Our verdict is Uncertain significance. Variant got 3 ACMG points: 3P and 0B. PM2PP2
The NM_001161352.2(KCNMA1):c.3353G>T(p.Cys1118Phe) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Uncertain significance (★★).
KCNMA1 (HGNC:6284): (potassium calcium-activated channel subfamily M alpha 1) This gene encodes the alpha subunit of calcium-activated BK channel. The encoded protein is involved in several physiological processes including smooth muscle contraction, neurotransmitter release and neuronal excitability. Mutations in this gene are associated with a spectrum of neurological disorders including Paroxysmal Nonkinesigenic Dyskinesia 3, Idiopathic Generalized Epilepsy 16 and Liang-Wang syndrome. [provided by RefSeq, Aug 2022]
Verdict is Uncertain_significance. Variant got 3 ACMG points.
PM2
Very rare variant in population databases, with high coverage;
PP2
Missense variant in the KCNMA1 gene, where missense mutations are typically associated with disease (based on misZ statistic). The gene has 12 curated pathogenic missense variants (we use a threshold of 10). The gene has 25 curated benign missense variants. Gene score misZ: 5.0622 (above the threshold of 3.09). Trascript score misZ: 6.5162 (above the threshold of 3.09). GenCC associations: The gene is linked to cerebellar atrophy, developmental delay, and seizures, generalized epilepsy-paroxysmal dyskinesia syndrome, Liang-Wang syndrome.
Review Status: criteria provided, single submitter
Collection Method: clinical testing
Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; Has not been previously published as pathogenic or benign to our knowledge -
Review Status: criteria provided, single submitter
Collection Method: clinical testing
This sequence change replaces cysteine, which is neutral and slightly polar, with phenylalanine, which is neutral and non-polar, at codon 1060 of the KCNMA1 protein (p.Cys1060Phe). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with KCNMA1-related conditions. ClinVar contains an entry for this variant (Variation ID: 2581976). Invitae Evidence Modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) indicates that this missense variant is not expected to disrupt KCNMA1 protein function with a negative predictive value of 80%. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -
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