FGF12

Gene Facts

• HGNC Symbol: FGF12 (HGNC:3668)
• HGNC Name: fibroblast growth factor 12
• Gene type: protein-coding gene
• Locus type: gene with protein product
• Previous symbols: FGF12B
• Alias symbols: FHF1
• %HI: 3.96
• pLI: 0.15
• LOEUF: 0.93
• Cytoband: 3q28-q29
• Genomic Coordinates:

  GRCh37/hg19:	chr3:191857179-192445330
  GRCh38/hg38:	chr3:192139390-192727541

• MANE Select Transcript: NM_004113.6 ENST00000445105.7
• Function: Involved in nervous system development and function. Involved in the positive regulation of voltage-gated sodium channel activity. Promotes neuronal excitability by elevating the voltage dependence of neuronal sodium channel SCN8A fast inactivation. {ECO:0000269|PubMed:27164707}. (Source: Uniprot)

Dosage Sensitivity Summary (Gene)

• Dosage ID: ISCA-4794
• ClinGen Curation ID: CCID:007136
• Curation Status: Complete
• Issue Type: Dosage Curation - Gene
• Haploinsufficiency: No Evidence for Haploinsufficiency (0)
• Triplosensitivity: Little Evidence for Triplosensitivity (1)
• Last Evaluated: 12/01/2021

Haploinsufficiency (HI) Score Details

• HI Score: 0
• HI Evidence Strength: No Evidence for Haploinsufficiency

HI Evidence

• PUBMED: 25217958
  Coe et al 2014 identified 13 cases with intellectual disability and/or autism and 1 control with a 1.5Mb deletion that overlaps the FGF12 gene. Insufficient evidence was provided regarding the exact genomic content the deletions and phenotype to fully assess for evidence of haploinsufficiency.
• PUBMED: 25232849
  Rigler et al 2015 identified a 224kb partial deletion of the FGF12 gene (hg19 coordinates chr3: 192,014,722–192,238,859) in a Hispanic individual with heterotaxy. No further details were provided and therefore this data cannot be scored for haploinsufficiency.
• PUBMED: 28446957
  Hagan et al, 2017 identified a 50kb deletion of FGF12 in 1 of 52 individuals with sex developmental issues. Imprecise breakpoints and minimal phenotype data were provided and therefore cannot be scored for haploinsufficiency.

• HI Evidence Comments: A small number of FGF12 deletions have been reported in individuals with varying phenotypes, including developmental delay, heterotaxy and sex development differences. These reports did not provide sufficient evidence to score the data and therefore we have scored this gene as a zero for haploinsufficiency.

Triplosensitivity (TS) Score Details

• TS Score: 1
• TS Evidence Strength: Little Evidence for Triplosensitivity

TS Disease

• developmental and epileptic encephalopathy

TS Published Evidence

• PUBMED: 32524056
  Willemsen et al, 2020 (PMID: 32524056) reported one individual with a de novo full gene duplication of FGF12 (not encompassing other genes) with severe developmental and intellectual delay and tonic-clonic seizures, among other features, however no evidence was provided to evaluate the mechanism of disease for this gene duplication; it is unclear whether this is resulting in true triplosensitivity. The authors also note that there are 3 additional full gene duplication cases in DECIPHER, though no phenotype information is provided.

• TS Evidence Comments: Activating missense variants in the FGF12 gene have been shown to have a gain-of-function effect resulting in developmental and epileptic encephalopathy. A similar phenotype has been observed in individuals with full and partial duplications of the FGF12 gene (PMIDs:29216221, 27637763, 30866059, 30866059, 28144627), however at this time it is unclear how these duplications lead to disease pathogenesis and may act by a gain-of-function mechanism similar to missense variants. Furthermore, of the 6 FGF12 duplications reported in the literature to date, all but one appear to be partial gene duplications, and are therefore unlikely to lead to an increased gene dosage effect and thus have not been scored with respect to triplosensitivity. Although there have been reports of full and partial FGF12 duplications in individuals with developmental and epileptic encephalopathy, there is minimal evidence to determine whether triplosensitivity is the mechanism of disease for these duplications. In summary, there is currently a single report of a patient with a full gene duplication providing minimal support for a role for triplosensitivity for this gene.