Our verdict is Uncertain significance. Variant got 5 ACMG points: 5P and 0B. PVS1_ModeratePM2PP5
The NM_000352.6(ABCC8):c.2695-1G>C variant causes a splice acceptor, intron change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000124 in 1,609,614 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).
ABCC8 (HGNC:59): (ATP binding cassette subfamily C member 8) The protein encoded by this gene is a member of the superfamily of ATP-binding cassette (ABC) transporters. ABC proteins transport various molecules across extra- and intra-cellular membranes. ABC genes are divided into seven distinct subfamilies (ABC1, MDR/TAP, MRP, ALD, OABP, GCN20, White). This protein is a member of the MRP subfamily which is involved in multi-drug resistance. This protein functions as a modulator of ATP-sensitive potassium channels and insulin release. Mutations in the ABCC8 gene and deficiencies in the encoded protein have been observed in patients with hyperinsulinemic hypoglycemia of infancy, an autosomal recessive disorder of unregulated and high insulin secretion. Mutations have also been associated with non-insulin-dependent diabetes mellitus type II, an autosomal dominant disease of defective insulin secretion. Alternatively spliced transcript variants have been found for this gene. [provided by RefSeq, Jul 2020]
Verdict is Uncertain_significance. Variant got 5 ACMG points.
PVS1
Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.026337968 fraction of the gene. Cryptic splice site detected, with MaxEntScore 6.2, offset of -36, new splice context is: tgaccaccattcctccccAGcca. Cryptic site results in inframe change. If cryptic site found is not functional and variant results in exon loss, it results in inframe change.
PM2
Very rare variant in population databases, with high coverage;
PP5
Variant 11-17408518-C-G is Pathogenic according to our data. Variant chr11-17408518-C-G is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 371626.We mark this variant Likely_pathogenic, oryginal submissions are: {Uncertain_significance=2, Pathogenic=3}.
Women's Health and Genetics/Laboratory Corporation of America, LabCorp
Dec 01, 2016
Variant summary: The ABCC8 c.2695-1G>C variant involves the alteration of a conserved intronic nucleotide, at a position known to affect splicing, which 5/5 splice prediction tools predict the loss of a splice site, although these predictions have yet to be functionally assessed. The variant of interest has not been observed in controls (ExAC, 1000 Gs, or ESP) and a publication indicates the variant was observed in one child diagnosed with Congenital Hyperinsulinism. A database has cited the variant as a disease causing mutation. Therefore, the variant of interest has been classified as Pathogenic. -
This sequence change affects an acceptor splice site in intron 22 of the ABCC8 gene. It is expected to disrupt RNA splicing. Variants that disrupt the donor or acceptor splice site typically lead to a loss of protein function (PMID: 16199547), and loss-of-function variants in ABCC8 are known to be pathogenic (PMID: 20685672, 23345197). This variant is not present in population databases (gnomAD no frequency). Disruption of this splice site has been observed in individuals with autosomal recessive congenital hyperinsulinism (PMID: 23275527). This variant is also known as c.2698-1G>C. ClinVar contains an entry for this variant (Variation ID: 371626). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. For these reasons, this variant has been classified as Pathogenic. -
Maturity onset diabetes mellitus in young Uncertain:1
Uncertain significance, criteria provided, single submitter
research
Clinical Genomics, Uppaluri K&H Personalized Medicine Clinic
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Mutations in ABCC8 gene are associated with both neonatal diabetes mellitus as well as MODY. Patients with this mutation may have a better response to sulfonylureas. However, no sufficient evidence is found to ascertain the role of this particular variant ( rs1057517420) in MODY yet. -
Transitory neonatal diabetes mellitus Uncertain:1
Uncertain significance, criteria provided, single submitter
research
Clinical Genomics, Uppaluri K&H Personalized Medicine Clinic
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Mutations in ABCC8 gene are associated with both neonatal diabetes mellitus as well as MODY. Patients with this mutation may have a better response to sulfonylureas. However, no sufficient evidence is found to ascertain the role of this particular variant ( rs1057517420) in neonatal diabetes yet. -