rs201038679 — ATP7B P992L

ATP7B P992L — Carrying One Dose of the Wilson Disease Gene

Every cell that makes proteins must also manage copper — an essential mineral that acts as a cofactor for dozens of enzymes yet becomes toxic when it accumulates. The ATP7B protein is the liver's primary copper disposal system: it pumps excess copper into bile for excretion and loads copper onto ceruloplasmin¹¹ ceruloplasmin
The major copper-carrying protein in blood, made in the liver; synthesised as apoprotein and activated when copper is loaded onto it by ATP7B. Low ceruloplasmin is one of the diagnostic markers of Wilson disease.. When both copies of ATP7B are damaged, copper builds up in the liver, then spills into the brain, cornea, and kidneys — this is Wilson disease.

The P992L variant (rs201038679) replaces proline with leucine at position 992 of the ATP7B protein. It is one of the best-characterised pathogenic ATP7B variants: classified as Pathogenic/Likely pathogenic by 16 independent clinical laboratories²² classified as Pathogenic/Likely pathogenic by 16 independent clinical laboratories
ClinVar VCV000188831, review status 2 stars: criteria provided, multiple submitters, no conflicts. In East Asian populations — particularly Chinese — it is the second most common Wilson disease allele, found in 13-16% of Wilson disease chromosomes³³ found in 13-16% of Wilson disease chromosomes
Yang et al. Genes, 2021; Li et al. BMC Gastroenterology, 2021.

The Mechanism

Position 992 sits in transmembrane domain 6 (TM6) of ATP7B — one of the eight membrane-spanning helices that form the copper-conducting channel. The proline at this position creates a structural kink in the helix that is conserved across P-type ATPase copper transporters in multiple species. Replacing proline with the bulkier, more flexible leucine disrupts this geometry, destabilising the channel.

Functional studies in Menkes fibroblast cell lines find that P992L retains approximately 17% of wild-type copper transport activity⁴⁴ approximately 17% of wild-type copper transport activity
Członkowska et al. 2018 and subsequent functional screens; PMC12259332 — substantially reduced but not zero. Notably, the variant retains near-normal phosphorylation activity (~129% of wild-type), meaning the ATP-binding machinery is intact; the defect is in copper translocation across the membrane rather than in the catalytic cycle itself. This partial activity is consistent with the clinical observation that P992L homozygotes tend to present at a younger average age (mean 9.7 ± 4.2 years) than patients with milder variants⁵⁵ younger average age (mean 9.7 ± 4.2 years) than patients with milder variants
Li et al. BMC Gastroenterol, 2021, while still occasionally showing incomplete penetrance.

The Evidence

Wilson disease is rare in the general population — estimated prevalence of 1:30,000, with a carrier frequency of approximately 1:90⁶⁶ 1:30,000, with a carrier frequency of approximately 1:90
Ferenci P. Wilson Disease. GeneReviews, 2010. Newer population genomic studies suggest the true prevalence may be closer to 1:7,000, because many carriers are compound heterozygotes with mild or asymptomatic presentations. P992L is globally rare (allele frequency ~0.00006 in TOPMED, ~0.00018 in Japanese/ToMMo data) but enriched in East Asian populations, particularly mainland Chinese, where it has a founder effect centred on Jiangxi province.

Among 715 unrelated Chinese Wilson disease patients⁷⁷ 715 unrelated Chinese Wilson disease patients
Yang et al. Genes, 2021, PMID 33668890, P992L accounted for 15.7% of all disease alleles, with regional allele frequencies ranging from 9.8% in Zhejiang to 22.1% in Jiangxi. Haplotype analysis identified six distinct P992L haplogroups, with haplogroup E dominating at 72.4% of affected chromosomes (vs. 3.4% in controls), consistent with a founder mutation.

A cohort of 196 Chinese patients⁸⁸ cohort of 196 Chinese patients
Li et al. BMC Gastroenterol, 2021, PMID 34470610 found that P992L homozygotes presented at a mean age of 9.7 ± 4.2 years, compound heterozygotes at 15.7 ± 11.6 years, and non-P992L patients at 20.5 ± 12.2 years (P = 0.01 and P = 0.017 respectively). Clinical presentation was predominantly hepatic (50.5%) or asymptomatic (16.8%).

Most Wilson disease patients are compound heterozygotes⁹⁹ compound heterozygotes
A person who carries two different pathogenic variants in the same gene — one on each chromosome. For Wilson disease, both variants together prevent adequate copper transport., carrying one P992L allele paired with a different ATP7B variant. Disease only manifests when both copies are non-functional.

Practical Implications

For heterozygous carriers (GA): you have one functioning and one P992L copy of ATP7B. One functioning copy is sufficient to maintain copper homeostasis; clinical disease is not expected in carriers. The primary significance is reproductive: if your partner also carries any pathogenic ATP7B variant, there is a 25% chance with each pregnancy that the child will inherit Wilson disease. First-degree relatives of known Wilson disease patients should be offered molecular genetic testing to determine their carrier status.

Treatment of Wilson disease (for homozygous or compound heterozygous individuals) relies on copper chelation with D-penicillamine (750–1,500 mg/day in divided doses) or trientine (1,200–2,000 mg/day)¹⁰¹⁰ D-penicillamine (750–1,500 mg/day in divided doses) or trientine (1,200–2,000 mg/day)
AASLD practice guidance; Roberts EA et al. Hepatology, 2008, or zinc salts (150 mg/day in three doses) for maintenance or asymptomatic patients. Neurological and hepatic manifestations respond well to early chelation — outcomes are excellent when diagnosis precedes organ damage.

Interactions

Wilson disease requires two damaged ATP7B copies. The most clinically relevant interaction is therefore between rs201038679 (P992L) and any other pathogenic ATP7B variant in trans (on the opposite chromosome). Common co-occurring variants in East Asian patients include R778L (rs755523048), A874V, and p.Ile1102Thr. The combination of P992L with a second severe loss-of-function allele (e.g. R778L) typically produces earlier onset and more severe hepatic disease than P992L compound-heterozygous with milder alleles.

There is no established interaction between heterozygous P992L carrier status and other copper-regulating genes (e.g. ATOX1, CCS) that would produce clinical effects in a single-carrier context.