Our verdict is Pathogenic. Variant got 17 ACMG points: 17P and 0B. PM1PM2PM5PP2PP3_ModeratePP5_Very_Strong
The NM_002074.5(GNB1):โc.229G>Aโ(p.Gly77Ser) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000657 in 152,140 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (โ โ ). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. G77A) has been classified as Likely pathogenic.
GNB1 (HGNC:4396): (G protein subunit beta 1) Heterotrimeric guanine nucleotide-binding proteins (G proteins), which integrate signals between receptors and effector proteins, are composed of an alpha, a beta, and a gamma subunit. These subunits are encoded by families of related genes. This gene encodes a beta subunit. Beta subunits are important regulators of alpha subunits, as well as of certain signal transduction receptors and effectors. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Sep 2013]
Verdict is Pathogenic. Variant got 17 ACMG points.
PM1
In a turn (size 2) in uniprot entity GBB1_HUMAN there are 16 pathogenic changes around while only 0 benign (100%) in NM_002074.5
PM2
Very rare variant in population databases, with high coverage;
PM5
Other missense variant is known to change same aminoacid residue: Variant chr1-1806513-C-A is described in ClinVar as [Pathogenic]. Clinvar id is 1700090.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
PP2
Missense variant in gene, where missense usually causes diseases (based on misZ statistic), GNB1. . Gene score misZ 3.8328 (greater than the threshold 3.09). Trascript score misZ 3.4817 (greater than threshold 3.09). GenCC has associacion of gene with intellectual disability, autosomal dominant 42.
PP3
MetaRNN computational evidence supports a deleterious effect, 0.869
PP5
Variant 1-1806513-C-T is Pathogenic according to our data. Variant chr1-1806513-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 224713.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr1-1806513-C-T is described in Lovd as [Pathogenic].
For these reasons, this variant has been classified as Pathogenic. This variant disrupts the p.Gly77 amino acid residue in GNB1. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 27759915). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive. ClinVar contains an entry for this variant (Variation ID: 224713). This missense change has been observed in individual(s) with GNB1-related neurodevelopmental delay and hypotonia (PMID: 27108799; Invitae). In at least one individual the variant was observed to be de novo. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces glycine, which is neutral and non-polar, with serine, which is neutral and polar, at codon 77 of the GNB1 protein (p.Gly77Ser). -
Pathogenic, criteria provided, single submitter
clinical testing
GeneDx
Jan 07, 2022
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; This variant is associated with the following publications: (PMID: 27108799, 27759915, 29174093, 30504930) -