GENE REFERENCE / HGNC:9498

PSAP

prosaposin

protein-coding gene10q22.1Gene information

What does this gene do?

The PSAP gene provides instructions for making a protein called prosaposin. This protein is involved in a number of biological functions, including the development of the nervous system and the reproductive system. Prosaposin is the precursor of four smaller proteins called saposin A, B, C, and D, which are produced when prosaposin is broken up (cleaved).

The individual saposins are found in cellular structures called lysosomes, which are the cell's recycling centers. The saposins help lysosomal enzymes break down fatty substances called sphingolipids.

The saposin B protein works with several enzymes to break down sphingolipids. Its most critical biological role seems to be associated with the enzyme arylsulfatase A. This enzyme is involved in breaking down a subgroup of sphingolipids called sulfatides, especially in the nervous system's white matter, which consists of nerve fibers covered by myelin. Myelin is a substance that insulates and protects nerves. Saposin B may also play a role in transporting lipids to the outer surface of the cell so they can be recognized by the immune system.

The saposin C protein works with the enzyme beta-glucocerebrosidase to break down another sphingolipid called glucocerebroside. Saposins A and D are also involved in processing sphingolipids.

Source: MedlinePlus, National Library of Medicine. Source publication: 2023-04-19. Source review: 2007-09.

ClinGen reviews

ClinGen reviews the evidence linking a particular gene to a condition. Each rating below describes the strength of that link. It does not classify a variant in your DNA file.

Condition	Inheritance	Evidence
metachromatic leukodystrophy due to saposin B deficiencyMONDO:0009590 · Evaluated 2023-07-20	Autosomal recessive	DefinitiveLysosomal Diseases Gene Curation Expert Panel
Krabbe disease due to saposin A deficiencyMONDO:0012720 · Evaluated 2025-09-12	Autosomal recessive	ModerateLysosomal Diseases Gene Curation Expert Panel
Gaucher disease due to saposin C deficiencyMONDO:0012517 · Evaluated 2023-06-26	Autosomal recessive	DefinitiveLysosomal Diseases Gene Curation Expert Panel
combined PSAP deficiencyMONDO:0012719 · Evaluated 2023-07-20	Autosomal recessive	DefinitiveLysosomal Diseases Gene Curation Expert Panel

ClinVar records

These numbers show what has been submitted to ClinVar. They cannot tell you how likely you are to have a condition.

Submitted alleles: 1,048
Submissions for variants in or overlapping this gene: 1,878
Submissions explicitly reporting this gene: 1,843
Alleles reported pathogenic / likely pathogenic: 103
VariationIDs with uncertain significance: 311
VariationIDs with conflicting classifications: 51

The rows count different things: alleles, submissions or VariationIDs. Their categories can overlap, so do not add them together. Pathogenic/likely pathogenic counts exclude structural variants that merely overlap a gene. A dash in the source means “not reported,” not zero.

NCBI produces the gene-summary file each week using counts recorded at the start of the month. The numbers may differ from those on the live ClinVar website. Read the field definitions ↗

View this gene in ClinVar ↗

YOUR DNA FILE

Can your DNA file tell you about PSAP?

From a DNA test kit (such as 23andMe, AncestryDNA or MyHeritage). These kits check a fixed list of about 600,000 to 700,000 positions across your whole genome. ClinVar lists 103 alleles in PSAP reported as pathogenic or likely pathogenic. A kit checks only some of these positions, and often none of them.

From whole genome sequencing (a VCF file). Sequencing reads most of your genome. Your file lists the places where your DNA differs from the reference genome. Some regions are hard to sequence, including parts of some genes that have near-identical copies elsewhere, and a VCF file does not record which positions were read well.

If a variant is not in your file, that does not mean you don’t have it.

What BioDecode checks

BioDecode compares every variant in your file with ClinVar, on your own computer. For each match, it shows the ClinVar classification, the review status and the condition it was reported for. Your file is not uploaded.

A ClinVar classification applies to one particular variant and the condition it was reported for. It does not tell you about other variants in PSAP.

BioDecode cannot fill gaps in your test, diagnose a condition or replace clinical testing.

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