Monogenic Diabetes

Gene: ZNF808

Green List (high evidence)

Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal

Phenotypes
Pancreatic agenesis 3, MIM# 620991

Green List (high evidence)

PMID: 37308312; Alqahtani, MA. et al. (2023) Clin Genet. doi: 10.1111/cge.14389. Three siblings in one consanguineous Saudi Arabian family with non-syndromic neonatal diabetes, all with a homozygous frameshift variant, NM_001321425.2:c.1448dupA, p.(Tyr483*), in ZNF808. (Same nucleotide and amino acid numbering as for the MANE SELECT transcript, NM_001039886.4). This variant has been entered as likely pathogenic in ClinVar by this group. This variant occurs in the last exon of the gene and is therefore not NMD-predicted. Instead it is predicted to cause a truncated protein. This paper shows a diagram with several other truncating variants in this exon, which were reported in the paper by De Franco, E. et al. (2021). (These patients also had low vitamin D levels, suggesting an association, and is consistent with other studies looking into loci that are associated with vitamin D). De Franco, E. et al. (2021) medRxiv 08.23.21262262. (Exeter, UK): Firstly, this group found a homozygous variant NM_001039886.3:c.637del, p.(Leu213*) that is predicted to cause a truncated protein, and also a homozygous CNV Chr19(GRCh37):g.53057128_53100968del (predicted to cause a deletion of exons 4 and 5) in two unrelated affected individuals. These patients had pancreatic agenesis, defined as insulin-dependent diabetes in the first 6 months of life (neonatal diabetes) and exocrine pancreatic insufficiency. Both were from consanguineous families. Parents were subsequently tested and shown to be heterozygous carriers. They then investigated 232 additional patients who had been diagnosed with neonatal diabetes before the age of 6 months and found ten more homozygous ZNF808 variants. Six were nonsense: p.(Gln194*), p.(Cys233*), p.(Tyr427*), p.(Lys458*), p.(Tyr528*) and p.(Arg727*), and three were frameshift variants: p.(Ala379Valfs*157), p.(Leu588Profs*118), p.(Asn770Ilefs*98) and one was a whole-gene deletion. All the frameshift and nonsense variants occurred in the last exon of the gene, which contains all 23 zinc finger domains; and therefore all of these variants are predicted to result in truncated proteins, and removal of some, if not all, those domains. This group also carried out functional studies using an in vitro model of pancreas development and showed an aberrant activation of many transposable elements (mostly MER11 elements) that would be normally be repressed during early pancreas development.
Sources: Literature

Created: 7 Jul 2023, 4:33 a.m.

Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal

Phenotypes
non-syndromic neonatal diabetes; MONDO:0016391

Publications

• PMID: 37308312