Reasoning
PS3 is met at strong strength. Four independent studies directly evaluated ATP7B p.His1069Gln (NM_000053.4:c.3207C>A) using complementary biochemical and cellular assays with wild-type comparators. Morgan et al. demonstrated minimal ATP binding by recombinant H1069Q ATP7B N-domain that did not saturate at 600 µM ATP, with at least three independent titrations per protein–nucleotide interaction (PMID:15205462). van Dijk et al. found approximately twofold weaker ATP affinity, reduced chemical and thermal stability, altered ATP-binding orientation, and increased structural flexibility in purified recombinant H1069Q N-domain (PMID:18692069). Tsivkovskii et al. reported reduced protein abundance without reduced transcript levels, endoplasmic-reticulum retention, and reduced copper-export capacity in transiently transfected cells; the cellular phenotype was partially temperature- and chaperone-responsive, supporting a folding/localization defect rather than an assay artifact (PMID:19937698). Besse et al. further reported impaired ATP binding, failure to form the catalytic phosphointermediate, reduced cellular protein abundance, and endoplasmic-reticulum localization with full-length ATP7B in HEK293 cells (PMID:21398519). These concordant results affect ATP binding, catalytic function, protein stability, localization, and copper export, all biologically relevant to ATP7B function. The studies are not described as validated clinical diagnostic-laboratory assays, so the evidence supports the ACMG/AMP strong category but not a higher-than-strong interpretation.
Rule
Well-established in vitro or in vivo functional studies supportive of a damaging effect on the gene or gene product. Note: Functional studies that have been validated and shown to be reproducible and robust in a clinical diagnostic laboratory setting are considered the most well-established.
Evidence considered
- Morgan et al. (PMID:15205462), Results/Fig. 5/Table II: recombinant ATP7B N-domain H1069Q showed minimal ATP binding that did not reach saturation at 600 µM ATP; circular dichroism assessed folding and at least three independent titrations were performed for each protein–nucleotide interaction.
- van Dijk et al. (PMID:18692069), Abstract/Results/Table 1: purified recombinant H1069Q N-domain had approximately twofold lower ATP affinity than wild type, reduced chemical and thermal stability, altered ATP-binding orientation, and increased structural flexibility.
- Tsivkovskii et al. (PMID:19937698), Results/Figs. 3 and 5–7/Table 1: H1069Q had reduced protein expression without reduced mRNA, endoplasmic-reticulum localization, reduced copper export, and temperature/chaperone responsiveness in HEK293T and U2OS cell assays.
- Besse et al. (PMID:21398519), Abstract/Results/Discussion: H1069Q reduced ATP binding and catalytic-phosphointermediate formation, destabilized the N-domain, and caused reduced full-length ATP7B abundance with endoplasmic-reticulum localization in HEK293 cells.
Still missing
- The available studies are research assays rather than validated and reproducible clinical diagnostic-laboratory assays.
Sources