12-120978482-GTC-G

Variant names:

• chr12-120978482-GTC-G
• rs2135818767
• ENST00000433033.4:n.153+1130_153+1131delGA

Variant summary

Our verdict is Uncertain significance. The variant received 2 ACMG points: 2P and 0B. PM2

The ENST00000433033.4(HNF1A-AS1):​n.153+1130_153+1131delGA variant causes a intron change. The variant was absent in control chromosomes in GnomAD project. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar.

• Frequency: Genomes: not found (cov: 31)
• Consequence: HNF1A-AS1 ENST00000433033.4 intron
• Clinical Significance: Uncertain significance reviewed by expert panel U:1
• Conservation: PhyloP100: 4.02
• Publications: 0 publications found

Genes affected

HNF1A-AS1 (HGNC:26785): (HNF1A antisense RNA 1)

HNF1A (HGNC:11621): (HNF1 homeobox A) The protein encoded by this gene is a transcription factor required for the expression of several liver-specific genes. The encoded protein functions as a homodimer and binds to the inverted palindrome 5'-GTTAATNATTAAC-3'. Defects in this gene are a cause of maturity onset diabetes of the young type 3 (MODY3) and also can result in the appearance of hepatic adenomas. Alternative splicing results in multiple transcript variants encoding different isoforms. [provided by RefSeq, Apr 2015]

HNF1A Gene-Disease associations (from GenCC):

• monogenic diabetes

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• type 1 diabetes mellitus 20

  Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: Laboratory for Molecular Medicine, Genomics England PanelApp
• diabetes mellitus, noninsulin-dependent

  Inheritance: AD Classification: STRONG Submitted by: Genomics England PanelApp
• maturity-onset diabetes of the young type 3

  Inheritance: AD Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae), Genomics England PanelApp
• hyperinsulinism due to HNF1A deficiency

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• maturity-onset diabetes of the young

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• nonpapillary renal cell carcinoma

  Inheritance: Unknown Classification: NO_KNOWN Submitted by: Labcorp Genetics (formerly Invitae)

ACMG classification

Our verdict: Uncertain_significance. The variant received 2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
HNF1A	NM_000545.8	c.-286_-285delTC		upstream_gene_variant		ENST00000257555.11	NP_000536.6
HNF1A	NM_001306179.2	c.-286_-285delTC		upstream_gene_variant			NP_001293108.2
HNF1A	NM_001406915.1	c.-286_-285delTC		upstream_gene_variant			NP_001393844.1
HNF1A	XM_024449168.2	c.-286_-285delTC		upstream_gene_variant			XP_024304936.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
HNF1A	ENST00000257555.11	c.-286_-285delTC		upstream_gene_variant		1	NM_000545.8	ENSP00000257555.5

Frequencies

GnomAD3 genomes Cov.: 31

We have no GnomAD4 exomes data on this position. Probably position not covered by the project.

GnomAD4 genome Cov.: 31

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: reviewed by expert panel

Submissions by phenotype

Monogenic diabetes Uncertain:1

Jul 24, 2025

ClinGen Monogenic Diabetes Variant Curation Expert Panel

Significance: Uncertain significance

Review Status: reviewed by expert panel

Collection Method: curation

The c.-286_-285del variant in the HNF1 homeobox A gene, HNF1A, is located in the promoter of NM_000545.8. This region is defined as critical for the protein’s function by the ClinGen MDEP (PM1_Supporting) and is absent from gnomAD v2.1.1 (PM2_Supporting). This variant was identified in an individual with a clinical history suggestive of HNF1A-MODY (MODY probability calculator result nearly 50%); however, HNF4A was not tested (internal lab contributors), and therefore PP4 was not applied. In summary, c.-286_-285del meets the criteria to be classified as a variant of uncertain significance for monogenic diabetes. ACMG/AMP criteria applied, as specified by the ClinGen MDEP (specification version 3.0.0, approved 6/30/2025): PM1_supporting, PM2_Supporting. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
PhyloP100		4.0

Splicing

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Other links and lift over

dbSNP: rs2135818767; hg19: chr12-121416285;