ClinVar Genomic variation as it relates to human health

This variant was observed as part of a predisposition screen in an ostensibly healthy population. A literature search was performed for the gene, cDNA change, and amino acid change (where applicable). Publications were found based on this search. However, the evidence from the literature, in combination with allele frequency data from public databases where available, was not sufficient to rule this variant in or out of causing disease. Therefore, this variant is classified as a variant of unknown significance.

Variant summary: ATP8B1 c.913T>A (p.Phe305Ile) results in a non-conservative amino acid change in the encoded protein sequence. Four of five in-silico tools predict a benign effect of the variant on protein function. The variant allele was found at a frequency of 0.0012 in 251422 control chromosomes. This frequency is not significantly higher than expected for a pathogenic variant in ATP8B1 causing Familial Intrahepatic Cholestasis (0.0012 vs 0.0022), allowing no conclusion about variant significance. c.913T>A has been reported in the literature in individuals affected with intrahepatic cholestasis of pregnancy (Mullenbach_2005) or FIC1 deficiency (van Wessel_2021). These reports do not provide unequivocal conclusions about association of the variant with Familial Intrahepatic Cholestasis. Four clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation (likely benign n=1, VUS n=3). Based on the evidence outlined above, the variant was classified as uncertain significance.

In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; Identified in the heterozygous state in individuals with intrahepatic cholestasis of pregnancy, chronic pancreatitis, or cryptogenic cholestasis in whom a second variant in ATP8B1 was not identified. This variant was also identified in multiple healthy control individuals (PMID: 15888793, 24260417, 29238877); This variant is associated with the following publications: (PMID: Barkaoui[Article]2018, 33666275, 24260417, 29238877, 28733223, 34679599, 15888793)

BS1

The ATP8B1 c.913T>A variant is predicted to result in the amino acid substitution p.Phe305Ile. This variant has been reported in patients with ATP8B1-related disease, including PFIC, cryptogenic cholestasis, intrahepatic cholestasis of pregnancy, and chronic pancreatitis (Müllenbach et al. 2005. PubMed ID: 15888793; van der Woerd et al. 2013. PubMed ID: 24260417; Dröge et al. 2017. PubMed ID: 28733223; Vitale et al. 2018. PubMed ID: 29238877). However, this variant has also been documented in healthy controls (Müllenbach et al. 2005. PubMed ID: 15888793; Woerd et al. 2013. PubMed ID: 24260417). This variant is found at an allele frequency of up to 0.42% in individuals of Ashkenazi Jewish descent in gnomAD. Additionally, in gnomAD v4 (available only on GRCh38), this variant is reported in 0.36% of individuals of Ashkenazi Jewish descent, including 8 homozygotes that were identified mostly in individuals of European descent. This population data is not consistent with this variant being a primary cause of disease. At this time, the clinical significance of this variant is uncertain due to the absence of conclusive functional and genetic evidence.