Atypical presentation of Dowling-Degos disease with novel and recurrent mutations in POFUT1

POFUT1 promotes gastric cancer progression through Notch/Wnt dual signaling pathways dependent on the parafibromin-NICD1-β-catenin complex

BACKGROUND

Aberrant glycosylation performed by glycosyltransferases is a leading cause of gastric cancer (GC). Protein O-fucosyltransferase 1 (POFUT1) expression is increased in GC specimens and cells. In this study, the biological effects and mechanisms of POFUT1 underlying the development of GC were investigated.

METHODS

POFUT1 downregulated and upregulated GC cells were established. The effects of POFUT1 on cell proliferation, metastasis and apoptosis were examined using cell counting kit-8 (CCK8) assay, transwell assay, and flow cytometry. Subcutaneous xenograft tumor models were established followed by immunohistochemistry staining of resected tumors. Facilitating modulators and transcription factors were detected by western blot, immunofluorescence, luciferase reporter assay, and co-immunoprecipitation.

RESULTS

POFUT1 played a pro-oncogenic role both in vivo and in vitro, which promoted proliferation and metastasis, as well as inhibited apoptosis in GC cells. POFUT1 promoted Cyclin D3 expression and inhibited the expression of apoptotic proteins, such as Bcl-2-associated X protein (Bax) and cleaved caspase 3, facilitating tumor growth. Moreover, POFUT1 accelerated matrix metalloproteases expression and attenuated E-cadherin expression, contributing to GC metastasis. In addition, POFUT1 expression promoted the expression and nuclear translocation of Notch1 intracellular domain (NICD1) and β-catenin and inhibited β-catenin phosphorylation degradation, accompanied by the activation of recombination signal binding protein-Jκ (RBP-J) and T-cell factor (TCF) transcription factors, respectively. It is notable that parafibromin integrated NICD1 and β-catenin, enabling the concerted activation of Wnt and Notch signaling targeted proteins.

CONCLUSION

These observations indicated that POFUT1 promoted GC development through activation of Notch and Wnt signaling pathways, which depended on the parafibromin-NICD1-β-catenin complex. This work provides new evidence for the further diagnosis and treatment of GC.

Diseases related to Notch glycosylation

The Notch receptors are a family of transmembrane proteins that mediate direct cell-cell interactions and control numerous cell-fate specifications in humans. The extracellular domains of mammalian Notch proteins contain 29-36 tandem epidermal growth factor-like (EGF) repeats, most of which have O-linked glycan modifications: O-glucose added by POGLUT1, O-fucose added by POFUT1 and elongated by Fringe enzymes, and O-GlcNAc added by EOGT. The extracellular domain is also N-glycosylated. Mutations in the glycosyltransferases modifying Notch have been identified in several diseases, including Dowling-Degos Disease (haploinsufficiency of POFUT1 or POGLUT1), a form of limb-girdle muscular dystrophy (autosomal recessive mutations in POGLUT1), Spondylocostal Dysostosis 3 (autosomal recessive mutations in LFNG), Adams-Oliver syndrome (autosomal recessive mutations in EOGT), and some cancers (amplification, gain or loss-of-function of POFUT1, Fringe enzymes, POGLUT1, MGAT3). Here we review the characteristics of these diseases and potential molecular mechanisms.

Scrotal Dowling-Degos disease caused by a novel frameshift variant in gamma-secretase subunit presenile enhancer gene

We reported a Chinese pedigree with scrotal Dowling-Degos disease and evaluated the phenotypic and genotypic characteristics. In affected cases, pigmented macules were identified on the scrotum. The rashes increased, and the colour deepened progressively. No pain or pruritus were noticed, and no other skin folds were involved. Skin histopathology showed characteristic features of Dowling-Degos disease. A heterozygous PSENEN frameshift variant c.292delC（p.L98Wfs*47） was identified in affected cases. The variant was not found in dbSNP, 1000 Genomes project database and the ExAC Browser. The p.L98 and adjacent amino acids are highly conserved among species. Our cases expand the phenotypic and genotypic spectrum of PSENEN-related Dowling-Degos disease.