ALPL Asp294Tyr (c.880G>T) is a missense variant that changes the amino acid at residue 294 from Aspartic acid to Tyrosine. This variant has been observed in a proband affected with hypophosphatasia (PMID:11438998). It has been observed in trans with a pathogenic variant (PMID:11438998). This variant has been described as Asp277Tyr in the literature. It is absent or not present at a significant frequency in gnomAD. In silico models agree that this variant is possibly or probably damaging. In conclusion, we classify ALPL p.Asp294Tyr (c.880G>T) as a likely pathogenic variant.

Infantile hypophosphatasia Uncertain:1

Aug 02, 2017

Counsyl

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: clinical testing

This submission and the accompanying classification are no longer maintained by the submitter. For more information on current observations and classification, please contact variantquestions@myriad.com.

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.91
BayesDel_addAF	Pathogenic	0.55	D
BayesDel_noAF	Pathogenic	0.55
CADD	Pathogenic	29
DANN	Uncertain	0.99
DEOGEN2	Pathogenic	0.97	D;.;.;D
Eigen	Pathogenic	0.77
Eigen_PC	Uncertain	0.66
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Benign	0.0	.;D;D;D
M_CAP	Pathogenic	0.48	D
MetaRNN	Pathogenic	0.99	D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.0	M;.;.;M
PhyloP100		9.5
PrimateAI	Uncertain	0.58	T
PROVEAN	Pathogenic	-7.5	D;D;D;D
REVEL	Pathogenic	0.96
Sift	Uncertain	0.0040	D;D;D;D
Sift4G	Uncertain	0.040	D;D;D;D
Vest4		0.99
ClinPred		1.0	D
GERP RS		3.9
Varity_R		0.88
gMVP		0.93
Mutation Taster		=0/100	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: rs1553414079; hg19: chr1-21900175;